File:Zebrafish neural crest model.jpg

Model for the role of H3.3-dependent histone replacement during CNC development

At the early embryonic blastula stage, cells have a broad potential with cis-regulatory elements for developmental genes existing in a “poised” chromatin state.

After gastrulation occurs to form the three major germ layers (ectoderm, mesoderm, and endoderm), genes associated with a particular germ layer are activated or maintained in a poised state, whereas genes for other layers are strongly repressed at the chromatin level.

The cranial neural crest (CNC) is unusual in that it is derived from ectoderm yet can give rise to mesoderm-like derivatives such as skeleton. H3.3-dependent histone replacement could thus be required to remodel the enhancers of mesodermal genes needed for ectomesenchymal fates, with the distinctive role of H3.3 in CNC correlating with the need to derepress mesodermal enhancers that have been previously silenced in the ectoderm germ layer (1).

Alternatively H3.3 incorporation could act to maintain mesoderm-like potential in the CNC ectoderm from an earlier time in development (2). It also remains unresolved the extent to which ectomesenchyme derivatives (e.g. head skeleton) and non-ectomesenchyme derivatives (e.g. pigment, glia, and neurons) derive from a common multipotent precursor. Hence, the cranial pigment and ectomesenchyme defects of h3f3adb1092 mutants could arise from altered histone replacement in a common multipotent precursor, or alternatively from independent defects in different subsets of heterogeneous CNC with more limited potential.

(text from figure legend)

Links: Zebrafish Development | Neural Crest Development | Head Development

Reference

<pubmed>23028350</pubmed>| PLoS Genet.

Copyright: © 2012 Cox et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Figure 10.

doi:10.1371/journal.pgen.1002938.g010