Abundance of ribosomal RNA gene copies in the genomes of schizophrenia patients

Objective: The ribosome is a critical component of the translation machinery. The key component of ribosomes is ribosomal RNA (rRNA). Dysregulation of rRNA biogenesis has been implicated in some human diseases. One of the factors affecting rRNA biogenesis is the ribosomal RNA genes (rDNA) copy number in the genome. The aim of this study was to examine the rDNA copy number (CN) variation in the genomes of patients with schizophrenia (SZ) compared to healthy controls (HC). Methods: Weevaluated rDNA CN in leukocytes of 179 subjects with SZ (108 male/71 female) in comparisonwith 122 HC (60 male/62 female) using two techniques: qPCR and nonradioactive quantitative hybridization (NQH), which is based on the use of biotinylated rDNA probes. Results: rDNA CN (NQH) and rDNA CN (qPCR) was higher in SZ patients than in controls (median 542 vs 384, p= 10- 25 and median 498 vs 370, p = 10- 12). NQH was experimentally proved to be less sensitive to severe DNA damage than qPCR. The more DNA damage, the higher the ratio R= CN (NQH)/CN (qPCR). 15% of the SZ patients had significantly higher rDNA damage degree than the HC. Conclusion: Genomes of some SZ patients containmore ribosomal genes than those of HC. The elevated ribosomal genes copy number in human genome can be one of the genetic factors of schizophrenia development. This hypothesis requires further experimental studies to be corroborated or disproved. (C) 2018 Elsevier B. V. All rights reserved.