Small proline-rich (SPR) proteins are structural components of the cornified cell envelope of stratified squamous epithelia. They are subdivided into three families, i.e., SPR1, SPR2, and SPR3, of which the SPR2 family is the most complex. To understand the significance of this complexity, we have isolated 11 mouse Sprr2 genes, constructed a provisional physical map of the Sprr2 locus on mouse Chromosome 3, and examined the expression patterns of the Sprr2 genes in mouse epithelial tissues. The 11 Sprr2 sequences are highly conserved with a central domain containing a variable number of repeats. In situ hybridization showed the Sprr2 expression to be confined to epithelia. RT-PCR using primers specific for each of the 11 Sprr2 members demonstrated varying degrees of expression among the individual Sprr2 members in different tissues. The correlation between the physical location of the genes in the Sprr2 locus and their expression patterns suggests multiple levels of controlled expression.
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