Question

Need help with this question about BMP,Cadherins, and Folic Acid in process of neurulation.

3. What is the role of BMP, Cadherins and Folic Acid in the process of neurulation?

Answer 1

Neurulation refers to the folding process in vertebrate embryo which includes the transformation of the neural plate into the neural tube.Different portions of the neural tube form by two different processes,called primary and secondary neurulation.
In primary neurulation,the neural plate creases inward until the edges come in contact and fuse.
In secondary neurulation,the tube forms by hollowing out of the interior of a solid precursor.
Ectodermal cells are induced to form neuroectoderm from a variety of signals.Ectoderm sends and receives signals of BMP4 and cells which receive BMP4 signal develop into epidermis.The inhibitory signals chordin ,noggin and follistatin are needed to form neural plate.These inhibitory signals are created and emitted by the Spemann organiser.Cells which do not receive BMP4 signaling due to the effects of the inhibitory signals will develop into the anterior neuroectoderm cells of the neural plate.
The process of the flat neural plate folding into the cylindrical neural tube is termed primary neurulation. As a result of the cellular shape changes,the neural plate forms the medial hinge point (MHP) .The expanding epidermis puts pressure on the MHP and causes the neural plate to fold resulting in neural plate and the creation of the neural groove.The neural folds form dorsolateral hinge point(DLHP) and pressure on this hinge causes the neural folds to meet and fuse at the midline.The fusion requires the regulation of cell adhesion molecules.The neural plate switches from E-cadherin expression to N-cadherin and N-CAM expression to recognize each other as the same tissue and close the tube.This change in expression stops the binding of the neural tube to the epidermis.

Neural tube defects seem to be related to defects in the folate-methionine metabolic pathways since preconception of vitamin B12 supplementation with folic acid proved to substantially reduce the risk for NTD affected pregnancies.Folate is a critical nutrient in maintaining normal cell growth and division and therefore it is important for human development.Folic acid and its derivatives are important in several reactions in the single carbon transfer,which include the biosynthesis of purines,thymidines and the remethylation of homocystine to methionine.Normal folic acid and vitamin B12 metabolism were reported to be essential for normal development of the neural tube.