Publications by authors named "Paweł Stankiewicz"

216 Publications

Do paternal deletions involving the FOXF1 locus on chromosome 16q24.1 manifest with more severe non-lung anomalies?

Eur J Med Genet 2022 Jun 6;65(6):104519. Epub 2022 May 6.

Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, TX, USA. Electronic address:

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal lung developmental disorder in neonates due to heterozygous loss-of-function of the mesenchymal transcription factor gene, FOXF1. Interestingly, unlike ACDMPV-causing point mutations in FOXF1 that can be inherited from the mother or father, causative copy-number variant (CNV) deletions arise de novo and almost exclusively on chromosome 16 inherited from the mother (n = 50 vs. n = 3). Here, we describe a fourth case of a de novo paternal CNV deletion encompassing FOXF1, its neighboring long non-coding RNA gene FENDRR, and their distant lung-specific enhancer, identified in a 21-week-old fetus with tetralogy of Fallot, gastrointestinal and genitourinary abnormalities, a single umbilical artery, and patchy histopathological findings of ACDMPV in autopsy lung. We also review the ACDMPV-causative CNV deletions detected prenatally and propose that the majority of paternal deletions manifest with more severe additional non-lung abnormalities.
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http://dx.doi.org/10.1016/j.ejmg.2022.104519DOI Listing
June 2022

Parental mosaicism for apparent de novo genetic variants: Scope, detection, and counseling challenges.

Prenat Diagn 2022 Apr 8. Epub 2022 Apr 8.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

The disease burden of de novo mutations (DNMs) has been evidenced only recently when the common application of next-generation sequencing technologies enabled their reliable and affordable detection through family-based clinical exome or genome sequencing. Implementation of exome sequencing into prenatal diagnostics revealed that up to 63% of pathogenic or likely pathogenic variants associated with fetal structural anomalies are apparently de novo, primarily for autosomal dominant disorders. Apparent DNMs have been considered to primarily occur as germline or zygotic events, with consequently negligible recurrence risks. However, there is now evidence that a considerable proportion of them are in fact inherited from a parent mosaic for the variant. Here, we review the burden of DNMs in prenatal diagnostics and the influence of parental mosaicism on the interpretation of apparent DNMs and discuss the challenges with detecting and quantifying parental mosaicism and its effect on recurrence risk. We also describe new bioinformatic and technological tools developed to assess mosaicism and discuss how they improve the accuracy of reproductive risk counseling when parental mosaicism is detected.
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http://dx.doi.org/10.1002/pd.6144DOI Listing
April 2022

Exacerbation of mild lung disorders to lethal pulmonary hypoplasia by a noncoding hypomorphic SNV in a lung-specific enhancer in trans to the frameshifting TBX4 variant.

Am J Med Genet A 2022 May 25;188(5):1420-1425. Epub 2022 Jan 25.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

Variants involving TBX4 are associated with a wide variety of disorders, including pulmonary arterial hypertension, ischiocoxopodopatellar syndrome (ICPPS)/small patella syndrome (SPS), lethal lung developmental disorders (LLDDs) in neonates, heart defects, and prenatally lethal posterior amelia with pelvic and pulmonary hypoplasia syndrome. The objective of our study was to elucidate the wide variable phenotypic expressivity and incomplete penetrance in a three-generation family with a truncating variant in TBX4. In addition to exome and genome sequencing analyses, a candidate noncoding regulatory single nucleotide variant (SNV) within the lung-specific TBX4 enhancer was functionally tested using an in vitro luciferase reporter assay. A heterozygous frameshift variant c.1112dup (p.Pro372Serfs*14) in TBX4 was identified in patients with mild interstitial lung disease (1), bronchiolitis obliterans (1), recurrent pneumothorax (1), ICPPS/SPS (1), LLDD (2), and in unaffected individuals (4). In two deceased neonates with LLDD, we identified a noncoding SNV rs62069651-C located in trans to the mutated TBX4 allele that reduced the TBX4 promoter activity by 63% in the reporter assay. Our findings provide a functional evidence for the recently reported model of complex compound inheritance in which both TBX4 coding and in trans noncoding hypomorphic variants in the lung-specific enhancer of TBX4 contribute to LLDD.
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http://dx.doi.org/10.1002/ajmg.a.62656DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8995354PMC
May 2022

Detection of low-level parental somatic mosaicism for clinically relevant SNVs and indels identified in a large exome sequencing dataset.

Hum Genomics 2021 12 20;15(1):72. Epub 2021 Dec 20.

Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.

Background: Due to the limitations of the current routine diagnostic methods, low-level somatic mosaicism with variant allele fraction (VAF) < 10% is often undetected in clinical settings. To date, only a few studies have attempted to analyze tissue distribution of low-level parental mosaicism in a large clinical exome sequencing (ES) cohort.

Methods: Using a customized bioinformatics pipeline, we analyzed apparent de novo single-nucleotide variants or indels identified in the affected probands in ES trio data at Baylor Genetics clinical laboratories. Clinically relevant variants with VAFs between 30 and 70% in probands and lower than 10% in one parent were studied. DNA samples extracted from saliva, buccal cells, redrawn peripheral blood, urine, hair follicles, and nail, representing all three germ layers, were tested using PCR amplicon next-generation sequencing (amplicon NGS) and droplet digital PCR (ddPCR).

Results: In a cohort of 592 clinical ES trios, we found 61 trios, each with one parent suspected of low-level mosaicism. In 21 parents, the variants were validated using amplicon NGS and seven of them by ddPCR in peripheral blood DNA samples. The parental VAFs in blood samples varied between 0.08 and 9%. The distribution of VAFs in additional tissues ranged from 0.03% in hair follicles to 9% in re-drawn peripheral blood.

Conclusions: Our study illustrates the importance of analyzing ES data using sensitive computational and molecular methods for low-level parental somatic mosaicism for clinically relevant variants previously diagnosed in routine clinical diagnostics as apparent de novo.
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http://dx.doi.org/10.1186/s40246-021-00369-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8686574PMC
December 2021

Perturbation of semaphorin and VEGF signaling in ACDMPV lungs due to FOXF1 deficiency.

Respir Res 2021 Jul 27;22(1):212. Epub 2021 Jul 27.

Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Rm ABBR-R809, Houston, TX, 77030, USA.

