Sperm and egg cells carry genetic and epigenetic information from parents to offspring, serving as a link between the past, present and future of a species. A striking difference between the sperm and egg is the structural organization of their genomes: oocytes package DNA with histones (as do all somatic cells), whereas sperm package DNA with protamines. Differential packaging of sperm and egg chromatin traces back >500 million years, yet its biological and evolutionary significance remains unknown. Since protamines package the majority of the sperm genome biologists have presumed sperm protamines to be simple, passive structural elements that don’t convey any instructive information. We and others have identified a number of PTMs on these proteins, and here we show that protamine PTMS are important for proper sperm packaging and embryonic development.
University of Michigan