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

Abstract

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 locusMyhse gene. We now describe a germ-line mutation in the BirtHogg-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 (10͞11) 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.

Interaction of folliculin (Birt-Hogg-Dubé gene product) with a novel Fnip1-like (FnipL/Fnip2) protein

“…Homozygous mutants are embryonic lethal in both Eker and Nihon rats (Okimoto et al, 2004a). In 2004, we identified a germline mutation in the rat homolog of BHD (Bhd) (Okimoto et al, 2004b). Subsequently, we demonstrated a suppression of the Nihon rat's phenotypes by transgenic introduction of a wild-type Bhd mini-gene (Togashi et al, 2006).…”

“…A mouse monoclonal anti-HA (12CA5) antibody was from Roche. Anti-Flcn C1 antibody was reported previously (Okimoto et al, 2004b). Rabbit polyclonal anti-Flcn 223 antibody was generated against a synthetic peptide (CNTAFTPFLHQRNGNAARSL) corresponding to aminoacid residues (aa) 223-241 of human Flcn (IBL, Fujioka Japan).…”

The Drosophila homolog of the human tumor suppressor gene BHD interacts with the JAK-STAT and Dpp signaling pathways in regulating male germline stem cell maintenance

“…However, folliculin homologs were identified in many species, including Drosophila, Caenorhabditis elegans, mouse, dog and rat, implying a critical biological role for folliculin. Moreover, germline mutation in the rat and dog homologs of the BHD gene also resulted in inherited kidney tumors (Lingaas et al, 2003;Okimoto et al, 2004), suggesting that the BHD gene has a tumor suppressor function. Furthermore, recent evidence of somatic second-'hit' mutations in renal tumors from BHD patients (Vocke et al, 2005) strongly supports the Knudson 'two-hit' tumor suppressor model for BHD.…”

Transgenic rescue from embryonic lethality and renal carcinogenesis in the Nihon rat model by introduction of a wild-type Bhd gene

“…Establishment of transgenic Nihon rats carrying wild-type Bhd transgene We reported that rat Bhd gene consists of 13 exons and shows CpG island-like property near exon 1 (Okimoto et al, 2004b). In addition, we detected promoter activity in a 0.75 kb 5 0 -upstream sequence in cultured cells by reporter assay (our unpublished observation).…”

“…Sequence analysis revealed that there was an insertion of a cytosine (C) in a C tract within exon 3. This germline mutation results in a frameshift and produces a stop codon 26 amino-acids downstream (Okimoto et al, 2004b).…”