Experimental Study of the Developing Mammalian Egg: Removal of the Zona Pellucida

Abstract

The zona pellucida may be removed from all stages of the mouse egg by digestion with pronase. Cumulus and corona cells are also dispersed by the enzyme. No change in membrane disgestibility occurs at fertilization. In tests thus far of two-cell eggs and later stages, development continues. Blastocysts exhibit "hatching" behavior despite absence of the zona. Functions of the zona include maintenance of the normal cleavage pattern and prevention of egg fusion.

Mouse zygotes as recipients in embryo cloning

“…Embryos were flushed from oviducts and tubo-uterine junctions around noon on the third day after mating (vaginal plug, day 1). Zonae pellucidae were removed from eight-cell embryos by treatment with 0.5% pronase in PBS for 3-5 min (Mintz 1962). After rinsing the embryos in three changes of M2 medium, they were transferred to Dulbecco's salt solution, which was devoid of Ca and Mg ions, for 15 min.…”

Established Preblastocyst- and Blastocyst-Derived ES Cell Lines Have Highly Similar Gene Expression Profiles, Despite Their Differing Requirements for Derivation Culture Conditions

“…It has been reported that early implantation stage embryos from which the zona pellucida was removed developed into blastocysts by in vitro culture without feeders (Mintz, 1962). In the present study, zona-free embryos that were cultured on feeders differed developmentally from intact embryos.…”

The role of the sex chromosomes in mammalian germ cell differentiation

“…However, Ohno and coworkers found that both X chromosomes were euchromatic (indicating functional capacity) in oogonia and oocytes from fetal ovaries of the rat, hamster, human and mouse (Ohno, Kaplan and Kinosita, 1961 ; Ohno and !/Veiler,1961 ;Ohno, Klinger and Atkin, 1962 ;Ohno, 1963). Recent biochemical observations have confirmed that both Xs are functional in oocytes (Epstein, 1969 ;Gartler et al, 1972 ;Gartler, Liskay and Gant, 1973 ;Kozak, McLean and Eicher, 1974 ;Gartler, Andina and Gant, 1975 ; Mangia, Abbo-Halbach and Epstein, 1975) and probably also in oogonia (Migeon and Jelalian, 1977 (Tarkowski, 1961 ;Mintz, 1962 Tarkowski,1968 ;Ford et al,1974 ;McLaren, 1975). In an XX *-+ XY chimaera in which the strain combination allowed the identification of the source of the sperm using morphological criteria, no sperm from the XX cell line were detected (Burgoyne, 1976 …”

“…Recent biochemical observations have confirmed that both Xs are functional in oocytes (Epstein, 1969 ;Gartler et al, 1972 ;Gartler, Liskay and Gant, 1973 ;Kozak, McLean and Eicher, 1974 ;Gartler, Andina and Gant, 1975 ; Mangia, Abbo-Halbach and Epstein, 1975) and probably also in oogonia (Migeon and Jelalian, 1977 (Goldstein and Wilson, 1974). These XY women have streak ovaries just like XO women, and it can again be argued that this is a consequence of X-dosage deficiency in the oocytes (Burgoyne, 1978 (Tarkowski, 1961 ;Mintz, 1962 Tarkowski,1968 ;Ford et al,1974 ;McLaren, 1975). In an XX *-+ XY chimaera in which the strain combination allowed the identification of the source of the sperm using morphological criteria, no sperm from the XX cell line were detected (Burgoyne, 1976 There is a considerable body of evidence supporting the generality of this conclusion.…”