5. MiRNA and RNA with possible expression abnormalities in ADHD¶
miRNAs are microRNAs. They regulate the expression of genes at the posttranscriptional level. Read more at ⇒ Building blocks of heredity and behavior: Genes, DNA, RNA, Proteins, and Co. In the section⇒ Genetic and epigenetic causes of ADHD - introduction in the section ⇒ Emergence.
miRNAs have been substantially implicated in the development of ADHD in children and adults.
5.1. MiR-let-7d¶
One study found significantly elevated levels of the microRNA let-7d in the blood of 35 children with ADHD. The elevated blood levels of miR-let-7d correlated with a 16.7-fold increased risk of ADHD. Elevated miR-let-7d levels were associated with decreased galectin-3 expression in 66%. In a follow-up 1 year later, improvements in ADHD symptomatology correlated with normalized miR-let-7d levels.
Meanwhile, one study found elevated galectin-3 blood plasma levels in ADHD-affected children.
5.2. Rno-let-7b-5d¶
In SHR, a rat species representing a purely genetic ADHD-HI, the miRNA let-7d is reported to be overexpressed in the PFC and to decrease the expression of galectin-3, leading to downregulation of tyrosine hydroxylase, which is a precursor of dopamine synthesis.
The synthesis of dopamine in the brain occurs in two steps. First, the amino acid tyrosine is catalyzed by the enzyme tyrosine hydroxylase and converted to l-3,4-dihydroxyphenylalanine (l-DOPA). L-dopa is converted to dopamine by aromatic l-amino acid decarboxylase.
5.3. MiR-let-7b-5p¶
One study found aberrant (but not significant) expression of this miRNA in ADHD affected versus unaffected individuals.
5.4. MiR-652-3p¶
One study found significant aberrant expression of this miRNA in ADHD affected versus unaffected individuals.
5.5. MiR-942-5p¶
One study found significant aberrant expression of this miRNA in ADHD affected versus unaffected individuals.
5.6. MiR-148b-3p¶
One study found significant aberrant expression of this miRNA in ADHD affected versus unaffected individuals.
5.7. MiR-181a-5p¶
One study found aberrant (but not significant) expression of this miRNA in ADHD affected versus unaffected individuals.
5.8. MiR-320a¶
One study found aberrant (but not significant) expression of this miRNA in ADHD affected versus unaffected individuals.
5.9. MiR-18a-5p¶
The expression of this microRNA is reported to be altered in ADHD.
5.10. MiR-22-3p¶
The expression of this microRNA is reported to be altered in ADHD.
5.11. MiR24-3p¶
The expression of this microRNA is reported to be altered in ADHD.
5.12. MiR-106b-5p¶
The expression of this microRNA is reported to be altered in ADHD.
5.13. MiR107¶
The expression of this microRNA is reported to be altered in ADHD.
5.14. MiR-155-5p¶
The expression of this microRNA is reported to be altered in ADHD.
5.15. MiR-26b-5p¶
A genome-wide miRNA expression study found that this miRNA significantly contributed to ADHD by altering the myo-inositol signaling pathway. d-Myo-inositol (1,4,5)-trisphosphate is an intracellular second messenger widely distributed in the brain that controls the biological response of a large number of hormones and neurotransmitters to target cells by regulating calcium release from intracellular stores.
5.16. MiR-185-5p¶
A genome-wide miRNA expression study found that this miRNA significantly contributed to ADHD by altering the myo-inositol signaling pathway. d-Myo-inositol (1,4,5)-trisphosphate is an intracellular second messenger widely distributed in the brain that controls the biological response of a large number of hormones and neurotransmitters to target cells by regulating calcium release from intracellular stores.
5.17. MiR-191-5p¶
A genome-wide miRNA expression study found that this miRNA significantly contributed to ADHD by altering the myo-inositol signaling pathway. d-Myo-inositol (1,4,5)-trisphosphate is an intracellular second messenger widely distributed in the brain that controls the biological response of a large number of hormones and neurotransmitters to target cells by regulating calcium release from intracellular stores.
5.18. MiR-101-3p¶
One report found significantly increased expression of this miRNA in ADHD.
5.19. MiR-130a-3p¶
One report found significantly increased expression of this miRNA in ADHD.
5.20. MiR-138-5p¶
One report found significantly increased expression of this miRNA in ADHD.
5.21. MiR-195-5p¶
One report found significantly increased expression of this miRNA in ADHD.
5.22. MiR-106b-5p¶
One report found significantly decreased expression of this miRNA in ADHD.
5.23. MiR-138¶
Significantly decreased expression was found for this miRNA in the ADHD-HI rat model of SRH, which was related to promoter inhibitory activity of glucocorticoid receptor Nr3c1.
5.24. MiR-138*¶
Significantly decreased expression was found for this miRNA in the ADHD-HI rat model of SRH, which was related to promoter inhibitory activity of glucocorticoid receptor Nr3c1.
5.25. MiR-34c*¶
Significantly decreased expression was found for this miRNA in the ADHD-HI rat model of SRH, which was related to promoter inhibitory activity of glucocorticoid receptor Nr3c1.
5.26. MiR-296¶
Significantly decreased expression was found for this miRNA in the ADHD-HI rat model of SRH, which was related to promoter inhibitory activity of glucocorticoid receptor Nr3c1.
5.27. MiR-494¶
Significantly decreased expression was found for this miRNA in the ADHD-HI rat model of SRH, which was related to promoter inhibitory activity of glucocorticoid receptor Nr3c1.
5.28. MiR-641¶
miR-641 targets SNAP-25. SNAP-25 is an essential component of the SNARE (soluble N-ethylmaleimide-sensitive factor-binding protein receptor) complex. The 3′-UTR SNPs of SNAP-25 modify the binding site of miR-641 and contribute to several psychiatric disorders, including ADHD.
5.29. MiR-96¶
miR-96 targets a SNP in the serotonin receptor HTR1B , which is associated with ADHD.
5.30. Pri-miR34b/c¶
SNP in the promoter of pri-miR34b/c are predicted to alter the expression of several genes, including
which promotes the development of ADHD.
5.31. HOTAIR, HOX TRANSCRIPT ANTISENSE RNA, NONCODING¶
OMIM: HOTAIR, HOX TRANSCRIPT ANTISENSE RNA, NONCODING
The rs1899663 polymorphism of HOTAIR RNA is a possible ADHD risk, according to a study.
5.32. MiRNA-4655-3p¶
In children with ADHD treated with MPH (Concerta) and atomoxetine, SNAP-V score of attention deficit symptoms correlated negatively with relative expression of miRNA-4655-3p and miRNA-7641 in one study. The authors suggest that serum expression of miR-4655-3p and miR-7641 could be used as biomarkers for diagnosis and outcome assessment of ADHD-HI,
5.33. MiRNA-7641¶
In children with ADHD treated with MPH (Concerta) and atomoxetine, SNAP-V score of attention deficit symptoms correlated negatively with relative expression of miRNA-4655-3p and miRNA-7641 in one study. The authors suggest that serum expression of miR-4655-3p and miR-7641 could be used as biomarkers for diagnosis and outcome assessment of ADHD-HI,
Further information about the affected genes can be found in the gene databases
http://omim.org/ and http://www.uniprot.org/