Neural disorders due to FAS, Maturation of the central nervous system

Maturation of the central nervous system

Both neurons and glia develop from the original neurectoderm forming the neural tube. Microglia are the exception: they develop from the monocyte-macrophage lineage of mesodermal (bone marrow) origin and migrate into the CNS.

Induction of regional differences in the developing CNS is regulated by retinoic acid (vitamin A). Overexposure of the cranial region to retinoic acid can result in “caudalization,” i.e., development more similar to the spinal cord.

During development, the spinal cord and presumptive brainstem develop three layers: 
  1. a germinal layer or ventricular zone, 
  2. an intermediate layer containing neuroblasts and comprising gray matter, and 
  3. a marginal zone containing myelinated fibers (white matter).

Other layers are added in the cerebrum and cerebellum by cell migration along glial scaffolds. The notochord induces the establishment of dorsal-ventral polarity in the neural tube. Ventral portions of the tube will become the basal plate and give rise to motor neurons, whereas the dorsal portions become the alar plates, derivatives of which subserve sensory functions.

Meninges are formed by mesoderm surrounding the neural tube with contributions to the arachnoid and pia from neural crest. Defects in the CNS may result from several causes including high maternal blood glucose levels and vitamin A overexposure and often involve bony defects (e.g., spina bifida and anencephaly). Defects are most common in the regions of neuropore closure.

Folic acid, also known as folate, is a B-vitamin that can be found in some enriched foods and vitamin supplements.Women who take folate before pregnancy have a decreased risk of neural tube defects (NTDs) including spina bifida and anencephaly. The U.S. Public Health Service recommends that all women who could possibly become pregnant get 400 µg (or 0.4 mg) of folic acid every day.
Folic acid, also known as folate, is a B-vitamin that can be found in some enriched foods and vitamin supplements.Women who take folate before pregnancy have a decreased risk of neural tube defects (NTDs) including spina bifida and anencephaly. The U.S. Public Health Service recommends that all women who could possibly become pregnant get 400 µg (or 0.4 mg) of folic acid every day.


This could prevent up to 70% of NTDs. Folic acid is found in some foods, such as enriched breads, pastas, rice, and cereals (some with 100% of the daily requirement). Fetal alcohol syndrome (FAS) is the most common cause of mental retardation; FAS includes the triad of growth retardation, characteristic facial dysmorphology and neurodevelopmental abnormalities. Alcohol rapidly crosses the placenta and the fetal blood-brain barrier. Damage is dependent on gestational age, alcohol dosage, and pattern of maternal alochol abuse. Altered neural crest cell migration, differentiation and programmed cell death (apoptosis) are hypothesized mechanisms for the congenital dysmorphologies associated with FAS.