Primary gene structure and expression studies of rodent paracellin-1

The novel member of the claudin multigene family. paracellin-1/claudin-16, encoded by the gene PCLN1, is a renal tight junction protein that is involv ed in the paracellular transport of magnesium and calcium in the thick asce nding limb of Henle's loop. Mutations in human PCLN1 are associated with fa milial hypomagnesemia with hypercalciuria and nephrocalcinosis, an autosoma l recessive disease that is characterized by severe renal magnesium and cal cium loss. The complete coding sequences of mouse and rat Pcln1 and the mur ine genomic structure are here presented. Full-length cDNAs are 939 and 151 4 bp in length in mouse and rat. respectively, encoding a putative open-rea ding frame of 235 amino acids in both species with 99% identity. Exon-intro n analysis of the human and mouse genes revealed a 100% homology of coding exon lengths and splice-site loci. By radiation hybrid mapping, the murine Pcln1 Gene was assigned directly to marker D 16Mit133 on mouse chromosome 1 6 (syntenic to a locus on human chromosome 3q27, which harbors the human PC LN1 gene), Mouse multiple-tissue Northern blot showed Pcln1 expression excl usively in the kidney. The expression profile along the nephron was analyze d by reverse transcriptase-PCR on microdissected nephron segments and immun ohistochemistry of rat kidney. Paracellin-1 expression was restricted to di stal tubular seg, merits including the thick ascending limb of Henle's loop , the distal tubule, and the collecting duct, The identification and charac terization of the rodent Pcln1 genes provide the basis for further studies of paracellin-1 function in suitable animal models.