Identification of novel mutations of the WFS1 gene in Brazilian patients with Wolfram syndrome

Objective: Wolfram syndrome (WS) is a rare, progressive, neurodegenerative disorder with an autosomal recessive pattern of inheritance. The gene for WS, WFS1, was identified on chromosome 4p16 and most WS patients carry mutations in this gene. However. some studies have provided evidence for genetic heterogeneity and the genotype-phenotype relationships are not clear. Our aim was to ascertain the spectrum of WFS1 mutations in Brazilian patients with WS and to examine the phenotype-genotype relationships in these patients. Design and methods: Clinical characterization and analyses of the WFS1. gene were performed in 27 Brazilian patients with WS from 19 families. Results: We identified 15 different mutations in the WFS1 gene in 26 patients, among which nine are novel. All mutations occurred in exon 8, except for one missense mutation which was located in exon 5. Although we did not find any clear phenotype-genotype relationship in patients with mutations in exon 8, the homozygous missense mutation in exon 5 was associated with a mild phenotype: onset of diabetes mellitus and optic atrophy during adulthood with good metabolic control being achieved with low doses of sulfonylurea Conclusions: Our data show that WFS1 is the major gene involved in WS in Brazilian patients and most mutations are concentrated in exon 8. Also, our study increases the spectrum of WFS1 mutations. Although no clear phenotype-genotype relationship was found for mutations in exon 8, a mild phenotype was associated with a homozygous missense mutation in exon 5.

Clinical and molecular characterization of Brazilian families with von Hippel-Lindau disease: a need for delineating genotype-phenotype correlation

von Hippel-Lindau (VHL) disease is an autosomal dominant hereditary cancer syndrome that predisposes to the development of a variety of benign and malignant tumours, especially cerebellar haemangioblastomas, retinal angiomas and clear-cell renal cell carcinomas (RCC). The etiology and manifestations are due to germline and somatic mutations in the VHL tumour suppressor gene. VHL disease is classified into type 1 and type 2, showing a clear genotype-phenotype correlation, as type 2 is associated with phaeochromocytoma and essentially caused by missense mutations. The aim of this study is to characterize the phenotype and genotype of families with VHL disease. Eighteen of twenty patients from ten unrelated families underwent genetic testing, nine of them fulfilled VHL disease criteria and one had an apparently sporadic cerebellar haemangioblastoma. Four different germline mutations in the VHL gene were identified: c.226_228delTTC (p.Phe76del); c.217C > T (p.Gln73X); IVS1-1 G > A and IVS2-1 G > C. The first three mutations were associated with type 1 disease and the last one with type 2B, which had never been identified in the germline. The transcriptional processing of a novel splice-site mutation was characterised. Three type 1 VHL families showed large deletions of the VHL gene, two of them encompassed the FANCD2/C3orf10 genes and were not associated with renal lesions. We also suggest that such families should be subclassified according to the risk of RCC and the extent of the VHL gene deletions. This study highlights the need for a through clinical and molecular characterisation of families with VHL disease to better delineate its genotype-phenotype correlation.