Purchase this article with an account.
Qulsum A Mir, Li Zheng, Iqbal Ahmad; Involvement of Lin28 and Ascl1 in Muller Glia-mediated neurogenesis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):411. doi: https://doi.org/.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Recent evidence suggests that Muller Glia (MG) possess evolutionary conserved neural stem cell properties. However, the mammalian MG displays low efficiency of differentiation along the neuronal lineage, which has emerged as a significant barrier to potential MG-mediated therapeutic regeneration. This barrier may be due to differential recruitment of molecular axes that leads to the inhibition of neuronal differentiation. Here, we have examined the involvement of an axis defined by Lin28, a heterochronic gene that regulates the timing of neurogliogensis, and Ascl1, a proneural gene during the differentiation of MG along the neuronal lineage.
The role of Lin28 and Ascl1 was examined in hypoxia-enriched rat MG, using the neurosphere assay (Das et al., 2007, Dev. Biol. 299:283-302). Neurospheres were generated in the presence of FGF and Noggin. Cells from secondary neurospheres were transduced with Ascl1 lentivirus/empty lentivirus or Lin28 retrovirus/empty retrovirus for Ascl1/Lin28 gain-of-function (GOF). Transduced cells were cultured in the presence of conditioned medium obtained from embryonic day 18 (E18)/postnatal day 1 (PN1) rat retinal cells, for eight days followed by qPCR and immunocytochemical analyses.
The glial morphology of a subset of cells in Ascl1 and Lin28 GOF groups changed to cells with bipolar processes, compared to empty virus controls. Cells in Ascl1 GOF groups expressed significantly higher levels of transcripts corresponding to ßIIItubulin, an early and generic neuronal marker. The increase in ßIIItubulin expression was accompanied by an increase and a decrease in Lin28 transcript and let7 miRNA levels, respectively, suggesting Ascl1-mediated activation of Lin28 expression, presumably through E box elements in Lin28 promoter. Cells in Lin28 GOF groups displayed higher expression of ßIIItubulin, accompanied by an expected decrease in levels of let7 miRNA, as Lin28 is known to prevent the maturation of let7 pre-miRNA into let 7 miRNA. Interestingly, the expression of Ascl1 was significantly increased in Lin28 GOF, presumably through the repression of let7, which could target Ascl1.
Our initial results suggest that the molecular axis underpinned by Lin28 and Ascl1 could be a potential target for improving the neuronal potential of the mammalian MG.
This PDF is available to Subscribers Only