HTT and autism: KALRN codes for a guanine nucleotide exchange factor (GEF) expressed in neuronal tissue during embryonic development23 and has been associated with schizophrenia risk through association analysis, and, postmortem analyses of cortical KALRN mRNA and protein levels within individuals with autism.24KALRN is strongly homologous to TRIO, a gene previously associated with autism.25 It is also a binding partner of the Huntingtin and a regulator of structural and functional plasticity at dendritic spines.