New observations on the location of renin gene expression in the mouse using hybridisation histochemistry.

A number of nucleic acid probes designed to hybridise to mouse renin messenger RNA (mRNA) have been prepared and used to study the localisation of renin gene expression in mouse tissue sections. The aims of the study were to compare the performance of the different probes in analysis of known sites of renin gene expression end then to employ them in order to elucidate the features of renin gene expression in the mouse embryo at different stages of develop-ment. The probes consisted of three oligonucleotides, each 30 bases and a riboprobe of 630, 177, or a variable number of bases in length. Their hybridisation properties were examined by Northern blot analysis and by in situ hybridisation to renin mRNA preserved in frozen or paraffin sections of adult mouse kidneys and salivary glands. The relative sensitivities of radio-labelled and bisbin-labelled oligonucleotide and riboprobes have been compared, and the problems associated with particular types of probe identified. Using a mixture of the radio-labelled oligonucleotide probes, renin gene expression has been identified in the mouse embryo. In addition to the expected expression within the immature metanephros on day 16 of gestation, evidence is present for relatively high renin gene expression outside, but adjacent to, the metanephros on day 15 of the gestation period. This discovery raises important questions concerning the role(s) of the renin-angiotensin system during development, and about the development of the highly local-ised nature of renin gene expression in the adult animal.