Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent complex psychiatric disorders in children as well as adults. ADHD impacts not only the affected individuals but also their families and social and professional networks. The clinical and diagnostic criteria for ADHD remain imprecise, in part, due to lack of robust biomarkers. ADHD comprises multiple subsets of diseases that present a shared set of downstream clinical findings, while displaying extensive molecular heterogeneity. This calls for innovation in diagnostic strategies that can help establish an ADHD diagnosis unequivocally as well as guiding precision medicine in this common mental health disorder. No study has examined, to the best of our knowledge, the upstream regulation of miRNAs that impact the downstream final ADHD phenotype. The latter focus on putative genetic biomarkers that regulate the regulators and can be tested empirically, for example, through genetic association analyses of the biogenesis pathways for miRNAs that impact the ADHD phenotype. Hence, we report here polymorphic variation in 10 miRNA biogenesis pathway candidate genes, including RNASEN, DGCR8, XPO5, RAN, DICER1, TARBP2, AGO1, AGO2, GEMIN3, and GEMIN4, in a large sample from the Eastern Mediterranean region (N = 355; 191 cases and 164 controls). We found that AGO1 rs595961 was significantly associated with ADHD susceptibility (p < 0.05). While polymorphic variation in other miRNA biogenesis pathway genes did not display a significant association in the present sample, the observations reported herein on miRNA biogenesis variation offer a new avenue of research for innovation in biomarker discovery concerning ADHD and other complex psychiatric diseases with major global health burden.
MicroRNAs (miRNAs) are small conserved non-coding RNA molecules that post-transcriptionally regulate gene expression. Although it is reported in many studies that there are associations between alterations of miRNA homeostasis and pathological conditions such as cancer, psychiatric and neurological diseases, cardiovascular disease and autoimmune disease, the effects of common genetic variants of these genes on male infertility are unclear. To better understand this effect, we performed a case-control study including a total of 108 infertile men with idiopathic azoospermia and 125 fertile control subjects. Real-time polymerase chain reaction was used to genotype six single-nucleotide polymorphisms (SNPs) of microRNA biogenesis pathway genes and the associations between individual and combined genotypes and idiopathic azoospermia were analysed. The results showed significant difference between the individual AA genotype frequency of the GEMIN3 (rs197388) gene in the patient and control groups, indicating that the AA genotype may be considered as indicative of a higher predisposition to idiopathic azoospermia. The combined genotype analysis, including six SNPs, revealed statistically significant differences between the patients and control subjects for some combinations. For example, the frequency of genotype distributions of the AA\CA-CC-TT-AT genotype combination for the XPO5-RAN-DICER1-GEMIN3 combined loci was significantly different, and it may be considered a predisposition to idiopathic azoospermia. According to the obtained results, both individual and combined genotypes of SNPs from miRNA genes may be used to predict the risk of male infertility with idiopathic azoospermia.
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