Molecular mechanisms governing the development of the mammalian cochlea, the hearing organ, remain largely unknown. Through genome sequencing in 3 subjects from 2 families with nonsyndromic cochlear aplasia, we identified homozygous 221-kb and 338-kb deletions in a noncoding region on chromosome 8 with an approximately 200-kb overlapping section. Genomic location of the overlapping deleted region started from approximately 350 kb downstream of GDF6, which codes for growth and differentiation factor 6. Otic lineage cells differentiated from induced pluripotent stem cells derived from an affected individual showed reduced expression of GDF6 compared with control cells. Knockout of Gdf6 in a mouse model resulted in cochlear aplasia, closely resembling the human phenotype. We conclude that GDF6 plays a necessary role in early cochlear development controlled by cis-regulatory elements located within an approximately 500-kb region of the genome in humans and that its disruption leads to deafness due to cochlear aplasia.

Prostate cancer is the most common cause of cancer deaths in men and is a major health problem worldwide. Methylene tetrahydrofolate reductase (MTHFR) plays an important role for folate metabolism and is also an important source for DNA methylation and DNA synthesis (nucleotide synthesis). The objective of this study was to investigate the relationship between the A1298C and C677T polymorphisms of the MTHFR gene and prostate cancer in the Turkish population. In our study, 93 prostate cancer patients between the ages of 50–89 and a control group of 166 benign prostate hyperplasia patients were evaluated. C677T and A1298C polymorphism ratios were compared among these two groups, and an analysis was made to see if there is a statistically meaningful difference. In this study, it has been observed that C677T polymorphism of the MTHFR gene produces no statistically significant difference for T allele frequency and the genotype frequency in prostate cancer patients and male controls with benign prostate hyperplasia not having prostate cancer, whereas it has been observed that A1298C polymorphism produces a statistically significant difference for C allele frequency in prostate cancer patients and controls and that it also produces a statistically marginal significance for genotype frequencies.

Chromosome 16 is one of the gene-rich chromosomes; however, approximately 10% of the chromosome 16 sequence is composed of segmental copies, which renders this chromosome instable and predisposes it to rearrangements via frequent nonallelic homologous recombination. Microarray technologies have enabled the analysis of copy number variations (CNV), which may be associated with the risk of developing complex diseases. Through comparative genomic hybridisation in 1,298 patients, we detected 18 cases with chromosome 16 CNV. We identified 2recurrent CNV regions, including 1 at 16p13.11 in 4 patients and another at 16p11.2 in 7 patients. We also detected atypical chromosome 16 rearrangements in 7 patients. Furthermore, we noted an increased frequency of co-occurring genomic changes, supporting the two-hit hypothesis to explain the phenotypic variability in the clinical presentation of CNV syndromes. Our findings can contribute to the creation of a chromosome 16 disease map based on regions that may be associated with disease development.

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant disorder with a variable clinical phenotype including synophrys, hypertelorism, thick eyebrows, long eyelashes, wide nasal bridge, long philtrum, hypertrichosis, growth retardation, and intellectual disability. Cornelia de Lange syndrome (CdLS) is a rare disease characterized by synophrys, long eyelashes, limb abnormalities, generalized hirsutism, growth retardation, and intellectual disability. In both WDSTS and CdLS, the malformations are due to transcriptome disturbance caused by defects in the genes encoding the components of chromatin regulation and transcription process. The overlapping features in these two syndromes may complicate the original diagnosis of a patient. Here, we report on a Wiedemann-Steiner patient found to have a de novo pathogenic KMT2A variation who had been clinically suspected as CdLS. We suggest that targeted next-generation sequencing is a feasible tool for the precise diagnosis of patients who have phenotypically and clinically overlapping features of CdLS and WDSTS.

Objective: The aim of this study was to investigate the molecular basis of maturity-onset diabetes of the young (MODY) by targeted-gene sequencing of 20 genes related to monogenic diabetes, estimate the frequency and describe the clinical characteristics of monogenic diabetes and MODY in the Trakya Region of Turkey. Methods: A panel of 20 monogenic diabetes related genes were screened in 61 cases. Illumina NextSeq550 system was used for sequencing. Pathogenicity of the variants were assessed by bioinformatics prediction software programs and segregation analyses. Results: In 29 (47.5%) cases, 31 pathogenic/likely pathogenic variants in the GCK, ABCC8, KCNJ11, HNF1A, HNF4A genes and in 11 (18%) cases, 14 variants of uncertain significance (VUS) in the GCK, RFX6, CEL, PDX1, KCNJ11, HNF1A, G6PC2, GLIS3 and KLF11 genes were identified. There were six different pathogenic/likely pathogenic variants and six different VUS which were novel. Conclusion: This is the first study including molecular studies of twenty monogenic diabetes genes in Turkish cases in the Trakya Region. The results showed that pathogenic variants in the GCK gene are the leading cause of MODY in our population. A high frequency of novel variants (32.4%-12/37) in the current study, suggests that multiple gene analysis provides accurate genetic diagnosis in MODY.