Background: Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal congenital lung disorder in neonates characterized by severe progressive respiratory failure and refractory pulmonary hypertension, resulting from underdevelopment of the peripheral pulmonary tree. Causative heterozygous single nucleotide variants (SNVs) or copy-number variant (CNV) deletions involving FOXF1 or its distant lung-specific enhancer on chromosome 16q24.1 have been identified in 80-90% of ACDMPV patients. FOXF1 maps closely to and regulates the oppositely oriented FENDRR, with which it also shares regulatory elements.

Methods: To better understand the transcriptional networks downstream of FOXF1 that are relevant for lung organogenesis, using RNA-seq, we have examined lung transcriptomes in 12 histopathologically verified ACDMPV patients with or without pathogenic variants in the FOXF1 locus and analyzed gene expression profile in FENDRR-depleted fetal lung fibroblasts, IMR-90.

Results: RNA-seq analyses in ACDMPV neonates revealed changes in the expression of several genes, including semaphorins (SEMAs), neuropilin 1 (NRP1), and plexins (PLXNs), essential for both epithelial branching and vascular patterning. In addition, we have found deregulation of the vascular endothelial growth factor (VEGF) signaling that also controls pulmonary vasculogenesis and a lung-specific endothelial gene TMEM100 known to be essential in vascular morphogenesis. Interestingly, we have observed a substantial difference in gene expression profiles between the ACDMPV samples with different types of FOXF1 defect. Moreover, partial overlap between transcriptome profiles of ACDMPV lungs with FOXF1 SNVs and FENDRR-depleted IMR-90 cells suggests contribution of FENDRR to ACDMPV etiology.

Conclusions: Our transcriptomic data imply potential crosstalk between several lung developmental pathways, including interactions between FOXF1-SHH and SEMA-NRP or VEGF/VEGFR2 signaling, and provide further insight into complexity of lung organogenesis in humans.
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http://dx.doi.org/10.1186/s12931-021-01797-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8314029PMC
July 2021

Haploinsufficiency of the Sin3/HDAC corepressor complex member SIN3B causes a syndromic intellectual disability/autism spectrum disorder.

Am J Hum Genet 2021 05 2;108(5):929-941. Epub 2021 Apr 2.

Etablissement Français du Sang, 44000 Nantes, France; CRCINA, INSERM, CNRS, Université d'Angers, Université de Nantes, 44000 Nantes, France; LabEx IGO, Nantes 44000, France.

Proteins involved in transcriptional regulation harbor a demonstrated enrichment of mutations in neurodevelopmental disorders. The Sin3 (Swi-independent 3)/histone deacetylase (HDAC) complex plays a central role in histone deacetylation and transcriptional repression. Among the two vertebrate paralogs encoding the Sin3 complex, SIN3A variants cause syndromic intellectual disability, but the clinical consequences of SIN3B haploinsufficiency in humans are uncharacterized. Here, we describe a syndrome hallmarked by intellectual disability, developmental delay, and dysmorphic facial features with variably penetrant autism spectrum disorder, congenital malformations, corpus callosum defects, and impaired growth caused by disruptive SIN3B variants. Using chromosomal microarray or exome sequencing, and through international data sharing efforts, we identified nine individuals with heterozygous SIN3B deletion or single-nucleotide variants. Five individuals harbor heterozygous deletions encompassing SIN3B that reside within a ∼230 kb minimal region of overlap on 19p13.11, two individuals have a rare nonsynonymous substitution, and two individuals have a single-nucleotide deletion that results in a frameshift and predicted premature termination codon. To test the relevance of SIN3B impairment to measurable aspects of the human phenotype, we disrupted the orthologous zebrafish locus by genome editing and transient suppression. The mutant and morphant larvae display altered craniofacial patterning, commissural axon defects, and reduced body length supportive of an essential role for Sin3 function in growth and patterning of anterior structures. To investigate further the molecular consequences of SIN3B variants, we quantified genome-wide enhancer and promoter activity states by using H3K27ac ChIP-seq. We show that, similar to SIN3A mutations, SIN3B disruption causes hyperacetylation of a subset of enhancers and promoters in peripheral blood mononuclear cells. Together, these data demonstrate that SIN3B haploinsufficiency leads to a hitherto unknown intellectual disability/autism syndrome, uncover a crucial role of SIN3B in the central nervous system, and define the epigenetic landscape associated with Sin3 complex impairment.
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http://dx.doi.org/10.1016/j.ajhg.2021.03.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8206166PMC
May 2021

Lung-specific distant enhancer cis regulates expression of FOXF1 and lncRNA FENDRR.

Hum Mutat 2021 06 6;42(6):694-698. Epub 2021 Apr 6.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

The FOXF1 gene, causative for a neonatal lethal lung developmental disorder alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), maps 1.7 kb away from the long noncoding RNA gene FENDRR on the opposite strand, suggesting they may be coregulated. Using RNA sequencing in lung tissue from ACDMPV patients with heterozygous deletions of the FOXF1 distant enhancer located 286 kb upstream, leaving FOXF1 and FENDRR intact, we have found that the FENDRR and FOXF1 expressions were reduced by approximately 75% and 50%, respectively, and were monoallelic from the intact chromosome 16q24.1. In contrast, ACDMPV patients with FOXF1 SNVs had biallelic FENDRR expression reduced by 66%-82%. Corroboratively, depletion of FOXF1 by small interfering RNA in lung fibroblasts resulted in a 50% decrease of FENDRR expression. These data indicate that FENDRR expression in the lungs is regulated both in cis by the FOXF1 distant enhancer and in trans by FOXF1. Our findings are compatible with the involvement of FENDRR in FOXF1-related disorders, including ACDMPV.
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http://dx.doi.org/10.1002/humu.24198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8284783PMC
June 2021

Variants in FLRT3 and SLC35E2B identified using exome sequencing in seven high myopia families from Central Europe.

Adv Med Sci 2021 Mar 9;66(1):192-198. Epub 2021 Mar 9.

Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland; Chair and Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland. Electronic address:

Purpose: High myopia (HM) is an eye disorder with both environmental and genetic factors involved. Many genetic factors responsible for HM were recognized worldwide, but little is known about genetic variants underlying HM in Central Europe. Thus, the aim of this study was to identify rare sequence variants involved in HM in families from Central Europe to better understand the genetic basis of HM.

Materials And Methods: We assessed 17 individuals from 7 unrelated Central European families with hereditary HM using exome sequencing (ES). Segregation of selected variants in other available family members was performed using Sanger sequencing.

