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Analysis of maternal molecules in th...

Howley, Cristin E.

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Analysis of maternal molecules in the early patterning of the zebrafish embryo.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Analysis of maternal molecules in the early patterning of the zebrafish embryo./
作者:	Howley, Cristin E.
面頁冊數:	136 p.
附註:	Source: Dissertation Abstracts International, Volume: 62-03, Section: B, page: 1227.
Contained By:	Dissertation Abstracts International62-03B.
標題:	Biology, Molecular. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3007218
ISBN:	0493166327

Analysis of maternal molecules in the early patterning of the zebrafish embryo.
Howley, Cristin E.

Analysis of maternal molecules in the early patterning of the zebrafish embryo. - 136 p.

Source: Dissertation Abstracts International, Volume: 62-03, Section: B, page: 1227.

Thesis (Ph.D.)--Princeton University, 2001.

Studies in <italic>Drosophila</italic> and <italic>Xenopus </italic> have shown that localized maternal mRNAs commonly establish polarity within the early embryo, determining dorsal/ventral (D/V) and anterior/posterior (A/P) axis specification. While embryological experiments suggest that maternal factors are important in axis formation in the zebrafish, <italic>Danio rerio </italic>, it is unclear whether mRNA localization is used to achieve this. When this study was initiated, most of the identified maternal mRNAs had been found to be expressed throughout the early embryo. However, these initial studies overlooked the possibility that localization may have occurred earlier during oogenesis. To investigate this possibility, in situ hybridizations to known mRNAs were performed on zebrafish ovaries. The results establish that maternal mRNA localization during zebrafish oogenesis can be categorized into the following four patterns: ubiquitous, animal pole, vegetal pole, and cortical localization. While these patterns suggest that the animal/vegetal axis, which correlates with the A/P axis, may be established by localized mRNAs, they fail to define a role for mRNA localization in D/V establishment. Prior to this study, a maternal T-box gene like <italic>Xenopus VegT</italic>, known to localize and pattern the early frog embryo, had not yet been identified in the zebrafish. A screen to identify a similar maternal T-box gene in zebrafish yielded <italic>eomesodermin</italic> (<italic>eom</italic>). <italic>eom </italic> transcript localizes cortically during oogenesis. During the cleavage stages of development, maternal <italic>eom</italic> mRNA localizes in a vegetal to animal gradient, with most of the mRNA concentrating at the yolk/blastomere interface. This expression pattern is novel among maternally expressed genes in the zebrafish. Overexpression studies show that <italic>eom</italic> can induce ectopic expression of a number of genes, including organizer markers. Furthermore, <italic>eom</italic> overexpressing embryos form secondary axes, the hallmark of an ectopically induced organizer. These studies suggest a role for <italic>eom</italic> in D/V patterning. Overexpression of <italic> eom-VP16</italic> (transcriptional activator) also induces secondary axes, suggesting <italic>eom</italic> behaves as an activator in organizer induction. Interestingly, <italic>eom-engrailed</italic> (transcriptional repressor) overexpression studies suggest a separate role for <italic>eom</italic> in early cell intercalation movements. In summary, this work demonstrates that maternal mRNA localization is a mechanism for establishing polarity in the early zebrafish embryo, as exemplified by <italic>eom</italic>.

ISBN: 0493166327Subjects--Topical Terms:

1017719
Biology, Molecular.

Analysis of maternal molecules in the early patterning of the zebrafish embryo.
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502 $a Thesis (Ph.D.)--Princeton University, 2001.
520 $a Studies in <italic>Drosophila</italic> and <italic>Xenopus </italic> have shown that localized maternal mRNAs commonly establish polarity within the early embryo, determining dorsal/ventral (D/V) and anterior/posterior (A/P) axis specification. While embryological experiments suggest that maternal factors are important in axis formation in the zebrafish, <italic>Danio rerio </italic>, it is unclear whether mRNA localization is used to achieve this. When this study was initiated, most of the identified maternal mRNAs had been found to be expressed throughout the early embryo. However, these initial studies overlooked the possibility that localization may have occurred earlier during oogenesis. To investigate this possibility, in situ hybridizations to known mRNAs were performed on zebrafish ovaries. The results establish that maternal mRNA localization during zebrafish oogenesis can be categorized into the following four patterns: ubiquitous, animal pole, vegetal pole, and cortical localization. While these patterns suggest that the animal/vegetal axis, which correlates with the A/P axis, may be established by localized mRNAs, they fail to define a role for mRNA localization in D/V establishment. Prior to this study, a maternal T-box gene like <italic>Xenopus VegT</italic>, known to localize and pattern the early frog embryo, had not yet been identified in the zebrafish. A screen to identify a similar maternal T-box gene in zebrafish yielded <italic>eomesodermin</italic> (<italic>eom</italic>). <italic>eom </italic> transcript localizes cortically during oogenesis. During the cleavage stages of development, maternal <italic>eom</italic> mRNA localizes in a vegetal to animal gradient, with most of the mRNA concentrating at the yolk/blastomere interface. This expression pattern is novel among maternally expressed genes in the zebrafish. Overexpression studies show that <italic>eom</italic> can induce ectopic expression of a number of genes, including organizer markers. Furthermore, <italic>eom</italic> overexpressing embryos form secondary axes, the hallmark of an ectopically induced organizer. These studies suggest a role for <italic>eom</italic> in D/V patterning. Overexpression of <italic> eom-VP16</italic> (transcriptional activator) also induces secondary axes, suggesting <italic>eom</italic> behaves as an activator in organizer induction. Interestingly, <italic>eom-engrailed</italic> (transcriptional repressor) overexpression studies suggest a separate role for <italic>eom</italic> in early cell intercalation movements. In summary, this work demonstrates that maternal mRNA localization is a mechanism for establishing polarity in the early zebrafish embryo, as exemplified by <italic>eom</italic>.
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