A germ-line insertion in the Birt–Hogg–Dubé (BHD) gene gives rise to the Nihon rat model of inherited renal cancer

摘要

A rat model of hereditary renal carcinoma (RC) was found in a rat colony of the Sprague–Dawley strain in Japan and named the “Nihon” rat. In heterozygotes, RCs, predominantly the clear cell type, develop from early preneoplastic lesions, which began to appear as early as 3 weeks of age, to adenocarcinomas by the age of 6 months. The Nihon rat is an example of a Mendelian dominantly inherited predisposition for development of RCs like the Eker (Tsc2 gene mutant) rat. We have previously shown that the Nihon mutation was tightly linked to genes that are located on the distal part of rat chromosome 10. The order of the genes is the Eker (Tsc2 gene (human 16p13.3)–Il3 gene–Nihon gene–Llgl1 locus– Myhse gene. We now describe a germ-line mutation in the Birt–Hogg–Dubé gene (Bhd) (human 17p11.2) caused by the insertion of a single nucleotide in the Nihon rat, resulting in a frameshift and producing a stop codon 26 aa downstream. We found that the homozygous mutant condition was lethal at an early stage of fetal life in the rat. We detected a high frequency of loss of heterozygosity (LOH) in primary RCs (10/11) at the Bhd locus and found a point mutation (nonsense) in one LOH-negative case, fitting Knudson's “two-hit” model. The Nihon rat may therefore provide insights into a tumor-suppressor gene that is related to renal carcinogenesis and an animal model of human BHD syndrome.