mortality/aging
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• fewer than expected mutants at E13.5
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embryo
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• defects are seen in structures arising from the first but not the second branchial arch
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• at E9.0, the first branchial arch is fused, lacking a midline division
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• primitive streak elongation is normal but significant reduction in the number of axial mesendoderm cells is detected in about 50% of mutants
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• fail to develop anterior neural folds
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• absent at E8.5 in the most severely affected embryos
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• at E9.0 expression of Shh, a marker of the notochord at this stage, is anteriorly truncated
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• the prechordal plate marker Gsc is significantly downregulated at the late headfold stage and the prechordal plate is absent in severely affected embryos
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craniofacial
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• severely affected embryos lack jaws, as shown by the absence of mandibles in skeleton preparations
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• defects are seen in structures arising from the first but not the second branchial arch
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• at E9.0, the first branchial arch is fused, lacking a midline division
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• seen in 68% of embryos at E13.5, associated with holoprosencephaly
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• severely affected embryos lack the entire tongue while mildly affected embryos lack the distal portion of the tongue
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• hypomorphic nasal septum resulting in a fused nasal cavity
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nervous system
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• seen in 68% of embryos at E13.5, associated with gross rostral truncation and cleft lip
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• thickening of the diencephalon seen in embryos with holoprosencephaly
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• a recessed third ventricle that fails to expand ventrally is seen in embryos with holoprosencephaly
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digestive/alimentary system
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• severely affected embryos lack the entire tongue while mildly affected embryos lack the distal portion of the tongue
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• at E9.0, in most embryos the foregut does not reach into the center of the first branchial arch unlike in wild-type mice
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respiratory system
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• hypomorphic nasal septum resulting in a fused nasal cavity
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skeleton
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• severely affected embryos lack jaws, as shown by the absence of mandibles in skeleton preparations
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growth/size/body
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• seen in 68% of embryos at E13.5, associated with holoprosencephaly
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• severely affected embryos lack the entire tongue while mildly affected embryos lack the distal portion of the tongue
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• hypomorphic nasal septum resulting in a fused nasal cavity
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