Further Evidence That MicroRNAs Can Play a Role in Hemophilia A Disease Manifestation: Gene Downregulation by miR-19b-3p and miR-186-5p.

Hemophilia A (HA) is a gene mutational disorder resulting in deficiency or dysfunctional FVIII protein. However, surprisingly, in few cases, HA is manifested even without mutations in . To understand this anomaly, we recently sequenced microRNAs (miRNAs) of two patients with mild and moderate HA with no gene mutations and selected two highly expressing miRNAs, miR-374b-5p and miR-30c-5p, from the pool to explain the FVIII deficiency that could be mediated by miRNA-based /FVIII suppression. In this report, an established orthogonal RNA-affinity purification approach was utilized to directly identify a group of -interacting miRNAs and we tested them for /FVIII suppression. From this pool, two miRNAs, miR-19b-3p and miR-186-5p, were found to be upregulated in a severe HA patient with a mutation in the coding sequence and two HA patients without mutations in the coding sequence were selected to demonstrate their role in gene expression regulation in mammalian cells. Overall, these results provide further evidence for the hypothesis that by targeting the 3'UTR of , miRNAs can modulate FVIII protein levels. This mechanism could either be the primary cause of HA in patients who lack mutations or control the severity of the disease in patients with mutations.