Neural fold

The neural fold is a structure that arises during neurulation in the embryonic development of both birds and mammals among other organisms.

The released calcium interacts with proteins that can modify the actin filaments in the outer epithelial tissue, or ectoderm, in order to induce the dynamic cell movements necessary to create the fold.

[1] When the cells fail to associate in a manner that is not part of the normal course of development, severe diseases can occur.

[7] The molecular mechanism behind this process lies in the expression and repression of bone morphogenetic proteins (BMPs).

BMPs are a wide family of proteins that perform many functions throughout the growing embryo, including stimulating the growth of cartilage and bone.

[8] The final adhesion of the converging neural folds is due to several different types of intercellular binding proteins.

[1] The neural fold is an extremely important structure in that this mechanism is needed to produce these diverse kinds of cells in the right places.

[12] If the caudal neuropore fails to close, a condition called spina bifida can occur, in which the bottom of the spinal cord remains exposed.

A strip of specialized cells called the notochord (A) induces the cells of the ectoderm directly above it to become the primitive nervous system (i.e., neuroepithelium). The neuroepithelium then folds over (B). As the tips of the folds fuse together, a hollow tube (the neural tube ) forms (C)—the precursor of the brain and spinal cord. Meanwhile, the ectoderm and endoderm continue to curve around and fuse to create the body cavity , completing the transformation of the embryo from a flattened disk to a three–dimensional body. Cells originating from the fused tips of the neuroectoderm ( neural crest cells ) migrate to various locations throughout the embryo, where they will initiate the development of diverse body structures (D). [ 5 ]
Cross section through the embryonic disc showing the fold.
A side view of an anencephalic fetus