Novel nonsense CDC73 mutations in Chinese patients with parathyroid tumors.

Hyperparathyroidism-jaw tumor syndrome (HPT-JT) is an autosomal dominant disease characterized by the occurrences of parathyroid tumors and ossifying fibroma of maxilla/mandible. It is caused by mutations in CDC73 gene and mutation carriers are at increased risk of parathyroid carcinoma. Hyperparathyroidism could be the sole manifestation. We reported two Chinese patients having parathyroid neoplasm with equivocal malignant potential and parathyroid carcinoma respectively with both germline and somatic CDC73 mutations detected. Both of them presented with severe hypercalcemia and primary hyperparathyroidism with no other HPT-JT associated tumors and negative family history. We identified one novel germline mutation CDC73 NM_024529.4: c.1475G > A; NP_078805.3: p.Trp492X and one novel somatic mutation CDC73 NM_024529.4: c.142G > T; NP_078805.3: p.Glu48X. The other germline mutation CDC73 NM_024529.4: c.226C > T; NP_078805.3: p.Arg76X and somatic mutation CDC73 NM_024529.4: c.85delG; NP_078805.3: p.Glu29SerfsX8 were previously reported. This is the first report of CDC73 mutations in the Chinese population. Genetic analysis is reliable to confirm the underlying hereditary basis of hyperparathyroidism. By identification of mutations, the patient and the family members could benefit from regular surveillance for early detection of tumors.

Is the c.3G>C mutation in the succinate dehydrogenase subunit D (SDHD) gene due to a founder effect in Chinese head and neck paraganglioma patients?

OBJECTIVES/HYPOTHESIS: Three Chinese patients with head and neck paragangliomas have been reported to carry the c.3G>C mutation in the succinate dehydrogenase subunit D (SDHD) gene. In addition, in our hospital, two further patients were identified who have the same mutation. It is unclear whether the c.3G>C mutation in Chinese patients is a recurrent mutation or if it is due to a founder effect. We conducted haplotype analysis on these patients to answer this question. STUDY DESIGN: Individual case-control study. METHODS: Germ-line mutations were confirmed in the patients and their families examined in this study using direct sequencing. We also constructed and analyzed haplotypes in four Chinese families. Genotype frequencies were compared to the control group. RESULTS: Three of four families shared the same haplotype, which rarely occurred in the control group. The last family shared a very short area on the physical map with the other three families. CONCLUSIONS: There is a founder effect in Chinese head and neck paraganglioma patients carrying the SDHD c.3G>C mutation.

Molecular basis of von Hippel-Lindau syndrome in Chinese patients.

BACKGROUND: Von Hippel-Lindau (VHL) syndrome is an autosomal dominant familial cancer syndrome predisposing the affected individuals to multiple tumours in various organs. The genetic basis of VHL in Southern Chinese is largely unknown. In this study, we characterized the mutation spectrum of VHL in nine unrelated Southern Chinese families. METHODS: Nine probands with clinical features of VHL, two symptomatic and eight asymptomatic family members were included in this study. Prenatal diagnosis was performed twice for one proband. Two probands had only isolated bilateral phaeochromocytoma. The VHL gene was screened for mutations by polymerase chain reaction, direct sequencing and multiplex ligation-dependent probe amplification (MLPA). RESULTS: The nine probands and the two symptomatic family members carried heterozygous germline mutations. Eight different VHL mutations were identified in the nine probands. One splicing mutation, NM_000551.2: c.463+1G > T, was novel. The other seven VHL mutations, c.233A > G [p.Asn78Ser], c.239G > T [p.Ser80Ile], c.319C > G [p.Arg107Gly], c.481C > T [p.Arg161X], c.482G > A [p.Arg161Gln], c.499C > T [p.Arg167Trp] and an exon 2 deletion, had been previously reported. Three asymptomatic family members were positive for the mutation and the other five tested negative. In prenatal diagnosis, the fetuses were positive for the mutation. CONCLUSIONS: Genetic analysis could accurately confirm VHL syndrome in patients with isolated tumours such as sporadic phaeochromocytoma or epididymal papillary cystadenoma. Mutation detection in asymptomatic family members allows regular tumour surveillance and early intervention to improve their prognosis. DNA-based diagnosis can have an important impact on clinical management for VHL families.

