Deficiency of MicroRNA-23-27-24 Clusters Exhibits the Impairment of Myelination in the Central Nervous System

Abstract

Several microRNAs (miRNAs), including miR-23 and miR-27a have been reportedly involved in regulating myelination in the central nervous system. Although miR-23 and miR-27a form clusters in vivo and the clustered miRNAs are known to perform complementary functions, the role of these miRNA clusters in myelination has not been studied. To investigate the role of miR-23-27-24 clusters in myelination, we generated miR-23-27-24 cluster knockout mice and evaluated myelination in the brain and spinal cord. Our results showed that 10-week-old knockout mice had reduced motor function in the hanging wire test compared to the wild-type mice. At 4 weeks, 10 weeks, and 12 months of age, knockout mice showed reduced myelination compared to wild-type mice. The expression levels of myelin basic protein and myelin proteolipid protein were also significantly lower in the knockout mice compared to the wild-type mice. Although differentiation of oligodendrocyte progenitor cells to oligodendrocytes was not inhibited in the knockout mice, the percentage of oligodendrocytes expressing myelin basic protein was significantly lower in 4-week-old knockout mice than that in wild-type mice. Proteome analysis and western blotting showed increased expression of leucine-zipper-like transcription regulator 1 (LZTR1) and decreased expression of R-RAS and phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) in the knockout mice. In summary, loss of miR-23-27-24 clusters reduces myelination and compromises motor functions in mice. Further, LZTR1, which regulates R-RAS upstream of the ERK1/2 pathway, a signal that promotes myelination, has been identified as a novel target of the miR-23-27-24 cluster in this study.

Myelin-Specific microRNA-23a/b Cluster Deletion Inhibits Myelination in the Central Nervous System during Postnatal Growth and Aging

“…Previous studies have reported the expression of miR-23a/b clusters in the liver, lungs, skeletal muscles, and CNS [14,18,19]. In this context, the present study assessed changes in the expression of these clusters in the organs of myelin-specific miR-23a/b cluster-deficient mice.…”

“…In our previous study using mice systemically deficient in miR-23a/b clusters, differences were noted between KO and control mice in the hanging wire test but not in the balance beam test [14]. The balance beam test described in a previous study used a 10 mm wide and 50 cm long beam.…”

“…Behavioral assessments were performed on 10-week-old and 12-month-old control and KO mice. Motor function tests were performed using methods described in previous reports, including the hanging wire and balance beam tests [14,24,25]. The hanging wire test assessed overall subacute muscle function and coordination.…”

“…Myelination is a complex, multistep process encompassing the proliferation of oligodendrocyte progenitor cells (OPCs), their differentiation, and the subsequent formation of myelin sheaths around axons [6,7]. Recent advancements have increasingly highlighted the pivotal role of microribonucleic acids (miRNAs) in the regulation of myelination [8][9][10][11][12][13][14].…”

“…Although miR-23a and miR-27a are part of the miR-23-27-24 cluster, they reportedly exert opposing effects on myelination regulation in the CNS [12,13]. In our previous study, mice with a global miR-23a/b cluster knockout (KO) from embryonic life, comprising miR-23a-27a-24-2 (miR-23a cluster) and miR-23b-27b-24-1 (miR-23b cluster), showed hypoplastic myelin sheath formation in the brain and spinal cord [14]. However, due to the widespread expression of miR-23a/b clusters in various tissues, including the lungs, skeletal muscle, liver, and CNS, studies using global miR-23a/b cluster KO mice have been unable to delineate tissue-specific mechanisms [18,19].…”