Neuronal Mislocalization of Mutant DHHC9 in X-Linked Intellectual DIsability

DHHC9 belongs to a family of protein acyl transferase (PAT) enzymes.  PATs enzymatically add fatty acid palmitate to cysteine residues on specific protein substrates resulting in increased hydrophobicity and membrane association. This modification is reversible by the action of depalmitoylating thioesterases. There are over 300 candidate palmitoylated proteins identified in rat cortical neurons, suggesting that this dynamic process plays a key role in the spatiotemporal distribution of proteins within the neuron. Neurons are polarized cells with discrete protein domains and DHHC9 and other PATs facilitate proper trafficking of proteins to these domains.   Recently, mutations in the zDHHC9 gene have been identified in individuals with X-Linked Intellectual Disability (XLID).  Here, we characterize a specific XLID nonsense mutation (*R298) in the zDHHC9 gene that results in the expression of a C-terminal truncated protein, in the context of the mature hippocampal neuron.