Publications by authors named "Patricia Wheeler"

50 Publications

De novo DHDDS variants cause a neurodevelopmental and neurodegenerative disorder with myoclonus.

Brain 2021 Aug 11. Epub 2021 Aug 11.

Undiagnosed Diseases Program, National Institutes of Health, Bethesda, MD 20892-2152, USA.

Subcellular membrane systems are highly enriched in dolichol, whose role in organelle homeostasis and endosomal-lysosomal pathway remains largely unclear besides being involved in protein glycosylation. DHDDS encodes for the catalytic subunit (DHDDS) of the enzyme cis-prenyltransferase (cis-PTase), involved in dolichol biosynthesis and dolichol-dependent protein glycosylation in the endoplasmic reticulum. An autosomal recessive form of retinitis pigmentosa (retinitis pigmentosa 59) has been associated with a recurrent DHDDS variant. Moreover, two recurring de novo substitutions were detected in a few cases presenting with neurodevelopmental disorder, epilepsy, and movement disorder. We evaluated a large cohort of patients (n=25) with de novo pathogenic variants in DHDDS and provided the first systematic description of the clinical features and long-term outcome of this new neurodevelopmental and neurodegenerative disorder. The functional impact of the identified variants was explored by yeast complementation system and enzymatic assay. Patients presented during infancy or childhood with a variable association of neurodevelopmental disorder, generalized epilepsy, action myoclonus/cortical tremor, and ataxia. Later in the disease course they experienced a slow neurological decline with the emergence of hyperkinetic and/or hypokinetic movement disorder, cognitive deterioration, and psychiatric disturbances. Storage of lipidic material and altered lysosomes were detected in myelinated fibers and fibroblasts, suggesting a dysfunction of the lysosomal enzymatic scavenger machinery. Serum glycoprotein hypoglycosylation was not detected and, in contrast to retinitis pigmentosa and other congenital disorders of glycosylation involving dolichol metabolism, the urinary dolichol D18/D19 ratio was normal. Mapping the disease-causing variants into the protein structure revealed that most of them clustered around the active site of the DHDDS subunit. Functional studies using yeast complementation assay and in vitro activity measurements confirmed that these changes affected the catalytic activity of the cis-PTase and showed growth defect in yeast complementation system as compared with the wild-type enzyme and retinitis pigmentosa-associated protein. In conclusion, we characterized a distinctive neurodegenerative disorder due to de novo DHDDS variants, which clinically belongs to the spectrum of genetic progressive encephalopathies with myoclonus. Clinical and biochemical data from this cohort depicted a condition at the intersection of congenital disorders of glycosylation and inherited storage diseases with several features akin to of progressive myoclonus epilepsy such as neuronal ceroid lipofuscinosis and other lysosomal disorders.
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http://dx.doi.org/10.1093/brain/awab299DOI Listing
August 2021

Missense NAA20 variants impairing the NatB protein N-terminal acetyltransferase cause autosomal recessive developmental delay, intellectual disability, and microcephaly.

Genet Med 2021 Jul 6. Epub 2021 Jul 6.

Department of Biomedicine, University of Bergen, Bergen, Norway.

Purpose: N-terminal acetyltransferases modify proteins by adding an acetyl moiety to the first amino acid and are vital for protein and cell function. The NatB complex acetylates 20% of the human proteome and is composed of the catalytic subunit NAA20 and the auxiliary subunit NAA25. In five individuals with overlapping phenotypes, we identified recessive homozygous missense variants in NAA20.

Methods: Two different NAA20 variants were identified in affected individuals in two consanguineous families by exome and genome sequencing. Biochemical studies were employed to assess the impact of the NAA20 variants on NatB complex formation and catalytic activity.

Results: Two homozygous variants, NAA20 p.Met54Val and p.Ala80Val (GenBank: NM_016100.4, c.160A>G and c.239C>T), segregated with affected individuals in two unrelated families presenting with developmental delay, intellectual disability, and microcephaly. Both NAA20-M54V and NAA20-A80V were impaired in their capacity to form a NatB complex with NAA25, and in vitro acetylation assays revealed reduced catalytic activities toward different NatB substrates. Thus, both NAA20 variants are impaired in their ability to perform cellular NatB-mediated N-terminal acetylation.

Conclusion: We present here a report of pathogenic NAA20 variants causing human disease and data supporting an essential role for NatB-mediated N-terminal acetylation in human development and physiology.
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http://dx.doi.org/10.1038/s41436-021-01264-0DOI Listing
July 2021

Loss-of-function and missense variants in NSD2 cause decreased methylation activity and are associated with a distinct developmental phenotype.

Genet Med 2021 08 3;23(8):1474-1483. Epub 2021 May 3.

Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.

Purpose: Despite a few recent reports of patients harboring truncating variants in NSD2, a gene considered critical for the Wolf-Hirschhorn syndrome (WHS) phenotype, the clinical spectrum associated with NSD2 pathogenic variants remains poorly understood.

Methods: We collected a comprehensive series of 18 unpublished patients carrying heterozygous missense, elongating, or truncating NSD2 variants; compared their clinical data to the typical WHS phenotype after pooling them with ten previously described patients; and assessed the underlying molecular mechanism by structural modeling and measuring methylation activity in vitro.

Results: The core NSD2-associated phenotype includes mostly mild developmental delay, prenatal-onset growth retardation, low body mass index, and characteristic facial features distinct from WHS. Patients carrying missense variants were significantly taller and had more frequent behavioral/psychological issues compared with those harboring truncating variants. Structural in silico modeling suggested interference with NSD2's folding and function for all missense variants in known structures. In vitro testing showed reduced methylation activity and failure to reconstitute H3K36me2 in NSD2 knockout cells for most missense variants.

Conclusion: NSD2 loss-of-function variants lead to a distinct, rather mild phenotype partially overlapping with WHS. To avoid confusion for patients, NSD2 deficiency may be named Rauch-Steindl syndrome after the delineators of this phenotype.
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http://dx.doi.org/10.1038/s41436-021-01158-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8354849PMC
August 2021

Haploinsufficiency of PRR12 causes a spectrum of neurodevelopmental, eye, and multisystem abnormalities.

Genet Med 2021 07 6;23(7):1234-1245. Epub 2021 Apr 6.

Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, Netherlands.

Purpose: Proline Rich 12 (PRR12) is a gene of unknown function with suspected DNA-binding activity, expressed in developing mice and human brains. Predicted loss-of-function variants in this gene are extremely rare, indicating high intolerance of haploinsufficiency.

Methods: Three individuals with intellectual disability and iris anomalies and truncating de novo PRR12 variants were described previously. We add 21 individuals with similar PRR12 variants identified via matchmaking platforms, bringing the total number to 24.

Results: We observed 12 frameshift, 6 nonsense, 1 splice-site, and 2 missense variants and one patient with a gross deletion involving PRR12. Three individuals had additional genetic findings, possibly confounding the phenotype. All patients had developmental impairment. Variable structural eye defects were observed in 12/24 individuals (50%) including anophthalmia, microphthalmia, colobomas, optic nerve and iris abnormalities. Additional common features included hypotonia (61%), heart defects (52%), growth failure (54%), and kidney anomalies (35%). PrediXcan analysis showed that phecodes most strongly associated with reduced predicted PRR12 expression were enriched for eye- (7/30) and kidney- (4/30) phenotypes, such as wet macular degeneration and chronic kidney disease.

Conclusion: These findings support PRR12 haploinsufficiency as a cause for a novel disorder with a wide clinical spectrum marked chiefly by neurodevelopmental and eye abnormalities.
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http://dx.doi.org/10.1038/s41436-021-01129-6DOI Listing
July 2021

Haploinsufficiency of POU4F1 causes an ataxia syndrome with hypotonia and intention tremor.

Hum Mutat 2021 06 15;42(6):685-693. Epub 2021 Apr 15.

Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.

De novo, heterozygous, loss-of-function variants were identified in Pou domain, class 4, transcription factor 1 (POU4F1) via whole-exome sequencing in four independent probands presenting with ataxia, intention tremor, and hypotonia. POU4F1 is expressed in the developing nervous system, and mice homozygous for null alleles of Pou4f1 exhibit uncoordinated movements with newborns being unable to successfully right themselves to feed. Head magnetic resonance imaging of the four probands was reviewed and multiple abnormalities were noted, including significant cerebellar vermian atrophy and hypertrophic olivary degeneration in one proband. Transcriptional activation of the POU4F1 p.Gln306Arg protein was noted to be decreased when compared with wild type. These findings suggest that heterozygous, loss-of-function variants in POU4F1 are causative of a novel ataxia syndrome.
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http://dx.doi.org/10.1002/humu.24201DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8162891PMC
June 2021

Dominant variants in PRR12 result in unilateral or bilateral complex microphthalmia.

Clin Genet 2021 03 16;99(3):437-442. Epub 2020 Dec 16.

Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin and Children's Wisconsin, Milwaukee, Wisconsin, USA.