DNA-based diagnosis of malignant osteopetrosis by whole-genome scan using a single-nucleotide polymorphism microarray: standardization of molecular investigations of genetic diseases due to consanguinity.

Malignant osteopetrosis, a severe disease causing early infantile death in humans, is caused by mutations in the TCIRG1, CLCN7, or OSTM1 genes. We have established the molecular basis of malignant osteopetrosis in a Chinese family by means of whole-genome scans based on high-density single-nucleotide polymorphism (SNP) microarrays. Because the parents were consanguineous, the disease-causing locus should be located in an autozygous chromosomal region. Mapping revealed that among the three possible causal loci, only the CLCN7 gene was located in an autozygous region. Mutational analysis of the CLCN7 gene showed that the proband was homozygous for a novel missense mutation, p.I261F. p.I261 is located in helix F of the chloride channel, near a critical site for gating of the channel. This mapping study prepares the ground for future mutation studies by decreasing the burden of completely sequencing all possible loci for this disease. This approach can be used to standardize molecular investigations of genetic diseases due to consanguinity to a whole-genome scan and subsequent sequencing of the mapped disease gene.

Genome-wide detection of allelic imbalance in renal cell carcinoma using high-density single-nucleotide polymorphism microarrays.

OBJECTIVE: Renal cell carcinoma (RCC) appears in both a sporadic form and a hereditary form. Eighty-five percent of sporadic RCCs are of the clear-cell histologic type. The cytogenetic analysis of RCCs has revealed several recurring sites of chromosomal aberrations (non-disjunction, deletion or mitotic recombination) including segments of loss of heterozygosity (LOH) identifiable by polymorphic markers. In this pilot study, we performed a comprehensive genome-wide scan to identify LOH sites of RCCs in three Chinese patients using high-density single-nucleotide polymorphism microarrays (HuSNP arrays). DESIGN AND METHODS: Three sporadic clear-cell RCCs specimens were diagnosed histologically. Tumor genomic DNA was extracted from paraffin-embedded sections after microdissection to avoid gross contamination by non-tumor cells. Germline DNA was obtained from paired normal adjacent tissues. Affymetrix HuSNP mapping assay was performed according to the manufacturer's instructions. RESULTS: Using high-density single-nucleotide polymorphism microarrays, we were able to identify the previously described and new LOH sites in RCCs of the three Chinese patients. CONCLUSION: The high-density single-nucleotide polymorphism microarrays and assays offer significant operating cost benefits in sample preparation, processing, and data analysis for identification of LOH sites in cancer samples. In contrast to the typical microsatellite genotyping strategy, the entire genome scan is completed in one experiment taking less than 2 days.

DNA-based diagnosis of xeroderma pigmentosum group C by Whole-genome scan using single-nucleotide polymorphism microarray.

In this study, we have established the molecular basis of xeroderma pigmentosum (XP) in two unrelated Chinese families. In the first patient with consanguineous parents, we mapped the disease-causing locus XPC using single-nucleotide polymorphism microarray. Mutational analysis of the XPC gene showed that the patient is homozygous for a nonsense mutation, E149X. After developing DNA-based diagnosis of XPC, we screened another XP patient for XPC mutations. We found that the second patient is a compound heterozygote of 1209delG and Q554X in this gene. These are the first XPC-causing mutations identified in Chinese patients.

Novel mutations in the PATCHED gene in basal cell nevus syndrome.

Basal cell nevus syndrome (BCNS) is an autosomal dominant disease characterized by the presence of multiple basal cell carcinomas, odontogenic keratocysts, palmoplantar pits, and calcification in the falx cerebri caused by mutational inactivation of the PTCH gene. To investigate the molecular basis of BCNS in Chinese, we did a mutational analysis of the PTCH gene by performing denaturing high-performance liquid chromatography in three BCNS families. In this study, three novel mutations, two 1-bp frameshift insertions, i.e., 1468insA and 2392insC, and one 8-bp deletion, i.e., IVS5 + 1delGTAAGTGT, affecting a donor splice site, were identified. All the mutations cause a shift of the open reading frames and lead to premature termination of PTCH protein translation. Our results showed that mutational inactivation of the PTCH gene causes BCNS in Chinese.