Regulation of BMP7 expression during kidney development

Area of Science:

• Developmental Biology
• Molecular Biology
• Genetics

Background:

• Bone Morphogenetic Proteins (BMPs) are crucial signaling molecules with complex roles in embryogenesis.
• Upstream regulators of BMPs, particularly BMP7 during kidney development, are not well understood.
• Previous studies suggested potential BMP autoregulation, similar to BMP4 in tooth development.

Purpose of the Study:

• To investigate the autoregulation of Bone Morphogenetic Protein 7 (BMP7) during embryonic kidney development.
• To identify upstream signals regulating BMP7 expression in the developing kidney.
• To utilize a novel BMP7/lacZ reporter allele for precise expression monitoring.

Main Methods:

• Generation of a beta-galactosidase (lacZ)-expressing reporter allele at the BMP7 locus.
• Analysis of BMP7/lacZ homozygous mutant embryos to assess autoregulation.
• Treatment of isolated kidney mesenchyme with survival factors (EGF, bFGF) and inducers (ureteric bud, spinal cord, LiCl).
• Disruption of proteoglycan synthesis using sodium chlorate.
• Heterologous recombination assays with ureteric bud and limb/lung mesenchyme.

Main Results:

• BMP7 expression is not autoregulated in any tissue, contrary to other studies.
• EGF and bFGF support mesenchyme survival but do not maintain BMP7 expression.
• BMP7 expression in mesenchyme is induced by signals, potentially involving Wnt pathway activation (suggested by LiCl treatment).
• Proteoglycan synthesis disruption abolishes BMP7 expression in mesenchyme but not in kidney epithelium.
• BMP7 expression in kidney epithelial components is independent of metanephric mesenchyme interactions.

Conclusions:

• BMP7 autoregulation is not a feature of kidney development.
• Epithelial BMP7 expression is independent of mesenchyme interactions.
• Metanephric mesenchyme BMP7 expression is dependent on proteoglycans and likely Wnt signaling, highlighting key regulatory mechanisms.