Clinical Genetics最新文献

Studies from the subcontinent on the utility of Whole Exome Sequencing (WES) in electro-clinical phenotypes of childhood-onset drug-resistant epilepsy (DRE) syndromes, particularly the developmental and epileptic encephalopathies (DEE), are rare in the literature. Patients with DRE phenotypes of presumed genetic etiology with an age of onset of epilepsy < 12 years, with/without developmental encephalopathy, were included in this study. Our study cohort (N = 175) included 158 trios, 6 duos, and 11 proband-only samples. Age at onset of seizures was ≤ 3 years in 76.6% and > 3 years in 23.4%, with developmental delay noted in 80.6% of the cohort. The overall yield of pathogenic/likely pathogenic variants in WES was 38.9% (68/175, 19 were novel); for trio-WES it was 41.1%. Predominantly de novo variants accounted for 45 out of 68 cases (66.2%), and the most frequent disease-causing variants were missense (74%). Younger age at onset of epilepsy, female gender and electroclinical diagnosis of Dravet syndrome were associated with a higher yield as opposed to focal epilepsies. Precision medicine was considered tenable in 25/68 (36.8%) cases. Our study reveals a significant yield of trio-WES for de novo variants in childhood-onset DRE/DEE. Female gender, early age at onset, and specific electro-clinical phenotypes have a higher likelihood of identifying a monogenic etiology.

Mediator of DNA damage checkpoint 1 (MDC1) is a protein closely associated with the repair of DNA damage. Recently, we identified three novel variants (NM_014641.3:c.C5977T; p.R1993X) (NM_014641.3:c.C5644T; p.R1882X; c.A1T; p.M1L) in MDC1 in two patients with severe oligoasthenoteratozoospermia (OAT). In vitro validation showed that the p.R1882X variant resulted in the truncation of the MDC1 protein, and the p.R1993X variant resulted in the degradation of the MDC1 protein after truncation. Immunofluorescence demonstrated that the truncated protein caused by the variants affected the colocalization relationship between MDC1 and its interacting protein γH2AX. Additionally, one of the patients and his wife underwent intracytoplasmic sperm injection (ICSI), but the result was unsatisfactory. We screened out the variants of MDC1 in patients with OAT for the first time, and this research could afford precise genetic diagnosis for the patients. It has broadened the variant spectrum of MDC1 , which is conducive to the development of targeted therapeutic strategies.

Genetic skeletal disorders (GSDs) comprise a diverse group of disorders that affect bone development and homeostasis. In some areas of Iran, GSD occurs more frequently than in other places for still unknown reasons. The aim of this study was to characterize the genetic landscape of GSDs in a cohort from southwestern Iran using Exome sequencing (ES), with a focus on identifying pathogenic and likely pathogenic variants. Osteogenesis Imperfecta (OI) was the most prevalent disorder, with an unexpectedly high frequency of autosomal recessive subtypes, likely due to a high consanguinity rate (61.3%) in the cohort. Achondroplasia (ACH) was the second most common disease and, comparable to another population, the NM_000142.5:c.1138G>A, p.(Gly380Arg), was the most common variant in FGFR3. ES identified twenty novel and fifteen previously reported pathogenic variants in several genes associated with GSDs. We provide the first comprehensive ES-based molecular diagnosis of GSDs in an Iranian population and uncover novel pathogenic variants that expand the known spectrum of variants. The results underscore the importance of genetic testing in the diagnosis of rare skeletal diseases and highlight the need for targeted genetic counseling in populations with high consanguinity.

LONP1 encodes a mitochondrial protease essential for protein quality control and metabolism. Variants in LONP1 are associated with a diverse and expanding spectrum of disorders, including Cerebral, Ocular, Dental, Auricular, and Skeletal anomalies syndrome (CODAS), congenital diaphragmatic hernia (CDH), and neurodevelopmental disorders (NDD), with some individuals exhibiting features of mitochondrial encephalopathy. We report 16 novel LONP1 variants identified in 16 individuals (11 with NDD, 5 with CDH), further expanding the clinical spectrum. Structural mapping of disease-associated missense variants revealed phenotype-specific clustering, with CODAS variants enriched in the proteolytic chamber and NDD variants more broadly distributed. CODAS is caused by biallelic variants and CDH by monoallelic variants, both of which are predicted to act through loss-of-function mechanisms. Both monoallelic and biallelic variants are associated with LONP1-related NDD, suggesting complex mechanisms such as dominant-negative effects. Our findings broaden the phenotypic and genetic spectrum of LONP1-associated disorders and highlight the essential role of LONP1 in mitochondrial function and development.

Autosomal recessive intellectual disability affects 1%–3% of the general population and is a major concern in countries where consanguineous marriages are common. Mental retardation autosomal recessive 48 (MRT 48) (OMIM 616269) is a recessive syndromic disorder characterized by progressive tremors, speech impairment, and behavioral problems. In the present study, we highlight a family with a case of MRT 48. The index patient was second born to healthy consanguineous parents with a history of intellectual disability. Whole exome sequencing of the patient was performed, which revealed a homozygous c.1693T>C;p.(Tyr565His) variant in the SLC6A17 gene. The variant segregated in the extended family with the phenotype. This study broadens the genotypic spectrum of SLC6A17 variants.

Myopathy with extrapyramidal signs (MPXPS) is a rare, autosomal-recessive, multisystem disorder caused by biallelic loss-of-function (LOF) variants in MICU1, the calcium-sensing gatekeeper of the mitochondrial calcium uniporter. We clinically and genetically characterized seven affected individuals from six Iranian-Turkish consanguineous families and combined these data with 54 previously published cases (total of 62). The targeted neuromuscular assessment, along with muscle biopsy and exome sequencing, identified six pathogenic MICU1 variants, including c.355C>T; p.Arg119*, c.493 + 1G>A, c.508C>T; p.Gln170*, c.547C>T; p.Gln183*, c.1226C>G; p.Ser409*, and c.553C>T; p.Arg185*. Notably, we report one adult-onset patient whose symptoms began at age 29 and progressed more rapidly than those in childhood-onset cases. A separate pedigree contained monozygotic twins who exhibited an indistinguishable clinical course, emphasizing the consistency of the genotype-driven phenotype. Across the combined cohort, the mean age at onset was 5.9 ± 7.3 years (median = 3 years); 61.5% presented before age 5, while 9.5% manifested after 15 years. Deep phenotyping of 61 patients from different ethnic backgrounds revealed that common symptoms included learning difficulties (72%), myopathy (51%), and speech impairments (51%). Functional studies targeting MCU modulation may provide future therapeutic options.