How an iPhone copies molecular biology

Now that I have your attention: 

In cell biology we have this really interesting set of problems where we need to pack a lot of information into a small space yet have a logical way to get to what we want....kind of like an iPhone and the zillions of Apps that most folks have 😉

So...how does the cell map its "Apps [genes]"? well thats a deep subject. I cover the why its important in my most recent podcast: [Google Podcasts,  Spotify,  Anchor]

Here I want to go through a little of the "Why should you care?"

How a cell goes from a naïve cell "baby cell" to neuron "brain cell". 

It's important to remember that no cell defines its own identity in a vacuum. It's surrounded by other cells that are also making decisions and there there's a lot of developmental biology I won't go into here but suffice it to say what happens is that at some point there's enough cells that have all made the same decision. There are a lot of variables so it is only semi-random that all of a sudden you get this core group of cells that say "I'm a brain cell" and then that reinforces the decision that now you have a grouping where you've all decided you're going to be "a brain". 

But you as a single cell still need to go through the process of becoming a brain cell. That is when we  gene regulation becomes really interesting! I still have additional decisions to make:

Am I going to become a dopamine brain cell OR serotonin brain cell OR one many of the other brain cell types!?!

Similar to the "Am I a brain decision?" it all depends on what's going on around you and the signals you're getting from your neighbors in a 3 dimensions. 

Remember ever cell has every gene!- but you only use a small number of those genes when you are a brain cell. Here is where I skip over a lot of really intereseting biochemistry and cell biology. The high level is that you need to mark genes as "not brain" and turn them off so that you dont change from brain to muscle (or cancer)- the process of turning off these genes is "epigenetics" (I go through a deeper explanation here)

 Epigenetics has a very interesting role in biology, years ago I created a primer for the International Rett Syndrome Foundation the presentation has a primer on epigenetics and brain development.

The struggle between packing a genome and finding the right gene to create a brain

So you know as I have hinted at the video the genome and chromosomes that you have seen described in text books.....is not quite right.

The chromosome which is made up of the chromatin looks like beads on a string- when you purify it and look at "naked chromatin" but as new technologies allowed use to recreate a 3D view of the chromosomes in a real, live cell (very cool technique known as 3C or Hi-C )

This has been a real fundamental change to how scientists visualize the genome- and the role that all of the "packaging" plays in what genes are expressed in what cell. I always have an image of a Plasma ball: 

 The DNA is connected to the nuclear membrane by protein anchors: It gives this multi layer way to organize related genes- even though they may not be on the same chromosome. where the connections between the chromatin and the nuclear surface and another nuclear surface across the ball you have these stretches of DNA where you've stretched it out. What regions of the genome are stretched out changes as a cell decides what it's final identity will be; the best article I could find to illustrate this is this one on B cell development (B cells are a type of immune system cell).

Very deep and complex topic but the coolest part is that cell biology figured out the direct link between form and function waaay before Jony Ive and Steve Jobs  😄

For a more general review of gene expression research- use this link to a Pubmed search

For a good review of the current state of "How we research gene expression- use this link"

How gene expression is related immune response to infections- use this link