Results: Detected 73 rare variants were selected for verification. We observed 2 missense variants, c.938C>T in SLC35E2B - encoding solute carrier family 35 member E2B, and c.1642G>C in FLRT3 - encoding fibronectin leucine rich transmembrane protein, segregating with HM in one family.

Conclusions: FLRT3 ​and/or ​SLC35E2B ​could represent disease candidate genes and identified sequence variants might be responsible for HM in the studied family.
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http://dx.doi.org/10.1016/j.advms.2021.02.005DOI Listing
March 2021

Phenotypic expansion of the BPTF-related neurodevelopmental disorder with dysmorphic facies and distal limb anomalies.

Am J Med Genet A 2021 05 31;185(5):1366-1378. Epub 2021 Jan 31.

Division of Medical Genetics, Nemours/Alfred I. duPont Hospital for Children, Wilmington, Delaware, USA.

Neurodevelopmental disorder with dysmorphic facies and distal limb anomalies (NEDDFL), defined primarily by developmental delay/intellectual disability, speech delay, postnatal microcephaly, and dysmorphic features, is a syndrome resulting from heterozygous variants in the dosage-sensitive bromodomain PHD finger chromatin remodeler transcription factor BPTF gene. To date, only 11 individuals with NEDDFL due to de novo BPTF variants have been described. To expand the NEDDFL phenotypic spectrum, we describe the clinical features in 25 novel individuals with 20 distinct, clinically relevant variants in BPTF, including four individuals with inherited changes in BPTF. In addition to the previously described features, individuals in this cohort exhibited mild brain abnormalities, seizures, scoliosis, and a variety of ophthalmologic complications. These results further support the broad and multi-faceted complications due to haploinsufficiency of BPTF.
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http://dx.doi.org/10.1002/ajmg.a.62102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048530PMC
May 2021

Long Non-Coding RNA : Gene Structure, Expression, and Biological Relevance.

Genes (Basel) 2021 01 27;12(2). Epub 2021 Jan 27.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.

The Adjacent Noncoding Developmental Regulatory RNA () plays an important role in the control of gene expression in mammals. It is transcribed in the opposite direction to the neighboring gene with which it shares a region containing promoters. In humans, is located on chromosome 16q24.1, and is positively regulated both by the distant lung-specific -acting enhancer and by -acting FOXF1. has been shown to function as a competing endogenous RNA, sponging microRNAs and protein factors that control stability of mRNAs, and as an epigenetic modifier of chromatin structure around gene promoters and other regulatory sites, targeting them with histone methyltrasferase complexes. In mice, is essential for development of the heart, lungs, and gastrointestinal system; its homozygous loss causes embryonic or perinatal lethality. Importantly, deregulation of expression has been causatively linked also to tumorigenesis, resistance to chemotherapy, fibrosis, and inflammatory diseases. Here, we review the current knowledge on the structure, expression, and involvement in development and tissue maintenance.
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http://dx.doi.org/10.3390/genes12020177DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7911649PMC
January 2021

Potential interactions between the TBX4-FGF10 and SHH-FOXF1 signaling during human lung development revealed using ChIP-seq.

Respir Res 2021 Jan 21;22(1):26. Epub 2021 Jan 21.

Department of Molecular & Human Genetics, Baylor College of Medicine, One Baylor Plaza, Rm ABBR-R809, Houston, TX, 77030, USA.

Background: The epithelial-mesenchymal signaling involving SHH-FOXF1, TBX4-FGF10, and TBX2 pathways is an essential transcriptional network operating during early lung organogenesis. However, precise regulatory interactions between different genes and proteins in this pathway are incompletely understood.

Methods: To identify TBX2 and TBX4 genome-wide binding sites, we performed chromatin immunoprecipitation followed by next-generation sequencing (ChIP-seq) in human fetal lung fibroblasts IMR-90.

Results: We identified 14,322 and 1,862 sites strongly-enriched for binding of TBX2 and TBX4, respectively, 43.95% and 18.79% of which are located in the gene promoter regions. Gene Ontology, pathway enrichment, and DNA binding motif analyses revealed a number of overrepresented cues and transcription factor binding motifs relevant for lung branching that can be transcriptionally regulated by TBX2 and/or TBX4. In addition, TBX2 and TBX4 binding sites were found enriched around and within FOXF1 and its antisense long noncoding RNA FENDRR, indicating that the TBX4-FGF10 cascade may directly interact with the SHH-FOXF1 signaling.

Conclusions: We highlight the complexity of transcriptional network driven by TBX2 and TBX4 and show that disruption of this crosstalk during morphogenesis can play a substantial role in etiology of lung developmental disorders.
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http://dx.doi.org/10.1186/s12931-021-01617-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7818749PMC
January 2021

Clinical genomics and contextualizing genome variation in the diagnostic laboratory.

Expert Rev Mol Diagn 2020 10 10;20(10):995-1002. Epub 2020 Oct 10.

Department of Molecular and Human Genetics, Baylor College of Medicine , Houston, TX, USA.

Introduction: The human genome contains the instructions for the development and biological homeostasis of the human organism and the genetic transmission of traits. Genome variation in human populations is the basis of evolution; individual or personal genomes vary tremendously, making each of us truly unique.

Areas Covered: Assaying this individual variation using genomic technologies has many applications in clinical medicine, from elucidating the biology of disease to designing strategies to ameliorate perturbations from homeostasis. Detecting pathogenic rare variation in a genome may provide a molecular diagnosis that can be informative for patient management and family healthcare.

Expert Opinion: Despite the increasing clinical use of unbiased genomic testing, including chromosome microarray analysis (CMA) with array comparative genomic hybridization (aCGH) or SNP arrays, clinical exome sequencing (cES), and whole-genome sequencing (WGS), to survey genome-wide for molecular aberrations, clinical acumen paired with an understanding of the limitations of each testing type will be needed to achieve molecular diagnoses. Potential opportunities for improving case solved rates, functionally annotating the majority of genes in the human genome, and further understanding genetic contributions to disease will empower clinical genomics and the precision medicine initiative.
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http://dx.doi.org/10.1080/14737159.2020.1826312DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8208305PMC
October 2020

Deciphering the complexity of simple chromosomal insertions by genome sequencing.

Hum Genet 2021 Feb 29;140(2):361-380. Epub 2020 Jul 29.

Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong, China.

