SOX10 Mutation Screening for 117 Patients with Kallmann Syndrome.

INTRODUCTION: Kallmann syndrome (KS) is a genetically heterogeneous condition characterized by hypogonadotropic hypogonadism (HH) and olfactory dysfunction. Although SOX10, a causative gene for Waardenburg syndrome (WS) and peripheral demyelinating neuropathy, central demyelination, WS, and Hirschsprung disease (PCWH) has previously been implicated in KS, the clinical significance of SOX10 variants as the cause of KS remains uncertain. PATIENTS AND METHODS: A total of 117 patients with KS underwent mutation screening of SOX10 and 14 other causative genes for KS/HH. Rare SOX10 variants were subjected to in silico and in vitro analyses. We also examined clinical data of the patients and their parents with SOX10 variants. RESULTS: Sequence analysis identified 2 heterozygous variants of SOX10 (c.1225G > T, p.Gly409* and c.475C > T, p.Arg159Trp) in patients 1-3, as well as in the parents of patients 1 and 3. The variants were assessed as pathogenic/likely pathogenic, according to the American College of Medical Genomics guidelines. Both variants lacked in vitro transactivating activity for the MITF promoter and exerted no dominant-negative effects. Patients 1-3 carried no pathogenic variants in other genes examined. The patients presented with typical KS, while such features were absent in the parents of patients 1 and 3. None of the 5 variant-positive individuals exhibited hypopigmentation, while 1 and 2 individuals exhibited complete and partial hearing loss, respectively. CONCLUSION: These results provide evidence that SOX10 haploinsufficiency accounts for a small percentage of KS cases. SOX10 haploinsufficiency is likely to be associated with a broad phenotypic spectrum, which includes KS without other clinical features of WS/PCWH.

MODY3, renal cysts, and Dandy-Walker variants with a microdeletion spanning the HNF1A gene.

Heterozygous hepatocyte nuclear factor-1-α gene (HNF1A) mutations are the most common cause of maturity-onset diabetes of the young (MODY), but they rarely involve extrahepatic manifestations. Renal cysts and diabetes syndrome can be caused by HNF1B mutations. No association between MODY3 and Dandy-Walker variants (DWV) has been reported. HNF1A mutations might be responsible for renal malformations. In a Japanese girl with glycosuria, developmental delay, mental retardation, renal cysts, and DWV, the HNF1B gene had no mutations. Array comparative genomic hybridization analysis identified a de-novo interstitial 12q24.22-q24.31 deletion of 5.6 Mb encompassing the HNF1A gene, which is compatible with a diagnosis of MODY3. The variety of phenotypes suggests a novel microdeletion syndrome spanning the HNF1A gene. Because HNF1B functions as an HNF1A/HNF1B heterodimer, haploinsufficient HNF1A interacts with a certain HNF1B haplotype. The resulting truncated heterodimer might engender renal cysts. More patients with well-defined deletion within 12q.24.31 must be evaluated to produce a detailed genotype-phenotype correlation and to elucidate this emerging microdeletion syndrome.
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