An overview on the diversity of cellular organelles during the germ cell cycle

In mammals, germ cells undergo a long journey from specification until sexual maturation. During this journey, which takes place during the entire life cycle of mammals, the germ cells dynamically change their morphology, their expression profile and also the number and character of their cellular bodies. The focus of this review will be the diversity of cellular organelles present in the nucleus and cytoplasm at the different phases of germ cell development. We discuss how these organelles associate and behave to form a multitude of bodies that have long been observed by scientists, and how their presence or absence is used to characterize different stages of germ cell development. These organelles include the female Barr body, polar bodies and Balbiani body; and the male sex body and chromatoid body. It is concluded that compartmentalization of organelles and molecules in the cytoplasm (in particular of mitochondria and RNAs) and of the sex chromosomes in the nucleus seems to be important for regulating germ cell development throughout the life cycle.