Esra Isik

Background: Inherited platelet disorders (IPDs) are a heterogeneous group of diseases characterized by thrombocytopenia and/or platelet functional abnormalities. This study aimed to identify novel candidate genes associated with hereditary thrombocytopenia using whole‐exome sequencing (WES). Methods: WES was performed in 40 patients with suspected IPDs. Functional characterization included segregation analysis, platelet‐based immunoblotting, and in silico structural modeling. Results: Rare variants in known IPD‐associated genes were identified in 32 patients (80%). Reanalysis of unresolved cases identified a novel homozygous ITGA10 (NM_003637.5) variant (c.2248C>T; p.Leu750Phe) in a 5‐year‐old female with severe thrombocytopenia. ITGA10 encodes the α10 subunit of the α10β1 integrin complex and is located within the recurrent 1q21.1 microdeletion region associated with thrombocytopenia‐absent radius syndrome. Immunoblotting studies demonstrated mildly reduced ITGA10 expression, an additional ∼80 kDa ITGA10‐related band, markedly reduced ITGB1 expression, and absence of β‐actin expression in platelet lysates despite wild‐type ACTB and ITGB1 genotypes. In silico structural analysis predicted reduced protein stability and impaired conformational flexibility associated with the p.Leu750Phe substitution. Conclusions: These findings support ITGA10 as a novel candidate gene for inherited thrombocytopenia and suggest that disruption of the ITGA10–ITGB1 integrin complex may contribute to abnormal platelet homeostasis and cytoskeletal organization. Further functional studies and additional patients will be important to clarify the biological mechanisms and establish the role of ITGA10 in inherited thrombocytopenia.

Sotos syndrome is an overgrowth disorder caused by heterozygous NSD1 variants, partial‐gene deletions, or 5q35 microdeletions. Malan syndrome, a phenotypically overlapping condition, results from haploinsufficiency of the NFIX gene due to either heterozygous chromosomal microdeletions involving the 19p13.2 region or heterozygous loss‐of‐function variants. This multicenter study aimed to characterize the clinical and molecular features of individuals with Sotos and Malan syndromes in Türkiye. We retrospectively analyzed clinical and molecular data from 48 individuals with genetically confirmed Sotos or Malan syndrome across 14 centers. Molecular analyses included whole‐exome sequencing, clinical exome sequencing, targeted gene panels, multiplex ligation–dependent probe amplification, and chromosomal microarray analysis. Forty‐two individuals were diagnosed with Sotos syndrome and six with Malan syndrome. All exhibited characteristic facial features, and 97.9% had developmental delay or intellectual disability. We identified a total of 38 NSD1 variants, of which 35 were classified as pathogenic or likely pathogenic and three as variants of uncertain significance; notably, 23 of these variants were novel. Three patients carried 5q35 microdeletions, and one had an intragenic deletion involving exons 10–11. Four distinct NFIX variants (two novel) were detected in five patients, and one carried a 19p13.13 deletion encompassing the entire gene. This nationwide study expands the genotype–phenotype spectrum of Sotos and Malan syndromes in Türkiye and supports improved diagnostic and clinical management strategies.

