Reversal of developmental restrictions in neural crest lineages: Transition from Schwann cells to glial-melanocytic precursors in vitro

Abstract

In vertebrate embryos, diversification of the lineages arising from the neural crest (NC) is controlled to a large extent by environmental factors. In previous work, we showed that endothelin 3 (ET3) peptide favors the development of glial and melanocytic NC precursors in vitro. This factor is also capable of inducing proliferation of cultured epidermal pigment cells and their conversion to glia. ET3 therefore strongly promotes the emergence of melanocytic and glial phenotypes from precursors and acts on the maintenance of these phenotypes. In the present work, we explored the capacity of ET3 to reprogram glial cells into melanocytes. Schwann cells expressing glial-specific markers [such as the Schwann cell myelin protein (SMP)] were isolated from sciatic nerves of quail embryos and cultured in vitro. We found that ET3 promotes cell growth and sequential expression of melanocyte differentiation markers in cultures of purified SMP-expressing cells, whereas it had no significant effect on SMP-negative cells from the same nerves. Moreover, we provide evidence for the transition of differentiated Schwann cells to melanocytes in clonal cultures. This transition involves the production of a mixed progeny of melanoblasts͞melanocytes, glia, and cells bearing differentiation markers of both phenotypes. Therefore, Schwann cells exposed to ET3 transdifferentiate to melanocytes through reversion to the stage of bipotent glial-melanocytic NC precursors. These findings show that NC-derived pigment and glial cells are phenotypically unstable in vitro and may undergo reversal of precursor hierarchy to function as bipotent stem cells.melanocytes ͉ quail embryo ͉ clonal cultures ͉ endothelin 3 D uring vertebrate embryogenesis, neural crest (NC) cells arise from the dorsal aspect of the closing neural tube and undergo extensive migration along distinct pathways as they proliferate. The NC gives rise to a wide range of cell types, including neurons and glia of the peripheral nervous system (PNS), melanocytes, craniofacial bones and cartilage, fibroblasts, smooth muscle cells, and endocrine cells (1, 2). Migrating NC cells are a heterogeneous collection of progenitors, including multipotent stem cells, cells with limited developmental potential and fate-restricted precursors (3-11). The influence of environmental signals is therefore crucial to ensure that postmigratory NC-derived cells express a defined phenotype corresponding to their position in the body (for reviews, see refs. 1, 2, and 12). Among such signals, endothelin 3 (ET3) signaling through endothelin receptor (ETR) B was shown in mouse and human to be required in vivo for proper development of melanocytes and posterior enteric nerve cells (13)(14)(15)(16). In vitro culture studies have revealed that ET3 exerts trophic and mitogenic activities on early avian and mammalian NC cells (17)(18)(19)(20). The main target cells of ET3 have been identified (18) and include faterestricted glial and melanocytic cells as well as a bipotent glialmelanocytic (GM) precursor previously e...

Self-renewal capacity is a widespread property of various types of neural crest precursor cells

“…Such dependency is consistent with our findings (26) that GM precursors of trunk origin are a privileged target for the survival-and proliferation-promoting effects of ET3 in vitro. The strong potential of ET3 to trigger expansion of GM stem cells may also underlie the capacity of differentiated glial cells and melanocytes to reverse their phenotypic program and transdifferentiate reciprocally in vitro (36,37,53). GM cells isolated from the cephalic NC showed a delayed response to ET3 because they were unaffected by treatment during the first cloning.…”

Schwann Cells Can Be Reprogrammed to Multipotency by Culture

“…The term "reprogramming" was used for the first time, as the conversion of glial cells into melanocytes succeeded [4]. In addition, multipotent rat neural crest stem cells can be derived from embryonic SNs [18].…”

“…Recently, it has been demonstrated that Schwann cells are highly plastic cells that are able to differentiate into melanocytes and myofibroblasts, undergo cellular reprogramming, dedifferentiate, and re-enter the cell cycle [4,5]. A hallmark of reprogramming of an adult cell to a stem cell is the alteration of its pattern in gene expression [6].…”

Therapeutic implications of autoimmune vitiligo T cells

“…In this respect it is of interest that the T cell clones originally isolated from a patient with leprosy that were used to demonstrate reactivity towards MHC class II expressing melanocytes were reactive with mycobacterial stress protein hsp65 [31]. This is noteworthy, particularly since Schwann cells harbor the causative M. leprae organism in leprosy, whereas Schwann cells are developmentally very closely related to melanocytes [35]. This similarity may ultimately contribute to cross reactivity or epitope spreading from Schwann cell antigens to melanocytes, explaining the similarity among lesions observed in tuberculoid leprosy and autoimmune vitiligo.…”