ADNP interactions with HP1 govern neuronal fate

Chromatin regulators play essential roles in brain development by orchestrating gene expression programs that guide neural lineage specification and differentiation. Among them, Activity-dependent neuroprotective protein (ADNP) is a critical chromatin regulator whose heterozygous mutations cause ADNP syndrome, a neurodevelopmental disorder associated with autism. ADNP contributes to the regulation of chromatin accessibility and genome organization, in part through interactions with the chromatin remodeler CHD4 and heterochromatin protein HP1 to form the ChAHP complex, though additional mechanisms may also be involved. We dissected the role of these interactions in neurodifferentiation using separation-of-function mutants in mouse embryonic stem cells (mESCs) that disrupt ADNP-HP1 (ADNPΔHP1) or ADNP-CHD4 (ADNPΔCHD4) interactions. Interestingly, ADNPΔHP1, but not ADNPΔCHD4, fails to differentiate into neural progenitor cells, highlighting a critical role for HP1 in mediating ADNP function during neurodifferentiation. Genome-wide profiling revealed that HP1 and CHD4 regulate ADNP binding to distinct genomic regions, with ADNPΔHP1 showing loss at lamin-associated domains (LADs) and pericentromeric heterochromatin, leading to derepression of major satellites and neural gene targets. Additionally, ADNPΔHP1 exhibited downregulation of NANOG, a crucial pluripotency marker, and the consequent upregulation of some NANOG-target neural genes. In contrast, ADNPΔCHD4 alters ADNP binding at promoters and CTCF-enriched sites without impairing neurodifferentiation, indicating distinct functional contributions of these interactions. Our findings highlight distinct contributions of ADNP interactions with HP1 and CHD4 in chromatin regulation and neural gene expression and point to a broader role of ADNP–HP1 interactions in orchestrating early neurodevelopmental programs, including those controlled by pluripotency factors such as NANOG.