Involvement of Nlrp9a/b/c in mouse preimplantation development

Area of Science:

• Reproductive biology
• Immunology
• Developmental biology

Background:

• Nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing proteins (NLRPS) are key inflammasome components.
• A subset of NLRPS, the reproductive clade, is vital for mammalian preimplantation development, forming the subcortical maternal complex (SCMC).
• Nlrp9b has a known immune role against rotavirus, but the function of Nlrp9a/b/c in reproduction is unclear.

Purpose of the Study:

• To investigate the role of Nlrp9a, Nlrp9b, and Nlrp9c in mammalian preimplantation development.
• To determine if Nlrp9 proteins function redundantly in early embryonic development.
• To explore the interaction of Nlrp9 with SCMC components.

Main Methods:

• Generation of Nlrp9 triple mutant (TMut) mice lacking all three Nlrp9a/b/c genes.
• Assessment of fertility and pup delivery in TMut females.
• In vivo and in vitro analysis of preimplantation embryo development (blastocyst development, two-cell stage block).
• Genotyping of double-mutant (DMut) oocytes to assess functional redundancy.
• Co-immunoprecipitation to detect Nlrp9 binding to SCMC components.

Main Results:

• Nlrp9 TMut females exhibited reduced litter sizes and increased preimplantation embryonic lethality.
• TMut embryos showed retarded blastocyst development in vivo.
• Fertilized eggs from TMut females arrested at the two-cell stage in vitro with asymmetric cell division.
• Nlrp9 double mutants (DMut) did not show the two-cell block, indicating functional redundancy among Nlrp9a/b/c.
• Nlrp9 proteins were found to bind to SCMC components.

Conclusions:

• Nlrp9 proteins are essential for mammalian preimplantation development.
• Functional redundancy exists among Nlrp9a, Nlrp9b, and Nlrp9c in preventing the two-cell block.
• Nlrp9 plays a critical role in early embryonic development, potentially through its interaction with the SCMC.