We further identified <i>MARK1</i> and <i>HNRNPUL2</i>, ASD-associated mRNAs, as ubiquitination-dependent targets of CSDE1, linking aberrant condensate dynamics to synaptic plasticity deficits.<h4>Conclusion</h4>Our study reveals an LLPS-coupled ubiquitination mechanism by which MKRN2 regulates CSDE1, providing a novel molecular pathway underlying neurodevelopmental disorders. Here, MARK1 is linked to neurodevelopmental disorder.