APOA2 and fragile X-associated tremor/ataxia syndrome: Indeed, some receptors activated by lipids (liver X receptor, retinoid X receptor, farnesoid X receptor), as well as several apolipoproteins (APOA1, APOA2, APOA4, APOC2 and APOD) are modulated in the cerebrospinal fluid of Fragile X-associated tremor/ataxia syndrome patients, as recently demonstrated [59].