Rat renin gene transcription is initiated at a single start site

Expression of a renin/GFP transgene in mouse embryonic, extra-embryonic, and adult tissues

A reporter construct was assembled with 4-kb of renin 5'-flanking sequence fused to humanized green fluorescent protein (GFP) cDNA. Transgenic mice carrying this construct were produced and assayed for GFP expression. In the adult, expression was detected in juxtaglomerular (JG) cells of the kidney and granular convoluted tubular cells of the submandibular gland. Furthermore, treatment of mice with captopril induced GFP expression in renal vascular smooth muscle cells. During embryogenesis, GFP expression was first detected at embryonic day E13 in the adrenal gland and Wolffian duct. Expression was also seen in the developing renal vasculature as early as E14 and remained detectable through birth. Renal GFP expression became restricted to JG cells in adults. Fetal adrenal and gonadal arteries also expressed GFP. In the placenta, GFP was observed in giant cell trophoblasts, consistent with reports of renin expression in chorionic cells of both humans and mice. We conclude that 4 kb of renin 5' flank is sufficient to direct multiple known renin expression patterns. Furthermore, the renin-GFP construct characterized here will provide a useful vital reporter for renin expression.

An alternative transcript of the rat renin gene can result in a truncated prorenin that is transported into adrenal mitochondria

Characterization of the local renin-angiotensin system in the rat adrenal zona glomerulosa indicated a dual targeting of renin both to the secretory pathway and mitochondria. To investigate the transport of renin into mitochondria, we constructed a series of amino-terminal deletion variants of preprorenin. One of these variants, lacking the complete signal sequence for the endoplasmic reticulum and 10 amino acids of the profragment, was transported efficiently into isolated mitochondria. The transport was further shown to be dependent on mitochondrial membrane potential and ATP synthesis. Analysis of adrenal RNA revealed the existence of 2 renin transcripts. While one of the transcripts corresponds to the known full-length transcript, the other one lacks exon 1; instead, exon 2 is preceded by a domain of 80 nucleotides originating from intron 1. This domain, as well as the following region of intron 1 being excised, shows all essential sequence elements defining an additional, so-far-unknown exon. The second mRNA possibly derives from an additional transcription start in intron 1 and an alternative splicing process. Translation of this mRNA could result in a truncated prorenin representing a cytosolic form of renin, which is required for transport into mitochondria. This truncated prorenin corresponds exactly to the deletion variant being imported into mitochondria in vitro.