Figure 1 (a) is about the sites of neural tube closure in mouse. Failure of Closure 1 will results in open spina bifida or myelomeningocele while failure of closure 2 and 3 will lead to cranial NTDs or anencephaly. Closure 2 site remains controversial while closures 1 and 3 definitely occur. Genetic risk factor for NTDs in human can be represented by closure 2 among different ethnic groups. Figure 2 is the exencephaly with arrowhead and spina bifida with arrow.
The journal “Toward understanding the genetic basis of neural tube defects” was published on 2007 is about the genetic basis that causing NTDs in recent studies. Studies focused mainly on folate-related genes based on the finding that folic acid supplementation can reduce the risk of NTDs by 60–70%. Neural tube defects (NTDs) are severe congenital malformations of the central nervous system that affected human pregnancies, and arise when the neural tube fails to form correctly during development. Anencephaly is the most NTDs, which results from failure of fusion of the cranial neural tube; while myelomeningocele, commonly called spina bifida, which results from the failure of fusion in the spinal region of the neural tube. Both are referred as “open” NTDs because the affected region is exposed to the body surface. Infants with anencephaly are stillborn or die shortly after birth, whereas many infants with spina bifida survive, usually as a result of extensive medical and surgical care. However, they are at risk for a range of physical and developmental disabilities. In this blog, we are concern for cellular site of neurulation at the molecular level where the genetic that causing NTDs. Nuerulation is a part of organogenesis where it include the formation of dorsal nerve cord eventually formation of the central nervous system. Neurulation can be divided for two phases: primary and secondary neurulation.
Primary neurulation involves formation of the neural plate, shaping of the neural plate into the cylindrical neural tube, bending and fusion of the neural plate at the midline. Each step is autonomous and controlled by distinct molecular pathways. During NTDs closure, a group of cells will involve in the structure at the spinal region. In this complex process, cells will produce polarized cellular protrusions that enable them to move directionally and to intercalate with other neighboring cells. Shape and movement are change in this stage and results in convergence toward the midline and extension of the tissue along the anteroposterior axis. Next is bending or folding of neural plate where it occur in dorsal midline and form two sites. Studies believed that neural tube closure is preceding bidirectionally in a zipper-like fashion.
Secondary neurulation is limited to the tail bud and occurs by proliferation and condensation of stem cells that subsequently cavitates. This process begin after primary nuerulation where the tail bud willproduce neural tube so a mass of stem cells representing the remnant of the primitive streak that are located at the caudal end of the embryo. Proliferation and condensation undergoes in stem cells and followed by cavitations and fusion with the central canal of the neural tube formed by primary neurulation. Basically, failure of secondary neurulation are less commonly lead to closed forms of NTDs where the developing neural tube fails to separate from other tissues of the tail bud.
NTDs in human can be prevented with the highly awareness during pregnancy and increase daily intake of folate acid though the studies finding it can be heritate by genetic and environmental problem.
Primary neurulation involves formation of the neural plate, shaping of the neural plate into the cylindrical neural tube, bending and fusion of the neural plate at the midline. Each step is autonomous and controlled by distinct molecular pathways. During NTDs closure, a group of cells will involve in the structure at the spinal region. In this complex process, cells will produce polarized cellular protrusions that enable them to move directionally and to intercalate with other neighboring cells. Shape and movement are change in this stage and results in convergence toward the midline and extension of the tissue along the anteroposterior axis. Next is bending or folding of neural plate where it occur in dorsal midline and form two sites. Studies believed that neural tube closure is preceding bidirectionally in a zipper-like fashion.
Secondary neurulation is limited to the tail bud and occurs by proliferation and condensation of stem cells that subsequently cavitates. This process begin after primary nuerulation where the tail bud willproduce neural tube so a mass of stem cells representing the remnant of the primitive streak that are located at the caudal end of the embryo. Proliferation and condensation undergoes in stem cells and followed by cavitations and fusion with the central canal of the neural tube formed by primary neurulation. Basically, failure of secondary neurulation are less commonly lead to closed forms of NTDs where the developing neural tube fails to separate from other tissues of the tail bud.
NTDs in human can be prevented with the highly awareness during pregnancy and increase daily intake of folate acid though the studies finding it can be heritate by genetic and environmental problem.
Student ID: 41876570
References link: http://www3.interscience.wiley.com/cgi-bin/fulltext/117984357/PDFSTART