Chromosomal insertions are thought to be rare structural rearrangements. The current understanding of the underlying mechanisms of their origin is still limited. In this study, we sequenced 16 cases with apparent simple insertions previously identified by karyotyping and/or chromosomal microarray analysis. Using mate-pair genome sequencing (GS), we identified all 16 insertions and revised previously designated karyotypes in 75.0% (12/16) of the cases. Additional cryptic rearrangements were identified in 68.8% of the cases (11/16). The incidence of additional cryptic rearrangements in chromosomal insertions was significantly higher compared to balanced translocations and inversions reported in other studies by GS. We characterized and classified the cryptic insertion rearrangements into four groups, which were not mutually exclusive: (1) insertion segments were fragmented and their subsegments rearranged and clustered at the insertion site (10/16, 62.5%); (2) one or more cryptic subsegments were not inserted into the insertion site (5/16, 31.3%); (3) segments of the acceptor chromosome were scattered and rejoined with the insertion segments (2/16, 12.5%); and (4) copy number gains were identified in the flanking regions of the insertion site (2/16, 12.5%). In addition to the observation of these chromothripsis- or chromoanasynthesis-like events, breakpoint sequence analysis revealed microhomology to be the predominant feature. However, no significant correlation was found between the number of cryptic rearrangements and the size of the insertion. Overall, our study provide molecular characterization of karyotypically apparent simple insertions, demonstrate previously underappreciated complexities, and evidence that chromosomal insertions are likely formed by nonhomologous end joining and/or microhomology-mediated replication-based DNA repair.
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http://dx.doi.org/10.1007/s00439-020-02210-xDOI Listing
February 2021

Low-level parental somatic mosaic SNVs in exomes from a large cohort of trios with diverse suspected Mendelian conditions.

Genet Med 2020 11 13;22(11):1768-1776. Epub 2020 Jul 13.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Purpose: The goal of this study was to assess the scale of low-level parental mosaicism in exome sequencing (ES) databases.

Methods: We analyzed approximately 2000 family trio ES data sets from the Baylor-Hopkins Center for Mendelian Genomics (BHCMG) and Baylor Genetics (BG). Among apparent de novo single-nucleotide variants identified in the affected probands, we selected rare unique variants with variant allele fraction (VAF) between 30% and 70% in the probands and lower than 10% in one of the parents.

Results: Of 102 candidate mosaic variants validated using amplicon-based next-generation sequencing, droplet digital polymerase chain reaction, or blocker displacement amplification, 27 (26.4%) were confirmed to be low- (VAF between 1% and 10%) or very low (VAF <1%) level mosaic. Detection precision in parental samples with two or more alternate reads was 63.6% (BHCMG) and 43.6% (BG). In nine investigated individuals, we observed variability of mosaic ratios among blood, saliva, fibroblast, buccal, hair, and urine samples.

Conclusion: Our computational pipeline enables robust discrimination between true and false positive candidate mosaic variants and efficient detection of low-level mosaicism in ES samples. We confirm that the presence of two or more alternate reads in the parental sample is a reliable predictor of low-level parental somatic mosaicism.
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http://dx.doi.org/10.1038/s41436-020-0897-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7606563PMC
November 2020

Genotype-phenotype correlation in two Polish neonates with alveolar capillary dysplasia.

BMC Pediatr 2020 06 29;20(1):320. Epub 2020 Jun 29.

Department of Neonatology, Neonatal Biophysical Monitoring and Cardiopulmonary Therapies Research Unit, Poznan University of Medical Sciences, Poznan, Poland.

Background: Alveolar capillary dysplasia (ACD) is a rare cause of severe pulmonary hypertension and respiratory failure in neonates. The onset of ACD is usually preceded by a short asymptomatic period. The condition is refractory to all available therapies as it irreversibly affects development of the capillary bed in the lungs. The diagnosis of ACD is based on histopathological evaluation of lung biopsy or autopsy tissue or genetic testing of FOXF1 on chromosome 16q24.1. Here, we describe the first two Polish patients with ACD confirmed by histopathological and genetic examination.

Case Presentation: The patients were term neonates with high Apgar scores in the first minutes of life. They both were diagnosed prenatally with heart defects. Additionally, the first patient presented with omphalocele. The neonate slightly deteriorated around 12 hour of life, but underwent surgical repair of omphalocele followed by mechanical ventilation. Due to further deterioration, therapy included inhaled nitric oxide (iNO), inotropes and surfactant administration. The second patient was treated with prostaglandin E1 since birth due to suspicion of aortic coarctation (CoA). After ruling out CoA in the 3 day of life, infusion of prostaglandin E1 was discountinued and immediately patient's condition worsened. Subsequent treatment included re-administration of prostaglandin E1, iNO and mechanical ventilation. Both patients presented with transient improvement after application of iNO, but died despite maximized therapy. They were histopathologically diagnosed post-mortem with ACD. Array comparative genomic hybridization in patient one and patient two revealed copy-number variant (CNV) deletions, respectively, ~ 1.45 Mb in size involving FOXF1 and an ~ 0.7 Mb in size involving FOXF1 enhancer and leaving FOXF1 intact.

Conclusions: Both patients presented with a distinct course of ACD, extra-pulmonary manifestations and response to medications. Surgery and ceasing of prostaglandin E1 infusion should be considered as potential causes of this variability. We further highlight the necessity of thorough genetic testing and histopathological examination and propose immunostaining for CD31 and CD34 to facilitate the diagnostic process for better management of infants with ACD.
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http://dx.doi.org/10.1186/s12887-020-02200-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7322906PMC
June 2020

Parental somatic mosaicism for CNV deletions - A need for more sensitive and precise detection methods in clinical diagnostics settings.

Genomics 2020 09 6;112(5):2937-2941. Epub 2020 May 6.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA. Electronic address:

To further assess the scale and level of parental somatic mosaicism, we queried the CMA database at Baylor Genetics. We selected 50 unrelated families where clinically relevant apparent de novo CNV-deletions were found in the affected probands. Parental blood samples screening using deletion junction-specific PCR revealed four parents with somatic mosaicism. Droplet digital PCR (ddPCR), qPCR, and amplicon-based next-generation sequencing (NGS) were applied to validate these findings. Using ddPCR levels of mosaicism ranged from undetectable to 18.5%. Amplicon-based NGS and qPCR for the father with undetectable mosaicism was able to detect mosaicism at 0.39%. In one mother, ddPCR analysis revealed 15.6%, 10.6%, 8.2%, and undetectable levels of mosaicism in her blood, buccal cells, saliva, and urine samples, respectively. Our data suggest that more sensitive and precise methods, e.g. CNV junction-specific LR-PCR, ddPCR, or qPCR may allow for a more refined assessment of the potential disease recurrence risk for an identified variant.
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http://dx.doi.org/10.1016/j.ygeno.2020.05.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7363577PMC
September 2020

Quantitative Assessment of Parental Somatic Mosaicism for Copy-Number Variant (CNV) Deletions.

