mortality/aging
• die at or before E7.5
• by E8.5, most embryos are in resorption or degenerating within the yolk sac
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embryo
• 35% of embryos at E6.5 show a reduced ectoderm region
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• in vitro differentiation of the mesoderm in ES cells is impaired
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• due to impaired visceral endoderm function
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• rescue of gastrulation defects by complementation with tetraploid embryonic cells results in chimeric embryos with mesoderm-derived tissue that show impaired anterior development/anterior truncations at E8.5
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• development is arrested at the onset of gastrulation
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• at E5.5
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• at E5.5, the embryonic region is reduced in size
• by E6.5, the embryonic region is reduced and poorly developed but displays a proamniotic cavity
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• no histological signs of mesoderm development at E6.5
• failure to form mesoderm is confirmed by the absence of mesodermal markers
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• at E6.5
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• embryos have a poorly defined boundary between the embryonic and the extraembryonic regions
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• extraembryonic region appears disorganized
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• poorly organized visceral endoderm at E5.5
• visceral endoderm development is abnormal and in vitro differentiation of the visceral endoderm in ES cells is impaired
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growth/size/body
• at E5.5
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cellular
• reduced cell proliferation in embryos at E6.5, as shown by BrdU staining
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