ATP8A2 and cerebellar ataxia: We note that murine P4-ATPases ATP8A1 and ATP8A2 are expressed in the nervous system, and knockout mice exhibit deficient hippocampal learning, sensory deficits, cerebellar ataxia, mental retardation, and spinal cord degeneration, and shortened photoreceptor NRE length (Coleman et al., 2014).