Presented by Ceara Rathie
In this paper the scientists are trying to figure out how the expression of bcl-2 and caspase-1 are involved in apoptosis in splenocytes and macrophages when they are exposed to THC. In this paper they found that in both cell types, that bcl-2 expression is decreased and that when caspase-1 is inhibited that cells are not undergoing apoptosis. These analyses were concluded from several different experiments done with these cells. From the research done the next step is to see THC's affect in Vivo.
Background:
There are two ways in which a cell can die, by apoptosis and by injury.
Apoptosis is also known as program cell death (PCD). This is where a cell commits suicide for the benefit of the organism and is a normal response both in the immune system, normal cells and during development. In this process cells express certain genes which aid in PCD. The cell shrinks, the chromosomes condense, and lastly the outer membrane of the cell begins to disintegrate as nearby cells take in the packaged components from this cell into their own.
Cells that die due to injury such as chemical or mechanical means, release all of their cell contents into the body when the cell membrane lyses. This is particularly not favorable due to these molecules causing the body to work hard to rid its self of this garbage in the blood system. This type of cell death is that which causes inflammation in the area due to water influx because of the increase of solutes in the body.
Important molecules involved with Apoptosis:
Bcl-2
- codes for a protein found on the exterior membrane of the endoplasmic
reticulum and is important in preventing the cell from undergoing apoptosis
- This is involved in the decision making process of whether or not to undergo
PCD -- when Bcl-2 is expressed the cell continues to live
- proto-oncogene, if mutated it could cause cancer
Caspase-1
- promotes apoptosis
- ICE protease (cleaves proteins between cystine and aspartate AA residues)
Links:
PubMed Abstract of the Article
Presented by Cassi Thompson
The American Brain Tumor Association has projected that in 2004 there will 3,140 children under the age of 20 diagnosed with a brain tumor. The most common malignant pediatric brain tumor is medulloblastoma. This brain tumor is located in the cerebellum and CNS. Mutations in the Wnt signaling are linked with incidence of medulloblastomas. The Wnt signaling pathway is important to the development of the brain, midbrain and cerebellum. This pathway includes a number of proteins that include APC, Frizzled, Axin and GSK3, all of which work together to degradate B-catenin. Mutations in the APC gene can cause a significant rise in B-catenin levels and a movement of B-catenin into the nucleus where it acts a transcription factor and regulates the transcription of c-myc, cyclin D and other oncogenes. This type of mutation is found in many cases of sporadic medulloblastomas. Turcot's syndrome is caused by such a mutation.
In this study researchers hypothesized that increased Wnt signaling in the adult CNS is sufficient to induce tumor formation. A murine PrP promoter fragment was used to control wild-type and mutant B-catenin transgene expression. This promoter is known to cause high levels of postnatal expression in the CNS. Stabilization of mutant B-catenin was accomplished by an alteration in codon 37 from serine to phenylalanine. B-catenin protein levels doubled in the cortex and cerebellum of adult animals that expressed the mutant transgene. In transgenic animals nuclear B-catenin was found in hippocampal, cortical and cerebellar neurons. No nuclear B-catenin was found in non-transgenic animals. Although no CNS malformations or tumors were found, tail kinking occurred in some of the transgenic animals.
From this study it was concluded that postnatal Wnt signaling in differentiated neurons may not be sufficient to induce CNS tumorigenesis as mice expressing stabilized B-catenin did not develop tumors or morphologic alterations in the brain.
Links related to the paper:
Abstract and full text of the article
Wnt Signaling Pathway and Its Role in Human Solid Tumors
Causes and Risk Factors of Brain and CNS tumors
Types of Brain and Spinal Cord Tumors
Information on Turcot Syndrome
Presented by Patrick Posadas
According to the Alzheimer's Association approximately 14 million people have Alzheimer's disease. This disease is characterized by a loss of cognitive ability, generally over 10 to 15 years, and is associated with the development and accumulation of abnormal tissues and proteins in the cerebral cortex. Some of these abnormal tissues are known as Neurofibrillary tangles which accumulations of the tau protein. The tau protein is a cytoskeletal protein and is cleaved by cysteine aspartate proteases, also known as caspases. The hypothesis of this experiment states that caspase-cleavage of tau is an early event in neurofibrillary tangle formation in both Alzheimer's disease and transgenic models of AD.
The results from this experiment yielded many useful conclusions. Because there were so many different aspects touched on in this experiment I will only mention a few. Some of the important information they derived included the cleavage of tau by executioner caspases, the correlation of tau with cognitive function, increase in insolubility of tau in later onset of AD, induction of filament formation, and a very important conformational change in tau which allows hyperphosphorylation of itself. Some of the experiments they performed include, radioimmunoprecipitation buffer fractions to determine insolubility, immunolabelling with Tau antibodies, observations of transgenic mice and neurofibrillary tangle accumulation. Please refer to the link to learn more about additional conclusions.
