Cloning and expression of the rat nephrin homolog

Despite of the increased availability of genetically modified mouse strains , the experimental models in the rat have provided the most widely employed and versatile models for the study of renal pathophysiology and functional genetics. The identification of the human gene mutated in the congenital n ephrotic syndrome of the Finnish type (NPHS1) has recently been reported, a nd its protein product has been termed nephrin. Here we report the molecula r cloning and characterization of rat nephrin cDNA, Rat nephrin cDNA has an open reading frame of 3705 bp, shows 82% sequence identity with human neph rin cDNA, and shows characteristic rat-specific splicing variants. The tran slated nucleotide sequence has 89% sequence identity at the amino acid leve l. The signal sequence, glycosylation, and cysteine localization patterns a re nearly identical to those of human nephrin. As in the human, the rat nep hrin transcript is expressed in a tissue-restricted pattern. Antipeptide an tibodies raised to the intracellular nephrin-specific domain identified imm unoreactivity exclusively within the rat kidney glomerulus by indirect immu nofluorescence. Initial results with semiquantitative reverse transcriptase -polymerase chain reaction analysis showed a remarkable down-regulation of nephrin-specific mRNA in the puromycin nephrosis of the rat.