Nuclear deformability depends on H3K9-methylated heterochromatin anchorage to the nuclear periphery in <i>Caenorhabditis elegans</i>

Nuclei adjust their deformability while migrating through constrictions to enable structural changes and maintain nuclear integrity. The effect of heterochromatin anchored at the nucleoplasmic face of the inner nuclear membrane on nuclear morphology and deformability during in vivo nuclear migration through constricted spaces remains unclear. Here, we show that abolishing peripheral heterochromatin anchorage by eliminating CEC-4, a chromodomain protein that tethers H3K9-methylated chromatin to the nuclear periphery, disrupts constrained P-cell nuclear migration in Caenorhabditis elegans larvae in the absence of the established linker of nucleoskeleton and cytoskeleton (LINC) complex-dependent pathway. This effect was suppressed by mutations that stabilize the lamin LMN-1. CEC-4 acts in parallel to an actin and CDC-42-based pathway. We also demonstrate the necessity for the chromatin methyltransferase MET-2 and the demethylase JMJD-1.2 during P-cell nuclear migration in the absence of functional LINC complexes. We conclude that H3K9-methylated chromatin needs to be anchored to the nucleoplasmic face of the inner nuclear membrane to help facilitate nuclear migration through constricted spaces in vivo.