Decrease in levels of the evolutionarily conserved microRNA miR-124 affects oligodendrocyte numbers in Zebrafish, Danio rerio
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Oligodendrocytes produce multi-lamellar myelin membranes that surround axons in the central nervous system (CNS). Preservation and generation of myelin are potential therapeutic targets for dysmyelinating and demyelinating diseases. MicroRNAs (miRNAs) play a vital role in oligodendrocyte differentiation and overall CNS development. miR-124 is a well-conserved neuronal miRNA with important roles in neuronal differentiation and function. miR-124 levels increase following loss of myelin in both human and rodent brains. While the role of neuronal miR-124 in neurogenesis has been established, its effects on axonal outgrowth and oligodendrocytes are not currently known. We therefore explored the possible effect of selective knockdown of miR-124 in Danio rerio using a morpholino-based knockdown approach. No morphological abnormalities or loss of motor neurons were detected despite loss of axonal outgrowth. Morpholino-based knockdown of miR-124 led to reciprocal increases in mRNA levels of target genes that inhibit axonal and dendritic projections. Importantly, loss of miR-124 led to decreased oligodendrocyte cell numbers and myelination of axonal projections in the ventral hindbrain. Taken together, our results add a new dimension to the existing complexity of neuron–glial relationships and highlight the utility of Danio rerio as a model system to investigate such interactions.
KeywordsDanio rerio miR-124 Neuron Oligodendrocyte miRNA
The authors would like to thank Dr. Stephen Stohlman for his comments and Dr. Christopher Nelson for manuscript editing.
Compliance with Ethical Standards
The work was supported by a Grant from the National Multiple Sclerosis Society, USA (RG-4280 to RD), and Baldwin Wallace University Faculty Development award (JKM).
Conflict of interests
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