Neural Crest – Head

This PNAS paper identifies in chicken, a neural crest stem cell isolated from the head region which can differentiate into many different cell types. It also identifies a role for Sonic hedgehog (Shh) to stimulate differentiation of endochondral, but not intramembranous, osteoblasts.

High frequency of cephalic neural crest cells shows coexistence of neurogenic, melanogenic, and osteogenic differentiation capacities.Calloni GW, Le Douarin NM, Dupin E. Proc Natl Acad Sci U S A. 2009 May 15. [Epub ahead of print] PMID: 19447928 | PNAS

The neural crest (NC) is a vertebrate innovation that distinguishes vertebrates from other chordates and was critical for the development and evolution of a “New Head and Brain.” …Here, we show that in avian embryos, a large majority of cephalic NC cells (CNCCs) have the ability to differentiate into cell types as diverse as neurons, melanocytes, osteocytes, and chondrocytes. Moreover, we find that the morphogen Sonic hedgehog (Shh) acts on CNCCs to increase endochondral osteogenesis while having no effect on osteoblasts prone to membranous ossification. We have developed culture conditions that demonstrate that “neural-mesenchymal” differentiation abilities are present in more than 90% of CNCCs. A highly multipotent progenitor (able to yield neurons, glia, melanocytes, myofibroblasts, chondrocytes, and osteocytes) comprises 7-13% of the clonogenic cells in the absence and presence of Shh, respectively.

(More? UNSW Embryology – Neural Crest | Head and Neck | SHH | Chicken)

Cartilage Development

This Development paper utilises a variation on the traditional quail/chicken chimera (embryo mixing of 2 species) model to study neural crest by using quail/duck chimeras. Cartilage, like all skeletal elements, needs to initially form the specific tissue (histogenesis) and then define its specific shape (morphogenesis).

Eames BF, Schneider RA. The genesis of cartilage size and shape during development and evolution. Development. 2008 Dec;135(23):3947-58. Epub 2008 Oct 30.

“Transplanting neural crest cells from quail to duck demonstrates that
mesenchyme imparts both stage-specific and species-specific size and
shape to cartilage by controlling the timing of preceding and requisite
molecular and histogenic events.”

(More? UNSW Embryology – Neural Crest | Cartilage | Head)

Neural Crest Development

Neural crest has an important contribution to the face and heart outflow tract. There are several known human developmental neural crest associated abnormalities in both these systems.  This PNAS paper identifies a signaling pathway (RAF/MEK/ERK/serum response factor) involved in mammalian neural crest development.

Mouse and human phenotypes indicate a critical conserved role for ERK2 signaling in neural crest development Jason Newbern, etal., PNAS  November 4, 2008   vol. 105  no. 44  17115-17120

“mammalian neural crest development is critically dependent on a
RAF/MEK/ERK/serum response factor signaling pathway and suggest that
the craniofacial and cardiac outflow tract defects observed in patients
with a distal 22q11.2 micro-deletion are explained by deficiencies in
neural crest autonomous ERK2 signaling.”

(More? UNSW Embryology – Neural Crest Notes | Neural Crest Abnormalities)