Hum Mutat. 2022 Jan 13. doi: 10.1002/humu.24330. Online ahead of print. ABSTRACT Iron-sulfur cluster proteins are involved in critical functions for gene expression regulation and mitochondrial bioenergetics including the oxidative phosphorylation system. The c.215G>A p.(Arg72Gln) variant in NFS1 has been previously reported to cause infantile mitochondrial complex II and III deficiency. We describe three additional unrelated patients with the same missense variant. Two infants with the same homozygous variant presented with hypotonia, weakness and lactic acidosis, and one patient with compound heterozygous p.(Arg72Gln) and p.(Arg412His) variants presented as a young adult with gastrointestinal symptoms and fatigue. Skeletal muscle biopsy from patients 1 and 3 showed abnormal mitochondrial morphology, and functional analyses demonstrated decreased activity in respiratory chain complex II and variably in complexes I and III. We found decreased mitochondrial and cytosolic aconitase activities but only mildly affected lipoylation of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase enzymes. Our studies expand the phenotypic spectrum and provide further evidence for the pathogenicity and functional sequelae of NFS1-related disorders with disturbances in both mitochondrial and cytosolic iron-sulfur cluster containing enzymes. PMID:35026043 | DOI:10.1002/humu.24330

Genet Med. 2022 Jan 10:S1098-3600(21)05422-8. doi: 10.1016/j.gim.2021.12.003. Online ahead of print. ABSTRACT PURPOSE: Gabriele-de Vries syndrome (GADEVS) is a rare genetic disorder characterized by developmental delay and/or intellectual disability, hypotonia, feeding difficulties, and distinct facial features. To refine the phenotype and to better understand the molecular basis of the syndrome, we analyzed clinical data and performed genome-wide DNA methylation analysis of a series of individuals carrying a YY1 variant. METHODS: Clinical data were collected for 13 individuals not yet reported through an international call for collaboration. DNA was collected for 11 of these individuals and 2 previously reported individuals in an attempt to delineate a specific DNA methylation signature in GADEVS. RESULTS: Phenotype in most individuals overlapped with the previously described features. We described 1 individual with atypical phenotype, heterozygous for a missense variant in a domain usually not involved in individuals with YY1 pathogenic missense variations. We also described a specific peripheral blood DNA methylation profile associated with YY1 variants. CONCLUSION: We reported a distinct DNA methylation episignature in GADEVS. We expanded the clinical profile of GADEVS to include thin/sparse hair and cryptorchidism. We also highlighted the utility of DNA methylation episignature analysis for classification of variants of unknown clinical significance. PMID:35027293 | DOI:10.1016/j.gim.2021.12.003

HGG Adv. 2021 Oct 14;2(4):100049. doi: 10.1016/j.xhgg.2021.100049. Epub 2021 Aug 10. ABSTRACT Xia-Gibbs syndrome (XGS; MIM: 615829) is a phenotypically heterogeneous neurodevelopmental disorder (NDD) caused by newly arising mutations in the AT-Hook DNA-Binding Motif-Containing 1 (AHDC1) gene that are predicted to lead to truncated AHDC1 protein synthesis. More than 270 individuals have been diagnosed with XGS worldwide. Despite the absence of an independent assay for AHDC1 protein function to corroborate potential functional consequences of rare variant genetic findings, there are also reports of individuals with XGS-like trait manifestations who have de novo missense AHDC1 mutations and who have been provided a molecular diagnosis of the disorder. To investigate a potential contribution of missense mutations to XGS, we mapped the missense mutations from 10 such individuals to the AHDC1 conserved protein domain structure and detailed the observed phenotypes. Five newly identified individuals were ascertained from a local XGS Registry, and an additional five were taken from external reports or databases, including one publication. Where clinical data were available, individuals with missense mutations all displayed phenotypes consistent with those observed in individuals with AHDC1 truncating mutations, including delayed motor milestones, intellectual disability (ID), hypotonia, and speech delay. A subset of the 10 reported missense mutations cluster in two regions of the AHDC1 protein with known conserved domains, likely representing functional motifs. Variants outside the clustered regions score lower for computational prediction of their likely damaging effects. Overall, de novo missense variants in AHDC1 are likely diagnostic of XGS when in silico analysis of their position relative to conserved regions is considered together with disease trait manifestations. PMID:34950897 | PMC:PMC8694554 | DOI:10.1016/j.xhgg.2021.100049

