Question: How do you know which sections of the DNA code for the hair cells? Is it trial and error?

Martin Minarik answered on 15 Mar 2024:

Hi! Great question! Trial and error is one way to look at this for sure. We call it the ‘candidate gene approach’ and it means we would look at genes that we know are expressed in similar cell types for example, and check if they are active in hair cells, too. What may be a better idea though is to take what we call an ‘unbiased approach’, where you use some experimental technique to get a better idea about candidate genes without picking them yourself. We have done this by cutting out pieces of skin that contain hair cells, sequenced all the RNA in them, and then did the same with pieces of skin without hair cells. This gives you a list of genes present in the first sample that are not present in the second sample, and those are more likely to be active in the hair cells, ideally. RNA shows you which genes are switched on in the cells, so that’s why I look at RNA (DNA would be the same in all cells). There won’t be many genes that ‘code’ specifically for hair cells. Most of them are used in different parts of the body at different times to do completely different things. What’s important is the combination of the genes that are switched on and how they interact with each other that is specific for hair cells. Some of them may be switched off in humans and active in fishes or other animals, and who knows, maybe it’ll give us clues as to why humans cannot regenerate hair cells, which can lead to hearing loss and vertigo in old age!