PHILADELPHIA - Male infertility is a common medical problem, affecting millions of men in the United States annually. Its causes include an inability to make productive sperm. Now, using yeast as a model organism, researchers at the University of Pennsylvania School of Medicine are beginning to identify the molecular signals that could in part underlie that problem.
Shelley Berger PhD, the Daniel S. Och University Professor, and director of the Epigenetics Program at Penn, with postdoctoral fellow Jrme Govin, PhD, and colleague Saadi Khochbin of INSERM in France, screened yeast to find mutants that were unable to form spores a process that is analogous to sperm formation in mammals. Their goal was to map epigenetic processes-- those that influence gene expression in cells as they undergo sperm formation. By piecing together the mechanics of the process, ultimately, they can understand how that process can go awry. They found several sites on proteins that may be important epigenetic regulators of sperm and egg formation: Novel chemical changes key to gamete formation could be potential biomarkers of human male infertility. They published their findings this month in Genes and Development.
Epigenetics, the factors influencing an organism's genetics that are not encoded in the DNA itself, are more subtle than genetic mutations, which typically affect the function of proteins a cell produces by following the recipe coded in the DNA. Epigenetic factors instead alter the readout of that code, ramping their expression up or down as if with a dimmer switch.
A process under strong epigenetic control is sperm and egg formation.
Sperm and eggs (gametes) contain only a single chromosome of each type -- they contain 23 chromosomes instead of the 46 found in most human body cells, which have two copies of each (one copy inherited from each parent). The process of gamete formation involves a specialized form of cell division called me
|Contact: Karen Kreeger|
University of Pennsylvania School of Medicine