Localised axial progenitor cell populations in the avian tail bud are not committed to a posterior Hox identity

Abstract

The outgrowth of the vertebrate tail is thought to involve the proliferation of regionalised stem/progenitor cell populations formed during gastrulation. To follow these populations over extended periods, we used cells from GFP-positive transgenic chick embryos as a source for donor tissue in grafting experiments. We determined that resident progenitor cell populations are localised in the chicken tail bud. One population, which is located in the chordoneural hinge (CNH), contributes descendants to the paraxial mesoderm, notochord and neural tube, and is serially transplantable between embryos. A second population of mesodermal progenitor cells is located in a separate dorsoposterior region of the tail bud, and a corresponding population is present in the mouse tail bud. Using heterotopic transplantations, we show that the fate of CNH cells depends on their environment within the tail bud. Furthermore, we show that the anteroposterior identity of tail bud progenitor cells can be reset by heterochronic transplantation to the node region of gastrula-stage chicken embryos.

FGF-dependent midline-derived progenitor cells in hypothalamic infundibular development

“…We propose that this zone shapes both the infundibulum and, potentially, the overlying hypothalamus, and that it can contribute cells to the infundibulum over an extended period. Intriguingly, other studies have shown that there is a second proliferative zone at the most caudal region of the forming neural tube, in which FGF signalling maintains cells in a proliferative, undifferentiated state (Diez del Corral et al, 2003;Delfino-Machin et al, 2005;McGrew et al, 2008). The two ends of the neural tube therefore share the ability to promote FGF signalling and establish proliferative zones.…”

The roof plate boundary is a bi-directional organiser of dorsal neural tube and choroid plexus development

“…Fertilised green fluorescent protein transgenic (GFP-tg) eggs (McGrew et al, 2008) and wild-type eggs (Henry Stewart, UK) were incubated at 38°C for 3 to 6 days before windowing with sharp surgical scissors. A number of embryos at embryonic day (E)4-6 were removed from eggs and neural tubes dissected in Tyrode's solution.…”

The chicken polydactyly (Po) locus causes allelic imbalance and ectopic expression of Shh during limb development

“…transgenic non-polydactylous Roslin Green embryos that express GFP ubiquitously (McGrew et al, 2008) and Slk embryos. We replaced the anterior half of the Slk leg bud with an equivalent half from a Roslin Green leg bud at stage 20HH and examined (Towers et al, 2008) in which posterior Shh signalling specifies digit number through growth across the anteroposterior axis and digit identity through a morphogen gradient across this field.…”