Question

Neural Tube.

a. How would over-expression of BMP signaling proteins in the surface ectoderm adjacent to the developing neural tube affect the formation of the dorsolateral hinge points (DHLPs)

b. Cells in the neural tube show an important change in the expression of cell adhesion proteins. What cell adhesion protein stops being produced and what is the effect on neural tube closure if this change does NOT occur?

PLEASE EXPLAIN as much as you can

Answer 1

The ability of the mesoderm to convert the overlying ectoderm into neural tissue is called neural induction. The neural plate folds outwards during the third week of gestation to form the neural groove. Beginning in the future neck region, the neural folds of this groove close to create the neural tube. The formation of the neural tube from the ectoderm is called neurolation. The ventral part of the neural tube is called the basal plate; the dorsal part is called the alar plate. The hollow interior is called the neural canal. the bending of the neural plate invovlves the formation of hinge regions. The cells at the midline of the neural plate are called the medial hinge joint. The cells lateral to the MHP do not undergo such a chnage. Shortly thereafter two other hinge regions from furrows near the connectionof the neural plate with the remainder of the ectoderm. the regions are called the dorsolateral hinge points.Cell wedging is intimately linked to changes in cell shape. In the DLHPs microtubules and microfilaments are both involvedin these changes.By the end of the fourth week of gestation,the open ends of the neural tube, called the neuropores close off.Neural indusers are molecules that can induce the expression of neural genes in ectoderm explants without inducing mesoderm genes as well. Neural induction is often studied in xenopus embryos since they have a simple body pattern. When embryonic ectrodermal cells are cultured at low density in the absence of mesodermal cells they undergo neural differntiation, suggesting that neural differentiation is the default fate of ectodermal cells. In explant cultures the same cells differentiate into epidermis. This is due to the action of BMP4 that induces ectodermal cultures to differentiate into epidermis. During neural induction, noggin and chordin are produced by the dorsal mesoderm and diffuse into the overlying ectoderm to inhibit the activity of BMP4. The inhibition of BMP4 causes the cells to differentiate into neural cells. Inhibition of TGF-beta and BMP signaling can efficiently induce neural neural tissue from human pluripotent stem cells,a model of early development.

b) Neural tube closure effect are birth defects of the brain spine or spinal cord. They happen in the first month of pregnanacy often before a woman even knows that she is pregnant. The two most common neural tube defects are spina bifida and anencephaly. In spina bifida, the fetal spinal column doesn't close completely. There is usually nerve damage that cause at least some paralysis of the legs. In anencephaly, most of the brain and skull do not develop. Babies with anencephaly are either stillborn or die shortly after birth. another type of defect, chiari malformation, causes the brain tissue to extend into the spinal canal. The exact causes of neural tube defects aren't known. you are greater risk of having an infant with a neural tube defect if you are obeese, have poorly controlled diabetes and take certain antiseizure medicines. Getting enough folic acid, a type of B vitamin, before and during pregnancy prevents most neural tube defects. Neural tube defects are usually diagnosed before the infant is born, through lab or imaging tests.