Nat Chem Biol. 2021 Dec 20. doi: 10.1038/s41589-021-00915-2. Online ahead of print. ABSTRACT Glutathione peroxidase 4 (GPX4), as the only enzyme in mammals capable of reducing esterified phospholipid hydroperoxides within a cellular context, protects cells from ferroptosis. We identified a homozygous point mutation in the GPX4 gene, resulting in an R152H coding mutation, in three patients with Sedaghatian-type spondylometaphyseal dysplasia. Using structure-based analyses and cell models, including patient fibroblasts, of this variant, we found that the missense variant destabilized a critical loop, which disrupted the active site and caused a substantial loss of enzymatic function. We also found that the R152H variant of GPX4 is less susceptible to degradation, revealing the degradation mechanism of the GPX4 protein. Proof-of-concept therapeutic treatments, which overcome the impaired R152H GPX4 activity, including selenium supplementation, selective antioxidants and a deuterated polyunsaturated fatty acid were identified. In addition to revealing a general approach to investigating rare genetic diseases, we demonstrate the biochemical foundations of therapeutic strategies targeting GPX4. PMID:34931062 | DOI:10.1038/s41589-021-00915-2

Orphanet J Rare Dis. 2021 Oct 23;16(1):446. doi: 10.1186/s13023-021-02048-0. ABSTRACT BACKGROUND: Extremely rare progressive diseases like Sedaghatian-type Spondylometaphyseal Dysplasia (SSMD) can be neonatally lethal and therefore go undiagnosed or are difficult to treat. Recent sequencing efforts have linked this disease to mutations in GPX4, with consequences in the resulting enzyme, glutathione peroxidase 4. This offers potential diagnostic and therapeutic avenues for those suffering from this disease, though the steps toward these treatments is often convoluted, expensive, and time-consuming. MAIN BODY: The CureGPX4 organization was developed to promote awareness of GPX4-related diseases like SSMD, as well as support research that could lead to essential therapeutics for patients. We provide an overview of the 21 published SSMD cases and have compiled additional sequencing data for four previously unpublished individuals to illustrate the genetic component of SSMD, and the role of sequencing data in diagnosis. We outline in detail the steps CureGPX4 has taken to reach milestones of team creation, disease understanding, drug repurposing, and design of future studies. CONCLUSION: The primary aim of this review is to provide a roadmap for therapy development for rare, ultra-rare, and difficult to diagnose diseases, as well as increase awareness of the genetic component of SSMD. This work will offer a better understanding of GPx4-related diseases, and help guide researchers, clinicians, and patients interested in other rare diseases find a path towards treatments. PMID:34688299 | DOI:10.1186/s13023-021-02048-0

Genome Med. 2021 Oct 14;13(1):153. doi: 10.1186/s13073-021-00965-0. ABSTRACT BACKGROUND: Clinical interpretation of genetic variants in the context of the patient’s phenotype is becoming the largest component of cost and time expenditure for genome-based diagnosis of rare genetic diseases. Artificial intelligence (AI) holds promise to greatly simplify and speed genome interpretation by integrating predictive methods with the growing knowledge of genetic disease. Here we assess the diagnostic performance of Fabric GEM, a new, AI-based, clinical decision support tool for expediting genome interpretation. METHODS: We benchmarked GEM in a retrospective cohort of 119 probands, mostly NICU infants, diagnosed with rare genetic diseases, who received whole-genome or whole-exome sequencing (WGS, WES). We replicated our analyses in a separate cohort of 60 cases collected from five academic medical centers. For comparison, we also analyzed these cases with current state-of-the-art variant prioritization tools. Included in the comparisons were trio, duo, and singleton cases. Variants underpinning diagnoses spanned diverse modes of inheritance and types, including structural variants (SVs). Patient phenotypes were extracted from clinical notes by two means: manually and using an automated clinical natural language processing (CNLP) tool. Finally, 14 previously unsolved cases were reanalyzed. RESULTS: GEM ranked over 90% of the causal genes among the top or second candidate and prioritized for review a median of 3 candidate genes per case, using either manually curated or CNLP-derived phenotype descriptions. Ranking of trios and duos was unchanged when analyzed as singletons. In 17 of 20 cases with diagnostic SVs, GEM identified the causal SVs as the top candidate and in 19/20 within the top five, irrespective of whether SV calls were provided or inferred ab initio by GEM using its own internal SV detection algorithm. GEM showed similar performance in absence of parental genotypes. Analysis of 14 previously unsolved cases resulted in a novel finding for one case, candidates ultimately not advanced upon manual review for 3 cases, and no new findings for 10 cases. CONCLUSIONS: GEM enabled diagnostic interpretation inclusive of all variant types through automated nomination of a very short list of candidate genes and disorders for final review and reporting. In combination with deep phenotyping by CNLP, GEM enables substantial automation of genetic disease diagnosis, potentially decreasing cost and expediting case review. PMID:34645491 | DOI:10.1186/s13073-021-00965-0

