Publications by authors named "Billur Moghaddam"

8 Publications

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Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.

Genome Med 2021 05 21;13(1):90. Epub 2021 May 21.

Département de Génétique, Hôpital La Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France.

Background: We aimed to define the clinical and variant spectrum and to provide novel molecular insights into the DHX30-associated neurodevelopmental disorder.

Methods: Clinical and genetic data from affected individuals were collected through Facebook-based family support group, GeneMatcher, and our network of collaborators. We investigated the impact of novel missense variants with respect to ATPase and helicase activity, stress granule (SG) formation, global translation, and their effect on embryonic development in zebrafish. SG formation was additionally analyzed in CRISPR/Cas9-mediated DHX30-deficient HEK293T and zebrafish models, along with in vivo behavioral assays.

Results: We identified 25 previously unreported individuals, ten of whom carry novel variants, two of which are recurrent, and provide evidence of gonadal mosaicism in one family. All 19 individuals harboring heterozygous missense variants within helicase core motifs (HCMs) have global developmental delay, intellectual disability, severe speech impairment, and gait abnormalities. These variants impair the ATPase and helicase activity of DHX30, trigger SG formation, interfere with global translation, and cause developmental defects in a zebrafish model. Notably, 4 individuals harboring heterozygous variants resulting either in haploinsufficiency or truncated proteins presented with a milder clinical course, similar to an individual harboring a de novo mosaic HCM missense variant. Functionally, we established DHX30 as an ATP-dependent RNA helicase and as an evolutionary conserved factor in SG assembly. Based on the clinical course, the variant location, and type we establish two distinct clinical subtypes. DHX30 loss-of-function variants cause a milder phenotype whereas a severe phenotype is caused by HCM missense variants that, in addition to the loss of ATPase and helicase activity, lead to a detrimental gain-of-function with respect to SG formation. Behavioral characterization of dhx30-deficient zebrafish revealed altered sleep-wake activity and social interaction, partially resembling the human phenotype.

Conclusions: Our study highlights the usefulness of social media to define novel Mendelian disorders and exemplifies how functional analyses accompanied by clinical and genetic findings can define clinically distinct subtypes for ultra-rare disorders. Such approaches require close interdisciplinary collaboration between families/legal representatives of the affected individuals, clinicians, molecular genetics diagnostic laboratories, and research laboratories.
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http://dx.doi.org/10.1186/s13073-021-00900-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8140440PMC
May 2021

Natural history of achondroplasia: A retrospective review of longitudinal clinical data.

Am J Med Genet A 2020 11 31;182(11):2540-2551. Epub 2020 Aug 31.

Division of Research, Kaiser Permanente, Oakland, California, USA.

There are limited data on the longitudinal frequency and severity of the symptoms and complications of achondroplasia. We undertook a retrospective electronic chart review of 114 patients to develop a more thorough understanding of the lifetime impact of achondroplasia. Craniocervical stenosis (involving the foramen magnum with or without cervical vertebrae C1 and/or C2) was noted in nearly 50% of patients with craniovertebral junction imaging; however, corrective decompression surgery was only needed in 6% of patients. No children in our cohort died at 4 years of age or under. Kyphosis was present in most patients but usually resolved in early childhood. Cervical and lumbar stenosis were diagnosed in children and adults while, genu varum, elbow contractures, and radial head dislocations were identified during childhood. Central sleep apnea and obstructive sleep apnea were present in children, while the diagnosis of obstructive sleep apnea was shown to recur in adulthood. Cardiovascular risk factors were present in only 7% of patients. A range of mental health disorders were identified, with most diagnoses being made before 18 years of age. Our data show that achondroplasia has a significant impact on patients' physical health, and complications continue to be reported and require intervention throughout patients' lifetimes. This highlights the need for continuous support beyond pediatric care, by adult care clinicians experienced with managing the long-term complications of achondroplasia.
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http://dx.doi.org/10.1002/ajmg.a.61825DOI Listing
November 2020

Recurrent HERV-H-mediated 3q13.2-q13.31 deletions cause a syndrome of hypotonia and motor, language, and cognitive delays.