Curr Protoc Hum Genet 2020 06;106(1):e99

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas.

As genome sequencing methodologies have become more sensitive in detecting low-frequency rare-variant events, the link between post-zygotic mutagenesis and somatic mosaicism in the etiology of several human genetic conditions other than cancers has become more clear. Given that current clinical-genomics diagnostic methods have limited detection sensitivity for mosaic events, a copy-number variant (CNV) deletion inherited from a parent with low-level (<10%) mosaicism can be erroneously interpreted in the proband to represent a de novo germline event. Here, we describe three sensitive, precise, and cost-efficient methods that can quantitatively assess the potential degree of parental somatic mosaicism levels for CNV deletions: droplet digital PCR (ddPCR), PCR amplicon-based next-generation sequencing (NGS), and quantitative PCR. ddPCR using the EvaGreen fluorescent dye protocol can specifically quantify the deleted or non-deleted alleles by analyzing the number of droplets positive for a fluorescent signal for each event. PCR amplicon-based NGS assesses the allele frequencies of a heterozygous single-nucleotide polymorphism within a deletion region. The difference in number of reads between the two genotypes indicates the level of somatic mosaicism for the CNV deletion. Quantitative PCR can be applied where the relative quantity of the deletion junction-specific product represents the level of mosaicism. Clinical implementation of these quantitative variant-detection methods enables potentially more accurate assessment of disease recurrence risk in family-based genetic counseling, allowing couples to engage in more informed family planning. © 2020 by John Wiley & Sons, Inc. Basic Protocol: Droplet digital PCR (ddPCR) Alternate Protocol 1: PCR amplicon-based next-generation sequencing Alternate Protocol 2: Quantitative real-time PCR (qPCR).
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http://dx.doi.org/10.1002/cphg.99DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7138410PMC
June 2020

A de novo 2.2 Mb recurrent 17q23.1q23.2 deletion unmasks novel putative regulatory non-coding SNVs associated with lethal lung hypoplasia and pulmonary hypertension: a case report.

BMC Med Genomics 2020 03 6;13(1):34. Epub 2020 Mar 6.

Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA.

Background: Application of whole genome sequencing (WGS) enables identification of non-coding variants that play a phenotype-modifying role and are undetectable by exome sequencing. Recently, non-coding regulatory single nucleotide variants (SNVs) have been reported in patients with lethal lung developmental disorders (LLDDs) or congenital scoliosis with recurrent copy-number variant (CNV) deletions at 17q23.1q23.2 or 16p11.2, respectively.

Case Presentation: Here, we report a deceased newborn with pulmonary hypertension and pulmonary interstitial emphysema with features suggestive of pulmonary hypoplasia, resulting in respiratory failure and neonatal death soon after birth. Using the array comparative genomic hybridization and WGS, two heterozygous recurrent CNV deletions: ~ 2.2 Mb on 17q23.1q23.2, involving TBX4, and ~ 600 kb on 16p11.2, involving TBX6, that both arose de novo on maternal chromosomes were identified. In the predicted lung-specific enhancer upstream to TBX4, we have detected seven novel putative regulatory non-coding SNVs that were absent in 13 control individuals with the overlapping deletions but without any structural lung anomalies.

Conclusions: Our findings further support a recently reported model of complex compound inheritance of LLDD in which both non-coding and coding heterozygous TBX4 variants contribute to the lung phenotype. In addition, this is the first report of a patient with combined de novo heterozygous recurrent 17q23.1q23.2 and 16p11.2 CNV deletions.
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http://dx.doi.org/10.1186/s12920-020-0701-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7060516PMC
March 2020

Highly Sensitive Blocker Displacement Amplification and Droplet Digital PCR Reveal Low-Level Parental FOXF1 Somatic Mosaicism in Families with Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins.

J Mol Diagn 2020 04 7;22(4):447-456. Epub 2020 Feb 7.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas. Electronic address:

Detection of low-level somatic mosaicism [alternate allele fraction (AAF) ≤ 10%] in parents of affected individuals with the apparent de novo pathogenic variants enables more accurate estimate of recurrence risk. To date, only a few systematic analyses of low-level parental somatic mosaicism have been performed. Herein, highly sensitive blocker displacement amplification, droplet digital PCR, quantitative PCR, long-range PCR, and array comparative genomic hybridization were applied in families with alveolar capillary dysplasia with misalignment of pulmonary veins. We screened 18 unrelated families with the FOXF1 variant previously determined to be apparent de novo (n = 14), of unknown parental origin (n = 1), or inherited from a parent suspected to be somatic and/or germline mosaic (n = 3). We identified four (22%) families with FOXF1 parental somatic mosaic single-nucleotide variants (n = 3) and copy number variant deletion (n = 1) detected in parental blood samples and an AAF ranging between 0.03% and 19%. In one family, mosaic allele ratio in tissues originating from three germ layers ranged between <0.03% and 0.65%. Because the ratio of parental somatic mosaicism have significant implications for the recurrence risk, this study further implies the importance of a systematic screening of parental samples for low-level and very-low-level (AAF ≤ 1%) somatic mosaicism using methods that are more sensitive than those routinely applied in diagnostics.
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http://dx.doi.org/10.1016/j.jmoldx.2019.12.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193866PMC
April 2020

Association of rare non-coding SNVs in the lung-specific FOXF1 enhancer with a mitigation of the lethal ACDMPV phenotype.

