Direct pericyte-to-neuron reprogramming via unfolding of a neural stem cell-like program

Abstract

Ectopic expression of defined transcription factors can force direct cell-fate conversion from one lineage to another in the absence of cell division. Several transcription factor cocktails have enabled successful reprogramming of various somatic cell types into induced neurons (iNs) of distinct neurotransmitter phenotype. However, the nature of the intermediate states that drive the reprogramming trajectory toward distinct iN types is largely unknown. Here we show that successful direct reprogramming of adult human brain pericytes into functional iNs by Ascl1 and Sox2 encompasses transient activation of a neural stem cell-like gene expression program that precedes bifurcation into distinct neuronal lineages. During this transient state, key signaling components relevant for neural induction and neural stem cell maintenance are regulated by and functionally contribute to iN reprogramming and maturation. Thus, Ascl1- and Sox2-mediated reprogramming into a broad spectrum of iN types involves the unfolding of a developmental program via neural stem cell-like intermediates.

Neural microvascular pericytes contribute to human adult neurogenesis

“…Demonstration of the endogenous reprogrammability (trans‐differentiation) of pericytes to generate various interneurons was an important aspect of the current study. The reprogrammability of pericytes is consistent with a recent report on forced ectopic expression of Ascl1 and Sox2 that triggers direct conversion of pericytes into interneurons (Karow et al, ). The dormant neurogenic capacity of microvascular pericytes can be traced back to the developmental origin of these cells.…”

In Vivo Neuroregeneration to Treat Ischemic Stroke in Adult Non-Human Primate Brains through NeuroD1 AAV-based Gene Therapy

“…Neuroregeneration in adult mammalian CNS has been proved to be one of the most difficult tasks in the entire regenerative medicine field, largely because neurons cannot divide to regenerate themselves and external cell transplantation yields very low number of functional new neurons (Goldman, 2016). To overcome the limitations of cell transplantation therapy, we, together with other research groups, have developed in vivo cell conversion technology to regenerate functional new neurons from endogenous glial cells for brain repair (Chen et al, 2019; Gascon et al, 2016; Guo et al, 2014; Karow et al, 2018; Liu et al, 2015; Niu et al, 2015; Niu et al, 2018; Pereira et al, 2017; Torper et al, 2015; Wang et al, 2016; Zhang et al, 2018). While stab injury model has been commonly used in various in vivo cell conversion studies, we have previously demonstrated in a mouse Alzheimer’s disease model that NeuroD1 can convert reactive astrocytes into functional neurons in 14-month old AD mouse brains (Guo et al, 2014).…”

Next‐generation disease modeling with direct conversion: a new path to old neurons

“…The most prominent conversion strategies using BAM, Ascl1/ Ngn2, and miR-9/9*-124 typically give rise to a major population of excitatory glutamatergic neurons, and the Ngn2-only protocols lead to excitatory cholinergic neurons ( Fig. Ascl1/Sox2-based iNs generated from pericytes in vivo resemble mixed GABAergic/glutamatergic cultures [69], and Ascl1 has been shown to induce oligodendroglial cells from adult neural stem cells in the dentate gyrus of mice [70]. While these observations somewhat imply a glutamatergic-by-default mechanism, or alternatively have led to the assumption that Ascl1 and Ngn2 are pro-glutamatergic and pro-cholinergic, respectively, reality appears less straightforward.…”

“…For example, iNs generated from iPSCs through Ngn2-only protocols are predominantly glutamatergic [16,68]. Ascl1/Sox2-based iNs generated from pericytes in vivo resemble mixed GABAergic/glutamatergic cultures [69], and Ascl1 has been shown to induce oligodendroglial cells from adult neural stem cells in the dentate gyrus of mice [70]. Also, both TFs are involved in midbrain and hindbrain neuronal differentiation and have varying capacities depending on the regional context [71,72].…”

“…With the establishment of (epi)genomic sequencing and epigenetic array technologies, single-cell technologies, and new insights into the complexity of neurological diseases, the historic neuron-electrophysiologycentric view on neuronal identity, function, and disease is fading [35,51,69,116]. Thus, also a broadened set of criteria on how to characterize a neuron using such new omics technologies in addition to the classical cell biological and electrophysiological measures is uprising (Fig.…”