glycine-specific transporter,影響卵子與早期胚胎之體積大小調控

卵子與胚胎體積變化   GV>MI>MII

卵細胞膜上的轉換系統 glycine-specific transporter, GLYT1, 會影響卵子與早期胚胎之體積大小調控


http://humupd.oxfordjournals.org/content/16/2/166.full

Figure 4

Volume decrease in oocytes after initiation of ovulation. (A) Volume of oocytes during meiotic maturation as a function of time after ovulation was initiated by hCG injection. Oocytes were retrieved from hCG-primed females at the times indicated, and were measured at the stages of meiotic maturation indicated by the inset key. Oocyte volume decreased progressively during MI. (B) Examples of oocytes as in (A) at the times indicated below each micrograph, with PVS in MI oocyte indicated by the arrow. (C) GV oocytes subjected to hypertonic shock (450 mOsm) immediately after retrieval from the follicle (0 h) or after 3 h in culture. Freshly isolated oocytes deformed the zona instead of shrinking uniformly like oocytes after time in culture. Bar indicates 100 µm. (D) Transmission electron microscopy image of thin section of a hypertonically shocked oocyte treated as in C, taken in an area where the zona pellucida was deformed by the shrinkage of the enclosed oocyte. A connection between the oocyte (o) and the zona (z) is apparently mediated by oocyte microvilli (m), as also visualized in the higher magnification of the portion enclosing the square, shown at right. The bar indicates 1 µm. Panels reproduced with the permission of Development (Company of Biologists) from Tartia et al. (2009).

Figure 5

Model of cell volume regulation in oocytes and preimplantation embryos. The developmental timeline is indicated schematically at top, showing stages of oocyte maturation and preimplantation development, with the approximate timing of the initiation of ovulation and fertilization indicated by arrows. The initiation of independent cell volume regulation begins with the release of the adhesion between the oocyte and the zona pellucida (A) just after ovulation, followed by the initiation of glycine transport via GLYT1 (B). The glycine-dependent mechanism controls cell volume starting during meiotic maturation and ending at around the 4- to 8-cell stage of embryogenesis. A second mechanism of volume regulation, depending on the betaine transport and accumulation, may function in cell volume homeostasis starting after fertilization and ending at the 2-cell stage (C). These mechanisms of cell volume regulation are unique to oocytes and early embryos. It is hypothesized that more conventional mechanisms of cell volume regulation may become activated around the time of compaction and formation of the morula (D).