Biology Reference
In-Depth Information
Figure 5.1
Summary of the miRNAs acting during different stages of neuronal devel-
opment. Only those miRNAs discussed in the text have been included.
point, miRNAs have been implicated in practically all steps of glia devel-
opment, particularly in the two glial types that produce myelin, OLs (in the
CNS), and Schwann cells (in the PNS). Here, we will illustrate the state of
our knowledge by discussing the roles of miRNAs in OL development.
The differentiation of oligodendrocyte progenitor cells (OPCs) into
OLs occurs in at least two steps. First, a series of intrinsic and external signals
promote differentiation into a premyelinating OL that is able to extend
processes to contact axons and initiate sheath formation. Subsequently,
myelin sheaths start being produced, and at this stage, new processes cannot
be extended to contact new axons. Thus, the timing of these events is
important for proper myelination. At least five different miRNAs are
involved in OL differentiation. mir-19, from the mir-17-92 cluster, first
promotes the expansion of the OPC pool, inducing proliferation through
the inhibition of its target
PTEN
(
Budde
et al
., 2010
)
.
OPCs are then
induced to differentiate by a number of factors including mir-219 and
mir-338. Together, these two miRNAs target a number of OPC-expressed
