KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3

Intellectual disability (ID) affects ~2% of the general population and is often genetic in origin. ID-associated genes are enriched for epigenetic factors, including those encoding the largest family of histone lysine acetyltransferases (KAT5-KAT8). Among them is KAT6A, whose de novo heterozygous mutations cause KAT6A Syndrome (or Arboleda-Tham Syndrome), with ID as a common clinical feature. However, the underlying molecular mechanisms remain elusive. Here, we show that haploinsufficiency of Kat6a impairs learning and memory in mice, and specific deletion of Kat6a in excitatory neurons recapitulates the hippocampus-dependent memory deficits. Unexpectedly, KAT6A deficiency results in impaired synaptic structure and plasticity in hippocampal CA3, but not in CA1 region. Combining single-nucleus RNA-sequencing and chromatin analysis, we identify a CA3-enriched gene Rspo2, encoding a Wnt activator R-spondin 2, as a key transcriptional target of KAT6A. Moreover, deletion of Rspo2 in excitatory neurons phenocopies the loss of Kat6a, resulting in defective Wnt/β-catenin signaling and synaptic plasticity in CA3, and abnormal cognitive behaviors in mice. Importantly, restoring RSPO2 expression in CA3 pyramidal neurons rescues the deficits in Wnt signaling and learning-associated behaviors in Kat6a mutant mice. Collectively, our results demonstrate that KAT6A plays a critical role in regulating synaptic plasticity and memory formation through RSPO2-mediated Wnt signaling in hippocampal CA3, shedding new light on the fundamental mechanisms of ID and providing potential therapeutic targets for the treatment of KAT6A Syndrome and related neurodevelopmental diseases.