Piezo2 channels are mechanosensors expressed in dorsal root ganglia and Merkel cells, and involved in proprioception and touch sensation. PIEZO2 pathogenic variants cause rare autosomal dominant and recessive disorders. Dominant forms include distal arthrogryposis type 3, 5, and Marden-Walker syndrome, whereas the recessive form corresponds to distal arthrogryposis with impaired proprioception and touch (DAIPT). Given the rarity of these conditions, additional reports are essential to refine their phenotypic characterization. We conducted a multicenter, retrospective study to identify patients with genetically confirmed PIEZO2-related disorders. We collected clinical data through a standardized assessment. Previously published cases were included when more detailed phenotypic information was available. We identified 44 individuals with a clinical diagnosis of PIEZO2-related disorders. Among them, we selected 42 patients with a confirmed molecular diagnosis. Sixteen of them (10 males and 6 females; median age at diagnosis: 8 years; range 0.9-14) carried biallelic pathogenic PIEZO2 variants. They typically presented with neonatal hypotonia and respiratory distress with feeding difficulties. Distal arthrogryposis was associated with a variable multisystemic involvement, including the musculoskeletal system with scoliosis, hip dislocation and laryngomalacia. Twenty-five patients (11 males and 14 females; median age at diagnosis: 7 years; range 0.3-39 years) carried monoallelic variants, exhibiting a broad phenotypic spectrum. An additional prenatal diagnosis (at 23 weeks of gestation) was reported among heterozygous cases. In our cohort, ten previously unpublished causative variants were identified. A systematic assessment of skeletal muscle involvement revealed a severe myofibrillar disarray in one case. This study provides a comprehensive and systematic phenotypic characterization of patients across the spectrum of PIEZO2-related disorders. Our findings support a clear clinical distinction between recessive and dominant forms. The clinical manifestations extend beyond the peripheral nervous system and the Merkel cells, suggesting a broader PIEZO2 tissue expression during early developmental stages. Dominant PIEZO2-related disorders are heterogeneous, ranging from mild to severe forms. Our study also suggests that many patients exhibit a respiratory involvement, emphasizing the need for regular respiratory follow-up in the long-term clinical management of both dominant and recessive forms.

Background: Hemophilia A, an X‐linked bleeding disorder caused by pathogenic variants in the F8 gene, requires precise genetic diagnosis for optimal management. Conventional stepwise sequence and copy number variation (CNV) analyses are time‐consuming and may leave some cases unresolved. Objectives: To evaluate the effectiveness of combining next‐generation sequencing (NGS)‐based sequence and CNV analysis in a single step for resolving previously undiagnosed Hemophilia A cases and identifying differential diagnoses. Methods: A cohort of 578 male patients with Factor VIII deficiency was assessed. Initial analyses included intron 22/intron 1 inversion testing and/or F8 sequencing. Twenty‐seven unresolved cases underwent a targeted 57‐gene coagulopathy panel using NGS with CNV analysis; CNVs were confirmed by multiplex ligation‐dependent probe amplification (MLPA). Results: The integrated NGS approach resolved 19 of 27 unresolved cases, increasing the overall diagnostic yield from 95.3% to 98.6%. Ten CNVs in F8 (8 deletions, 2 duplications) were identified and confirmed by MLPA. Variants in VWF and LMAN1 genes led to diagnoses of von Willebrand disease ( n = 6) and combined Factor V/VIII deficiency ( n = 1). One F8 intronic variant was detected, while 8 cases remained unresolved by the NGS‐based approach. Conclusions: Integrating NGS‐based CNV analysis into genetic diagnostic workflows enables simultaneous detection of sequence variants and CNVs, improves diagnostic yield, and facilitates identification of related bleeding disorders. This streamlined approach supports adoption as a first‐line test for mild/moderate Hemophilia A and a secondary test for severe cases.

Background: Optical genome mapping (OGM) is a novel technology that enables high-resolution detection of structural variants. This study aimed to evaluate the diagnostic contribution of OGM in early-onset developmental epileptic encephalopathies (DEEs) with unresolved genetic causes. Materials and methods: A total of 38 children with early-onset DEEs (aged 0–18 years) who remained undiagnosed despite conventional karyotyping, chromosomal microarray analysis (CMA) and whole-exome sequencing (WES) were included. All patients underwent detailed phenotypic reassessment and WES reanalysis. One patient received a definitive molecular diagnosis following WES reanalysis. Four patients subsequently withdrew consent, and one patient was excluded due to inadequate DNA quality for OGM. OGM was therefore performed in the remaining 32 patients. Potential OGM findings were validated using appropriate laboratory techniques. Results: Among the 32 patients who underwent OGM, three candidate structural variants were identified. Two variants (2/32, 6.3%), ogm[GRCh38] ins(X;?)(q27.3;?) and ogm[GRCh38] 6p24.1 (13083829_13279761)x1, were confirmed using orthogonal validation methods, resulting in the molecular diagnoses of Fragile X syndrome and PHACTR1- related DEE, respectively. Conclusion: OGM contributed to the identification of clinically relevant structural variants in genetically undiagnosed early-onset DEEs. These findings support the complementary role of OGM in the genetic evaluation of complex neurodevelopmental disorders.

