Do Fathers Matter?: What Science Is Telling Us About the Parent We've Overlooked Read Online Free PDF Page B

found alterations in the workings of 642 genes related to islet cells—the cells that produce insulin. There was only one explanation for this link: the fathers’ high-fat diets had produced alterations in their sperm, which then led to the occurrence of adult-onset disease in their daughters.
    These alterations are referred to as epigenetic changes. They do not change the DNA sequence of genes, but they affect whether or not certain genes are expressed—meaning whether they are turned on or off. The findings of the Överkalix and obesity studies reflect such epigenetic changes.
    Other studies have shown a similar connection in other ailments. A group at the University of Massachusetts led by Oliver J. Rando found that feeding male mice a diet low in protein substantially altered many genes involved in the metabolism of cholesterol and fats in their offspring. The group offered some interesting speculation about why this might be the case. Perhaps the father’s body, detecting that it is in an environment in which protein is in short supply, is altering the genes it passes on to its children to help them adapt to scarcity. “Mechanisms exist that could allow organisms to ‘inform’ their progeny about prevailing environmental conditions,” the researchers wrote. That is a remarkable and unexpected way for a father to help ensure the survival of his offspring.
    Each of these findings led to more research, and the evidence that poor health in fathers can adversely affect their children is mounting. In a more recent finding, Eric J. Nestler of the Mount Sinai School of Medicine in New York and his colleagues exposed adult male mice to chronic stress, and then bred them with normal females. The pups showed physiological and behavioral changes resembling those of depression and anxiety. Lorena Saavedra-Rodríguez and Larry A. Feig at Tufts University School of Medicine in Boston found that female mice passed the effects of stress on to their offspring, but fathers passed those effects on to their offspring and to the next generation as well—another example of the grandfather effect found in the Överkalix studies.
    Studies such as these are appearing all the time. The more that researchers look for these changes, the more they find them. In a study presented at the annual meeting of the Society for Neuroscience in November 2013 and later published in Nature , Brian G. Dias and Kerry J. Ressler of Emory University in Atlanta reported that the fear produced by traumatic experiences can be passed on from males to their offspring. They gave male mice small shocks when the mice were exposed to a certain odor, until the mice would show a startle response when exposed to that particular odor, not to others. When the mice were mated, Dias and Ressler found that the offspring showed an increased startle response to the same odor. And this fear was passed on to the next generation, too.
    It’s important to remember that until the past decade, researchers did not anticipate finding anything like these epigenetic changes in fathers. It’s not surprising that the health of mothers would affect their unborn children; a mother and her fetus have a very intimate connection. But the only connection between fathers and the fetus is the single sperm that fertilizes the egg. It carries within a rich, and sometimes harmful, legacy. The question that remains is how these experiences of the fathers manage to change the epigenetic marks on their sperm so that the health risks or fears of the fathers are passed on to their offspring. Researchers have only hypotheses; nobody knows for sure.
    *   *   *
    Other researchers have looked at the threats to fathers from toxins and pollution, to see whether exposure to these substances can produce changes in their offspring. Can toxins alter the operation of fathers’ genes the way stress, diet, and anxiety can? The first studies to address this question were done by Michael K. Skinner, a