PROCEEDINGS |
GLEPP1, a membrane tyrosine phosphatase, is found exclusively on glomerular podocytes of adult kidneys and chiefly on foot processes of these cells. To investigate the expression patterns of GLEPP1, we cloned its full length cDNA from newborn mouse kidney. Computer sequence analysis showed that mouse GLEPP1 encoded a protein of ~135 kD, was ~91% identical to human and rabbit GLEPP1, and contained 9-11 additional amino acid residues in the ectodomain. Northern analysis showed a transcript of ~6 kb in E15 and newborn kidney that became ~3 fold more abundant in adult kidney. In situ hybridization showed that GLEPP1 mRNA was first detected in immature podocytes of comma- and S-shaped nephric structures. GLEPP1 protein was not seen by immunofluorescence or immunogold electron microscopy until the capillary loop stage however, when it was found on all membrane surfaces of developing podocytes. As these cells differentiated, GLEPP1 protein was detected most abundantly on foot processes, and no specific labeling was found elsewhere in the kidney. Although the ligand for GLEPP1 is not known, its expression pattern is consistent for a role in podocyte foot process development and maintenance.