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PubMed2002

Alterations of the SDHD gene locus in midgut carcinoids, Merkel cell carcinomas, pheochromocytomas, and abdominal paragangliomas.

Several types of endocrine tumors show frequent somatic deletions of the distal part of chromosome arm 11q, where the tumor-suppressor gene SDHD (succinate-ubiquinone oxidoreductase subunit D), constitutionally mutated in paragangliomas of the head and neck, is located. In this study, we screened 18 midgut carcinoids, 7 Merkel cell carcinomas, 46 adrenal pheochromocytomas (37 sporadic and 9 familial), and 7 abdominal paragangliomas for loss of heterozygosity (LOH) and/or mutations at the SDHD gene locus. LOH was detected in 5 out of 8 (62%) informative midgut carcinoids, in 9 out of 30 (30%) sporadic pheochromocytomas, in none of the familial pheochromocytomas (0%), and in 1 out of 6 (17%) abdominal paragangliomas. No sequence variants were detected in the pheochromocytomas or paragangliomas. However, two constitutional putative missense mutations, H50R and G12S, were detected in two midgut carcinoids, which were both associated with LOH of the other allele. The same sequence variants were also detected in two Merkel cell carcinomas. In addition, the S68S polymorphism was found to coexist with the G12S sequence variant in both cases. In conclusion, we show that alterations of the SDHD gene seem to be involved in the tumorigenesis of both midgut carcinoids and Merkel cell carcinomas.

Abdominal Neoplasms↗
PubMed2001

Novel mutations in the SDHD gene in pedigrees with familial carotid body paraganglioma and sensorineural hearing loss.

Paraganglioma (PGL) is a rare disorder characterized by tumors of the head and neck region. Between 10% and 50% of cases of PGL are familial, and the disease is autosomal dominant and subject to age-dependent penetrance and imprinting. The paraganglioma gene (PGL1) has been mapped to 11q22.3-q23, and recently germline mutations in the SDHD gene have been identified. The SDHD region contains another gene, DPP2/TIMM8B, the homolog of which causes dystonia and deafness seen in Mohr-Tranebjaerg syndrome. Using four PGL pedigrees, two of which exhibit coinheritance of PGL and sensorineural hearing loss or tinnitus, analysis of 14 microsatellite markers provided support for linkage to the PGL1 locus. Sequence analysis identified novel mutations in exon 1 and exon 3 of the SDHD gene, including a novel two base pair deletion in exon 3 creating a premature stop codon at position 67; a novel three base pair deletion in exon 3 resulting in the loss of Tyr-93; a missense mutation in exon 3 resulting in the substitution of Leu-81 for Pro-81; and a novel G-to-C substitution in exon 1 resulting in the substitution of Met-1 for Ile-1. No base changes were detected in the DPP2/TIMM8B gene. There was no apparent loss of heterozygosity at the site of the SDHD mutations. However, RT-PCR analysis of tumor samples showed monoallelic expression of the mutant (paternal) allele as expected for imprinting. This has not previously been shown for this disorder. The inheritance and expression of the SDHD gene is consistent with the PGL1 gene being subject to genomic imprinting.

Adolescent↗