miRNAs AS POTENTIAL REGULATORS OF MYELIN BASIC PROTEIN RECOVERY DURING DEVELOPMENT IN A MURINE MODEL OF PHENYLKETONURIA

Untreated phenylketonuria (PKU) patients and PKU animal models show hypomyelination in the central nervous system and white matter damages. These cerebral alterations are accompanied by myelin basic protein (MBP) impairment, which could be the reason of the clinical traits mentioned above, as MBP is crucial for the correct assembling of the myelin sheath. In this study, we analyzed MBP protein and mRNA expression on brains of WT and phenylketonuric (ENU2) mice during post-natal development (14-60-180-270-360-540 post-natal days, PND). The results showed a progressive MBP protein expression recovery during post-natal development, together with an unaltered MBP mRNA expression. Furthermore, for the same time intervals, a significant decrease of the phenylalanine concentration in the bloodstream of PKU mice was detected, as well as in the PKU mice brains from 14 to 60 PND. To try to explain this scenario, we hypothesized a hindrance during MBP translation in the early development, leading us to perform a microRNA microarray analysis on 60 PND mice. Microarray output and the following in silico analyses underlined the potential role of microRNAs in the PKU cerebral outcomes. In addition, in order to link predictive analysis with concrete data, we performed a proteomic assay on ENU2 brains of 60 and 360 PND. Taken together, we assessed miR-218-1-3p, miR-1231-3p and miR-217-5p as the most promising microRNAs, since that an alteration on their predicted and downregulated targets (MAG, CNTNAP2 and ANLN, respectively) could indirectly lead to a low MBP protein expression. Moreover, their expression shows an opposite trend to that observed for MBP protein during development, except for miR-217-5p. Furthermore, target proteins revealed a complete normalization in aged ENU2 mice. In conclusion, these results provide a new perspective on the PKU pathophysiology understanding and treatment, emphasizing the possible role of differentially expressed microRNAs in PKU brains, especially during early development.