Cloning of a new familial t(3;8) translocation associated with conventional renal cell carcinoma reveals a 5 kb microdeletion and no gene involved in the rearrangement.

This study describes the molecular cloning of a familial translocation, t(3;8)(p14.2;q24.2), that segregates with the conventional renal cell carcinoma (conventional RCC). We had previously reported the family history and, through loss of heterozygosity and comparative genomic hybridization, detected the loss of the 3p chromosome arm and somatic mutation in the retained von Hippel-Lindau gene in some members of the family. With the help of array painting and sequence tagged site-PCR on flow-sorted derivative chromosomes, we have cloned the breakpoints of the translocation. We have studied the junctions on both derivative chromosomes at the genomic and expression levels. The analysis of the sequence revealed a 5 kb microdeletion at the chromosome 3 breakpoint together with a high density of repetitive motifs (Alu, short interspersed nuclear element) and an AT-rich region. Both chromosome 3 and 8 rearranged regions were very poor in gene content. We tested an expressed sequence tag, two predicted genes, one novel gene and LRIG1, a gene located more than 200 kb apart from the breakpoint on chromosome 3. None of these genes, except LRIG1, showed expression in any of the tested tissues (including normal adult and fetal kidney, sporadic kidney tumours and tumour samples from the proband's family). Taken together, all these data suggest that, rather than deregulation of specific genes that may be rearranged by the translocation, the proposed three-step model of tumour development (translocation, loss of the 3p chromosome, and mutation in a tumour suppressor gene located within that region) could be the biological mechanism that takes place in this familial form of conventional RCC.