The involucrin genes of the mouse and the rat: study of their shared repeats

The involucrin genes of the mouse (Mus musculus) and the rat (Rattus norvegicus) have been cloned and sequenced. The coding region of each gene contains, at site P, a segment of repeats homologous to that of other nonanthropoid mammals. In contrast to the repeats of species belonging to different mammalian orders, many individual repeats of the mouse and the rat can be matched. Both before and after the divergence of the two species, these repeats have been the site of systematic alterations in nucleotide sequence. One of the alterations is the correction of nucleotides of one repeat by those of another. Corrected nucleotides may be closely linked to flanking nucleotides that are uncorrected; the systematic correction process therefore appears to be due to gene conversion. There is a stretch of 18 reiterated CAGs in the segment of repeats of the Mus gene; most of these reiterations were introduced recently, supporting the idea that the gene was generated originally from poly CAG. An antiserum to a synthetic peptide encoded by the segment of repeats of the Mus gene reveals differentiation-specific expression of the gene in the epidermis.