Hum Mutat 2013 Oct 13;34(10):1415-23. Epub 2013 Aug 13.

Signature Genomic Laboratories, PerkinElmer, Inc, Spokane, Washington.

We describe the molecular and clinical characterization of nine individuals with recurrent, 3.4-Mb, de novo deletions of 3q13.2-q13.31 detected by chromosomal microarray analysis. All individuals have hypotonia and language and motor delays; they variably express mild to moderate cognitive delays (8/9), abnormal behavior (7/9), and autism spectrum disorders (3/9). Common facial features include downslanting palpebral fissures with epicanthal folds, a slightly bulbous nose, and relative macrocephaly. Twenty-eight genes map to the deleted region, including four strong candidate genes, DRD3, ZBTB20, GAP43, and BOC, with important roles in neural and/or muscular development. Analysis of the breakpoint regions based on array data revealed directly oriented human endogenous retrovirus (HERV-H) elements of ~5 kb in size and of >95% DNA sequence identity flanking the deletion. Subsequent DNA sequencing revealed different deletion breakpoints and suggested nonallelic homologous recombination (NAHR) between HERV-H elements as a mechanism of deletion formation, analogous to HERV-I-flanked and NAHR-mediated AZFa deletions. We propose that similar HERV elements may also mediate other recurrent deletion and duplication events on a genome-wide scale. Observation of rare recurrent chromosomal events such as these deletions helps to further the understanding of mechanisms behind naturally occurring variation in the human genome and its contribution to genetic disease.
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http://dx.doi.org/10.1002/humu.22384DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4599348PMC
October 2013

Minor physical anomalies in children with autism spectrum disorders.

Autism 2011 Nov 24;15(6):746-60. Epub 2011 May 24.

University of California, Davis, USA.

Objective: There is clinical heterogeneity among the autism spectrum disorders (ASD). The presence of dysmorphology (minor physical anomalies; MPAs) is one possible tool for defining a clinically relevant subset in ASD. This study employs an adaptation of Miles and Hillman's (2000) classifications by using photographs to identify a subgroup with significant dysmorphology among children with ASD, typical development (TYP), and developmental delay (DD).

Method: Children with ASD, DD, and TYP between 2 and 5 years old were part of the CHARGE Study. Pediatric specialists blinded to diagnostic group classified photographs based on the number of MPAs present: 'dysmorphic' if >3 and 'nondysmorphic' if <3 MPAs.

Results: Photographs for 324 children were included. Significantly more children with ASD were classified as dysmorphic compared to TYP children (p = .007). In children with ASD, seizures were more prevalent in those rated dysmorphic (p = .005). Frequencies were similar between ASD versus DD (p = .19) after removing those with known syndromes.

Conclusion: Photographic assessment can be used to detect generalized dysmorphology in children who are often difficult to examine. This has clinical relevance, as children with multiple MPAs can be identified through the use of photographs and prioritized for investigation of brain abnormalities and underlying genetic disorders.
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http://dx.doi.org/10.1177/1362361310397620DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4245022PMC
November 2011

Monosomy 21q22.11-q22.13 presenting as a Fanconi anemia phenotype.

Am J Med Genet A 2011 Jan;155A(1):120-5

Davis Medical Center, Department of Pediatrics, University of California, Sacramento, 95817, USA.

We report on a 5-year-old Caucasian female with multiple anomalies whose deletion, 46,XX,del(21)(q22.11q22.13), was determined by a 105K oligonucleotide-based microarray. This case is a unique deletion that mimicked Fanconi anemia (combination of thrombocytopenia, thumb anomalies, congenital heart defects, borderline small head circumference, strabismus, hydronephrosis, and significant developmental delay) but testing for Fanconi anemia was negative, as was testing for a wide array of genetic/metabolic conditions. Microarray testing done at 5 months failed to demonstrate the interstitial deletion that was found on a newer generation microarray test performed after 3 years of age. When compared to other reported cases of partial monosomy 21q, the unique features of this case include: (1) cleft palate, although high palate is reported in other cases; (2) neonatal thrombocytopenia requiring platelet transfusion; (3) a platelet function defect, reported previously as platelet storage pool defect as part of a familial platelet disorder; and (4) an immune function defect. Similar to other reported patients with terminal 21q deletion, this child had significant developmental delay, and feeding and growth problems. This case also highlights the ability for newer technology microarrays to identify small interstitial deletions previously missed by an earlier version microarray. The advances in the microarray technologies are allowing us to better define new phenotypes and leading to the identification of a diagnosis for many patients who have been previously undiagnosed. Review of the genes involved in these novel deletions allows the caring physician to design surveillance strategies that are custom-designed for these unique patients.
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http://dx.doi.org/10.1002/ajmg.a.33801DOI Listing
January 2011

