Cell divisions are not essential for the direct conversion of fibroblasts into neuronal cells

Abstract

These authors equally contributed to this work.Keywords: cell division, direct conversion, fibroblast, neuron, reprogramming, transdifferentiation Abbreviations: iPS cells, induced pluripotent stem cells; ES cells, embryonic stem cells; BAM, Brn2, Ascl1 and Myt1l; BAMCM, Brn2, Ascl1, Myt1l and cMyc; DOX, doxycycline; BrdU, bromodeoxyuridine; MEF, mouse embryonic fibroblasts.Direct lineage conversion is a promising approach for disease modeling and regenerative medicine. Cell divisions play a key role in reprogramming of somatic cells to pluripotency, however their role in direct lineage conversion is not clear. Here we used transdifferentiation of fibroblasts into neuronal cells by forced expression of defined transcription factors as a model system to study the role of cellular division in the direct conversion process. We have shown that conversion occurs in the presence of the cell cycle inhibitors aphidicolin or mimosine. Moreover, overexpression of the cell cycle activator cMyc negatively influences the process of direct conversion. Overall, our results suggest that cell divisions are not essential for the direct conversion of fibroblasts into neuronal cells.

Evaluating cell reprogramming, differentiation and conversion technologies in neuroscience

“…Although it has not yet been decisively demonstrated whether fibroblast-based iNs pass through an intermediate progenitor-like epigenetic state (as studies based on glia as starting cells suggest 104,105 ), it is well established that iN conversion requires no proliferation 98,106 . Cell division is deemed essential during in vivo and hPSC differentiation because it stimulates the chromatin remodelling required to provide transcription factor access to previously closed regions 92 .…”

Direct neuronal reprogramming: learning from and for development

“…However, direct reprogramming has clearly demonstrated that proliferation is not a prerequisite for the cell fate switch, as many cell types can convert into neurons without cell division (Fishman et al, 2015;Gascón et al, 2016;Heinrich et al, 2010;Karow et al, 2012;Marro et al, 2011). In fact, the overexpression of the cell cycle activator Myc actually reduced the efficiency of fibroblast conversion to neuronal cells (Fishman et al, 2015).…”

“…However, direct reprogramming has clearly demonstrated that proliferation is not a prerequisite for the cell fate switch, as many cell types can convert into neurons without cell division (Fishman et al, 2015;Gascón et al, 2016;Heinrich et al, 2010;Karow et al, 2012;Marro et al, 2011). In fact, the overexpression of the cell cycle activator Myc actually reduced the efficiency of fibroblast conversion to neuronal cells (Fishman et al, 2015). This supports the observation that BETbromodomain inhibitors enhance neuronal reprogramming mediated by small molecules (Hu et al, 2015;Zhang et al, 2015), as these compounds cause cell cycle arrest and inhibit Myc expression at transcriptional levels (Cheng et al, 2007;Delmore et al, 2011;Gallagher et al, 2014).…”

Programming and reprogramming neural cell types using synthetic transcription factors

“…While cells which completed transdifferentiation process stay as epithelial cells, other cells which are still undergoing the process can return back to hepatocyte fate if stimulus is removed (Tarlow et al 2014). Lastly, while cell division seems to be a critical requirement and an enhancing condition during iPSCs reprograming (Hanna et al 2009), it is not required during transdifferentiation of fibroblasts into neural cells (Iwafuchi-Doi et al 2014;Fishman et al 2015).…”