SMC2 ablation impairs bovine embryo development shortly after blastocyst hatching

Area of Science:

• Reproductive Biology
• Developmental Biology
• Genetics

Background:

• Condensins are crucial protein complexes for chromosome assembly and segregation during cell division.
• SMC2 is a core component of both condensins I and II.
• The precise developmental stage at which bovine embryos lacking SMC2 arrest is not well-defined.

Purpose of the Study:

• To investigate the developmental consequences of SMC2 absence in bovine embryos.
• To determine the timing of developmental arrest in bovine embryos lacking functional condensins I and II.

Main Methods:

• Utilized a naturally occurring mutation (HH3) and CRISPR-mediated gene ablation to create SMC2-deficient bovine embryos.
• Assessed embryonic development at various stages, including E14 and in vitro culture up to D12.
• Quantified cell numbers in blastocysts (total, trophectoderm, inner cell mass) and analyzed telomere length.

Main Results:

• Embryos homozygous for the HH3 allele failed to elongate and lacked an embryonic disc by E14.
• SMC2 knockout embryos formed blastocysts but showed significantly reduced cell proliferation at D8.
• SMC2-deficient embryos arrested development in vitro by D12 and could not survive to maternal recognition of pregnancy.

Conclusions:

• Condensins I and II, via SMC2, are indispensable for early bovine embryonic development.
• SMC2 is required for successful blastomere mitosis post-blastocyst formation.
• Embryonic development arrests shortly after blastocyst hatching in the absence of functional condensins.