Rare FBXO18 variations and risk of schizophrenia: Whole-exome sequencing in two parent-affected offspring trios followed by resequencing and case-control studies.

Aim: Rare variations are suggested to play a role in the genetic etiology of schizophrenia; to further investigate their role, we performed a three-stage study in a Japanese population.

Methods: In the first stage, we performed whole-exome sequencing (WES) of two parent-affected offspring trios. In the second stage, we resequenced the FBXO18 coding region in 96 patients. In the third stage, we tested rare non-synonymous FBXO18 variations for association with schizophrenia in two independent populations comprising a total of 1376 patients and 1496 controls.

Results: A rare frameshift variation (L116fsX) in the FBXO18 gene was recurrently identified by WES in both trios. Resequencing FBXO18 coding regions, we detected three rare non-synonymous variations (V15L, L116fsX, and V1006I). However, there were no significant associations between these rare FBXO18 variations and schizophrenia in the case-control study.

Conclusion: Our present study does not provide evidence for the contribution of rare non-synonymous FBXO18 variations to the genetic etiology of schizophrenia in the Japanese population. However, to draw a definitive conclusion, further studies should be performed using sufficiently large sample sizes.