|Unscrambling the egg-cellular, biochemical, molecular and endocrine advances in oogenesis|
Tyler, C.R.; Santos, E.M.; Prat, F. (2000). Unscrambling the egg-cellular, biochemical, molecular and endocrine advances in oogenesis, in: Norberg, B. et al. (Ed.) Proceedings of the 6th International Symposium on the Reproductive Physiology of Fish, Bergen, Norway, July 4-9, 1999. pp. 273-280
In: Norberg, B. et al. (Ed.) (2000). Proceedings of the 6th International Symposium on the Reproductive Physiology of Fish, Bergen, Norway, July 4-9, 1999. Department of Fisheries and Marine Biology, University of Bergen: Bergen. ISBN 82-7461-048-2. 499 pp., more
In: International Symposium on the Reproductive Physiology of Fish. Museo Nacional de Ciencias Naturales, more
|Authors|| || Top |
- Tyler, C.R.
- Santos, E.M.
- Prat, F.
An oocyte autonomously makes most of the machinery for DNA and protein synthesis, as well as mRNA needed immediately after fertilisation for the developing embryo. In fish, specialised egg constituents, such as yolk and some egg coat substances, are synthesised outside the ovary and have to be transported to the oocyte for uptake. Many (if not all) of the processes in the co-ordinated assembly of an oocyte involve an interplay of endocrine, paracrine and autocrine control. Knowledge of the processes governing the synthesis of an oocyte is central in our understanding of what makes a viable egg. This keynote paper focuses on the recent advances in the cellular, biochemical, molecular and endocrine biology of oocyte growth in fish. Vitellogenesis, when yolk is provisioned in the oocyte, and zonagenesis, where the 'egg shell' is formed, are topics that have received much of the recent focus in the study of oogenesis and the cDNAs for vitellogenin (VTG), the VTG receptor (VTGR), zona radiata proteins (ZRPs) and various yolk processing enzymes (cathepsins and lipoprotein lipase) have been cloned and sequenced. Recent advances in our knowledge of the endocrine control of oogenesis are limited, but there is now strong evidence for the involvement of follicle stimulating hormone (FSH - GtH I) in oocyte growth. Evidence has been forthcoming to the support roles of insulin-like growth factors and activin/inhibins in oogenesis in fish, but an oocyte-specific growth factor(s) has yet to be identified. Our knowledge on the mechanisms controlling oocyte recruitment in fish, as in all other animals is still minimal. Some features of ovarian physiology, including zonagenesis, vitellogenesis, formation of an ovarian cavity, and the presence of oocytes in the 'testis' of 'male' fish are now key biomarkers for studies on environmental oestrogens.