Lrp5 and Lrp6 play compensatory roles in mouse intestinal development

Area of Science:

• Developmental Biology
• Molecular Biology
• Gastroenterology

Background:

• Low-density lipoprotein receptor-related proteins 5 and 6 (Lrp5 and Lrp6) are critical co-receptors for Wnt ligands, mediating Wnt/β-catenin signaling.
• Germline deletion of Lrp6 leads to embryonic lethality, while Lrp5 deficiency results in viable mice.

Purpose of the Study:

• To investigate the specific roles and redundancy of Lrp5 and Lrp6 in mouse intestinal epithelium development.
• To elucidate the impact of conditional Lrp5 and Lrp6 deletion in the gut on Wnt/β-catenin signaling and stem cell maintenance.

Main Methods:

• Conditional knockout mice were generated by crossing floxed Lrp5 and Lrp6 alleles with villin-Cre recombinase.
• Immunohistochemistry and other staining methods were employed to assess morphological changes, cell differentiation, and protein expression.
• Analysis focused on embryonic intestinal epithelium lacking Lrp5, Lrp6, or both.

Main Results:

• Conditional deletion of Lrp5 or Lrp6 alone in the gut did not significantly alter intestinal development or differentiation.
• Mice with combined deletion of Lrp5 and Lrp6 in the gut (Lrp5(gut-/-); Lrp6(gut-/-)) exhibited embryonic lethality within 1 day of birth.
• Lrp5(gut-/-); Lrp6(gut-/-) embryos showed progressive cell loss, absent proliferation, and premature differentiation of crypt stem/progenitor cells.
• Expression of Wnt/β-catenin target gene cyclin D1 was significantly reduced in the double knockout embryos.

Conclusions:

• Lrp5 and Lrp6 play redundant roles in the development and maintenance of intestinal epithelium.
• The combined loss of Lrp5 and Lrp6 disrupts intestinal stem/progenitor cell homeostasis, likely through impaired Wnt/β-catenin signaling.
• These findings highlight the essential, albeit redundant, function of Lrp5/6 in ensuring intestinal development via Wnt pathway regulation.