Development of the neural crest and its derivatives (LD) - Essay Example

The neural crest is demonstrated in the figure below. Fig. 1. Embryo of the gray short-tailed opossum (Monodelphis domestica) at stage 24. E is the optic pit; O is the otic sulcus; PO is the preotic sulcus; 1 is the first arch neural crest; 2 is the second arch neural crest; and 3 is the region from which third arch neural crest will appear (Smith 124). As described in Wikipedia, neural crest cells can be classified into four groups according to function or their derivatives: the cranial neural crest cells, vagal and sacral neural crest cells, trunk neural crest cells, and the cardiac neural crest cells.

The cranial neural crest develops into cartilage, bones, nerves, and connective tissues in the head. These cells also contribute to the formation of the skull, dentin of teeth, blood vessels, and a few skeletal muscles. This category is responsible for the craniofacial derivatives. Vagal and sacral neural crest cells give rise to parasympathetic neurons. The trunk neural crest forms the melanocytes or pigment cells, adrenal medulla, sympathetic neurons, and dorsal root ganglia. Cardiac neural crest cells form the connective tissues of the heart (Seeley, Stephens, and Tate 957).

Roberto Mayor's Millennium Nucleus for Developmental Biology pointed out that the induction or stimulation of the neural crest is initiated by first inducing the neural plate and its border by bone morphogenic protein (BMP) signal inhibition. When BMP signaling is strongly inhibited, the neural plate is specified. In contrast, weak inhibition of BMP signaling leads to the specification of the neural plate border. An intermediate level of BMP activity required for the specification of the neural plate border can be created by interactions between the neural plate and epidermis.

This intermediate level of BMP signaling has been tested to induce the neural crest of Xenopus (frog) and fish. Results show that the BMP signaling target, Msx1, is induced only by an intermediate level of BMP signal activity in Xenopus (Trainor and Nieto 5060). Fibroblast growth factor (FGF) and Wnt can also induce the neural crest (Trainor and Nieto 5060). According to Mayor of UCL, these signal molecules together with retinoic acid originate from the posterior part of the embryo and are required to specify which part of the neural plate border will give rise to the neural crest cell population.

The signals elicited by the inducer molecules may either act synergistically or require interference between the involved genetic pathways to promote neural crest formation. This population will in turn give rise to the derivatives, the type of which will depend on the length of migration and final location of the cells after the travel (Trainor and Nieto 5060). Furthermore, Wikipedia stated that cells which are to become the neural crest are induced by BMP, Wnt, and FGF to express the proteins Fox3D, RhoB, and Slug and to lose expression of E-cadherin.

Slug is a repressor involved in the activation of factors that dissociate tight junctions. RhoB is also responsible for cell migration by signaling cytoskeletal changes which are prerequisites of the process. E-cadherin is a marker of non-neural epithelia (Trainor and Nieto 5060). M. Bronner-Fraser emphasized that, as posted in the Scienceweek Web