Background: The disruption of neural progenitor proliferation is a key mechanism underlying primary microcephaly, yet how cell cycle arrest leads to progenitor loss remains only partially understood. Cyclin-dependent kinases, CDK4 and CDK6, are central regulators of the G₁/S transition, but their role in cellular stress responses during neurodevelopment remains unclear. Methods: We studied fibroblasts from affected individuals in two families: siblings homozygous for a CDK4 frameshift (p.Glu94Argfs*65) presenting with microcephaly and pontine hypoplasia and a child homozygous for a CDK6 missense variant (p.Thr154Ile) with microcephaly, brain atrophy, neutropenia and ovarian failure. Results: Loss-of-function variants in CDK4 and CDK6 , core G₁/S regulators, impaired proliferation and induced mitochondrial stress responses and apoptosis. Mutant fibroblasts exhibited significantly reduced DNA synthesis and cell cycle progression, along with increased mitochondrial activity, elevated reactive oxygen species and increased apoptosis. Mitochondrial responses differed by gene: CDK4 deficiency caused mitochondrial hyperpolarisation, while CDK6 deficiency resulted in depolarisation, suggesting differences in mitochondrial apoptotic dynamics. Both variants affected mTOR pathway signalling, linking cell cycle kinase loss to disrupted metabolic regulation. Conclusion: These findings uncover a previously unrecognised mitochondrial stress response accompanying proliferative failure, offering mechanistic insight into how cell cycle arrest could lead to neural progenitor depletion and brain growth disorders. More broadly, our results connect cyclin-dependent kinase dysfunction with mitochondrial homeostasis in neurodevelopment, highlighting shared pathways with neurodegeneration and cancer.

A subset of genetic conditions, particularly skeletal dysplasias, comprises a heterogeneous group of inherited disorders characterized by abnormal bone development, joint stiffness, and short stature. Their musculoskeletal manifestations frequently mimic those of rheumatic diseases, especially Juvenile Idiopathic Arthritis (JIA), complicating accurate diagnosis. We conducted a comprehensive clinical, radiological, and molecular evaluation of 47 individuals (23 males, 24 females) from 22 distinct families who presented primarily with non‐inflammatory musculoskeletal complaints. Genomic investigations included targeted next‐generation sequencing panels, chromosomal microarray analysis, and multiplex ligation‐dependent probe amplification. Pathogenic or likely pathogenic variants were identified in all cases, establishing the following diagnoses: Hereditary Multiple Exostoses (n = 9), Camptodactyly‐Arthropathy‐Coxa Vara‐Pericarditis syndrome (n = 12), Progressive Pseudorheumatoid Dysplasia (n = 7), Trichorhinophalangeal Syndrome types I/II (n = 5), Spondyloenchondrodysplasia with Immune Dysregulation (n = 6), Pseudoachondroplasia (n = 3), Primary Hypertrophic Osteoarthropathy type 1 (n = 1), Ehlers–Danlos Syndrome (n = 2), Multicentric Osteolysis‐Nodulosis‐Arthropathy (n = 1), and Mucopolysaccharidosis type VI (n = 1). Certain genetic disorders may present with musculoskeletal manifestations that closely resemble those of rheumatic diseases. Therefore, a comprehensive evaluation for underlying genetic causes is essential in patients with non‐inflammatory skeletal findings, as it improves diagnostic precision and guides appropriate management strategies. This study aims to investigate the clinical and molecular features of patients with non‐inflammatory musculoskeletal involvement, with a particular focus on the phenotypic overlap between genetic disorders and rheumatic diseases. Furthermore, seven novel variants were identified, expanding the mutational spectrum associated with these rare conditions and contributing new insights to the existing literature.