Primary Gene Structure and Expression Studies of Rodent Paracellin-1

Abstract

ABSTRACT. The novel member of the claudin multigene family, paracellin-1/claudin-16, encoded by the genePCLN1, is a renal tight junction protein that is involved in the paracellular transport of magnesium and calcium in the thick ascending limb of Henle’s loop. Mutations in humanPCLN1are associated with familial hypomagnesemia with hypercalciuria and nephrocalcinosis, an autosomal recessive disease that is characterized by severe renal magnesium and calcium loss. The complete coding sequences of mouse and ratPcln1and the murine genomic structure are here presented. Full-length cDNAs are 939 and 1514 bp in length in mouse and rat, respectively, encoding a putative open-reading frame of 235 amino acids in both species with 99% identity. Exon-intron analysis of the human and mouse genes revealed a 100% homology of coding exon lengths and splice-site loci. By radiation hybrid mapping, the murinePcln1gene was assigned directly to marker D16Mit133 on mouse chromosome 16 (syntenic to a locus on human chromosome 3q27, which harbors the humanPCLN1gene). Mouse multiple-tissue Northern blot showedPcln1expression exclusively in the kidney. The expression profile along the nephron was analyzed by reverse transcriptase-PCR on microdissected nephron segments and immunohistochemistry of rat kidney. Paracellin-1 expression was restricted to distal tubular segments including the thick ascending limb of Henle’s loop, the distal tubule, and the collecting duct. The identification and characterization of the rodentPcln1genes provide the basis for further studies of paracellin-1 function in suitable animal models.