Irene Gutierrez Thesis: Two Very Important Aspects Of Brain Development

developed to start working like other peoples'. The rapid birth of neurons in a young brain

How are medially-positioned progenitors affected by diffusible signals? The number of neurons belonging to populations found near or at the centre of the dorsoventral axis of the cord is influenced by signal levels, including Shh and BMPs. A moderate concentration of BMP signaling is needed to generate the correct number of medial interneurons. In zebrafish mutants in which a particular BMP protein is functionally reduced, there was a resulting increase in Lim1+ interneurons (medial interneurons) post-mitotically (Nguyen et al., 2000). Interestingly, further BMP reduction decreases medial interneuron counts, illustrating the fine balance of BMP levels that is needed to establish appropriate medial interneuron expression. Perturbing natural

Scientists have discovered that interneurons are responsible for the majority of new brain growth. They hope that the discovery that neurons can grow in the adult brain will allow for advancements in neuroplasticity research, such as determining the conditions necessary for this growth to occur. Dr. Nedivi, one of the scientists on the project, stated, “If we can identify what aspect of this location allows growth in an otherwise stable brain, we can perhaps use it to coax growth in cells and regions that are normally unable to repair or adjust to a changing

The development of the cortex is a delicate balance between proliferation, differentiation and migration of neural progenitors (NPs). Throughout developmental process, various cellular mechanisms ensure that NPs are differentiating into the correct cell subtypes, migrating to their correct regions, and forming the correct cortical and sub-cortical layers. The cortex is comprised of both excitatory and inhibitory neurons, which interact within neuronal circuits to mediate cortical functions. Though both types of neurons reside in the cortex, they arise from different embryonic brain regions, and from different neural progenitors. Excitatory neurons are generated from neural progenitors residing in the ventricular zone (VZ)/subventricular

In mice, this process starts around Embryonic Day 11.5 as the neural progenitor cells located in the Ventricular and Subventricular Zones (SVZ) migrate upwards to form what will later become Layers 2 through 6. Neurons are formed as these neural progenitor cells become Radial Glial Cells (RGC), a subpopulation of stem cells, and differentiate. The timing of the differentiation determines when neurons will form the lower or upper layers. When the differentiation occurs early in neurogenesis, the neurons migrate slightly to form the lower layers. In later neurogenesis, the differentiated neurons migrate past the lower layers and begin forming the upper layers. The formation of the upper layers tends to arise from differentiation of Intermediate Progenitor Cells (IPCs) rather than RGC differentiation. IPCs are formed from neural progenitor cells alongside RGCs (Kwan et al. 1538). While neurogenesis in humans may lead to differing relative sizes of the layers and SVZ, the structure of six specified layers is the same. The divisions between the layers do not occur in humans until around gestational week 9 to 11 (Deboer et al.

These findings can be best interpreted through the lens of structural and functional changes to the brain which occur in HTN.

Node of Ranvier formation requires the simultaneous expression of neurofascin and gliomedin. The expression of gliomedin is induced by contact between the Schwann cell and the

Since connectivity in neuronal circuits is vital to the brain function, this article explores how the specificity synaptic connection occurs during brain development. The synaptic specificity function is to examine the unique polarization that neuronal organisms have with their structures. This synaptic specificity is a journey that takes place in the cell migration, axon and dendrite development and regulation, and layer and synapse formation. It requires a lot of synaptic partners to function. Therefore, in order for any activity to take place, the synapse elimination is needed because it enables the neuronal connectivity to occur. Also, we need to understand that the synapse elimination and temporal control are the main functions that control

Neuronal multiplication, differentiation, and migration are occurring by the third week of embryonic life. Germinal cells proliferate in the matrix layer adjacent to the neuroaxis lumen and undergo transformation into neuroblasts which periodically migrate with great predictability to the marginal layer, which will later becomes the cortex. Migration is completed near the fifth fetal month and mitotic figures disappear by the end of the sixth fetal month. Thus by twenty-four weeks, the embryo has its full quota of neuronal mass. Further gross brain development continues to birth with the enfolding of the surface to form sulci and gyri and this predictable pattern is a reliable estimate of fetal age. Definitive cytoarchitectural patterns are evidenced at birth, which are the products of myelination having occurred at various levels at specific times, as well as the growth of glial cells. Visual tracts become myelinated soon after birth, and the corticospinal tracts continue to myelinate into the second year of postnatal life, after which time most myelination of the cerebrum is becoming complete.

suggested to be critical for neuron growth(Turner et al. 2003, Vasto et al. 2008, Priller et

After the neural tube forms, the cells’ fates are determined and neurogenesis occurs. Often, this neurogenesis/ cell fate determination stage overlaps with migration. Cell fate determination is regulated by many factors, including extrinsic signaling, intrinsic signaling, location/cell migration pathway, and timing of differentiation. One example of extrinsic signaling is notch signaling. In a proneural cluster, there is initially an equal amount of notch and delta signaling. However, one cell starts expressing a higher amount of delta. This signals the other cell to express a lower amount of delta. The imbalance in signaling is amplified. The cell with a higher amount of delta signaling becomes specified as a neuroblast, and the cell that has higher

The zebrafish Sod1 transgenic fish lines were generated according to protocols previously described by Ramesh et al (2010). The zebrafish sod1 gene was isolated by BLASTing the zebrafish genome with the mouse cDNA; then a Bacterial Arterial Chromosome (BAC) containing the sod1 gene was identified. However, as the BAC contained other genes, Ramesh and Colleagues isolated a fragment of the BAC containing an 11.7-kb upstream region, and 5.06kb and 4.5kb downstream sequences of the sod1 gene, and recombineered into the BAC5 chromosome at the p arm (pBAC5). I-Scel meganuclease was added to increase the rate of transgenesis; I-Scel meganuclease is considered to be the most specific naturally occurring restriction enzyme. The zebrafish heat shock protein 70 (hsp70) promoter and the DsRed (Discosoma sp. red fluorescent protein) marker gene were also introduced into the pBAC5 recombineering.

Second, ectopic (in an abnormal place or position) expression of identical Dscam isoforms on the dendrites of different cells, which normally overlap, promoted growth away from each other.

During the development of the human brain, the layers of the cerebral cortex are formed by migrating neurons which come from specialized proliferating regions lying deep in the brain. This neural migration comprises neurons moving as far as one thousand times their own body lengths before they arrive at their destination. During this developmental process, the cortex is divided into six organized layers. In Lissencephaly, this organized cortical layering is disrupted and instead forms four unorganized layers1. It is a severe developmental brain disorder which is characterized by a smooth brain with an abnormal thick cortex, enlarged ventricles, and very few or no gyri2. At the basis of this disease lies failure of proper migration of

Sea urchin embryos have been studied as model organisms for over 100 years. This organism is a great resource because of its straightforward artificial spawning, fertilization, and its embryo optical transparency. Also, the sea urchin simple organization makes it great to study morphogenetic movements and effects (Hardin et al., 1995).