Nat Commun. 2021 Sep 20;12(1):5529. doi: 10.1038/s41467-021-25515-5. ABSTRACT Inherited disorders of neurotransmitter metabolism are rare neurodevelopmental diseases presenting with movement disorders and global developmental delay. This study presents the results of the first standardized deep phenotyping approach and describes the clinical and biochemical presentation at disease onset as well as diagnostic approaches of 275 patients from the registry of the International Working Group on Neurotransmitter related Disorders. The results reveal an increased rate of prematurity, a high risk for being small for gestational age and for congenital microcephaly in some disorders. Age at diagnosis and the diagnostic delay are influenced by the diagnostic methods applied and by disease-specific symptoms. The timepoint of investigation was also a significant factor: delay to diagnosis has decreased in recent years, possibly due to novel diagnostic approaches or raised awareness. Although each disorder has a specific biochemical pattern, we observed confounding exceptions to the rule. The data provide comprehensive insights into the phenotypic spectrum of neurotransmitter disorders. PMID:34545092 | DOI:10.1038/s41467-021-25515-5

Mov Disord Clin Pract. 2021 Sep 3;8(Suppl 1):S40-S41. doi: 10.1002/mdc3.13304. eCollection 2021 Aug. NO ABSTRACT PMID:34514047 | PMC:PMC8414503 | DOI:10.1002/mdc3.13304

J Pediatr. 2021 Sep 8:S0022-3476(21)00877-5. doi: 10.1016/j.jpeds.2021.09.005. Online ahead of print. ABSTRACT OBJECTIVES: To assess associations between maternal smoking and congenital heart defects (CHDs) in offspring. STUDY DESIGN: We performed a retrospective case-control study using data for cases of CHD (n=8,339) and non-malformed controls (n=11,020) children from all years (1997-2011) of the National Birth Defects Prevention Study. Maternal self-reported smoking one month before through three months after conception was evaluated as a binary (none, any) and categorical (light, medium, heavy) exposure. Multivariable logistic regression was used to estimate adjusted odds ratios (aOR) and 95% confidence intervals. Stratified analyses were performed for septal defects according to maternal age, pre-pregnancy body mass index, and maternal race/ethnicity. RESULTS: Multiple CHDs displayed modest associations with any level of maternal periconceptional smoking independent of potential confounders; the strongest associations were for aggregated septal defects (OR 1.5 [1.3-1.7]), tricuspid atresia (OR 1.7 [1.0-2.7]), and double outlet right ventricle (DORV) (1.5 [1.1-2.1]). TA and DORV also displayed dose-response relationships. Among heavy smokers, the highest odds were again observed for TA (aOR 3.0 [1.5-6.1]) and DORV (aOR 1.5 [1.1-2.2]). Heavy smokers ≥35 years old more frequently had a child with a septal defect when compared with similarly aged non-smokers (aOR 2.3 [1.4-3.9]). CONCLUSIONS: Maternal periconceptional smoking is most strongly associated with septal defects, TA and DORV; the risk for septal defects is modified by maternal age. PMID:34508749 | DOI:10.1016/j.jpeds.2021.09.005

Child Neurol Open. 2021 Aug 5;8:2329048X211030723. doi: 10.1177/2329048X211030723. eCollection 2021 Jan-Dec. ABSTRACT We present a case of a young child with a rare metabolic disorder whose clinical presentation resembled that of autoimmune myasthenia gravis. The differential diagnosis was expanded when autoantibody testing was negative and the patient did not respond to standard immunomodulatory therapies. Rapid whole genome sequencing identified 2 rare variants of uncertain significance in the SLC52A3 gene shown to be in compound heterozygous state after parental testing. Biallelic mutations in SLC52A3 are associated with Riboflavin Transporter Deficiency, which in its untreated form, results in progressive neurodegeneration and death. Supplementation with oral riboflavin has been shown to limit disease progression and improve symptoms in some patients. When the diagnosis is suspected, patients should be started on supplementation immediately while awaiting results from genetic studies. PMID:34395718 | PMC:PMC8361551 | DOI:10.1177/2329048X211030723