POSTER NO: 592

Two VHL Germline Mutations in a Family with Distinct VHL-Phenotype

¹Gregor Weirich, ²Thorsten Wöhl, ³Hiltrud Brauch
¹Institute of Pathology, Technische Universität München, Trogerstrasse 18, D-81675 München, Germany, ²Wilex Biotechnology GmbH, Grillparzerstrasse 10, D-81675 München, Germany, ³Dr. Margarete Fischer Bosch Institute for Clinical Pharmacology, Auerbachstrasse 112, D-70376 Stuttgart, Germany

Background: The VHL tumor suppressor gene is involved in hereditary and sporadic tumors. VHL germline mutations predispose to von Hippel-Lindau disease (VHL), a tumor syndrome involving multiple sites including eyes, cerebellum, spinal cord, kidney, adrenal gland, pancreas and epididymis. VHL is distinguished into type 1 disease without pheochromocytoma, and type 2 disease with pheochromocytoma. Somatic VHL mutations are mainly associated with renal cell carcinoma. VHL encodes the pVHL protein that interacts with ElonginC and ElonginB to form a ternary complex VCB involved in regulatory functions including controlled protein degradation. There are more than 140 known germline mutations many of which destabilize the VCB complex. Most frequently mutations are associated with the development of vascular tumors. However, some germline mutations show a preponderance for adrenal gland tumors. These mutations are located at nucleotides affecting amino acid changes in the pVHL alpha- or beta-domain critical for protein-protein interaction. Two important pheochromacytoma associated VHL mutations are at nucleotide 505 affecting the pVHL beta-domain, and at nucleotides 712/713 affecting the pVHL alpha-domain. Carriers of these mutations differ phenotypically with a low or high risk for additional renal cell carcinoma. Here we describe a family with two VHL germline mutations affecting both the pVHL alpha- and beta-domain resulting in a pheochromocytoma only phenotype. Methods: Among 18 members of a VHL family 9 members were previously diagnosed for pheochromocytoma and identified to carry a nucleotide 775 C>G (Leu188Val) germline mutation (Glavac et al. Hum Genet 98:271-280, 1996). Repeated analysis of the entire VHL gene was performed with published primers for exon 1, 2 and 3 as well as novel primers 1-3F, 1-3R for exon 1. Analytical methods included SSCP, DHPLC and sequencing analysis. Lymphocyte DNA of 100 individuals without disease was used for controls. Results: In addition to the previously identified 775 (C>G; Leu188Val) germline mutation refined VHL mutation analysis detected a second co-segregating mutation at nucleotide 454 (C>T; Pro81Ser) in all patients. Also, both mutations were identified presymptomatically in a new familiy member. Control samples showed no indication of any mutations. Conclusions: Refined VHL analysis detected a second germline mutation predicted to cause a proline to serine change at amino acid 81 in the pVHL beta-domain, which may influence the phenotypic consequences of VHL disease resulting in the rare pheochromocytoma only phenotype (VHL type 2C).