Preimplantation embryo development involves four stages: fertilization, cell cleavage, morula andblastocyst formation. During these stages, maternal and zygotic epigenetic factors play crucial roles.The gene expression profile is changed dramatically, chromatin is modified and core histoneelements undergo significant changes. Each preimplantation embryo stage has its own characteristicepigenetic profile, consistent with the acquisition of the capacity to support development.Moreover, histone modifications such as methylation and acetylation as well as other epigeneticevents can act as regulatory switches of gene transcription. Because the epigenetic profile is largelyrelated to differentiation, epigenetic dysfunction can give rise to developmental abnormalities.Thus, epigenetic profiling of the embryo is of pivotal importance clinically. Given the importance ofthese aspects, this review will mainly focus on the epigenetic profile during preimplantation embryodevelopment, as well as interactions between epigenetic and genetic regulation in these earlydevelopmental stages.

Stem cells represent a unique population of cells with self-renewal capacity. However, the molecular control of self-renewal and differentiationof stem cells has remained enigmatic. Here, we show that short-type PB-cadherin (STPB-C) promoted self-renewal of spermatogonial stem cells(SSCs) via activating Janus kinase/signal transducer and activator of transcription (JAK-STAT) and phosphoinositide-3 kinase (PI3-K)/Akt, andblocking transforming growth factor (TGF)-β1 signaling. These data were obtained with varied approaches, including the use of RNA interference(RNAi), SSC cultures infected by STPB-C retroviral vector, bromodeoxyuridine (BrdU) incorporation assay, and other techniques. These findingshave important implications for germ cell biology and create the possibility of using SSCs for biotechnology and medicine. They are also criticalin understanding tissue homeostasis, the aging process, tumor formation and degenerative diseases.