Mutation of TRPM6 causes familial hypomagnesemia with secondary hypocalcemia.

Familial hypomagnesemia with secondary hypocalcemia (OMIM 602014) is an autosomal recessive disease that results in electrolyte abnormalities shortly after birth. Affected individuals show severe hypomagnesemia and hypocalcemia, which lead to seizures and tetany. The disorder has been thought to be caused by a defect in the intestinal absorption of magnesium, rather than by abnormal renal loss of magnesium. Restoring the concentrations of serum magnesium to normal values by high-dose magnesium supplementation can overcome the apparent defect in magnesium absorption and in serum concentrations of calcium. Life-long magnesium supplementation is required to overcome the defect in magnesium handling by these individuals. We previously mapped the gene locus to chromosome 9q in three large inbred kindreds from Israel. Here we report that mutation of TRPM6 causes hypomagnesemia with secondary hypocalcemia and show that individuals carrying mutations in this gene have abnormal renal magnesium excretion.

Seizure 6-like (SEZ6L) gene and risk for lung cancer.

DNA pooling in combination with high-throughput sequencing was done as a part of the Sequenom-Genefinder project. In the pilot study, we tested 83,715 single nucleotide polymorphisms (SNP), located primarily in gene-based regions, to identify polymorphic susceptibility variants for lung cancer. For this pilot study, 369 male cases and 287 controls of both sexes (white Europeans of Southern German origin) were analyzed. The study identified a candidate region in 22q12.2 that contained numerous SNPs showing significant case-control differences and that coincides with a region that was shown previously to be frequently deleted in lung cancer cell lines. The candidate region overlies the seizure 6-like (SEZ6L) gene. The pilot study identified a polymorphic Met430Ile substitution in the SEZ6L gene (SNP rs663048) as the top candidate for a variant modulating risk of lung cancer. Two replication studies were conducted to assess the association of SNP rs663048 with lung cancer risk. The M. D. Anderson Cancer Center study included 289 cases and 291 controls matched for gender, age, and smoking status. The Liverpool Lung Project (a United Kingdom study) included 248 cases and 233 controls. Both replication studies showed an association of the rs663048 with lung cancer risk. The homozygotes for the variant allele had more than a 3-fold risk compared with the wild-type homozygotes [combined odds ratio (OR), 3.32; 95% confidence interval (95% CI), 1.81-7.21]. Heterozygotes also had a significantly elevated risk of lung cancer from the combined replication studies with an OR of 1.15 (95% CI, 1.04-1.59). The effect remained significant after adjusting for age, gender, and pack-years of tobacco smoke. We also compared expression of SEZ6L in normal human bronchial epithelial cells (n = 7), non-small cell lung cancer (NSCLC; n = 52), and small cell lung cancer (SCLC; n = 22) cell lines by using Affymetrix HG-U133A and HG-U133B GeneChips. We found that the average expression level of SEZ6L in NSCLC cell lines was almost two times higher and in SCLC cell lines more than six times higher when compared with normal lung epithelial cell lines. Using the National Center for Biotechnology Information Gene Expression Omnibus database, we found a approximately 2-fold elevated and statistically significant (P = 0.004) level of SEZ6L expression in tumor samples compared with normal lung tissues. In conclusion, the results of these studies representing 906 cases compared with 811 controls indicate a role of the SEZ6L Met430Ile polymorphic variant in increasing lung cancer risk.

Molecular genetic analysis of NBS1 in German melanoma patients.

The aim of this study was to investigate the role of NBS1 in the pathogenesis of malignant melanoma of the skin. To exclude the common 657del5 founder mutation, a total of 376 melanoma patients from Southern Germany were analyzed for sequence alterations in exon 6 of NBS1 by direct sequencing. Analyses revealed one 657del5 mutation and three nonsynonymous sequence variations in exon 6 of NBS1 (V210F, R215W, and F222L). Analysis of an additional sample of 629 melanoma patients and 604 controls revealed no F222L mutation, indicating that this newly identified sequence alteration is not a common polymorphism. In a case-control association study including 632 melanoma patients and 615 cancer-free control participants from Southern Germany, three publicly known single nucleotide polymorphisms located in the NBS1 gene region were analyzed. No significant associations between single nucleotide polymorphisms (rs9995, rs867185 and rs1063045) or referring calculated haplotypes and melanoma risk were identified. These results suggest that NBS1 does not play a major role in predisposition to melanoma in the Southern German population but that alterations of this gene might contribute to the risk of this cancer.

