mRNA Expression of the CUB and Sushi Multiple Domains 1 (CSMD1) and Its Serum Protein Level as Predictors for Psychosis in the Familial High-Risk Children and Young Adults

[Image: see text] Background: Schizophrenia (SCZ) is still a challenging, refractory, and severe disorder. It is not a fully understood disease with genetic and epigenetic susceptibility and about 80% substantial heritability. The CUB and Sushi multiple domains 1 (CSMD1) gene is implicated in neurogenesis, memory, immunity, neuropsychology, and monoamine metabolism. Thus, it is one of the powerful genes involved in the pathogenesis of SCZ. Purpose: To evaluate the possible role of the CSMD1 gene’s mRNA expression and its serum protein as markers for the early diagnosis of the first-episode SCZ in familial high-risk (FHR) Egyptian children and young adults. Subjects and methods: This case–control study included 80 first-episode drug-naïve SCZ patients from FHR Egyptian children and young adults and 80 healthy participants, as controls, from the FHR-susceptible children and young adults but did not develop SCZ. In this study, the CSMD1 gene’s mRNA expression and CSMD1 serum levels were measured in the peripheral blood, and these levels were correlated with the lipid profile of the study populations. Results: The CSMD1 gene’s mRNA expression and its’ protein levels were significantly decreased in the SCZ patients compared to controls. The receiver operating characteristic (ROC) curve analysis succeeded in distinguishing SCZ patients from those not having SCZ using cutoff points of ≤0.711 and ≤4.83 ng/mL for the CSMD1 gene’s mRNA expression and serum protein level, respectively. At these levels, the diagnostic sensitivities were 93.75 and 91.25%; specificity was 92.5%; positive predictive value (PPV) were 92.6 and 92.4%; and negative predictive values (NPVs) were 93.7 and 91.4%, respectively. Also, the ROC curve analysis succeeded in discriminating those with suicidal tendencies. Conclusion: CSMD1 gene’s mRNA expression might be a reliable and early diagnostic predictor of first-episode SCZ in the FHR Egyptian children and young adults.