Hdac4 Interactions in Huntington's Disease Viewed Through the Prism of Multiomics

The histone deacetylase Hdac4 is known to contribute to the progression of Huntington's Disease (HD), but the underlying mechanisms remain unknown. Here, we defined the endogenous interactome of Hdac4 in the brain of HD mouse models, characterizing their polyQ- and age-dependence in affected tissues. Further integration with proteome and transcriptome data sets reveals the disease-induced enhancement of Hdac4 interactions with vesicular sorting proteins, including the WASH complex. This may contribute to the known decreased synaptic functions in Huntington's Disease. [Display omitted] Highlights •Endogenous interactomes of Hdac4 and Hdac5 in mouse whole brain and striata.•Hdac4 exhibits polyQ- and age-dependent interactions in Huntington's Disease models.•Hdac4 associates with vesicular trafficking proteins, including the WASH complex.•Multiomics analysis supports functional Hdac4 interactions in Huntington's Disease. Huntington's disease (HD) is a monogenic disorder, driven by the expansion of a trinucleotide (CAG) repeat within the huntingtin (Htt) gene and culminating in neuronal degeneration in the brain, predominantly in the striatum and cortex. Histone deacetylase 4 (Hdac4) was previously found to contribute to the disease progression, providing a potential therapeutic target. Hdac4 knockdown reduced accumulation of misfolded Htt protein and improved HD phenotypes. However, the underlying mechanism remains unclear, given its independence on deacetylase activity and the predominant cytoplasmic Hdac4 localization in the brain. Here, we undertook a multiomics approach to uncover the function of Hdac4 in the context of HD pathogenesis. We characterized the interactome of endogenous Hdac4 in brains of HD mouse models. Alterations in interactions were investigated in response to Htt polyQ length, comparing mice with normal (Q20) and disease (Q140) Htt, at both pre- and post-symptomatic ages (2 and 10 months, respectively). Parallel analyses for Hdac5, a related class IIa Hdac, highlighted the unique interaction network established by Hdac4. To validate and distinguish interactions specifically enhanced in an HD-vulnerable brain region, we next characterized endogenous Hdac4 interactions in dissected striata from this HD mouse series. Hdac4 associations were polyQ-dependent in the striatum, but not in the whole brain, particularly in symptomatic mice. Hdac5 interactions did not exhibit polyQ dependence. To identify which Hdac4 interactions and functions cou