Complex microphthalmia is characterized by small eyes with additional abnormalities that may include anterior segment dysgenesis. While many genes are known, a genetic cause is identified in only 4-30% of microphthalmia, with the lowest rate in unilateral cases. We identified four novel pathogenic loss-of-function alleles in PRR12 in families affected by complex microphthalmia and/or Peters anomaly, including two de novo, the first dominantly transmitted allele, as well as the first splicing variant. The ocular phenotypes were isolated with no additional systemic features observed in two unrelated families. Remarkably, ocular phenotypes were asymmetric in all individuals and unilateral (with structurally normal contralateral eye) in three. There are only three previously reported PRR12 variants identified in probands with intellectual disability, neuropsychiatric disorders, and iris anomalies. While some overlap with previously reported cases is seen, nonsyndromic developmental ocular anomalies are a novel phenotype for this gene. Additional phenotypic expansions included short stature and normal development/cognition, each noted in two individuals in this cohort, as well as absence of neuropsychiatric disorders in all. This study identifies new associations for PRR12 disruption in humans and presents a genetic diagnosis resulting in unilateral ocular phenotypes in a significant proportion of cases.
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http://dx.doi.org/10.1111/cge.13897DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8259391PMC
March 2021

De Novo Variants in the ATPase Module of MORC2 Cause a Neurodevelopmental Disorder with Growth Retardation and Variable Craniofacial Dysmorphism.

Am J Hum Genet 2020 08 20;107(2):352-363. Epub 2020 Jul 20.

Clinical Genetics, Stanford Children's Health, San Francisco, CA 94109, USA.

MORC2 encodes an ATPase that plays a role in chromatin remodeling, DNA repair, and transcriptional regulation. Heterozygous variants in MORC2 have been reported in individuals with autosomal-dominant Charcot-Marie-Tooth disease type 2Z and spinal muscular atrophy, and the onset of symptoms ranges from infancy to the second decade of life. Here, we present a cohort of 20 individuals referred for exome sequencing who harbor pathogenic variants in the ATPase module of MORC2. Individuals presented with a similar phenotype consisting of developmental delay, intellectual disability, growth retardation, microcephaly, and variable craniofacial dysmorphism. Weakness, hyporeflexia, and electrophysiologic abnormalities suggestive of neuropathy were frequently observed but were not the predominant feature. Five of 18 individuals for whom brain imaging was available had lesions reminiscent of those observed in Leigh syndrome, and five of six individuals who had dilated eye exams had retinal pigmentary abnormalities. Functional assays revealed that these MORC2 variants result in hyperactivation of epigenetic silencing by the HUSH complex, supporting their pathogenicity. The described set of morphological, growth, developmental, and neurological findings and medical concerns expands the spectrum of genetic disorders resulting from pathogenic variants in MORC2.
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http://dx.doi.org/10.1016/j.ajhg.2020.06.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7413887PMC
August 2020

De novo and inherited variants in ZNF292 underlie a neurodevelopmental disorder with features of autism spectrum disorder.

Genet Med 2020 03 14;22(3):538-546. Epub 2019 Nov 14.

New York State Institute for Basic Research in Developmental Disability, NY, Staten Island, USA.

Purpose: Intellectual disability (ID) and autism spectrum disorder (ASD) are genetically heterogeneous neurodevelopmental disorders. We sought to delineate the clinical, molecular, and neuroimaging spectrum of a novel neurodevelopmental disorder caused by variants in the zinc finger protein 292 gene (ZNF292).

Methods: We ascertained a cohort of 28 families with ID due to putatively pathogenic ZNF292 variants that were identified via targeted and exome sequencing. Available data were analyzed to characterize the canonical phenotype and examine genotype-phenotype relationships.

Results: Probands presented with ID as well as a spectrum of neurodevelopmental features including ASD, among others. All ZNF292 variants were de novo, except in one family with dominant inheritance. ZNF292 encodes a highly conserved zinc finger protein that acts as a transcription factor and is highly expressed in the developing human brain supporting its critical role in neurodevelopment.

Conclusion: De novo and dominantly inherited variants in ZNF292 are associated with a range of neurodevelopmental features including ID and ASD. The clinical spectrum is broad, and most individuals present with mild to moderate ID with or without other syndromic features. Our results suggest that variants in ZNF292 are likely a recurrent cause of a neurodevelopmental disorder manifesting as ID with or without ASD.
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http://dx.doi.org/10.1038/s41436-019-0693-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7060121PMC
March 2020

DYRK1A-related intellectual disability: a syndrome associated with congenital anomalies of the kidney and urinary tract.

Genet Med 2019 12 2;21(12):2755-2764. Epub 2019 Jul 2.

Renal Section, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.

Purpose: Haploinsufficiency of DYRK1A causes a recognizable clinical syndrome. The goal of this paper is to investigate congenital anomalies of the kidney and urinary tract (CAKUT) and genital defects (GD) in patients with DYRK1A variants.

