Between the years 2010 and 2021, the number of average yearly suicide deaths in Slovenia reached 407, making us one of the countries with the highest suicide rates in the world. The risk factors for suicidal behaviour cannot be attributed to a single cause, as they are usually a combination of multiple factors, such as genetic and environmental factors, which are expressed as psychological, biological and sociological indicators. It has already been shown that in the context of suicidal behaviour altered regulation of certain genes at the RNA level can occur. As both the serotonin system and RNA editing are involved in the aetiology of suicidal behaviour, it is crucial to investigate both systems simultaneously. In this research, we analysed single nucleotide polymorphisms rs9983925 and rs4819035 in the ADARB1 gene, that is involved in the RNA editing process, as well as rs4290270 in the TPH2 gene, which codes for tryptophan hydroxylase 2, the rate-determining enzyme of serotonin synthesis in the central nervous system. The aim of our study was to identify which of the alleles of the selected polymorphisms are differentially represented in the sub-groups of suicide victims compared to the control group and thus contribute to a better understanding of the molecular genetics of suicidal behaviour. Our study included a large number of suicide victims of Slovenian origin as well as a control group - 690 people in total. After isolation of genomic DNA, we used TaqMan hydrolysis probes and real-time quantitative PCR to determine which alleles were present in each sample. The statistical analysis was performed using PLINK program. For the TPH2 rs4290270, ADARB1 rs4819035 and ADARB1 rs9983925 polymorphisms, we did not find any statistically significant differences in genotype/allele frequency distribution between controls and Slovenian suicide victims.
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