olig2 Is Required for Zebrafish Primary Motor Neuron and Oligodendrocyte Development

Abstract

Oligodendrocytes are produced from the same region of the ventral spinal cord that earlier generated motor neurons in bird and rodent embryos. Motor neuron and oligodendrocyte precursor cells express Olig genes, which encode basic helix-loop-helix transcription factors that play important roles in the development of both motor neurons and oligodendrocytes. We found that oligodendrocytes develop similarly in zebrafish embryos, in that they arise from ventral spinal cord and migrate to new positions. Developing primary motor neurons and oligodendrocytes express olig2 as do neural plate cells that give rise to both primary motor neurons and oligodendrocytes. Loss of olig2 function prevented primary motor neuron and oligodendrocyte development, whereas olig2 overexpression promoted formation of excess primary motor neurons and oligodendrocytes. We provide genetic evidence that Hedgehog signaling is required for zebrafish olig2 expression and oligodendrocyte development. However, olig2 overexpression did not promote primary motor neuron or oligodendrocyte development in embryos with reduced Hedgehog signaling activity. One possibility consistent with these data is that Hedgehog signaling, partly by inducing olig2 expression, specifies neural precursor cells that have potential for primary motor neuron or oligodendrocyte fate.

Expression of the transcription factor Olig2 in proliferating cells in the adult zebrafish telencephalon

“…To this end, transverse sections through the telencephalon of Tg(olig2:EGFP) animals were labelled immunohistochemically with anti-GFP antibody and by fluorescent in situ hybridisation with sox10 antisense probe, a marker of the oligodendrocyte lineage (Kuhlbrodt et al, 1998;Park et al, 2002). Among 754 Tg(olig2:EGFP)-positive cells examined, we observed 98% cells co-expressing sox10 ( Fig.…”

“…During development, Olig2 plays a role in spinal cord patterning, being important for the formation of motorneurons, interneurons, and oligodendrocytes as well as of astrocytes and ependymal cells (Lu et al, 2000;Zhou et al, 2000;Park et al, 2002;Takebayashi et al, 2002;Masahira et al, 2006). A recent study found that slowly proliferating Tg(olig2:EGFP)-positive radial glia-like cells are present in the adult zebrafish spinal cord, where they seem to act as progenitors restricted to the oligodendrocyte lineage (Park et al, 2007).…”

nkx2.2apromotes specification and differentiation of a myelinating subset of oligodendrocyte lineage cells in zebrafish

“…Probes included olig2 (Park et al, 2002), nkx2.2a (Barth and Wilson, 1995), plp/ dm20 and mbp (Brosamle and Halpern, 2002). Plasmids were linearized with appropriate restriction enzymes and cRNA preparation was carried out using Roche DIG-labeling reagents and T3, T7 or SP6 RNA polymerases (New England Biolabs).…”

MiRNA expression analysis during normal zebrafish development and following inhibition of the Hedgehog and Notch signaling pathways

“…Multiple developmental events require both signaling cascades. For example, both pathways are involved in oligodendrocyte development and muscle formation Eisen, 2000, 2002;Scheer et al, 2001;Park et al, 2002). Neuronal differentiation of motor neurons and oligodendrocytes requires Olig2 expression in the neural plate and Olig2 expression requires both ngn1, a Notch activator, as well as intact Hedgehog signaling (Park et al, 2002).…”