This is a cross-section of a juvenile mouse testis, with cells that are on their way to becoming mature sperm. Spermatogenesis takes ~35 days in mice, and one important process that happens during spermatogenesis is “meiosis,” a special cell cycle that helps generates cells with half the amount of DNA. Shown here is a high enrichment of cells that are undergoing meiosis; the green labeling depicts a special “chromosome dance” that happens during meiosis.

In the mouse testis, spermatogenesis is usually a very asynchronous process, such that one can observe germ cells at many different stages of development, from germline stem cells to highly differentiated sperm. With the manipulation of retinoic acid metabolism, however, we now have the ability to “synchronize” the process of spermatogenesis. I took these particular images to assess whether the synchronization protocol had worked properly, and to determine what stage of development was most enriched in this particular sample.