ZC3H14 phosphorylation is required for nuclear speckle assembly during zygotic splicing activation in mice.

Phosphorylation of ZC3H14 by CDK12/13 is essential for nuclear speckle formation during zygotic splicing activation in mice, impacting early embryonic development.

• Why it matters: Understanding the regulation of nuclear speckle assembly during ZSA is crucial because it underpins early developmental processes, yet remains poorly characterized.
• What they did: The study used knockout mice, localization analysis, and mutant ZC3H14 proteins to demonstrate that phosphorylation by CDK12/13 controls ZC3H14’s role in speckle formation and splicing regulation during ZSA.
• The result: Disruption of ZC3H14 phosphorylation impairs speckle assembly and splicing, leading to embryonic arrest, and highlights the importance of this modification for female fertility and early development.