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BackgroundRare variants in the TRIO gene are associated with schizophrenia and autism spectrum disorders (ASD), which are commonly comorbid. ASD may define a specific schizophrenia subtype. This study examined person-specific hippocampal metabolite concentrations for 4 schizophrenia cases harboring rare variants in TRIO or its interaction partner ARMS/KIDINS220 and 5 cases with other rare variants.MethodsNine of 19 cases from a prior imaging study underwent targeted exome sequencing. Multi-voxel 1H-MRS imaging of the entire 3-dimensional hippocampus found only increased Creatine [Cr] (cellular energy use) concentration, distinguished cases at the group level. However, concentrations of N-acetyl-aspartate [NAA] (neuronal integrity) and choline [Cho] (membrane turnover/myelination) concentrations had a greater variance in cases than controls.ResultsFour cases with rare, missense-coding mutations or non-frameshift deletions in TRIO or ARMS/KIDINS220 had significantly lower [Cho] than the other 5 (1.78 ± 0.18 mM versus 2.67 ± 0.8 mM: t = 3.55, p = 0.005) but similar [NAA]. Two cases harboring rare variants in the SLC39A1 zinc transporter had the lowest [NAA]. (8.41 ± 0 80 mM versus 10.35 ± 2.03 mM, t = 4.52, p = 0.001). The highest [Cho] accompanied rare variants in SORCS2 and SORT, associated with schizophrenia and Alzheimer’s Disease.LimitationsThis preliminary study of a small sample of exceptionally well characterized cases requires replication in larger samples for clinical utility.ConclusionsThe hippocampus is vulnerable to more than one pathology causing schizophrenia. TRIO rare variants predicted significantly lower Cho, indicating reduced myelin. [Cho] and [NAA] may have importance for choosing and monitoring schizophrenia treatment.

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