Links to the related paper:
Presented by Katie Warpinski
Neurological diseases may arise through many different mutations found in various genes. One gene in particular, L1 CAM, has extensive phenotyoic effects when mutated causing disorders such as X-linked hydrocephalus, MASA syndrome or spastic paraplegia type I. L1 is a member of a superfamily of immunoglobulin related cell adhesion molecules. L1 functions are very important in the growth of the developing nervous system through axon growth and guidance.
Researchers used 25 missense mutations on the L1 CAM gene for the study. The mutations were distributed across IG (immunoglobulin) and FN (fibronectin) domains. When there are missense mutations in the gene it can affect either homophilic binding to L1 or heterophilic binding to the TAX-1 gene. The binding of these genes is determined through the various domains of L1. When missense mutations occur they affect the structure of domains on the gene which affect the binding to various other genes and the function of the protein. For mutations affecting the key residues in either type of domain it was found to be more likely to produce a phenotype with severe hydrocephalus than were mutations affecting surface residues. However, mutations affecting the FN domains were found to be more likely than those affecting Ig domains to produce a phenotype with severe hydrocephalus. Links related to the paper:
Oxford
Journals Abstract and Paper
Hydrocephalus
Overview
The L1
Family of Neural Adhesion Molecules
Presented by Vanessa Ruiz
Ethanol ingestion by pregnant women is the primary cause of fetal alcohol syndrome, which is characterized by brain abnormalities and decreased mental capacity. It has been shown that ethanol greatly reduces the number of neurons during development. Neuronal growth and survival depends heavily on growth factors, especially the family of neurotrophins. These neurotrophins include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), neurotrophin 4/5 (NT-4/5), and neurotrophin 6 (NT-6). Neurotrophins are released by target tissues and bind to high-affinity transmembrane receptors and to low-affinity binding sites. While each neurotrophin has its specific high-affinity receptor, all neurotrophins are able to bind to p75, a low-affinity receptor.
In this study the authors hypothesized that the neurotoxic effect of ethanol is caused by the blocking of neurotrophic factors. Primary cultured cortical neurons from 16-day-old rat fetuses were used to determine the direct effect of ethanol. The total number of cortical neurons was determined followed by the addition of NGF, BDNF, or NT-3 to each of the cultures. Half of the cultures were then exposed to 400 mg/dl of ethanol. The number of living cells and the amount of cell proliferation in the cultures was then determined in order to see the effect of the ethanol.
They found that ethanol caused a 40.9% loss in neuronal cell number. It was determined that ethanol completely blocked the NGF-mediated survival of cortical neurons. Another significant finding was the 40% reduction in the expression of the p75 receptor in ethanol-treated cultures. From this study four conclusions were made. NGF promotes the survival of developing cortical neurons. Ethanol induces the death of these neurons. Ethanol can completely block the NGF-mediated survival of these neurons. Ethanol reduces the expression of the p75 receptor, but not the expression of the high-affinity trk receptors. With these findings the neurodegenerative effects of Fetal Alcohol Syndrome can be better understood and it supports the findings that alcohol consumption during pregnancy can affect the developing brain of a fetus thereby leading to mental retardation in the child.
Links related to the paper:
PubMed Abstract of the Article
GDNF and p75 Neurotrophin Receptor in Development and Disease
Sobering Work - Fetal alcohol syndrome research
Neurotrophic Factors - Background on Neurotrophic factors
Presented by Monica Peterson
Nodal genes in vertebrates are involved in the development of Spemmanâs Organizer, which includes the dorsal lip cells and other bodies like the notochord and prechordal mesoderm. Nodal expression is detected in vertebrates at different stages. For example, in Xenopus, it is found just before the gastrula stage, while in zebrafish it is at the blastode rm margin. Nodal genes also induce mesoderm formation and pattern it dorsoventrally and rostrocaudally. In zebrafish, the nodal genes actually start patterning the embryo rostrocaudally even before gastrulation begins, and later on cause the dorsoventral pattern. The development of the left-right axis is caused by two events. The first is the development of asymmetrical nodal gene signaling and then the transfer of positional information to the left-right axis.
The nodal gene, AmphiNodal, is taken from amphioxus, which is the closest related invertebrate to the vertebrates. By comparing, and testing, this gene to other vertebrate genes, like nodal, goosecoid, and sonic hedgehog, scientists are able to detect an evolutionary relationship between the vertebrates and invertebrates. We are also able to find out what has developed in vertebrate development since the split in chordate evolution from invertebrates.
Links related to the paper:
PubMed Abstract of the Article
Wnt signaling and PKA control Nodal expression and left-right determination in the chick embryo
PITX2 - The Heart of the Heart and the Guts of the Guts? H. Joseph Yost, Professor of Oncological Sciences, Research References