Methods: A large database of clinical exome sequencing (ES) was queried for de novo DYRK1A variants and CAKUT/GD phenotypes were characterized. Xenopus laevis (frog) was chosen as a model organism to assess Dyrk1a's role in renal development.

Results: Phenotypic details and variants of 19 patients were compiled after an initial observation that one patient with a de novo pathogenic variant in DYRK1A had GD. CAKUT/GD data were available from 15 patients, 11 of whom presented with CAKUT/GD. Studies in Xenopus embryos demonstrated that knockdown of Dyrk1a, which is expressed in forming nephrons, disrupts the development of segments of embryonic nephrons, which ultimately give rise to the entire genitourinary (GU) tract. These defects could be rescued by coinjecting wild-type human DYRK1A RNA, but not with DYRK1A or DYRK1A RNA.

Conclusion: Evidence supports routine GU screening of all individuals with de novo DYRK1A pathogenic variants to ensure optimized clinical management. Collectively, the reported clinical data and loss-of-function studies in Xenopus substantiate a novel role for DYRK1A in GU development.
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http://dx.doi.org/10.1038/s41436-019-0576-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6895419PMC
December 2019

Correction: The ARID1B spectrum in 143 patients: from nonsyndromic intellectual disability to Coffin-Siris syndrome.

Genet Med 2019 Sep;21(9):2160-2161

University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands.

The original version of this Article contained an error in the spelling of the author Pleuntje J. van der Sluijs, which was incorrectly given as Eline (P. J.) van der Sluijs. This has now been corrected in both the PDF and HTML versions of the Article.
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http://dx.doi.org/10.1038/s41436-018-0368-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752317PMC
September 2019

De novo mutations in the GTP/GDP-binding region of RALA, a RAS-like small GTPase, cause intellectual disability and developmental delay.

PLoS Genet 2018 11 30;14(11):e1007671. Epub 2018 Nov 30.

HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America.

Mutations that alter signaling of RAS/MAPK-family proteins give rise to a group of Mendelian diseases known as RASopathies. However, among RASopathies, the matrix of genotype-phenotype relationships is still incomplete, in part because there are many RAS-related proteins and in part because the phenotypic consequences may be variable and/or pleiotropic. Here, we describe a cohort of ten cases, drawn from six clinical sites and over 16,000 sequenced probands, with de novo protein-altering variation in RALA, a RAS-like small GTPase. All probands present with speech and motor delays, and most have intellectual disability, low weight, short stature, and facial dysmorphism. The observed rate of de novo RALA variants in affected probands is significantly higher (p = 4.93 x 10(-11)) than expected from the estimated random mutation rate. Further, all de novo variants described here affect residues within the GTP/GDP-binding region of RALA; in fact, six alleles arose at only two codons, Val25 and Lys128. The affected residues are highly conserved across both RAL- and RAS-family genes, are devoid of variation in large human population datasets, and several are homologous to positions at which disease-associated variants have been observed in other GTPase genes. We directly assayed GTP hydrolysis and RALA effector-protein binding of the observed variants, and found that all but one tested variant significantly reduced both activities compared to wild-type. The one exception, S157A, reduced GTP hydrolysis but significantly increased RALA-effector binding, an observation similar to that seen for oncogenic RAS variants. These results show the power of data sharing for the interpretation and analysis of rare variation, expand the spectrum of molecular causes of developmental disability to include RALA, and provide additional insight into the pathogenesis of human disease caused by mutations in small GTPases.
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http://dx.doi.org/10.1371/journal.pgen.1007671DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6291162PMC
November 2018

CHD3 helicase domain mutations cause a neurodevelopmental syndrome with macrocephaly and impaired speech and language.

Nat Commun 2018 11 5;9(1):4619. Epub 2018 Nov 5.

AP-HP, Hôpital de la Pitié-Salpêtrière, Département de Génétique, Paris, 75013, France.

Chromatin remodeling is of crucial importance during brain development. Pathogenic alterations of several chromatin remodeling ATPases have been implicated in neurodevelopmental disorders. We describe an index case with a de novo missense mutation in CHD3, identified during whole genome sequencing of a cohort of children with rare speech disorders. To gain a comprehensive view of features associated with disruption of this gene, we use a genotype-driven approach, collecting and characterizing 35 individuals with de novo CHD3 mutations and overlapping phenotypes. Most mutations cluster within the ATPase/helicase domain of the encoded protein. Modeling their impact on the three-dimensional structure demonstrates disturbance of critical binding and interaction motifs. Experimental assays with six of the identified mutations show that a subset directly affects ATPase activity, and all but one yield alterations in chromatin remodeling. We implicate de novo CHD3 mutations in a syndrome characterized by intellectual disability, macrocephaly, and impaired speech and language.
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http://dx.doi.org/10.1038/s41467-018-06014-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6218476PMC
November 2018

The ARID1B spectrum in 143 patients: from nonsyndromic intellectual disability to Coffin-Siris syndrome.

