The process of oocytes maturation in mammals is regulated by the expression of many types of cell-specific genes. Both nuclear and cytoplasmic maturation is based on activation of biochemical and metabolic pathways that lead to reaching the full maturation stage (MII) of oocytes. The most recent data indicates that the proteins belonging to transforming the growth factor beta (TGF-β) superfamily play an important role in the process of oocytes maturation, as well as of reaching full developmental capacity by these cells. Moreover, it has been clearly showed that the proteins belonging to TGF-β such as inhibins (INHA, INHB) and activins regulate both folliculo- and oogenesis by the stimulation and/or inhibition of several biochemical pathways. In this review, the most recent knowledge about the role of proteins belonging to TGF-β superfamily in the regulation of folliculogenesis, oogenesis and oocytes maturation has been presented and discussed.
This review presents the molecular basis of mechanisms regulating oogenesis and folliculogenesis, as well as the species specificity of these mechanisms and genetic determinants of successful fertilization in pigs. Oogenesis and folliculogenesis are species-specific processes, although several features are common to all mammals. These features are especially visible in the molecular basis of these processes. The most important genetic factors regulating normal oogenesis and folliculogenesis include the transforming growth factor beta (TGFβ) and several other proteins from the TGFβ family. Several experiments have indicated the influence of this gene’s expression on the ability of oocytes to mature, be successfully fertilized, and form a zygote and a blastocyst. However, the regulation of this gene’s expression shows a considerable species specificity. Similarly, mechanisms regulating the fertilization process have several features common to all mammalian species, which is especially conspicuous in the structure of genes that are responsible for fertilization. Two important determinants of fertilization ability are oocyte morphology and follicular size.