POSTTRANSLATIONAL PROCESSING AND RENAL EXPRESSION OF MOUSE INDIAN HEDGEHOG

The full-length mouse Indian hedgehog (Ihh) cDNA was cloned from an em bryonic 17.5-day kidney library and was used to study the post-transla tional processing of the peptide and temporal and spatial expression o f the transcript, Sequence analysis predicted two putative translation initiation sites. Ihh translation was initiated at both initiation si tes when expressed in an in vitro transcription/translation system. Ex pression of an Ihh mutant demonstrated that the internal translation i nitiation site was sufficient to produce the mature forms of Ihh, Ihh post-translational processing proceeded in a fashion similar to Sonic and Drosophila hedgehog; the unprocessed form underwent signal peptide cleavage as well as internal proteolytic processing to form a 19-kDa amino-terminal peptide and a 26-kDa carboxyl-terminal peptide. This pr ocessing required His(313) present in a conserved serine protease moti f. Ihh transcript was detected by in situ RNA hybridization as early a s 10 days postcoitum (dpc) in developing gut, as early as 14.5 dpc in the cartilage primordium, and in the developing urogenital sinus, In s emiquantitative reverse transcription-polymerase chain reaction experi ments, Indian hedgehog transcript was first detected in the mouse meta nephros at 14.5 dpc; transcript abundance increased with gestational a ge, becoming maximal in adulthood, In adult kidney, Ihh transcript was detected only in the proximal convoluted tubule and proximal straight tubule.