All organisms originated from one single common ancestor

February 11, 2019 0 Comment

All organisms originated from one single common ancestor, LUCA which stands for last universal common ancestor. From this one ancestor countless different cells arose each having their own unique structure and function. The chick cranial neural crest cells are a specific cell that scientist use to study human neural crest cells. These cells are only found in eukaryotic vertebrates. The main function of these cells is to create the bone structure of the face and head. So, in humans these are what make you look like you essentially. These cells are used in research to see how they impact the results of facial birth defects and how they can be detected earlier. These cells during embryo growth transform into cells that that are in fully developed babies. In Chicks neural crest cells develop key survival features like the beak and jaw. The way these cells are signaled to transform is through the overlying epithelium. They are formed at the junction of the neural plate and the ectoderm where they then travel during fetus growth the temple. We will see the actual steps of formation later in the paper. Throughout this paper we will see the specific functions, fun facts and formation of the cells.
Chick cranial neural crest cells are classified into a group of ecto-mesenchymes, this is due to the function of them acting as stem cells which can transform into a variety of different body cells with a multitude of functions. As a group of ecto-mesenchymal cells, neural crest cells derive bilaterally from the margins of the dorsal-side of the neural tube and extensively migrate shortly before and after neural tube closure into specific locations. Subsequently, they differentiate into many tissue derivatives within developing embryos. Due to these extraordinary abilities, Neural Crest Cells are sometimes referred to as the fourth embryonic germ layer. Neural Crest Cells undergo the processes of neural induction, delamination, epithelial-mesenchymal transition and migration to give rise to the different tissues. The Neural Crest Cells rising from the lateral tips of embryonic diencephalon, mesencephalon and rhombencephalon are defined as cranial neural crest, which is distinct from the cardiac and trunk neural crest. Unlike trunk Neural Crest Cells which show minimal skeletogenic capacity, cranial neural crest cells possess the ability to form cartilage and bone. During craniofacial development, the CNC contributes to all of the craniofacial skeleton.
Scientists have been studying the effects that neural crest cells have on birth defects on humans. Of all the babies born with birth defects, approximately one-third display anomalies of the head and face including cleft lip, cleft palate, small or absent facial and skull bones and improperly formed nose, eyes, ears, and teeth. Neural crest cells therefore generate the scaffold upon which the head and face are constructed and are largely responsible for facial shape and variation. it is critical that the embryo generates and maintains a sufficient pool of neural crest progenitors that survive, proliferate, migrate, and differentiate appropriately as deficiencies in these processes underlie several congenital craniofacial malformation disorders. In fact, depending on which phase of neural crest cell development is disrupted, very different craniofacial anomalies can manifest. For example, if neural crest cell formation or migration is perturbed such that too few neural crest cells are produced, or they fail to migrate to their final destinations, this can result in babies with small noses, jaws, and ears as well as cleft palate. These phenotypes are characteristic of Treacher Collins syndrome.
The formation of chick cranial neural crest cells has three steps to it these include induction at the neural crest, specification and then goes through Epithelial- mesenchymal transition, EMT and emigration to its specified location in the body. Neural crest cells have been defined morphologically, as they emerge from the edge of the neural folds. At head levels, the cranial neural crest forms before neural folds fusion, resulting in two bilateral masses of premigratory neural crest cells lying on both sides of the neural plate. Soon after, cranial neural crest cells initiate migration toward the craniofacial areas, either as individuals or via collective migration recently described by live imaging. These cells are then specified to their specific structure and location by neural crest specifier genes including FoxD3 and Snail. EMT is then induced by the transcription factor Slug and then finally the emigration occurs upon tube closure in avian embryos, whereas it is well underway in the cephalic regions of mouse embryos by the time closure occurs. Cells become unorganized, lose tight junctions bw cells, have transient contact with other cells, different cell shape and organization, highly motile.
Cranial neural crest cells, through their interactions with facial epithelium and neuroectoderm, contribute to the development of most craniofacial structures in vertebrates. Different species have different facial morphologies. To examine whether species-specific facial patterning is intrinsic to neural crest cells or determined by cues from the facial ectoderm, neural crest cells destined to form the upper beak from duck were transplanted into quail embryos and vice versa. The resultant chimeric ‘qucks’ (duck embryos containing quail frontonasal neural crest cells) had short beaks typical of quail, and ‘duails’ (quail embryos containing duck neural crest cells) possessed flattened ducklike beaks. These transplantation experiments showed that neural crest cells intrinsically contain species-specific information, which is a major determinant of facial morphology. The genes involved in facial patterning are well conserved between species, and different facial morphologies are probably in part generated by differences in the temporal patterns of expression of these genes. Quail cranial neural crest cells transplanted into duck not only retained their own temporal pattern of gene expression but also altered the pattern of gene expression in nonneural crest-derived host tissue.
There are 5 methods used by scientist to identify the neural crest cells and derivative. These 5 ways include surgically remove defined regions of the neural crest, and then determine which structures fail to develop, construction of chick quail chimeras to identify the quail cells in the chick embryo using chromatin stain, label pre-migratory cells with fluorescent dyes or radioactive substances. intrinsic markers of neural crest cells, including localization by immunohistochemistry or in situ hybridization transgenic animals expressing reporter genes. Each of these methods have advantages and disadvantages to them. Surgical removal is advantageous because it shows the importance of particular regions of neural crest, but its disadvantage is you can’t see how the cells get there, or if other cells compensate for the loss of regions. Identifying the quail cells in chick’s advantage is an identify cells during migration (using fixed embryos) and cells are permanently identified. The disadvantages are you cant image in live embryos. Fluorescently labeling’s advantages can image the cells in live embryos and its disadvantages the labels are not permanent and are diluted out of the cells over time.