Nr5a2 ensures inner cell mass formation in mouse blastocyst

Area of Science:

• Developmental Biology
• Genetics
• Epigenetics

Background:

• Nuclear receptor subfamily 5 group A member 2 (Nr5a2) has been implicated in early mouse embryonic development.
• Previous studies suggested Nr5a2's role in zygotic genome activation, but its precise function in early lineage specification remained unclear.

Purpose of the Study:

• To investigate the role of Nr5a2 in the critical period of first lineage differentiation.
• To elucidate the molecular mechanisms by which Nr5a2 influences inner cell mass (ICM) formation.

Main Methods:

• Nr5a2 ablation in mouse embryos.
• RNA sequencing (RNA-seq) to analyze gene expression.
• CUT&Tag assay to determine genomic binding sites of Nr5a2.
• Manipulation of Nr5a2 levels in single blastomeres.

Main Results:

• Nr5a2 ablation led to blastocysts lacking an inner cell mass (ICM), despite some embryos reaching the blastocyst stage.
• Nr5a2 was found to transcriptionally regulate ICM-specific genes, including Oct4, essential for establishing pluripotency.
• Altering Nr5a2 levels in early blastomeres affected daughter cell fate, confirming its role in lineage determination.

Conclusions:

• Nr5a2 is essential for the formation of the inner cell mass (ICM) in mouse blastocysts.
• Nr5a2 acts as a key regulator, controlling the gene network required for establishing pluripotency and first lineage differentiation.
• Nr5a2 functions as a critical 'doorkeeper' ensuring proper ICM development.