Genomic organisation of the mouse Ret proto-oncogene.

The RET proto-oncogene is involved in the development of both kidney and neural crests derived tissues. RET deleterious mutations cause hereditary neuroendocrine tumours and congenital intestinal agangliono-sis. Ongoing efforts aimed at elucidating the function of this gene include expression studies in different species and in transgenic mice. As first step in the study of Ret expression in mouse, we obtained the mouse Ret genomic structure. Intron-exon boundaries were determined and sequenced, all introns but the first one were amplified and cloned, and exons positioned in a restriction map. Mouse and human genes comparison indicates a highly conserved genomic organisation, except for exon 21 which is not conserved in mouse. A region extending 386 bp 5′ to the first exon was sequenced and compared with its human counterpart. Some features, reported for the human promoter, like the absence of TATA or CAAT boxes and a high GC content, are conserved.