For long, it used to be thought that the mother-to-be offers the baby in the womb much more than the father. She provides the egg which is fertilized by the sperm of father. All he does is to deliver a lot sperm cells, one of which enters the egg cell of the woman and fertilizes it. The sperm contains the DNA or the entire gene collection (called the genome) of the man. Beyond supplying his genome, the father-to-be seems to have no other biological role to play; his job is done. On the other hand, the egg cell of the mother supplies not only her genome to the baby, but also all the nutrition needed for the growth of the baby. Plus, the egg cell contains mitochondria which are the “power houses” for the cell. The mother thus offers the baby more than her DNA. The father’s sperm does not have mitochondria, just plain DNA for injection into the egg. It is the pregnant lady who has to take care of the growing fetus and thus the health of the baby In the womb.
It is for this reason that a lot of advice is offered to the mother: do not smoke, don’t drink, take vitamins, eat this and not that, walk carefully, so on and so forth. And as the baby grows within the womb for over 35 weeks, the mother goes through a lot of physical exertion-and the moment of birth is always the climax of exertion and pain. Traditional culture in the South has the phrase “ Prasava Vairagyam ” or the vow taken by the lady during delivery that she will no longer allow her husband to come near her!
Thus, for long the role of the father has been discounted or given the short shrift. But over the last decade or so, the role of the father has been found to be a little more than just a gene provider. A group in New Zealand studied, about 15 years ago, over 2000 couples in order to look at the connection between the health of the father and that of the baby. They found that if the father is obese, there was over 60 per cent risk that the baby is born with low birth weight. On the other hand, it did not matter if the mother was overweight or obese. What is it then that relates this connection between the weight of the father and that of the baby? Is there something in the sperm of the father that is responsible for this inverse connection?
Experiments using the mouse as the model have given some clues. Dr Sarah Kimmins from McGill University in Canada published a paper in the journal Nature Communications in 2013, where she grew male mice with some deficiency in folic acid (or vitamin B9). When these mice mated with healthy female mice, the baby mice had problems- some with extra fingers and some with weak bones. Kimmins wondered whether there was something “epigenetic” in the sperm of the male mice, or some factors affecting the DNA of the male mice in their sperms.
The answer appears to have come from two recent studies, both published together, on line on December 31, 2015 in the journal Science . A Chinese group, led by Dr Qi Chen (of the Chinese Academy of Sciences and the University of Nevada), fed one group of mice high fat diet and a “control” group normal diet. They then isolated sperms from both groups and used them to impregnate healthy, normal female mice ( in vitro fertilization). The baby mice born out of the sperm of the high-fat-fed males had signs of diabetes; they had glucose intolerance and resistance to insulin. The ones born out of healthy sperm fathers had none of these problems. The researchers concluded that pre-birth diet of the male affects the health of the future offspring. About the same time, the group of Dr Oliver Rando from the University of Massachusetts Medical School did a similar set of experiments with mice. This time the males were fed with low protein diet. While there was no great difference in weight, or no observable changes between the offspring of the experimental and control groups, the former had differences in a group of genes responsible for cell growth. They also identified that diet alters the levels of small RNA molecules, including transfer RNAs (or tRNAs), important in protein synthesis. It is clear that the father’s dietary habits tell on the content, composition and health of his sperms. Sperm is now realized to carry not just a DNA package of the male genome but also small molecules that subtly change the health of the offspring. So, fathers-to-be, beware! To quote Dr. Rando: “You are eating for two”. You too must eat right, not smoke nor drink too much- just as your wife does. They tell in your sperm.
D. BALASUBRAMANIAN
dbala@lvpei.org
