Say thank you to your Dad!

Coming from a Mexican family, it is common for the male to be upset with his wife for not giving him a son. However, we now know that the sperm is actually whom determines if the child is a boy or girl, so technically it is the father's fault he didn't get a son. According to this article, there may be more things fathers may be responsible for.

Researchers at the University of Pennsylvania have discovered that males who experience a lot of stress through their life can cause their children to have problems with stress as well. Apparently, the sperm of the stressed males have an increase in expression on nine microRNAs. They are not yet sure how these nine miRs have an effect on stress, but they performed three separate studies on mice to confirm that these nine were the ones responsible.

In their first study in 2013, they stressed mice by changing them from cage to cage or by having them smell the urine of a fox (which is their predator). These mice were then allowed to mate, and their offspring were observed in stressful settings. As they expected, the offspring could not cope with stress very well. The sperm of the stressed fathers was compared to the sperm of the mice who were not placed in stressful situations. This is where the researchers noticed the difference in levels of those nine miRs.

To have a better understanding and further confirm that the difference in levels was relevant, the researchers performed a second study. They isolated the nine miRs and microinjected them into mouse zygotes, the control groups were either injected with only one of those miRNAs or with a random, irrelevant miRNA. The zygotes were then injected into surrogate female mice for reproduction. When the offspring became adults, their response to stress was observed and they had the same results as the mice from the 2013 study. The study also showed low cortisone levels for the offspring that received the nine miRs (not sure how this is related).

So how are these nine miRNAs causing stressed mice to pass their problems with stress to their offspring? From what I understood, the miRNAs are targeting “stored maternal mRNA” during the short period of time that it takes the sperm and the egg to fuse and direct zygotic development. In a third study, they injected the nine miRs into new zygotes and controlled injections into other zygotes. The zygotes were incubated for 8 hours and the mRNA from each cell was amplified. The expression of mRNA in the miRs injected mice was lower than the controlled. The miRNAs seem to decide which mRNAs get translated, and in this case it relates to chromatin remodeling genes.

Their next step is to figure out if intervening in the stress of adult male mice may have a positive effect on their offspring. They will also look at the genes upstream of the chromatic remodeling genes to maybe find a way of stopping this trait from being passed on to their offspring. Article