Raymond Teck Ho Lee1, Hiroki Nagai2, Yukiko Nakaya2, Guojun Sheng2, Paul A. Trainor3,4, James A. Weston5 and Jean Paul Thiery1,6,7*.
1 - Institute of Molecular Cell Biology, A*STAR, 61 Biopolis Drive, 138673, Singapore.
2 - Laboratory for Early Embryogenesis, RIKEN Center for Developmental Biology, 2-2-3
Minatojima-minamimachi, Chuo-Ku, Kobe, Hyogo 650-0047, Japan.
3 - Stowers Institute for Medical Research, 1000 E 50th Street, Kansas City, MO 64110, USA
4 - Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403-1254, USA.
- Cancer Science Institute, National University of Singapore, 14 Medical Drive, 117599, Singapore.
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 8 Medical Drive, 117596, Singapore.
* Author for correspondence (email@example.com)
Published online in Development on 6 November 2013.
The neural crest is a transient structure unique to vertebrate embryos that gives rise to multiple lineages along the rostrocaudal axis. In cranial regions, neural crest cells are thought to differentiate into chondrocytes, osteocytes, pericytes and stromal cells, which are collectively termed ectomesenchyme derivatives, as well as pigment and neuronal derivatives. There is still no consensus as to whether the neural crest can be classified as a homogenous multipotent population of cells. This unresolved controversy has important implications for the formation of ectomesenchyme and for confirmation of whether the neural fold is compartmentalized into distinct domains, each with a different repertoire of derivatives. Here we report in mouse and chicken that cells in the neural fold delaminate over an extended period from different regions of the cranial neural fold to give rise to cells with distinct fates. Importantly, cells that give rise to ectomesenchyme undergo epithelial-mesenchymal transition from a lateral neural fold domain that does not express definitive neural markers, such as Sox1 and N-cadherin. Additionally, the inference that cells originating from the cranial neural ectoderm have a common origin and cell fate with trunk neural crest cells prompted us to revisit the issue of what defines the neural crest and the origin of the ectomesenchyme.
Figure Legend: Cells delaminate from the non-neural ectoderm before the neural ectoderm in chicken embryos. (A-C) DiI and DiO were used to label different regions of the neural fold. (A) Non-neural ectoderm was DiI labeled at 5 somites. The embryos were grown until 8 somites (Ab,c). Labeled cells can be seen at the leading edge of the migrating cells. (B) Neural ectoderm was labeled with DiI at 7 somites. The embryos were grown until 11 somites (Bb,c). Labeled cells are found in the trailing edge of the migrating cells; the white dotted line represents migrating Snail2-positive cells. (C) Labeling was performed at 4 somites and embryos were grown until 10 somites (Cd-f). These two populations of labeled cells do not intermingle. (Cd) DiO-labeled cells form the leading edge of the migrating cells, whereas (Ce) DiI-labeled cells form the trailing edge; yellow dotted line represents migrating Snail2-positive cells. (D,E) Schematics of (D) cell delamination and movement away from the neural fold at 4 and 7 somites based on the results from general tissue movements, loss of basal/apical polarity and the short-term tracing of cells and (E) how they contribute to the migrating mass of cells. The red gradient in the figures represents the two waves of delaminating cells, with red and white representing cells originating from the non-neural and neural ectoderm, respectively. s, somites. Scale bars: 100 μm.
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