X chromosome. Computer model from Peter Fraser/Babraham Institute
X chromosome. Computer model from Peter Fraser/Babraham Institute

X Marks The Genetic Mystery

In today’s New York Times, I have a feature about the X chromosome. The X chromosome is one of those things that we learn about early on in school, and yet it still contains mysteries–ones that potentially have a direct impact on our health. Men have one X chromosome and one Y, while women have two X’s. This imbalance has led to all sorts of remarkable things–most remarkable of which is the fact that women shut down one of their X chromosomes–but which chromosome (mom or dad’s) depends on the cell.

I explore several lines of research in this piece, but the original nudge came from one new study in particular. Jeremy Nathans of Johns Hopkins and his colleagues came up with a way to light up cells based on which X chromosome they used. The complexity is gorgeous.

Here are three images that we didn’t have room for in the news article. Red cells use the father’s X, green cells the mother’s. Bear in mind that each chromosome carries different versions of the 1,000+ genes on the X. What these patterns mean for female biology is anyone’s guess.

First, an auditory hair cell from the inner ear of a mouse:

View Images
Jeremy Nathans and Hao Wu/Neuron

Then the tongue in cross-section (note the side-to-side differences):

View Images
Jeremy Nathans and Hao Wu/Neuron

And, finally, the heart:

View Images
Jeremy Nathans and Hao Wu/Neuron