Hum Genet 2019 Dec 4;138(11-12):1301-1311. Epub 2019 Nov 4.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Haploinsufficiency of FOXF1 causes alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), a lethal neonatal lung developmental disorder. We describe two similar heterozygous CNV deletions involving the FOXF1 enhancer and re-analyze FOXF1 missense mutation, all associated with an unexpectedly mitigated disease phenotype. In one case, the deletion of the maternal allele of the FOXF1 enhancer caused pulmonary hypertension and histopathologically diagnosed MPV without the typical ACD features. In the second case, the deletion of the paternal enhancer resulted in ACDMPV rather than the expected neonatal lethality. In both cases, FOXF1 expression in lung tissue was higher than usually seen or expected in patients with similar deletions, suggesting an increased activity of the remaining allele of the enhancer. Sequencing of these alleles revealed two rare SNVs, rs150502618-A and rs79301423-T, mapping to the partially overlapping binding sites for TFAP2s and CTCF in the core region of the enhancer. Moreover, in a family with three histopathologically-diagnosed ACDMPV siblings whose missense FOXF1 mutation was inherited from the healthy non-mosaic carrier mother, we have identified a rare SNV rs28571077-A within 2-kb of the above-mentioned non-coding SNVs in the FOXF1 enhancer in the mother, that was absent in the affected newborns and 13 unrelated ACDMPV patients with CNV deletions of this genomic region. Based on the low population frequencies of these three variants, their absence in ACDMPV patients, the results of reporter assay, RNAi and EMSA experiments, and in silico predictions, we propose that the described SNVs might have acted on FOXF1 enhancer as hypermorphs.
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http://dx.doi.org/10.1007/s00439-019-02073-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6874894PMC
December 2019

Disruption of normal patterns of FOXF1 expression in a lethal disorder of lung development.

J Med Genet 2020 05 29;57(5):296-300. Epub 2019 Oct 29.

Pediatrics, University of Rochester, Rochester, New York, USA.

Background: Alveolar capillary dysplasia with misalignment of the pulmonary veins (ACDMPV) is a lethal disorder of lung development. ACDMPV is associated with haploinsufficiency of the transcription factor , which plays an important role in the development of the lung and intestine. CNVs upstream of the FOXF1 gene have also been associated with an ACDMPV phenotype, but mechanism(s) by which these deletions disrupt lung development are not well understood. The objective of our study is to gain insights into the mechanisms by which CNVs contribute to an ACDMPV phenotype.

Methods: We analysed primary lung tissue from an infant with classic clinical and histological findings of ACDMPV and harboured a 340 kb deletion on chromosome 16q24.1 located 250 kb upstream of .

Results: In RNA generated from paraffin-fixed lung sections, our patient had lower expression of than age-matched controls. He also had an abnormal pattern of FOXF1 protein expression, with a dramatic loss of expression in the lung. To gain insights into the mechanisms underlying these changes, we assessed the epigenetic landscape using chromatin immunoprecipitation, which demonstrated loss of histone H3 lysine 27 acetylation (H3K27Ac), an epigenetic mark of active enhancers, in the region of the deletion.

Conclusions: Together, these data suggest that the deletion disrupts an enhancer responsible for directing FOXF1 expression in the developing lung and provide novel insights into the mechanisms underlying a fatal developmental lung disorder.
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http://dx.doi.org/10.1136/jmedgenet-2019-106095DOI Listing
May 2020

Disruptive mutations in TANC2 define a neurodevelopmental syndrome associated with psychiatric disorders.

Nat Commun 2019 10 15;10(1):4679. Epub 2019 Oct 15.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA.

Postsynaptic density (PSD) proteins have been implicated in the pathophysiology of neurodevelopmental and psychiatric disorders. Here, we present detailed clinical and genetic data for 20 patients with likely gene-disrupting mutations in TANC2-whose protein product interacts with multiple PSD proteins. Pediatric patients with disruptive mutations present with autism, intellectual disability, and delayed language and motor development. In addition to a variable degree of epilepsy and facial dysmorphism, we observe a pattern of more complex psychiatric dysfunction or behavioral problems in adult probands or carrier parents. Although this observation requires replication to establish statistical significance, it also suggests that mutations in this gene are associated with a variety of neuropsychiatric disorders consistent with its postsynaptic function. We find that TANC2 is expressed broadly in the human developing brain, especially in excitatory neurons and glial cells, but shows a more restricted pattern in Drosophila glial cells where its disruption affects behavioral outcomes.
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http://dx.doi.org/10.1038/s41467-019-12435-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6794285PMC
October 2019

A recurrent 8 bp frameshifting indel in FOXF1 defines a novel mutation hotspot associated with alveolar capillary dysplasia with misalignment of pulmonary veins.

Am J Med Genet A 2019 11 22;179(11):2272-2276. Epub 2019 Aug 22.

Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, Texas.

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal lung developmental disease. Affected infants manifest with severe respiratory distress and refractory pulmonary hypertension and uniformly die in the first month of life. Heterozygous point mutations or copy-number variant deletions involving FOXF1 and/or its upstream lung-specific enhancer on 16q24.1 have been identified in the vast majority of ACDMPV patients. We have previously described two unrelated families with a de novo pathogenic frameshift variant c.691_698del (p.Ala231Argfs*61) in the exon 1 of FOXF1. Here, we present a third unrelated ACDMPV family with the same de novo variant and propose that a direct tandem repeat of eight consecutive nucleotides GCGGCGGC within the ~4 kb CpG island in FOXF1 exon 1 is a novel mutation hotspot causative for ACDMPV.
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http://dx.doi.org/10.1002/ajmg.a.61338DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6849398PMC
November 2019

A clinical survey of mosaic single nucleotide variants in disease-causing genes detected by exome sequencing.

Genome Med 2019 07 26;11(1):48. Epub 2019 Jul 26.

Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030-3411, USA.

Background: Although mosaic variation has been known to cause disease for decades, high-throughput sequencing technologies with the analytical sensitivity to consistently detect variants at reduced allelic fractions have only recently emerged as routine clinical diagnostic tests. To date, few systematic analyses of mosaic variants detected by diagnostic exome sequencing for diverse clinical indications have been performed.

Methods: To investigate the frequency, type, allelic fraction, and phenotypic consequences of clinically relevant somatic mosaic single nucleotide variants (SNVs) and characteristics of the corresponding genes, we retrospectively queried reported mosaic variants from a cohort of ~ 12,000 samples submitted for clinical exome sequencing (ES) at Baylor Genetics.

Results: We found 120 mosaic variants involving 107 genes, including 80 mosaic SNVs in proband samples and 40 in parental/grandparental samples. Average mosaic alternate allele fraction (AAF) detected in autosomes and in X-linked disease genes in females was 18.2% compared with 34.8% in X-linked disease genes in males. Of these mosaic variants, 74 variants (61.7%) were classified as pathogenic or likely pathogenic and 46 (38.3%) as variants of uncertain significance. Mosaic variants occurred in disease genes associated with autosomal dominant (AD) or AD/autosomal recessive (AR) (67/120, 55.8%), X-linked (33/120, 27.5%), AD/somatic (10/120, 8.3%), and AR (8/120, 6.7%) inheritance. Of note, 1.7% (2/120) of variants were found in genes in which only somatic events have been described. Nine genes had recurrent mosaic events in unrelated individuals which accounted for 18.3% (22/120) of all detected mosaic variants in this study. The proband group was enriched for mosaicism affecting Ras signaling pathway genes.

