cDNA cloning of the murine Pex gene implicated in X-linked hypophosphatemia and evidence for expression in bone. Du L; Desbarats M; Viel J; Glorieux FH; Cawthorn C; Ecarot B Genomics, 1996 Aug 15, 36: 22-8

The recently identified human PEX gene apparently encodes for a

neutral endopeptidase that is mutated in patients with X-linked

hypophosphatemia. The 3' and 5' ends of the coding region of PEX have

not been cloned, nor has the tissue expression of the gene been

identified. Here we report the isolation and characterization of the

complete open reading frame of the mouse Pex gene and the

demonstration of its expression in bone. Mouse Pex cDNA is predicted

to encode a protein of 749 amino acids with 95% identity to the

available human PEX sequence and significant homology to members of

the membrane-bound metalloendopeptidase family. Northern blot analysis

revealed a 6.6-kb transcript in bone and in cultured osteoblasts from

normal mice that was not detectable in samples from the Hyp mouse, the

murine homolog of human X-linked hypophosphatemia. Pex transcripts

were, however, detectable in Hyp bone by RT-PCR amplification. Of

particular interest, a cDNA clone from rat incisor shows 93% sequence

identity to the 5' end of Pex cDNA, suggesting that Pex may be

expressed in another calcified tissue, the tooth. The association of

impaired mineralization of bone and teeth and disturbed renal

phosphate reabsorption with altered expression of Pex suggests that

the Pex gene product may play a critical role in these processes.