Genet Med 2019 06 8;21(6):1295-1307. Epub 2018 Nov 8.

University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands.

Purpose: Pathogenic variants in ARID1B are one of the most frequent causes of intellectual disability (ID) as determined by large-scale exome sequencing studies. Most studies published thus far describe clinically diagnosed Coffin-Siris patients (ARID1B-CSS) and it is unclear whether these data are representative for patients identified through sequencing of unbiased ID cohorts (ARID1B-ID). We therefore sought to determine genotypic and phenotypic differences between ARID1B-ID and ARID1B-CSS. In parallel, we investigated the effect of different methods of phenotype reporting.

Methods: Clinicians entered clinical data in an extensive web-based survey.

Results: 79 ARID1B-CSS and 64 ARID1B-ID patients were included. CSS-associated dysmorphic features, such as thick eyebrows, long eyelashes, thick alae nasi, long and/or broad philtrum, small nails and small or absent fifth distal phalanx and hypertrichosis, were observed significantly more often (p < 0.001) in ARID1B-CSS patients. No other significant differences were identified.

Conclusion: There are only minor differences between ARID1B-ID and ARID1B-CSS patients. ARID1B-related disorders seem to consist of a spectrum, and patients should be managed similarly. We demonstrated that data collection methods without an explicit option to report the absence of a feature (such as most Human Phenotype Ontology-based methods) tended to underestimate gene-related features.
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http://dx.doi.org/10.1038/s41436-018-0330-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752273PMC
June 2019

A homozygous KAT2B variant modulates the clinical phenotype of ADD3 deficiency in humans and flies.

PLoS Genet 2018 05 16;14(5):e1007386. Epub 2018 May 16.

Laboratory of Epithelial Biology and Disease, Institut National de la Santé et de la Recherche Médicale (Inserm) UMR1163, Imagine Institute, Paris, France.

Recent evidence suggests that the presence of more than one pathogenic mutation in a single patient is more common than previously anticipated. One of the challenges hereby is to dissect the contribution of each gene mutation, for which animal models such as Drosophila can provide a valuable aid. Here, we identified three families with mutations in ADD3, encoding for adducin-γ, with intellectual disability, microcephaly, cataracts and skeletal defects. In one of the families with additional cardiomyopathy and steroid-resistant nephrotic syndrome (SRNS), we found a homozygous variant in KAT2B, encoding the lysine acetyltransferase 2B, with impact on KAT2B protein levels in patient fibroblasts, suggesting that this second mutation might contribute to the increased disease spectrum. In order to define the contribution of ADD3 and KAT2B mutations for the patient phenotype, we performed functional experiments in the Drosophila model. We found that both mutations were unable to fully rescue the viability of the respective null mutants of the Drosophila homologs, hts and Gcn5, suggesting that they are indeed pathogenic in flies. While the KAT2B/Gcn5 mutation additionally showed a significantly reduced ability to rescue morphological and functional defects of cardiomyocytes and nephrocytes (podocyte-like cells), this was not the case for the ADD3 mutant rescue. Yet, the simultaneous knockdown of KAT2B and ADD3 synergistically impaired kidney and heart function in flies as well as the adhesion and migration capacity of cultured human podocytes, indicating that mutations in both genes may be required for the full clinical manifestation. Altogether, our studies describe the expansion of the phenotypic spectrum in ADD3 deficiency associated with a homozygous likely pathogenic KAT2B variant and thereby identify KAT2B as a susceptibility gene for kidney and heart disease in ADD3-associated disorders.
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http://dx.doi.org/10.1371/journal.pgen.1007386DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5973622PMC
May 2018

Mutations That Alter the Carboxy-Terminal-Propeptide Cleavage Site of the Chains of Type I Procollagen Are Associated With a Unique Osteogenesis Imperfecta Phenotype.

J Bone Miner Res 2018 07 18;33(7):1260-1271. Epub 2018 Apr 18.

Department of Pathology, University of Washington, Seattle, WA, USA.

