Figure 1. Development Cycle of Male Mouse Germ Cell.

A. Timeline of sex specification and development of male mouse. Successful fertilization promotes the formation of a zygote, which after cell divisions and cleavage will form a blastocyst. The outer layer of blastocyst gives rise to the trophectoderm while the inner cell mass (ICM) contains embryonic stem cells (ESCs). During gastrulation the blastocyst cavitates and develops the three germ layers and the epiblast. The primordial germ cells (PGCs) are specified and localize near the extra-embryonic ectoderm, at the base of the allantois. Once PGCs are specified, they migrate to the fetal gonads and undergo sex-specific development to male and female gonocytes. Subsequently, male gonocytes undergo spermatogenesis and finally produced spermatozoa at puberty (30-35days). B. Sequence and timeline of male mouse germ cell development and marker expression. A temporal representation of male mouse germ cells sequence and differentiation. At each germ cell developmental stage, panels of germ cell markers are expressed at definite time points to drive germline differentiation in vivo. At each cellular stage, important molecular and somatic signals controlling that stage are indicated above the diagram. Some of genes are observed both in human and mouse germ cells (Green Color).