Central Nervous System

A. Starting at the epiblast, describe five developmental events leading up to the generation of upper motor neurons that reside in layer 5 of the motor cortex.

As stated previously, the proteins, a1-chimaerin and a2-chimaerin, are important in the facilitation of neural growth. The a2-chimaerin protein regulates the movement between the different neurons, so that neural structures can develop properly. When a mutation takes place in the CHN1 gene, it causes the a2-chimaerin to not work properly. This mutation causes some of the nerves that are created by the CHN1 proteins to either be underdeveloped or missing altogether. Jeon-Min Hwang and associates found that the absence of the CHN1 caused the subsequent absence of cranial nerves IV and VI (18). Cranial nerve four, also known as the trochlear nerves, serves to lower the eye as it is adducted by the superior oblique muscles; in

According to Moroz (2009) two hypotheses are given to describe the evolution of the CNS. These are monophyly and polyphyly. According to monophyly all the neuronal cells originated from a single ancestral cell lines. Another hypothesis known as polyphyly, complex brains originated from multiple origins in different animal lineages. In 1830, Geoffroy suggested the homology of ventral and dorsal sides of the vertebrates. In 1994, Arendt et al., repotedted that during the evolution of chordates inversion of the dorso-ventral body axis took place and the ventral side of the ancestral arthropods become the dorsal side of the

In all organisms with neural systems, neurogenesis undoubtedly happens during the developmental stage right from conception. Although first presented in the 1960’s, the idea of “Adult Neurogenesis” - the generation of new fully functional neurons from neural stem cells in adults - didn’t really catch on till the 80’s and 90’s. This was mostly due to development of better scientific methods by which to actually prove that neurogenesis happens. But since then, it has grown into one of the biggest topics of study in Neuroscience today.

The human neurocranium develops from the mesenchymal cells that condense around the cerebral vesicles of the developing brain. Although most of the skeleton passes through blastemal and cartilaginous stages before ossification occurs, some parts of the neurocranium do not follow this process and do not pass through

Human brain development represents a dynamic and complex process that requires fine tuning of biochemical, genetic, environmental and physical events. Neuronal migration is a significant part of neurodevelopment, which is a term that describes moving of nerve cells from their origin to their ultimate location.

Cbln1 is significantly known for its role in early stages of brain development (Miura et al. 2006). Deans et al., in 2010 reported that during inner ear formation Cbln1 interacts with Otolin. The important point about CBLN1 protein is, it helps signaling in the brain (Hirai et al., 2005), and modulates endocrine secretion (Rucinski et al., 2009). Later Gyurján et al. in 2011 showed that during early stages of limb development in mouse Cbln1 expressed only at E11.5, but for normal limb formation this gene should rapidly down-regulated. An interesting point regarding wild type and TP63-null mouse is overall development of central nervous system is normal and mutation of both TP63 alleles don’t affect nervous tissues (Holembowski et al., 2011), also my ISH showed that the expression of Cbln1 in cerebellum is similar in both normal and TP63-null mice in early stages of tooth development

What is known is that the forebrain roof plate starts to develop soon after neurulation, when roof plate cells, which are the first cohort of cell to exit the cell cycle (Kahane and Kalcheim, 1998) begin to form a thin monolayer. This is the time point when the roof plate starts expressing multiple signaling molecules such as members of the Bmp, Wnt and Fgf families exhibiting different gradients along the anterior-posterior axis (Crossley et al., 2001; Furuta et al., 1997; Shimogori et al., 2004). Roof plate development is a complex process and requires the activity of the same set of signaling molecules which later pattern the dorso-medial structures in the forebrain. Evidence gathered primarily from studies in the chick embryo suggest that correct dorsal-ventral patterning of the forebrain is a pre-requisite for subsequent establishment of roof plate identity. In fact the dorsal-ventral identity of the forebrain is acquired as early as the neural fold stage where Wnt signaling first imparts dorsal character to the forebrain cells which otherwise would exhibit ventral characteristics. However, Wnt signaling alone can only impart the initial dorsal forebrain characteristics manifested as the expression of certain markers. Nonetheless, Wnt signaling together with Fgf8 induces the definitive dorsal forebrain characteristics (Gunhaga et

Tissir, and Goffinet (2013) suggest that the nervous system, is the of core the planar cell polarity, genes, vertebrates, and axons. The planar cell polarity (PCP) is paired to the essential division of the distinct cells and refers to the overall synchronization of the cell behavior in, the pathways that directs it.

Neural crest cells are transient vertebral cell types, which form at the boundary between the neural plate and surface ectoderm. They are multipotent and able to migrate and differentiate into numerous derivatives resulting in them being referred to as the ‘fourth germ layer’.

Nevertheless, late pre-progenitor cells have similar properties as stem cells. We can culture NG2 positive cells present in the subventricular zone (SVZ) with the fetal calf serum (FCS), cytokines and basic fibroblast growth factor (bFGF) and convert them back to their stem cell state. We can then transdifferentiate these multipotent cells to other neural

Nerve growth factor (NGF), a neurotrophin that regulates cell differentiation, plays an important part in various pathways and signals (Sofroniew et al. 2001). For instance, NGF plays an

Previous study reported that the extracellular guidance cues, including UNC-6/Netrin and its receptor have role in determining the axon outgrowth

Ngns (class II bHLH transcription factors) are known as pro-neural factors as they are necessary to initiate differentiation of NSPCs and are important to specify a neuronal subtype[3]. Ngns activate downstream several pro-neural factors for the formation of neurons from NSPCs. Earlier studies showed that development of neurogenic machinery is mediated by cascade of transcriptional activation which begins by activation of Ngn1 and Ngn2. This then activates NeuroD1 and NeuroD6 (other bHLH factors). In turn NeuroD1 and NeuroD6 activates Nsc1 which then activated terminal transcription factors and triggers neurogenesis[4]. Thoma et al observed that Ngn2 alone is sufficient to induce neuronal differentiation in embryonic stem cells. In this study they used murine embryonic stem cells and transfected with Ngn2 expression and after five days post transfection they observed that cells expressed Tuj1 and MAP2 (both are neuronal markers). This indicates that presence of a single pro-neural factor as well could promote neurogenesis. Ectopic expression of Ngn2 was sufficient to form mature neurons from embryonic stem cells[5]. Ngn2 was also seen to have a vital role in the development of dentate gyrus (DG). Galichet et al observed that in Ngn2 knockout mice there was a strong reduction in the size of DG. They also showed a marked reduction in the number of neural stem progenitors in DG. These Ngn2 mutant

The Spemann Organiser has a major role in the development of the central nervous system in the embryos of amphibians. The cells of the Spemann Organiser have a unique ability to alter the surrounding cells’ fates, in a process known as induction. The discovery of the Spemann organiser garnered large amounts of attention, causing Spemann to win the Nobel Prize in Medicine, in 1935, for his work in the discovery of induction. The Spemann organiser, as it has roles in developing the central nervous system, must turn off signals that encourage cells to transform into, for example, skin cells, and to turn on signals for cells that induce the formation of the central nervous system. It does this by releasing a number of molecules, including Chordin, Follistatin and Noggin, the main focus of this essay being on the function of Chordin. Chordin results