Chorion-deficient Mutants ?
corley at sfu.ca
Sun Oct 23 17:09:20 EST 1994
RE: message of 23 Oct 94 15:44:18 -0230 from pvalerio at leif.ucs.mun.ca
regarding possibility of making chorion-deficient mutants.
I find the concept of producing chorion deficient mutants intriguing.
However, I was under the impression that the
chorion is extremely important in fertilization for reasons most of you I
am sure are familiar with. For example, if the chorion was lost, would not
also the micropyle be lost? Therefore, losing a primary block to
polyspermy? Is anyone aware of experiments where the chorion has been
removed before fertilization and viable progeny have been produced?
P.S. In hope that it may help save time to anyone that decides to
investigate chorion deficient mutants or mutants that have softer
chorions, I have attached below, a list of a few references that
Paul.Becker, K. A. and N. H. Hart (1989) Polar body formation in
zebrafish eggs. Annual meeting of the American Society
of Zoologists, American Microscopical Society, Animal
Behavior Society, Crustacean Society, International
Assoc. of Astacology, and the Society of Systematic
Zoology, Boston, MA, USA, December 27-30, 1989. Am.
Zool. 29, 108A. 
Becker, K. A. and N. H. Hart (1990) Stage-specific effects
of cytochalasin D on polar body formation in the teleost
egg. 13th annual meeting of the American Soc. for Cell
Biology, San Diego, CA, USA, December 9-13, 1990. J.
Cell Biol. 111, 111A. 
Donovan, M. J., Hart N. H. (1986). Cortical granule
exocytosis is coupled with membrane retrieval in the egg
of Brachydanio. J. Exp. Zool. 237:391- 406. 
Donovan, M. J., Hart, N. H. (1983). Sensitivity of the
cortical reaction to cytochalasin B in eggs of
Brachydanio-rerio. Am. Zool. 23:984. 
Hart, N. H. (1970). Artifical activation of the ripe egg in
Brachydanio. Anat. Rec. 166:315. 
Hart, N. H. (1987). Morphological features of the plasma
membrane during activation of the Brachydanio egg. J.
Cell. Biol. 105:254A. 
Hart, N. H., Collins, G. C., Wolenski, J. S. (1986).
Ultrastructure of the egg cortex of Brachydanio. Am.
Zool. 26:11A. 
Hart, N. H., Donovan, M. (1983). Fine structure of the
chorion and site of sperm entry in the egg of Brachydanio
rerio. J. Exp. Zool. 227:277-296. 
Hart, N. H., Messina, M. (1972). Artificial insemination of
ripe eggs in the zebrafish, Brachydanio rerio. Copeia
Hart, N. H., Wolenski, J. S., (1989). Actin in the cortex of
the teleost egg. J. Cell Biol. 107:174a. 
Hart, N.H. and G.C. Collins (1991) An electron-microscope
and freeze-fracture study of the egg cortex of
Brachydanio rerio. Cell Tissue Res. 265, 317-328. 
Hart, N.H., Becker, K.A., Wolenski, J.S. (1992). The sperm
entry site during fertilization of the zebrafish egg:
localization of actin. Mol. Reprod. Dev. 32:217-228.
Nugent, J., Hart, N. H., Schalkoff, M. (1981). The cortical
cytoplasm and sites of sequestered calcium in the teleost
egg. Am. Zool. 21:984. 
Wolenski, J. S., Hart, N. H. (1987). Scanning electron
microscope studies of sperm incorporation into the
zebrafish (Brachydanio) egg. J. Exp. Zool. 243:259-274.
Wolenski, J. S., Hart, N. H. (1987). Sperm incorporation and
ferilization cone formation in eggs of the zebrafish
Brachydanio. J. Cell Biol. 105:338A. 
Wolenski, J. S., Hart, N. H. (1988). Effects of
cytochalasins B and D on the fertilization of zebrafish
Brachydanio eggs. J. Exp. Zool. 246:202-215. 
Wolenski, J. S., Hart, N. H. (1988). Sperm incorporation
independent of fertilization cone formation in the danio
egg. Dev. Growth Differ. 30:619-628. 
Wolenski, J. S., Hart, N. H. (1988). The fertilization cone
develops in the presence of actin filament cappers. J.
Cell Biol. 107:452a. 
Wolenski, J., Hart, N. H. (1984). Surface events at
fertilization in the teleost egg. Am. Zool. 4:23A. 
Wolenski, J., Hart, N. H. (1985). Sperm incorporation into
the teleost egg. Am Zool. 25:96A. 
Harvey, B., Kelley, R. N., Ashwood-Smith, M. J. (1983).
Permeability ofintact and dechorionated zebra fish
(Brachydanio rerio) embryos to glycerol and dimethyl
sulfoxide. Cryobiology 20:432-439. 
Hisaoka, K. K. (1958). Microscopic studies of the teleost
chorion. Trans. Am. Micro. Soc. 77:240-243. 
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In Message 23 Oct 94 15:44:18 -0230, pvalerio at leif.ucs.mun.ca writes:
> I am curious to know whether anyone is currently working on, or has
>considered the possibility of exploring, the following research topic with
> Many people working with fish embryos need to routinely remove the chorion
>as part of their experimental protocol. This can be time-consuming, and perhaps
>harmful to the embryo. Is there a possibility of creating a chorion-deficient
>mutant of, say a zebrafish, analogous to the cell-wall deficient algal cells
>that are used by plant molecular biologists ? The rationale behind this
>procedure is as follows:
>1. Mechanical or enzymatic dechorionation can be harmful to
>2. Although the chorion may be required for osmoregulation
> (eg. by retaining colloid released during cortical
> granule breakdown), dechorionated embryos can have similar survival
> rates in freshwater (+ marine ?) fishes.
>3. Chorion-deficient embryos could be used for a variety of experiments
> that are difficult or impossible with normal embryos: eg. cell fusion,
> gene transfer, organelle or cell ablation by lasers, other forms of
> microsurgery, etc...
>4. Perhaps chorion-deficient embryos could be cryopreserved, since the
> problem of supercooling would be circumvented by exposing the embryo
> directly to cooled cryoprotectant solutions.
> I understand that the chorion protein may be derived from more than one
>cell type in the ovary, but even if a mutation could be produced that prevents
>the 'hardening' process at the time of cortical granule breakdown, the
>chorions could be more easily removed. If this could be achieved with a model
>species like the zebrafish, it might make life a lot easier for people working
>with other species having a very tough chorion - if the method could be
>adapted to work with other species. At the moment, many studies must involve
>more time-consuming procedures, such as microinjection through the micropyle,
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Graham E. Corley-Smith
Institute of Molecular Biology and Biochemistry
Biological Sciences Department
Simon Fraser University
Phone: (604) 291-3021
Fax: (604) 291-5583
e-mail: corley at sfu.ca
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