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RESEARCH |
J Bayley, Department of Human Genetics, Leiden University Medical Centre, Leiden, 2300 RC , Netherlands
M Weiss, Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
A Grimbergen, Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
B van Brussel, Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
F Hes, Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
J Jansen, ENT, LUMC, Leiden, Netherlands
S Verhoef, The Netherlands Cancer Institute, Amsterdam, Netherlands
P Devilee, Department of Pathology and Department of Human and Clinical Genetics, Leiden University Medical Centre, Leiden, Netherlands
E Corssmit, Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, Netherlands
A Vriends, Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
Correspondence: Jean-Pierre Bayley, Email: J.P.L.Bayley{at}lumc.nl
Abstract
A major cause of paraganglioma and pheochromocytoma is germline mutation of the tumor suppressor genes SDHB, SDHC and SDHD, encoding subunits of succinate dehydrogenase (SDH). While many SDH missense/nonsense mutations have been identified, few large deletions have been described. We performed MLPA deletion analysis in 126 point-mutation negative patients and here we describe four novel deletions of SDHD and SDHC. Long-range PCR was used for the fine mapping of deletions. One patient had a 10kb AluSg-AluSx mediated deletion including SDHD exons 1 and 2, the entire TIMM8B gene and deletion of exons of C11orf57. A second patient had a deletion of SDHD exons 1 and 2 and exon 1 of the TIMM8B gene. A third patient showed a deletion of exon 2 of SDHD, together with a 235bp MIRb-Tensin gene insertion. In a fourth patient, a deletion of exons 5 and 6 of the SDHC gene was found, only the second SDHC deletion currently known. The deletions of the TIMM8B and C11orf57 genes are the first to be described but do not appear to result in an additional phenotype in these patients. Four of the eight breakpoints occurred in Alu sequences and all 3 SDHD deletions showed an intron 2 breakpoint. This study underlines the fact that clinically relevant deletions may encompass neighbouring genes, with the potential to modify phenotype. Gene deletions of SDHD and SDHC represent a substantial proportion of all mutations, and must be considered in paraganglioma patients shown to be negative for mutations by sequencing.
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