Apoptosis in metanephric development.

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Biology

Background:

• Metanephric development requires mesenchymal cells to form epithelial nephron structures.
• Induction involves extracellular matrix proteins and factors from the ureteric bud or heterologous cells.
• Programmed cell death (apoptosis) occurs in cells surrounding newly formed epithelia.

Purpose of the Study:

• To investigate the role of apoptosis in metanephric development.
• To identify mechanisms by which inducers prevent apoptosis and promote differentiation.
• To elucidate the signaling pathways involved in mesenchymal-to-epithelial transition.

Main Methods:

• In vitro and in vivo induction of embryonic mesenchyme.
• Morphological assessment of apoptosis.
• Biochemical analysis of DNA degradation.
• Treatment with apoptosis inhibitors (actinomycin-D, cycloheximide) and calcium buffering.
• Testing effects of protein kinase C modulators (phorbol esters, staurosporine) and EGF.

Main Results:

• Uninduced mesenchyme exhibits DNA degradation, a marker of apoptosis.
• Apoptosis is prevented by actinomycin-D, cycloheximide, calcium buffering, and heterologous inducers.
• Protein kinase C activation mimics inducer effects; inhibition blocks them.
• EGF prevents DNA degradation but not differentiation.

Conclusions:

• Metanephric mesenchyme is programmed for apoptosis during development.
• Mesenchymal-to-epithelial conversion requires two distinct steps: rescue from apoptosis and induction of differentiation.
• Protein kinase C signaling is involved in preventing apoptosis during this process.