Analysis Tools
mortality/aging
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• at E8.5, about 25% of decidua contain abnormal conceptuses in which the embryos are either very small or completely resorbed
• no homozygous embryos are recovered at, or after, E9.5
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cellular
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• homozygous null ES cells injected into wild-type blastocysts are capable of forming mesoderm in chimeric embryos; however, primitive streak formation is impaired
• wild-type ES cells injected into homozygous null blastocysts form relatively normal extraembryonic tissues and extraembryonic mesoderm; however, the embryo proper develops poorly, suggesting a severe gastrulation defect
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embryo
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• expression of Brachyury (T), an early mesoderm marker, is absent at E7.5 and E8.5, suggesting that developmental arrest occurs before gastrulation
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• at E6.5, the epiblast of some embryos is hypoplastic and often located ectopically
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• molecular marker analysis of prestreak stage embryos confirmed that the visceral endoderm fails to form the squamous cell type in the distal region of the egg cylinder
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• at E7.5, mutant embryos contain no mesoderm
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• at E7.5, 12 out of 38 homozygous null embryos appear smaller and lack a discernible primitive streak
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• at E6.5, the extraembryonic ectoderm cells fail to form an epithelial layer and often intrude into the distal region
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• at E6.5, the epiblast and the extraembryonic ectoderm appear to be intertwined and disorganized
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• at E8.5, the visceral endoderm layer is folded, possibly as a result of extensive cell death and shrinkage of the ectoderm
• no morphological defects are noted in the trophoblast or parietal endoderm throughout early development
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• at E5.5, in ~22% of mutant embryos, the distal visceral endoderm cells are slightly more vacuolated and detached from the epiblast
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