Osteogenesis imperfecta (OI) is a genetic bone disorder characterized by fractures, low bone mass, and skeletal fragility. It most commonly arises from dominantly inherited mutations in the genes COL1A1 and COL1A2 that encode the chains of type I collagen. A number of recent reports have suggested that mutations affecting the carboxyl-terminal propeptide cleavage site in the products of either COL1A1 or COL1A2 give rise to a form of OI characterized by unusually dense bones. We have assembled clinical, biochemical, and molecular data from 29 individuals from 8 families with 7 different mutations affecting the C-propeptide cleavage site. The phenotype was generally mild: The median height was ∼33th centile. Eighty percent of subjects had their first fracture by the age of 10 years, and one-third had a femoral or tibial fracture by the age of 25 years. Fractures continued into adulthood, though rates varied considerably. Healing was normal and rarely resulted in long bone deformity. One-third of subjects older than 15 years had scoliosis. The teeth and hearing were normal in most, and blue sclerae were not observed. Other features noted included fibro-osseous dysplasia of the mandible and Achilles tendon calcification. The mean spinal bone mineral density Z-score was +2.9 (SD 2.1) compared with -2.2 (0.7) in subjects with COL1A1 haploinsufficiency mutations. Bone mineral density distribution, assessed by quantitative backscattered electron imaging in bone showed higher levels of mineralization than found in any other disorder. Bone histology showed high trabecular volume and increased cortical thickness, with hyperosteoidosis and delayed mineralization. In vitro studies with cultured skin fibroblasts suggested that these mutations interfere with processing of the chain in which the sequence alteration occurs, but the C-propeptide is eventually cleaved (and detectable in blood), suggesting there are alternative sites of cleavage. The precise mechanism of the bony pathology is not yet clear. © 2018 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbmr.3424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6031457PMC
July 2018

WDR26 Haploinsufficiency Causes a Recognizable Syndrome of Intellectual Disability, Seizures, Abnormal Gait, and Distinctive Facial Features.

Am J Hum Genet 2017 Jul;101(1):139-148

Division of Medical Genetics, Stead Family Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA.

We report 15 individuals with de novo pathogenic variants in WDR26. Eleven of the individuals carry loss-of-function mutations, and four harbor missense substitutions. These 15 individuals comprise ten females and five males, and all have intellectual disability with delayed speech, a history of febrile and/or non-febrile seizures, and a wide-based, spastic, and/or stiff-legged gait. These subjects share a set of common facial features that include a prominent maxilla and upper lip that readily reveal the upper gingiva, widely spaced teeth, and a broad nasal tip. Together, these features comprise a recognizable facial phenotype. We compared these features with those of chromosome 1q41q42 microdeletion syndrome, which typically contains WDR26, and noted that clinical features are consistent between the two subsets, suggesting that haploinsufficiency of WDR26 contributes to the pathology of 1q41q42 microdeletion syndrome. Consistent with this, WDR26 loss-of-function single-nucleotide mutations identified in these subjects lead to nonsense-mediated decay with subsequent reduction of RNA expression and protein levels. We derived a structural model of WDR26 and note that missense variants identified in these individuals localize to highly conserved residues of this WD-40-repeat-containing protein. Given that WDR26 mutations have been identified in ∼1 in 2,000 of subjects in our clinical cohorts and that WDR26 might be poorly annotated in exome variant-interpretation pipelines, we would anticipate that this disorder could be more common than currently appreciated.
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http://dx.doi.org/10.1016/j.ajhg.2017.06.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5501873PMC
July 2017

Heterozygous Pathogenic Variant in DACT1 Causes an Autosomal-Dominant Syndrome with Features Overlapping Townes-Brocks Syndrome.

Hum Mutat 2017 04 2;38(4):373-377. Epub 2017 Feb 2.

Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York.

A heterozygous nonsense variant was identified in dapper, antagonist of beta-catenin, 1 (DACT1) via whole-exome sequencing in family members with imperforate anus, structural renal abnormalities, genitourinary anomalies, and/or ear anomalies. The DACT1 c.1256G>A;p.Trp419 variant segregated appropriately in the family consistent with an autosomal dominant mode of inheritance. DACT1 is a member of the Wnt-signaling pathway, and mice homozygous for null alleles display multiple congenital anomalies including absent anus with blind-ending colon and genitourinary malformations. To investigate the DACT1 c.1256G>A variant, HEK293 cells were transfected with mutant DACT1 cDNA plasmid, and immunoblotting revealed stability of the DACT1 p.Trp419 protein. Overexpression of DACT1 c.1256G>A mRNA in Xenopus embryos revealed a specific gastrointestinal phenotype of enlargement of the proctodeum. Together, these findings suggest that the DACT1 c.1256G>A nonsense variant is causative of a specific genetic syndrome with features overlapping Townes-Brocks syndrome.
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http://dx.doi.org/10.1002/humu.23171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390682PMC
April 2017

SRD5A3-CDG: Expanding the phenotype of a congenital disorder of glycosylation with emphasis on adult onset features.

Am J Med Genet A 2016 12 2;170(12):3165-3171. Epub 2016 Aug 2.

Human Genetics Program, Sanford-Burnham Prebys Medical Discovery Institute, La Jolla, California.

