Vitellogenesis and Vitellogenin Uptake into Oocytes

Abstract

The yolk proteins found in the oocyte of oviparous animals are synthesized by the liver as a large lipophosphoglycoprotein precursor, vitellogenin (Vtg), which represents a vital, sole source of nutrient for the developing larvae. Vitellogenesis underlies early development of oviparous animals. The Vtg gene is extremely sensitive to estrogen and other steroid hormones. Thus, vitellogenesis is a useful model for studying hormonal regulation of eukaryotic gene expression. The Oreochromis aureus vitellogenin, OaVtg gene spans 9 kb and contains 34 exons. Although the OaVtg promoter has a nonconsensus TATA, this promoter is capable of driving basal transcription. Two imperfect estrogen response elements, ERE p (proximal) and ERE d (distal), located in the promoter at Ϫ532 and Ϫ1352 elicit a significant increase in estrogen-dependent reporter gene activity. Competition gel mobility shift assays have demonstrated that ERE p and a novel ERE exon2 (located within exon 2) exhibit specific binding of estrogen receptor. Thus, nonconsensus OaVtg EREs contribute to the estrogen-dependent regulation of the OaVtg gene in vivo. During estrogen-induced vitellogenesis, the massive rate of transcription and translation of Vtg followed by its secretion into the blood makes this a major circulating protein that is taken up by membrane-bound vitellogenin receptors (VtgR) found on oocytes. The VtgR, which belongs to the low density lipoprotein receptor family, interacts with the N-terminal region of Vtg Hormones and Their Receptors in Fish Reproduction Downloaded from www.worldscientific.com by UNIVERSITY OF BIRMINGHAM LIBRARY -INFORMATION SERVICES on 03/20/15. For personal use only. Vitellogenesis and Vitellogenin Receptor 255via electrostatic attraction. Once in the oocytes, Vtg is cleaved into yolk proteins (lipovitellin and phosvitin), which are stored as nutrients for the developing embryo.

Effects of elevated dissolved carbon dioxide and perfluorooctane sulfonic acid, given singly and in combination, on steroidogenic and biotransformation pathways of Atlantic cod

“…PFOS has previously been suggested to be a weak ER ligand (Benninghoff et al, 2011;Cheng et al, 2010;Liu et al, 2007), but such a direct interaction may appear as a less plausible explanation when taking into consideration the long lag-time between PFOSexposure and transcriptional responses. Several factors besides E2 might also modulate expression of E2-regulated genes, including pituitary factors (Vaisius et al, 1991), other hormones or receptor cross-talks (Ding, 2005;Mori et al, 1998;Nuñez et al, 1997). Several nuclear receptors have been suggested to affect estrogenic gene expression.…”

Profile of 17ß-estradiol, vitellogenin, and egg diameter during gonad maturation process of striped catfish Pangasianodon hypophthalmus

“…Ding (2005) reported that Vtg has a MW between 200−700 kDa, similar to killifish, Fundulus heteroclitus (200 kDa). In mature female of teleost oviparous species, the Vtg is an essential nutrition source for oocyte and embryo development through vitellogenesis process (Lubzens et al, 2010;Ding, 2005). In the natural condition, the level of Vtg indicates the stage of gonad maturation in female species (Hara et al, 2016).…”

“…In several species, Vtg has a molecular weight (MW) between 140−200 kDa (Komatsu & Hayashi, 1997). Ding (2005) reported that Vtg has a MW between 200−700 kDa, similar to killifish, Fundulus heteroclitus (200 kDa). In mature female of teleost oviparous species, the Vtg is an essential nutrition source for oocyte and embryo development through vitellogenesis process (Lubzens et al, 2010;Ding, 2005).…”

The interaction between maternal stress and the ontogeny of the innate immune system during teleost embryogenesis: implications for aquaculture practice

“…The VtG lipoproteins are the major yolk precursors; they are synthesized by hepatocytes, secreted into the general circulation and are taken up from the maternal circulation by developing oocytes. The hepatic vtg genes are highly responsive to oestrogen stimulation (Ding, 2005; Hiramatsu et al , 2006), and as oestrogen secretion increases during ovarian recrudescence into the vitellogenesis stage, so does plasma total Vtg concentration (Hiramatsu et al , 2006; Babin et al , 2007). By mid‐vitellogenesis, the plasma total Vtg fraction, which comprises a mixture of different Vtg lipoprotein species, is a major contributor to the total plasma lipoprotein concentration.…”

“…This transfer presumably occurs at the apices of the extensions of the oocyte cytoplasm that traverse the ZP. Within the oocytes, the Vtgs are cleaved into lipovitellin (Lv) derivatives (Ding (2005), the spectrum of which is sensitive to the physiological status of the maternal brood stock (Gündel et al , 2007). The lipovitellin (Lv) derivatives of the Vtgs, together with lipids in the ooplasm, represent the major nutrients for the developing embryo.…”