What's Going On In There?

I first met Leonid at a huge Neuroscience meeting in Atlanta I think. I had read a little of his molecular magic. That is where I first heard the term “transcriptome.” This is similar to a genome, which is the entirety of the genetic material stored in the DNA in the nucleus of the cells of a particular species. The first genome to be sequenced was the human genome, an effort that was HUGELY expensive, but totally cool. Bottom line: a genome represents all the potential genetic instructions of an individual.

By contrast, a transcriptome refers to all the genetic instructions that are actually being sent out to the rest of the cell (by the process known as transcription). Transcriptomes are species specific, but they are also tissue specific, and even cell specific. These instructions represent a subset of the genome, but they also represent what the cell does. For example, the Beta-cells in the islets of Langerhans in your pancreas have one job, and that is to produce lots and lots of insulin to be used by your body. The genome of these Beta-cells is the same as all the other cells in your body, and very close to the now-registered “human genome”. Again, the genome represents genetic potential. But your Beta-cells shut down almost all of those potential genes. Their single function is to make insulin, so it is the insulin gene whose instructions are sent out in huge volumes for manufacture into insulin.

The transcriptome is different from cell to cell. We know that much. We don’t know much about how transcriptomes of particular cells changes across evolution. For example, we don’t know how the transcriptome of different parts of the brain change across evolution.

Here's a part of the brain of an Aplysia (borrowed from Wikipedia). Each little yellow sphere is an individual nerve cell. This is the focus of our research.