Gene expression of brain natriuretic peptide (BNP) in mouse embryos

Abstract

The natriuretic peptide family regulate blood pressure and body fluid by vasorelaxation, diuresis and natriuresis. The family consists of 3 members; atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP). Although ANP and BNP mRNAs have been detected in extracts of embryo heart tissue, no publication to date describes the distribution of any member of this family throughout the developing embryo. The primary objective of this investigation was to determine the tissue distribution of mRNA transcripts encoding BNP in mouse embryos in the latter half of gestation and compare these expression patterns throughout mouse embryonic development. After polymerase chain reaction (PCR) amplification of Exon 2 of the murine BNP gene and sequence analysis of this fragment, BNP sense and antisense cRNA riboprobes were generated by PCR and subsequent in vitro transcription with T3 and T7 RNA polymerases in the presence of ³⁵S-UTP. The generated riboprobes were used in the technique of in situ hybridisation on appropriately prepared embryonic mouse tissue sections to determine BNP expression. Mouse embryos were collected at daily intervals from 11.5 days to full term (19.5 days). Intense BNP expression was observed only in the atrial and ventricular tissues of the heart in embryos of these gestational ages. In a previously unreported finding, placental sections from 15.5 day mouse embryos showed positive BNP expression in the outer layer of the decidua basalis. Hybridisation of adult mouse heart was used as a positive control in this study. BNP expression in the heart was most intense in left and right atria, followed by left ventricle. Expression signals were weakest in the right ventricle. This study is the first to describe the distribution of BNP gene expression in developing embryos and placenta.