Figure 1

Podocin mRNA expression and sequence analysis reveals the existence of a podocin isoform and proves singular podocin extrarenal expression in human and murine testis. (a) Two podocin isoforms (Podo-1 and Podo-2) could be detected by RT–PCR analysis of kidney fetal (fet) and adult (adu) kidney RNA due to alternative splicing of the podocin pre-mRNA (right). The alternative mRNA form, missing 204 bp, was generated by skipping exon 5 of the NPHS2 gene, as could be confirmed by sequencing of the corresponding cDNA. GAPDH RNA was selected as an endogenous RNA control (GAPDH), mRNA of a renal clear cell carcinoma (derived from tubular cells) was used as a negative control (−). Lane M, 100 bp DNA ladder. (b) Constant expression of both isoforms; podocin isoform 1 (Podo-1) and podocin isoform 2 (Podo-2) in three different healthy kidneys (1, 2 and 3) demonstrates that isoform 2 is constitutively expressed and is not an allelic variant of the NPHS2 gene. (c) RT–PCR analysis of podocin expression in human testis (Te), pancreas (Pa) and brain (Br). Podocin isoform 1 was only detected in testis. Isoform 2 is not expressed in any of the tissues. Expression of the housekeeping gene GAPDH was used as an internal control as well as a loading control (GAPDH). (d) Detection of podocin isoform 1 in murine kidney (Ki) and testis (Te) demonstrates that isoform 2 is human specific. Podocin expression in the mouse liver served as a negative control (Li).