Transgenic mouse models to study human mineralocorticoid receptor function in vivo

Area of Science:

• Molecular Biology
• Endocrinology
• Genetics

Background:

• The mineralocorticoid receptor (MR) is crucial for aldosterone action, mediating effects in various tissues including epithelia and nonepithelial cells.
• Understanding the molecular mechanisms of MR signaling and its regulated genes is incomplete.
• The human MR (hMR) gene has two 5'-untranslated exons (1alpha and 1beta) with distinct promoter regions (P1 and P2).

Purpose of the Study:

• To investigate the tissue-specific expression and function of the mineralocorticoid receptor (MR).
• To establish transgenic mouse models to analyze the differential activities of the P1 and P2 promoters of the hMR gene.
• To create models for studying aldosterone-regulated proteins and MR functions in vivo.

Main Methods:

• Generation of transgenic mice using targeted oncogenesis (SV40 TAg) driven by P1 and P2 promoters.
• Analysis of transgene expression (TAg mRNA) to assess promoter utilization and tissue specificity.
• Establishment of immortalized cell lines from transgenic models for further study.
• Development of mouse models for MR cDNA overexpression.

Main Results:

• P1 and P2 promoters exhibited differential transcriptional activity and tissue-specific utilization.
• P1 promoter showed broad activity in MR-expressing tissues, including the distal nephron.
• P2 promoter displayed weak and spatially restricted activity, with P1.TAg mice developing hibernomas and P2.TAg mice developing tumors (cerebral neuroectodermal tumors and leiomyosarcomas).

Conclusions:

• The P1 and P2 promoters of the hMR gene play distinct roles in regulating MR expression and function.
• Transgenic mouse models provide valuable systems for dissecting MR's complex roles in vivo.
• These models offer new avenues for investigating aldosterone-regulated processes and associated diseases.