title: Role of miRNA-9 in Brain Development.
abstract: MicroRNAs (miRNAs) are a class of small regulatory RNAs involved in gene regulation. The regulation is effected by either translational inhibition or transcriptional silencing. In vertebrates, the importance of miRNA in development was discovered from mice and zebrafish dicer knockouts. The miRNA-9 (miR-9) is one of the most highly expressed miRNAs in the early and adult vertebrate brain. It has diverse functions within the developing vertebrate brain. In this article, the role of miR-9 in the developing forebrain (telencephalon and diencephalon), midbrain, hindbrain, and spinal cord of vertebrate species is highlighted. In the forebrain, miR-9 is necessary for the proper development of dorsoventral telencephalon by targeting marker genes expressed in the telencephalon. It regulates proliferation in telencephalon by regulatingFoxg1, Pax6, Gsh2, andMeis2genes. The feedback loop regulation between miR-9 andNr2e1/Tlxhelps in neuronal migration and differentiation. TargetingFoxp1andFoxp2, andMap1bby miR-9 regulates the radial migration of neurons and axonal development. In the organizers, miR-9 is inversely regulated byhairy1andFgf8to maintain zona limitans interthalamica and midbrain-hindbrain boundary (MHB). It maintains the MHB by inhibiting Fgf signaling genes and is involved in the neurogenesis of the midbrain-hindbrain by regulatingHergenes. In the hindbrain, miR-9 modulates progenitor proliferation and differentiation by regulatingHergenes andElav3. In the spinal cord, miR-9 modulates the regulation of Foxp1 and Onecut1 for motor neuron development. In the forebrain, midbrain, and hindbrain, miR-9 is necessary for proper neuronal progenitor maintenance, neurogenesis, and differentiation. In vertebrate brain development, miR-9 is involved in regulating several region-specific genes in a spatiotemporal pattern.
authors.affiliation: School of Engineering and Science, Jacobs University Bremen, Bremen, Germany.
authors.forename: Balachandar
authors.initials: B
authors.lastname: Radhakrishnan
authors.affiliation: Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Alwin Prem Anand
keywords: diencephalon; hindbrain; miR-9; midbrain; spinal cord; telencephalon