Conclusions: In sum, an estimated 1.5% of all molecular diagnoses made in this cohort could be attributed to a mosaic variant detected in the proband, while parental mosaicism was identified in 0.3% of families analyzed. As ES design favors breadth over depth of coverage, this estimate of the prevalence of mosaic variants likely represents an underestimate of the total number of clinically relevant mosaic variants in our cohort.
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http://dx.doi.org/10.1186/s13073-019-0658-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6660700PMC
July 2019

Heterozygous CTNNB1 and TBX4 variants in a patient with abnormal lung growth, pulmonary hypertension, microcephaly, and spasticity.

Clin Genet 2019 10 22;96(4):366-370. Epub 2019 Jul 22.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas.

The canonical wingless (Wnt) and fibroblast growth factor (FGF) signaling pathways involving CTNNB1 and TBX4, respectively, are crucial for the regulation of human development. Perturbations of these pathways and disruptions from biological homeostasis have been associated with abnormal morphogenesis of multiple organs, including the lung. The aim of this study was to identify the underlying genetic cause of abnormal lung growth, pulmonary hypertension (PAH), severe microcephaly, and muscle spasticity in a full-term newborn, who died at 4 months of age due to progressively worsening PAH and respiratory failure. Family trio exome sequencing showed a de novo heterozygous nonsense c.1603C>T (p.Arg535*) variant in CTNNB1 and a paternally inherited heterozygous missense c.1198G>A (p.Glu400Lys) variant in TBX4, both predicted to be likely deleterious. We expand the phenotypic spectrum associated with CTNNB1 and TBX4 variants and indicate that they could act synergistically to produce a distinct more severe phenotype. Our findings further support a recently proposed complex compound inheritance model in lethal lung developmental diseases and the contention that dual molecular diagnoses can parsimoniously explain blended phenotypes.
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http://dx.doi.org/10.1111/cge.13605DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6953252PMC
October 2019

The S52F FOXF1 Mutation Inhibits STAT3 Signaling and Causes Alveolar Capillary Dysplasia.

Am J Respir Crit Care Med 2019 10;200(8):1045-1056

Department of Pediatrics.

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a lethal congenital disorder causing respiratory failure and pulmonary hypertension shortly after birth. There are no effective treatments for ACDMPV other than lung transplant, and new therapeutic approaches are urgently needed. Although ACDMPV is linked to mutations in the gene, molecular mechanisms through which FOXF1 mutations cause ACDMPV are unknown. To identify molecular mechanisms by which S52F FOXF1 mutations cause ACDMPV. We generated a clinically relevant mouse model of ACDMPV by introducing the S52F FOXF1 mutation into the mouse gene locus using CRISPR/Cas9 technology. Immunohistochemistry, whole-lung imaging, and biochemical methods were used to examine vasculature in lungs and identify molecular mechanisms regulated by FOXF1. FOXF1 mutations were identified in 28 subjects with ACDMPV. knock-in mice recapitulated histopathologic findings in ACDMPV infants. The S52F FOXF1 mutation disrupted STAT3-FOXF1 protein-protein interactions and inhibited transcription of , a critical transcriptional regulator of angiogenesis. STAT3 signaling and endothelial proliferation were reduced in mice and human ACDMPV lungs. S52F FOXF1 mutant protein did not bind chromatin and was transcriptionally inactive. Furthermore, we have developed a novel formulation of highly efficient nanoparticles and demonstrated that nanoparticle delivery of STAT3 cDNA into the neonatal circulation restored endothelial proliferation and stimulated lung angiogenesis in mice. FOXF1 acts through STAT3 to stimulate neonatal lung angiogenesis. Nanoparticle delivery of STAT3 is a promising strategy to treat ACDMPV associated with decreased STAT3 signaling.
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http://dx.doi.org/10.1164/rccm.201810-1897OCDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6794119PMC
October 2019

Clinical, Histopathological, and Molecular Diagnostics in Lethal Lung Developmental Disorders.

Am J Respir Crit Care Med 2019 11;200(9):1093-1101

Department of Molecular and Human Genetics and.

Lethal lung developmental disorders are a rare but important group of pediatric diffuse lung diseases presenting with neonatal respiratory failure. On the basis of histopathological appearance at lung biopsy or autopsy, they have been termed: alveolar capillary dysplasia with misalignment of the pulmonary veins, acinar dysplasia, congenital alveolar dysplasia, and other unspecified primary pulmonary hypoplasias. However, the histopathological continuum in these lethal developmental disorders has made accurate diagnosis challenging, which has implications for recurrence risk. Over the past decade, genetic studies in infants with alveolar capillary dysplasia with misalignment of the pulmonary veins have revealed the causative role of the dosage-sensitive gene and its noncoding regulatory variants in the distant lung-specific enhancer at chromosome 16q24.1. In contrast, the molecular bases of acinar dysplasia and congenital alveolar dysplasia have remained poorly understood. Most recently, disruption of the TBX4-FGF10-FGFR2 epithelial-mesenchymal signaling pathway has been reported in patients with these lethal pulmonary dysplasias. Application of next-generation sequencing techniques, including exome sequencing and whole-genome sequencing, has demonstrated their complex compound inheritance. These data indicate that noncoding regulatory elements play a critical role in lung development in humans. We propose that for more precise lethal lung developmental disorder diagnosis, a diagnostic pathway including whole-genome sequencing should be implemented.
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http://dx.doi.org/10.1164/rccm.201903-0495TRDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6888654PMC
November 2019

Copy number variant and runs of homozygosity detection by microarrays enabled more precise molecular diagnoses in 11,020 clinical exome cases.

Genome Med 2019 05 17;11(1):30. Epub 2019 May 17.

Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030-3411, USA.

Background: Exome sequencing (ES) has been successfully applied in clinical detection of single nucleotide variants (SNVs) and small indels. However, identification of copy number variants (CNVs) using ES data remains challenging. The purpose of this study is to understand the contribution of CNVs and copy neutral runs of homozygosity (ROH) in molecular diagnosis of patients referred for ES.

