Association between P2X7 Receptor Polymorphisms and Bone Status in Mice.

Area of Science:

• Bone Biology
• Immunology
• Genetics

Background:

• Purinergic receptor P2X7 (P2X7R) is expressed in bone cells and influences bone physiology.
• A naturally occurring mutation, P451L, impairs P2X7R function in macrophages.
• The bone phenotype associated with the P451L mutation in P2X7R is not well understood.

Purpose of the Study:

• To investigate the bone phenotype of mouse strains harboring the P451L mutation in the purinergic receptor P2X7 gene.
• To determine the impact of P2X7R variants on bone density, strength, and resorption markers.
• To assess the in vitro osteoclast function related to ATP-induced pore formation.

Main Methods:

• Sequencing of common inbred mouse strains to identify P2X7R genotypes (P451 vs. P451L).
• Comparative analysis of bone phenotype using dual energy X-ray absorptiometry (DXA), bone markers (CTX), and three-point bending tests.
• In vitro assessment of ATP-induced pore formation in osteoclasts derived from different mouse strains.

Main Results:

• Mouse strains with the P451 allele exhibited stronger femurs and higher C-telopeptide collagen (CTX) levels, indicating increased bone resorption.
• Strains carrying the P451L allele displayed weaker bones and lower CTX levels, suggesting reduced bone resorption.
• Osteoclasts from strains with the P451L allele showed diminished ATP-induced pore formation in vitro.

Conclusions:

• The P451L mutation in purinergic receptor P2X7 is associated with a distinct bone phenotype characterized by weaker bones and lower resorption.
• Decreased ATP-induced pore formation in osteoclasts may underlie the observed bone phenotype in P451L mutant strains.
• These findings are crucial for interpreting previous P2X7R studies in mice and for developing P2X7R-targeted therapies for conditions like postmenopausal osteoporosis.