White matter abnormalities in 22q11.2 deletion syndrome: preliminary associations with the Nogo-66 receptor gene and symptoms of psychosis.

[22q11.2 deletion syndrome]

This study utilized diffusion tensor imaging (DTI ) to analyze white matter tractography in the anterior limb of the internal capsule (ALIC ), fornix , and uncinate fasciculus (UF ) of individuals with 22 q 11 .2 deletion syndrome and controls . Aberrations in these tracts have been previously associated with schizophrenia . With up to 25 % of individuals with 22 q 11 .2 DS developing schizophrenia in adulthood , we hypothesized reduction in structural integrity of these tracts , including an association with prodromal symptoms of psychosis . We further predicted an association between allelic variation in a functional polymorphism of the Nogo-66 receptor gene and 22 q 11 .2 DS white matter integrity .Tractography was conducted using fiber assignment by streamline tracking algorithm in DTI Studio . Subjects were genotyped for the rs 701428 SNP of the Nogo-66 receptor gene , and assessed for presence of prodromal symptoms .We found significant group differences between 22 q 11 .2 DS and controls in DTI metrics for all three tracts . DTI metrics of ALIC and UF were associated with prodromal symptoms in 22 q 11 .2 DS . Further , ALIC DTI metrics were associated with allelic variation of the rs 701428 SNP of the Nogo-66 receptor gene in 22 q 11 .2 DS .Alterations in DTI metrics suggest white matter microstructural anomalies of the ALIC , fornix , and UF in 22 q 11 .2 DS . Structural differences in ALIC appear to be associated with the Nogo-66 receptor gene , which has been linked to myelin-mediated axonal growth inhibition . Moreover , the association between psychosis symptoms and ALIC and UF metrics suggests that the Nogo-66 receptor gene may represent a susceptibility gene for psychosis through its disruption of white matter microstructure and myelin-associated axonal growth .