Multipotency of melanoblasts isolated from murine skin depends on the Notch signal.

BACKGROUND: Melanoblasts (MBs), derived from neural crest cells, only differentiate into melanocytes (Ms) in vivo. We previously showed that MBs isolated from mouse skin were multipotent, generating neurons (Ns) and glial cells (Gs) together with Ms. Using Sox10-IRES-Venus mice and mouse embryonic stem cells, we investigated how MBs expressed their multipotency. RESULTS: MBs generated colonies containing Ns, Gs, and Ms in the presence of ST2 stromal cells, but they generated only M colonies when incubated with keratinocytes or ST2 culture supernatant, thus showing that MBs required contact with ST2 stromal cells for expression of their multipotency. Notch signaling was shown to be one of the important cues for the maintenance and differentiation of MBs through cell-cell contact. When Notch signaling was inhibited, MBs mainly generated colonies that contained just one type of cells, Ns, Gs, or Ms; the number of colonies containing two or three types of cells markedly decreased even on ST2 stromal cells, showing restriction of their differentiation potency. Whereas when Notch signaling was activated, the number of colonies containing two or three types of cells increased, indicating that their multipotency had been maintained. CONCLUSIONS: Our results demonstrate that Notch signaling played novel roles in MB multipotency.

Sox10 Functions as an Inducer of the Direct Conversion of Keratinocytes Into Neural Crest Cells.

Neural crest cells (NCCs) are highly migratory multipotent cells that play critical roles in embryogenesis. The generation of NCCs is controlled by various transcription factors (TFs) that are regulated by each other and combine to form a regulatory network. We previously reported that the conversion of mouse fibroblasts into NCCs was achieved by the overexpression of only one TF, Sox10; therefore, Sox10 may be a powerful inducer of the conversion of NCCs. We herein investigated whether Sox10 functions in the direct conversion of other somatic cells into NCCs. Sox10 directly converted bone marrow-derived mesenchymal cells, but not keratinocytes, into P75+ NCCs. However, by the co-expression of four TFs (Snail1, Snail2, Twist1, and Tcfap2a) that are involved in NCC generation, but unable convert cells into NCCs, Sox10 converted keratinocytes into P75+ NCCs. P75+ NCCs mainly differentiated into glial cells, and to a lesser extent into neuronal cells. On the other hand, when Sox10 was expressed after the four TF expression, which mimicked the expression order in in vivo NCC generation, it converted keratinocytes into multipotent NCCs. These results demonstrate that Sox10 functions as an inducer of direct conversion into NCCs in cooperation with the TFs involved in NCC generation. The sequence of expression of the inducer and cooperative factors is important for the conversion of somatic cells into bona fide target cells.

Galectin-1 enhances the generation of neural crest cells.

Neural crest (NC) cells are multipotent cells that emerge from the dorsal region of the neural tube. After delaminating from the neural tube, NC cells migrate throughout the developing embryo and differentiate into various cells: neurons and glial cells of the peripheral nervous system, melanocytes of skin, and skeletal elements of the face and head. We previously analyzed the gene expression profile of a NC subpopulation isolated from Sox10-IRES-Venus mice and found that the carbohydrate-binding protein, Galectin-1 (Gal-1) was strongly expressed in generating NC cells. In the present study, we identified GAL-1 as a factor that promotes NC cell generation. Gal-1 was significantly expressed in NC cells generated in explanted neural tubes. The presence of GAL-1 enhanced the generation of NC-like cells from mouse embryonic stem (ES) cells. In the differentiation of ES cells into NC-like cells, GAL-1 enhanced neurogenesis in the early stages and facilitated NC-like cell generation in the later stages. GAL-1 also enhanced the generation of NC cells from explanted neural tubes. These results suggest that GAL-1 plays a facilitative role in NC cell generation.