ATCAY encodes caytaxin, a protein essential for cerebellar development and neuronal function. The protein localizes to mitochondria and interacts with kinesin light chains, suggesting roles in mitochondrial distribution within axons and dendrites 1. ATCAY may regulate glutaminase to modulate glutamate neurotransmission, though its precise molecular mechanism remains incompletely characterized 2. ATCAY expression correlates directly with phenotypic severity in animal models; complete absence causes severe ataxia while reduced expression produces milder motor deficits 1. The protein is highly expressed in developing cerebellar cortex, particularly in molecular and granular layers during postnatal maturation, with transcript levels peaking around postnatal day 7-14 2. Loss of ATCAY function impairs Purkinje neuron firing and increases deep cerebellar nuclear neuron excitability, contributing to both ataxia and dystonic symptoms 3. Homozygous ATCAY mutations cause Cayman cerebellar ataxia, an autosomal recessive disorder featuring psychomotor retardation, cerebellar dysfunction, nystagmus, intention tremor, and ataxic gait 45. Recent evidence suggests elevated anti-ATCAY autoantibodies correlate with Alzheimer's disease risk and cognitive impairment severity 6. Additionally, ATCAY homologs mediate antiviral defense against dengue virus in both human cells and mosquito vectors, indicating evolutionary conservation of function beyond neural development 7.