Glycine acts as an obligatory co-agonist with glutamate on N-methyl-D-aspartate (NMDA) receptors. Brain glycine availability is determined by glycine transporters (GlyT1 or SLC6A9), which mediate glycine reuptake into nerve terminals. Since hypofunction of NMDA receptors has been implicated in the pathophysiology of schizophrenia, this study tests the hypothesis that GlyT1 genetic variants confer susceptibility to schizophrenia. Four GlyT1 polymorphisms were studied in a sample population of 249 people with schizophrenia and 210 normal controls. One polymorphism (rs16831541) was not informative in our Chinese population while the other three polymorphisms (rs1766967, rs2248632 and rs2248253) were analysed with chi-square tests and haplotype analysis. Significant linkage disequilibrium was obtained among the three polymorphisms. Neither single marker nor haplotype analysis revealed an association between variants at the GlyT1 locus and schizophrenia, suggesting that it is unlikely that the GlyT1 polymorphisms investigated play a substantial role in conferring susceptibility to schizophrenia in the Chinese population. Further studies with other GlyT1 variants, relating either to schizophrenia, psychotic symptoms or to therapeutic response in schizophrenia, are suggested.