BRCA1/2 mutation screening and LOH analysis of lung adenocarcinoma tissue in a multiple-cancer patient with a strong family history of breast cancer.

BACKGROUND: Germline mutations in BRCA1/2 greatly elevate risks of breast and ovarian cancers, but the role of these genes in tumourigenesis of other cancer types is still being investigated. OBJECTIVE: We report on an investigation of BRCA1/2 mutations and their loss of heterozygosity (LOH) in a patient with a strong family history of breast cancer who was diagnosed with consecutive primary cervical, ovarian and lung carcinomas. METHODS AND RESULTS: BRCA1/2 mutation screening of the proband revealed a common familial breast- and ovarian cancer-associated germline BRCA2 mutation (3034del4bp). We then performed LOH analysis for BRCA2 in lung adenocarcinoma tissue of the patient. Using the laser-capture microdissection (LCM) technique, we obtained pure populations of neoplastic cells from which DNA could be extracted. Mutation analysis by denaturing high-performance liquid chromatography (DHPLC) and direct sequencing revealed loss of the mutant allele in the adenocarcinoma tumour tissue. CONCLUSION: To our knowledge, this is the first report of investigation for LOH for BRCA2 in primary lung adenocarcinoma tissue of a patient with multiple primary tumours related to a familial germline BRCA2 mutation. Interestingly, it was the mutant, not the wild-type, allele which was lost in the lung adenocarcinoma tissue.

Colobomas of the iris and choroid and high signal intensity cerebral foci on T2-weighted magnetic resonance images in Klinefelter's syndrome.

A 5-year-old boy presented with ocular anomalies including microphthalmos, colobomas of the iris, choroid, and optic nerve head, and strabismus. Magnetic resonance imaging of the head showed multiple bilateral asymmetric high signal intensity foci in the subcortical and periventricular white matter. Genetic counseling disclosed a 47,XXY karyotype.

ARLTS1 variants and melanoma risk.

Variants in the tumor suppressor gene ARLTS1 (ADP-ribosylation factor-like tumor-suppressor gene 1) have been shown to influence familial cancer risk. Both Cys148Arg and Trp149Stop were associated with an increased risk of familial or high-risk familial breast cancer, respectively. We studied the impact of these gene variants on melanoma risk, investigating 351 melanoma patients and 804 control subjects. While ARLTS1 Trp149Stop did not influence melanoma risk (OR = 0.83, 95% CI = 0.37-1.88, p = 0.65), Cys148Arg revealed a statistically significant association with an increased risk for heterozygous carriers (OR = 1.43, 95% CI = 1.05-1.95, p = 0.02). An additional risk enhancement, though statistically non-significant, was observed in individuals with multiple melanomas (OR = 2.33, 95% CI = 0.87-6.26, p = 0.08).

Exclusion of BRAFV599E as a melanoma susceptibility mutation.

Very recently, BRAF mutations were found in about 2/3 of malignant melanomas and at lower frequencies in other human cancers. The BRAF gene codes for a protein in the mitogen-activated protein kinase (MAPK) pathway. All mutations identified to date are within the kinase domain, with a single missense mutation (V599E) accounting for 80%. We investigated the hypothesis that this common somatic BRAF mutation (V599E) would contribute to melanoma predisposition in familial and polygenic malignant melanoma if occurring as a germ-line mutation. We performed comprehensive mutational screening of exon 15 of BRAF using DHPLC (denaturing high-performance liquid chromatography) and DNA sequencing techniques. No V599E mutation could be detected in 172 melanoma patients comprising 46 familial cases, 21 multiple melanoma patients and 106 cases with at least one first-degree relative suffering from other cancers. We therefore conclude that the common somatic BRAF mutation V599E does not contribute to polygenic and familial melanoma predisposition.