An allelic series reveals the genetic requirement for Adnp in cortical neurogenesis and learning behavior

Transcriptional regulators and chromatin remodellers are among the most important risk gene categories across the genetic landscape of neurodevelopmental disorders (NDDs). The zinc finger and homeodomain transcription factor ADNP is prominently associated with Helsmoortel-Van der Aa Syndrome (HVDAS), which is characterized by intellectual disability and autism spectrum disorder. Heterozygous frameshifting mutations account for the majority of HVDAS mutations, but it remains unclear how HVDAS mutations affect ADNP dosage, and how dosage in turn relates to neurodevelopmental and behavioral phenotypes. Here, we compared an allelic series of Adnp cKOs and germline heterozygotes. Using a conditional allele, we first deleted Adnp throughout the neural tube using Nestin-Cre . At E15.5, cKO brains exhibited altered upper-layer neuron production. However, Adnp ^Nestin cKOs exhibited perinatal lethality, precluding further behavioral characterization. Next, we compared germline heterozygotes (gHets) versus cKOs generated using the Emx1-Cre driver. We found that Adnp ^Del/+ and Adnp ^L822fs6/+ gHets exhibited cortical hypoplasia that was quantitatively identical, albeit less severe in comparison to Adnp ^Emx cKOs. In behavioral testing, Adnp ^Emx cKOs accordingly exhibited the strongest phenotypes, including hallmarks of elevated anxiety. However, both Adnp ^Emx cKOs and Adnp ^L822fs6/+ gHets exhibited remarkably similar sex-specific deficits in learning during Morris Water Maze testing. Taken together, our work suggests that cortical growth and learning represent core phenotypes shared across Adnp mutant models irrespective of dosage. Moreover, since Adnp mutant phenotypes closely correspond with our prior findings in Chd4 mutants, our results collectively suggest that Adnp regulates behavior via the ChAHP chromatin remodelling complex.