Gene knockout experiments

The importance of P0 in PNS myelin has been clearly demonstrated. In P0 gene knockout experiments in mice [40], severe hypomyelination and a virtual absence of compact myelin in the PNS is observed. In humans, there are two disease states associated with mutations in the P0 gene Charcot-Marie-Tooth type I disease (see Ch. 38) and Dejerine-Sottas disease, both dysmyelinating diseases that exhibit a spectrum of severity depending on the particular mutation. 

While the conditional gene knockout experiments are supportive of a role for the NMDA receptors in memory, they are less than fully conclusive in linking the synaptic coincidence-detection feature of the NMDA receptor to memory formation. Like all loss-of-function studies, CA1-specific gene-knockout experiments could, in theory, produce memory impairment via a mechanism independent of the coincidence-detection function of the NMDA receptor. For example, one may argue that the physical absence of the NMDA receptor channels may cause subtle structural reconfiguration at the synapse, thereby altering normal synaptic transmission. Therefore, the memory impairment in CA1-specific NR1 knockout mice does not allow a firm conclusion that the coincidence-detection function of NMDA receptors controls learning and memory processes at the cellular level. 

In general, gene knockout experiments include the following four steps. First, a targeting vector is created, in which a particular gene is disrupted and... 

Plasmids used for knockout vector. The plasmid pPNT is widely used for gene knockout experiments. This vector contains neo and HSV-TK (25). The two arms of the homologous sequences can be inserted into two cloning sites flanking neo. In case the cloning sites do not exist in the homologous sequences, PCR-amplified products can be used, in which appropriate sites are created. 

Further confirmation of the role of the oc2-receptor comes from gene knockout experiments (Figure 10.7b). There are actually three discernible subtypes (or subsubt) es - have as many subs as you please) of the tx receptor, named A/D, B and C, with distinct genes on different chromosomes. In the particular cell type used in the experiment shown, the A/D subtype was evidently responsible for most of the inhibition of transmitter release. 

In addition to their core subunits related to the E. coli RNA polymerase subunits, all three yeast RNA polymerases contain four additional small subunits, common to them but not to the bacterial RNA polymerase. Finally, each eukaryotic polymerase has several enzyme-specific subunits that are not present In the other two polymerases. Gene-knockout experiments In yeast Indicate that most of these subunits are essential for cell viability. Disruption of the few polymerase subunit genes that are not absolutely essential for viability nevertheless results in very poorly growing cells. Thus It... 

Gene knockout experiments have dramatically confirmed the Importance of both pro-apoptotic and anti-apoptotic Bcl-2 family members In neuronal development. Mice lacking the bcl xl gene, which encodes an anti-apoptotic protein, have massive defects in nervous system development with widespread cell death In the spinal cord, dorsal root ganglion, and brain of developing embryos. In contrast, bax knockouts exhibit a marked Increase In neurons In some regions of the... 

Gene knockout experiments in mice clearly indicate that cell surface carbohydrates play many vital roles in development and health. Evidence suggests that cell surface carbohydrates function in many cellular activities by interacting with their microenvironment in vivo. Future studies should identify mechanisms underlying activation of cells by cell surface carbohydrates, which are vital for understanding the activities of malignant cancer cells. 

---