Figure 6. Neural differentiation in merm embryos.

(A) The e10.5 merm neural tube (b, d) contained fewer post-mitotic neurons (TuJ1- positive, a–b; Map2-positive, c–d), even compared to an e9.5 control (a, c). Wild-type and merm neural tubes expressed comparable levels of Sox2 (a–b), a marker of both epiblast and neural progenitor cells, and of Sox1 (e–f), a marker of neural progenitor cells. The persistence of Id1-positive cells throughout the merm neuroepithelium (h) indicated that the progenitors were more immature than those in the e9.5 wild-type neuroepithelium (g). (B) The patterning of neural progenitors was comparable between wild-type and merm neural tubes at e10.5 (a–h). (C) Markers of the G1 phase of the cell cycle were mostly absent in the merm neural tube (cyclin D1, a–b; cyclin D2, c–d; and p27Kip1, e–f), whereas expression of phosphorylated histone H3 (phospho-H3) indicated that merm and wild-type cells were undergoing mitosis at similar levels (g–h). Immunofluorescence with the indicated antibodies was performed on cryosections of neural tubes prepared from e9.5 or e10.5 merm and wild-type embryos and imaged by confocal or widefield microscopy.