Increasing numbers of congenital disorders of glycosylation (CDG) have been reported recently resulting in an expansion of the phenotypes associated with this group of disorders. SRD5A3 codes for polyprenol reductase which converts polyprenol to dolichol. This is a major pathway for dolichol biosynthesis for N-glycosylation, O-mannosylation, C-mannosylation, and GPI anchor synthesis. We present the features of five individuals (three children and two adults) with mutations in SRD5A3 focusing on the variable eye and skin involvement. We compare that to 13 affected individuals from the literature including five adults allowing us to delineate the features that may develop over time with this disorder including kyphosis, retinitis pigmentosa, and cataracts. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37875DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5115938PMC
December 2016

De novo truncating variants in the AHDC1 gene encoding the AT-hook DNA-binding motif-containing protein 1 are associated with intellectual disability and developmental delay.

Cold Spring Harb Mol Case Stud 2015 Oct;1(1):a000562

Departments of Pediatrics and Medicine, Columbia University Medical Center, New York, New York 10032, USA.

Whole-exome sequencing (WES) represents a significant breakthrough in clinical genetics, and identifies a genetic etiology in up to 30% of cases of intellectual disability (ID). Using WES, we identified seven unrelated patients with a similar clinical phenotype of severe intellectual disability or neurodevelopmental delay who were all heterozygous for de novo truncating variants in the AT-hook DNA-binding motif-containing protein 1 (AHDC1). The patients were all minimally verbal or nonverbal and had variable neurological problems including spastic quadriplegia, ataxia, nystagmus, seizures, autism, and self-injurious behaviors. Additional common clinical features include dysmorphic facial features and feeding difficulties associated with failure to thrive and short stature. The AHDC1 gene has only one coding exon, and the protein contains conserved regions including AT-hook motifs and a PDZ binding domain. We postulate that all seven variants detected in these patients result in a truncated protein missing critical functional domains, disrupting interactions with other proteins important for brain development. Our study demonstrates that truncating variants in AHDC1 are associated with ID and are primarily associated with a neurodevelopmental phenotype.
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http://dx.doi.org/10.1101/mcs.a000562DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4850891PMC
October 2015

De novo POGZ mutations are associated with neurodevelopmental disorders and microcephaly.

Cold Spring Harb Mol Case Stud 2015 Oct;1(1):a000455

Departments of Pediatrics and Medicine, Columbia University Medical Center, New York, New York 10032, USA.

Seven patients with similar phenotypes of developmental delay and microcephaly were found by whole-exome sequencing to have de novo loss-of-function mutations in POGZ. POGZ is a pogo transposable element-derived protein with a zinc finger cluster. The protein is involved in normal kinetochore assembly and mitotic sister chromatid cohesion and mitotic chromosome segregation. POGZ deficiency may affect mitosis, disrupting brain development and function.
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http://dx.doi.org/10.1101/mcs.a000455DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4850885PMC
October 2015

Mutations in HIVEP2 are associated with developmental delay, intellectual disability, and dysmorphic features.

Neurogenetics 2016 07 22;17(3):159-64. Epub 2016 Mar 22.

Department of Pediatrics, Columbia University Medical Center, 1150 St. Nicholas Avenue, New York, 10032, NY, USA.

Human immunodeficiency virus type I enhancer binding protein 2 (HIVEP2) has been previously associated with intellectual disability and developmental delay in three patients. Here, we describe six patients with developmental delay, intellectual disability, and dysmorphic features with de novo likely gene-damaging variants in HIVEP2 identified by whole-exome sequencing (WES). HIVEP2 encodes a large transcription factor that regulates various neurodevelopmental pathways. Our findings provide further evidence that pathogenic variants in HIVEP2 lead to intellectual disabilities and developmental delay.
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http://dx.doi.org/10.1007/s10048-016-0479-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4907844PMC
July 2016

Novel, compound heterozygous, single-nucleotide variants in MARS2 associated with developmental delay, poor growth, and sensorineural hearing loss.

Hum Mutat 2015 Jun 8;36(6):587-92. Epub 2015 Apr 8.

Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York.

Novel, single-nucleotide mutations were identified in the mitochondrial methionyl amino-acyl tRNA synthetase gene (MARS2) via whole exome sequencing in two affected siblings with developmental delay, poor growth, and sensorineural hearing loss.We show that compound heterozygous mutations c.550C>T:p.Gln 184* and c.424C>T:p.Arg142Trp in MARS2 lead to decreased MARS2 protein levels in patient lymphoblasts. Analysis of respiratory complex enzyme activities in patient fibroblasts revealed decreased complex I and IV activities. Immunoblotting of patient fibroblast and lymphoblast samples revealed reduced protein levels of NDUFB8 and COXII, representing complex I and IV, respectively. Additionally, overexpression of wild-type MARS2 in patient fibroblasts increased NDUFB8 and COXII protein levels. These findings suggest that recessive single-nucleotide mutations in MARS2 are causative for a new mitochondrial translation deficiency disorder with a primary phenotype including developmental delay and hypotonia. Identification of additional patients with single-nucleotide mutations in MARS2 is necessary to determine if pectus carinatum is also a consistent feature of this syndrome.
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http://dx.doi.org/10.1002/humu.22781DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4439286PMC
June 2015

Whole exome sequence analysis of Peters anomaly.

