Over the course of the summer, my main goal was to track the monoallelic expression of differentiating cells as they specificated from embryonic stem cells to neural progenitor cells.
Embryonic stem cells (ESCs), cells every human has during the fetal stage of their development, have the ability to specificate into any type of cell that is carried within and on the body. The environmental influences of any given ESC determines the type of adult cell it will turn into. In the same talking, every adult cell we have has come from a set of ESCs that have specificated, or differentiated, to become whatever the adult cell is currently. The many possibilities ESCs can eventually become is a major factor in why they are being used across many areas of biological research now. We have found major similarities in the biological evolution and function between humans and mice, so we have resorted to using embryonic stem cells within mice for our research.
Unfortunately the cost of doing such research calls for euthanizing impregnated mice-- this is the time in which the mouse’s fetus has an abundance of ESCs before full development-- that we can receive the ESCs for. To keep these ESCs in their embryonic cell state, we plate them on a dish and feed them ESC media. However the goal of our project was not to keep them in their ESC state, so we give the cells a certain type of media and growth factors respective to whichever type of cell we would like them to turn into. For our project, we wanted our embryonic stem cells to turn into neural progenitor cells (NPCs) because we wanted to look at the gene expression of cells as they differentiated from ESCs to NPCs, which would allow us to study the function of gene expression within the brain. We gave the ESCs NPC media and growth factors, EGF and FGF, allowing the ESCs to turn into the NPCs desired. Important to us was not the ESC state or NPC state, but the differentiation process in between.
In our cells we carry thousands of genes, and what makes up those genes is DNA. Ninety-eight percent of our DNA is similar to all other humans, but the two-percent that isn’t similar is where we carry our differences. When fragments of DNA are expressed, or transcribed, for protein synthesis, RNA forms. When the coded RNA is called for use, or translated, proteins form that create function for the cells within our body. In a given cell, certain genes may or may not be expressed. And for each gene, we have two copies, one maternal and one paternal. Most often, both copies of each gene are either both expressed, biallelic expression, or not. However in the occasional cases where one copy is on and the other is off, monoallelic expression, a situation arises. For each copy of a gene, it can be normal or mutant. If one copy is normal and the other is mutant and both of them are expressed, the normal copy can act in compensation for the mutant copy. However if the gene is monoallelic and the mutant copy is the only one expressed, then the cell will have deleterious function. Therefore by tracking when these differentiating cells make the switch from biallelic to monoallelic gene expression in the formation of neurons, we have better grounds to probe into the cause of monoallelic expression in Pde7b and Slc27a6 within NPCs.
It’s safe to say I've had a very intriguing summer.