Methods: In a cohort of 11,020 consecutive ES patients, an Illumina SNP array analysis interrogating mostly coding SNPs was performed as a quality control (QC) measurement and for CNV/ROH detection. Among these patients, clinical chromosomal microarray analysis (CMA) was performed at Baylor Genetics (BG) on 3229 patients, either before, concurrently, or after ES. We retrospectively analyzed the findings from CMA and the QC array.

Results: The QC array can detect ~ 70% of pathogenic/likely pathogenic CNVs (PCNVs) detectable by CMA. Out of the 11,020 ES cases, the QC array identified PCNVs in 327 patients and uniparental disomy (UPD) disorder-related ROH in 10 patients. The overall PCNV/UPD detection rate was 5.9% in the 3229 ES patients who also had CMA at BG; PCNV/UPD detection rate was higher in concurrent ES and CMA than in ES with prior CMA (7.2% vs 4.6%). The PCNVs/UPD contributed to the molecular diagnoses in 17.4% (189/1089) of molecularly diagnosed ES cases with CMA and were estimated to contribute in 10.6% of all molecularly diagnosed ES cases. Dual diagnoses with both PCNVs and SNVs were detected in 38 patients. PCNVs affecting single recessive disorder genes in a compound heterozygous state with SNVs were detected in 4 patients, and homozygous deletions (mostly exonic deletions) were detected in 17 patients. A higher PCNV detection rate was observed for patients with syndromic phenotypes and/or cardiovascular abnormalities.

Conclusions: Our clinical genomics study demonstrates that detection of PCNV/UPD through the QC array or CMA increases ES diagnostic rate, provides more precise molecular diagnosis for dominant as well as recessive traits, and enables more complete genetic diagnoses in patients with dual or multiple molecular diagnoses. Concurrent ES and CMA using an array with exonic coverage for disease genes enables most effective detection of both CNVs and SNVs and therefore is recommended especially in time-sensitive clinical situations.
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http://dx.doi.org/10.1186/s13073-019-0639-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6525387PMC
May 2019

Interchromosomal template-switching as a novel molecular mechanism for imprinting perturbations associated with Temple syndrome.

Genome Med 2019 04 23;11(1):25. Epub 2019 Apr 23.

Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Room 604B, Houston, TX, 77030-3498, USA.

Background: Intrachromosomal triplications (TRP) can contribute to disease etiology via gene dosage effects, gene disruption, position effects, or fusion gene formation. Recently, post-zygotic de novo triplications adjacent to copy-number neutral genomic intervals with runs of homozygosity (ROH) have been shown to result in uniparental isodisomy (UPD). The genomic structure of these complex genomic rearrangements (CGRs) shows a consistent pattern of an inverted triplication flanked by duplications (DUP-TRP/INV-DUP) formed by an iterative DNA replisome template-switching mechanism during replicative repair of a single-ended, double-stranded DNA (seDNA), the ROH results from an interhomolog or nonsister chromatid template switch. It has been postulated that these CGRs may lead to genetic abnormalities in carriers due to dosage-sensitive genes mapping within the copy-number variant regions, homozygosity for alleles at a locus causing an autosomal recessive (AR) disease trait within the ROH region, or imprinting-associated diseases.

Methods: Here, we report a family wherein the affected subject carries a de novo 2.2-Mb TRP followed by 42.2 Mb of ROH and manifests clinical features overlapping with those observed in association with chromosome 14 maternal UPD (UPD(14)mat). UPD(14)mat can cause clinical phenotypic features enabling a diagnosis of Temple syndrome. This CGR was then molecularly characterized by high-density custom aCGH, genome-wide single-nucleotide polymorphism (SNP) and methylation arrays, exome sequencing (ES), and the Oxford Nanopore long-read sequencing technology.

Results: We confirmed the postulated DUP-TRP/INV-DUP structure by multiple orthogonal genomic technologies in the proband. The methylation status of known differentially methylated regions (DMRs) on chromosome 14 revealed that the subject shows the typical methylation pattern of UPD(14)mat. Consistent with these molecular findings, the clinical features overlap with those observed in Temple syndrome, including speech delay.

Conclusions: These data provide experimental evidence that, in humans, triplication can lead to segmental UPD and imprinting disease. Importantly, genotype/phenotype analyses further reveal how a post-zygotically generated complex structural variant, resulting from a replication-based mutational mechanism, contributes to expanding the clinical phenotype of known genetic syndromes. Mechanistically, such events can distort transmission genetics resulting in homozygosity at a locus for which only one parent is a carrier as well as cause imprinting diseases.
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http://dx.doi.org/10.1186/s13073-019-0633-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6480824PMC
April 2019

Novel parent-of-origin-specific differentially methylated loci on chromosome 16.

Clin Epigenetics 2019 04 8;11(1):60. Epub 2019 Apr 8.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Background: Congenital malformations associated with maternal uniparental disomy of chromosome 16, upd(16)mat, resemble those observed in newborns with the lethal developmental lung disease, alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV). Interestingly, ACDMPV-causative deletions, involving FOXF1 or its lung-specific upstream enhancer at 16q24.1, arise almost exclusively on the maternally inherited chromosome 16. Given the phenotypic similarities between upd(16)mat and ACDMPV, together with parental allelic bias in ACDMPV, we hypothesized that there may be unknown imprinted loci mapping to chromosome 16 that become functionally unmasked by chromosomal structural variants.

Results: To identify parent-of-origin biased DNA methylation, we performed high-resolution bisulfite sequencing of chromosome 16 on peripheral blood and cultured skin fibroblasts from individuals with maternal or paternal upd(16) as well as lung tissue from patients with ACDMPV-causative 16q24.1 deletions and a normal control. We identified 22 differentially methylated regions (DMRs) with ≥ 5 consecutive CpG methylation sites and varying tissue-specificity, including the known DMRs associated with the established imprinted gene ZNF597 and DMRs supporting maternal methylation of PRR25, thought to be paternally expressed in lymphoblastoid cells. Lastly, we found evidence of paternal methylation on 16q24.1 near LINC01082 mapping to the FOXF1 enhancer.

Conclusions: Using high-resolution bisulfite sequencing to evaluate DNA methylation across chromosome 16, we found evidence for novel candidate imprinted loci on chromosome 16 that would not be evident in array-based assays and could contribute to the birth defects observed in patients with upd(16)mat or in ACDMPV.
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http://dx.doi.org/10.1186/s13148-019-0655-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6454695PMC
April 2019
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