Hum Genet 2014 Dec 3;133(12):1497-511. Epub 2014 Sep 3.

Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.

Peters anomaly is a rare form of anterior segment ocular dysgenesis, which can also be associated with additional systemic defects. At this time, the majority of cases of Peters anomaly lack a genetic diagnosis. We performed whole exome sequencing of 27 patients with syndromic or isolated Peters anomaly to search for pathogenic mutations in currently known ocular genes. Among the eight previously recognized Peters anomaly genes, we identified a de novo missense mutation in PAX6, c.155G>A, p.(Cys52Tyr), in one patient. Analysis of 691 additional genes currently associated with a different ocular phenotype identified a heterozygous splicing mutation c.1025+2T>A in TFAP2A, a de novo heterozygous nonsense mutation c.715C>T, p.(Gln239*) in HCCS, a hemizygous mutation c.385G>A, p.(Glu129Lys) in NDP, a hemizygous mutation c.3446C>T, p.(Pro1149Leu) in FLNA, and compound heterozygous mutations c.1422T>A, p.(Tyr474*) and c.2544G>A, p.(Met848Ile) in SLC4A11; all mutations, except for the FLNA and SLC4A11 c.2544G>A alleles, are novel. This is the first study to use whole exome sequencing to discern the genetic etiology of a large cohort of patients with syndromic or isolated Peters anomaly. We report five new genes associated with this condition and suggest screening of TFAP2A and FLNA in patients with Peters anomaly and relevant syndromic features and HCCS, NDP and SLC4A11 in patients with isolated Peters anomaly.
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http://dx.doi.org/10.1007/s00439-014-1481-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4395516PMC
December 2014

Haploinsufficiency of HDAC4 does not cause intellectual disability in all affected individuals.

Am J Med Genet A 2014 Jul 8;164A(7):1826-9. Epub 2014 Apr 8.

Divison of Genetics, Nemours Children's Clinic, Orlando, Florida.

Haploinsufficiency of HDAC4 gene has been reported to result in brachydactyly-"mental retardation" syndrome (BDMR), a condition with significant intellectual impairment, brachydactyly type E, and typical facial features. Presented here are three individuals with haploinsufficiency of HDAC4 who have brachydactyly type E, non-dysmorphic facial features, and normal intelligence. This is in contradistinction to previous reports that haploinsufficiency of HDAC4 is sufficient to cause BDMR.
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http://dx.doi.org/10.1002/ajmg.a.36542DOI Listing
July 2014

Novel mutations widen the phenotypic spectrum of slow skeletal/β-cardiac myosin (MYH7) distal myopathy.

Hum Mutat 2014 Jul 21;35(7):868-79. Epub 2014 May 21.

Neurogenetic Unit, Department of Neurology, Royal Perth Hospital, Western Australia, Australia; Diagnostic Genomics Laboratory, Pathwest, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.

Laing early onset distal myopathy and myosin storage myopathy are caused by mutations of slow skeletal/β-cardiac myosin heavy chain encoded by the gene MYH7, as is a common form of familial hypertrophic/dilated cardiomyopathy. The mechanisms by which different phenotypes are produced by mutations in MYH7, even in the same region of the gene, are not known. To explore the clinical spectrum and pathobiology, we screened the MYH7 gene in 88 patients from 21 previously unpublished families presenting with distal or generalized skeletal muscle weakness, with or without cardiac involvement. Twelve novel mutations have been identified in thirteen families. In one of these families, the father of the proband was found to be a mosaic for the MYH7 mutation. In eight cases, de novo mutation appeared to have occurred, which was proven in four. The presenting complaint was footdrop, sometimes leading to delayed walking or tripping, in members of 17 families (81%), with other presentations including cardiomyopathy in infancy, generalized floppiness, and scoliosis. Cardiac involvement as well as skeletal muscle weakness was identified in nine of 21 families. Spinal involvement such as scoliosis or rigidity was identified in 12 (57%). This report widens the clinical and pathological phenotypes, and the genetics of MYH7 mutations leading to skeletal muscle diseases.
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http://dx.doi.org/10.1002/humu.22553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112555PMC
July 2014
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