Paralog-specific miRNA regulation uncouples ASER gene repression from the canonical die-1 / cog-1 switch.

The Pristionchus pacificus ASER-specific Ppa-gcy-22 .3 and Ppa-gcy-22 .5 paralogs differ in their regulatory dependencies despite sharing an upstream terminal selector machinery. P. pacificus gcy-22.3 expression is sensitive to Ppa-die-1 and Ppa-cog-1 perturbation, while Ppa-gcy-22 .5 is largely independent of these canonical ASE laterality regulators. Both paralogs require the miRNA, Ppa-miR-8345 , for repression in ASEL; loss of Ppa-miR-8345 produces a complete ASEL-to-ASER conversion, in contrast to the hybrid ASEL/ASER states caused by Ppa-die-1 or Ppa-cog-1 mutation alone. These findings indicate Ppa-miR-8345 acts through additional regulatory outputs beyond the die-1 / cog-1 feedback loop, revealing gene-by-gene rewiring of terminal differentiation programs.