A novel mutation in a Fijian boy with Shwachman-Diamond syndrome.

J Pediatr Hematol Oncol 2009 Nov;31(11):847-9

Department of Pediatrics, University of California, Davis Medical Center, Sacramento, CA, USA.

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by pancreatic insufficiency, bone marrow dysfunction, and metaphyseal chondrodysplasia. SDS is associated with mutations in the Shwachman-Bodian-Diamond Syndrome gene, with 90% of reported mutations in exon 2. We present a Fijian boy with SDS who has a novel A>G substitution in exon 1 of the Shwachman-Bodian-Diamond Syndrome gene that has not been reported in the literature. This patient's unique clinical course includes the presence of a cleft lip and episodic hypoglycemia. SDS lacks a clear genotype-phenotype correlation, as is showed by the heterogeneity in its clinical presentation.
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http://dx.doi.org/10.1097/MPH.0b013e3181b9c949DOI Listing
November 2009

Floating-Harbor syndrome and intramedullary spinal cord ganglioglioma: case report and observations from the literature.

Am J Med Genet A 2009 Oct;149A(10):2265-9

Department of Pediatrics, University of California at Davis, Sacramento, California 95817, USA.

We report on a 5-year-old male with expressive language delay, developmental delay, short stature, and facial anomalies consistent with Floating-Harbor syndrome (FHS). In addition, he developed an intramedullary ganglioglioma. This is the first reported case of a tumor associated with FHS, and may represent an as yet undefined genetic link between spinal cord tumors and FHS, adding this syndrome to the growing list of disorders with a predisposition for tumor development.
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http://dx.doi.org/10.1002/ajmg.a.33014DOI Listing
October 2009

Molecular and clinical analyses of Greig cephalopolysyndactyly and Pallister-Hall syndromes: robust phenotype prediction from the type and position of GLI3 mutations.

Am J Hum Genet 2005 Apr 28;76(4):609-22. Epub 2005 Feb 28.

National Institutes of Health, National Human Genome Research Institute, Bethesda, MD 20892-4472, USA.

Mutations in the GLI3 zinc-finger transcription factor gene cause Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS), which are variable but distinct clinical entities. We hypothesized that GLI3 mutations that predict a truncated functional repressor protein cause PHS and that functional haploinsufficiency of GLI3 causes GCPS. To test these hypotheses, we screened patients with PHS and GCPS for GLI3 mutations. The patient group consisted of 135 individuals: 89 patients with GCPS and 46 patients with PHS. We detected 47 pathological mutations (among 60 probands); when these were combined with previously published mutations, two genotype-phenotype correlations were evident. First, GCPS was caused by many types of alterations, including translocations, large deletions, exonic deletions and duplications, small in-frame deletions, and missense, frameshift/nonsense, and splicing mutations. In contrast, PHS was caused only by frameshift/nonsense and splicing mutations. Second, among the frameshift/nonsense mutations, there was a clear genotype-phenotype correlation. Mutations in the first third of the gene (from open reading frame [ORF] nucleotides [nt] 1-1997) caused GCPS, and mutations in the second third of the gene (from ORF nt 1998-3481) caused primarily PHS. Surprisingly, there were 12 mutations in patients with GCPS in the 3' third of the gene (after ORF nt 3481), and no patients with PHS had mutations in this region. These results demonstrate a robust correlation of genotype and phenotype for GLI3 mutations and strongly support the hypothesis that these two allelic disorders have distinct modes of pathogenesis.
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http://dx.doi.org/10.1086/429346DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1199298PMC
April 2005
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