Ooplasmic segregation

Yoshida M, Horiuchi Y, Sensui N, Morisawa M. 2003. Signaling pathway from [Ca2+]i transients to ooplasmic segregation involves small GTPase rho in the ascidian egg. Dev Growth Differ 45(3) 275-281. 

This phenomenon, which has been called ooplasmic segregation, may be demonstrated particularly clearly in the so-called mosaic oocytes in which physiological and biochemical differentiation of the cytoplasm is particularly clearly defined, being accompanied by other additional external characteristics pigmentation, granule-formation, etc. This phenomenon has become a classical object of study in embryology, and the subject of much research, so that I shall mention only one or two typical examples by way of illustration. 

Primary differentiation of the cytoplasm of the oocyte of this type has now been studied not only in relation to the external characteristics of the membrane or incorporation of the cytoplasm, but also in relation to many biochemical and physico-chemical indices, such as redox potential, content of lipids, enzymes, and RNA, rate of protein synthesis, and so on, in many species of animals. It is impossible even to make a short examination of the many different variants of ooplasmic segregation. However, it is extremely important, because it determines the primary directions of differentiation. 

In the unicellular period maturing of the gametes takes place. Maturation of the oocyte (a very prolonged process), moreover, is associated with complex phenomena of special cytoplasmic differentiation (ooplasmic segregation) and often (but not always) with a special state of the chromosomes. 

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