Person
Maischein, Hans-Martin
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Biography and Research Interest
The earliest patterning events in vertebrate embryogenesis are still poorly understood. In lower vertebrates, these events are initiated by maternal factors present in the egg (such as involved in bicoid localization in Drosophila). In order to identify genes coding for such factors, we are carrying out a screen for maternal-effect mutations in the zebrafish. Mutations are induced in the germ line of parental (P) males by exposing them to the point-mutagen N-ethyl-N-nitroso-urea (ENU). P males are then mated to produce F1 progeny heterozygous for the induced mutations. Eggs are stripped from the F1 females and gynogenesis is artificially induced using early pressure, which inhibits the second meiotic division of the egg. This allows mutations to become homozygous in the gynogenetic F2 generation. Finally, F2 adult females are screened for maternal-effects by crossing them to wild type males and testing their progeny for embryonic phenotypes.
In a pilot screen we raised 204 gynogenetic clutches to adulthood. This led to the identification of one maternal effect mutation. Females homozygous for this mutation are 100% sterile and the embryonic phenotype is independent of the paternal genotype. The mutant embryos can be distinguished as early as the one-cell stage by an increased turbidity in the cytoplasm. We are currently carrying out a larger scale maternal-effect screen in which we planto produce over 1200 gynogenetic adult clutches and screen over 350 genomes. The efficiency of this screen is improved about threefold compared to our pilot screen due the use of lines selected for a more favorable sex ratio under gynogenetic conditions.
In our gynogenetic clutches we also find mutations affecting adult pigmentation and body shape (4 of each type were found in our pilot screen). Thus the use of gynogenesis is useful to identify not only maternal-effect genes, but also genes involved in juvenile and adult traits. Our current screen attempts to combine screens for visual function and adult behavior (H. Baier), skeletal defects (H. Grandel) and fin development and regeneration.
One maternal gene was identified by its zygotic phenotype, unpigmented larval xanthophores. Homozygous yobo females produce embryos which display a number of general defects irrespective of the paternal genotype (Odenthal et al., 1996a).
In a pilot screen we raised 204 gynogenetic clutches to adulthood. This led to the identification of one maternal effect mutation. Females homozygous for this mutation are 100% sterile and the embryonic phenotype is independent of the paternal genotype. The mutant embryos can be distinguished as early as the one-cell stage by an increased turbidity in the cytoplasm. We are currently carrying out a larger scale maternal-effect screen in which we planto produce over 1200 gynogenetic adult clutches and screen over 350 genomes. The efficiency of this screen is improved about threefold compared to our pilot screen due the use of lines selected for a more favorable sex ratio under gynogenetic conditions.
In our gynogenetic clutches we also find mutations affecting adult pigmentation and body shape (4 of each type were found in our pilot screen). Thus the use of gynogenesis is useful to identify not only maternal-effect genes, but also genes involved in juvenile and adult traits. Our current screen attempts to combine screens for visual function and adult behavior (H. Baier), skeletal defects (H. Grandel) and fin development and regeneration.
One maternal gene was identified by its zygotic phenotype, unpigmented larval xanthophores. Homozygous yobo females produce embryos which display a number of general defects irrespective of the paternal genotype (Odenthal et al., 1996a).
Non-Zebrafish Publications