mortality/aging
• homozygotes die of respiratory failure shortly after birth
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skeleton
• at 19.5 dpc, mutant skulls have thinner cartilaginous plates than wild-type skulls
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• in homozygotes, the tooth primordia are severely hypoplastic; however, differentiation into the different layers proceeds normally
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• at 19.5 dpc, homozygotes lack a cellular clavicular mesenchyme; as a result, no cartilaginous head is identified
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• at 17.5 dpc, homozygotes fail to exhibit detectable osteoblastic differentiation and lack ossification centers or marrow formation
• at this stage, the mesenchymal cell layer is small and inactive, and osteoblasts are absent
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• at 19.5 dpc, the cartilage appears underdeveloped but displays some organization into growth plates near the diaphyseal end plates
• no osteoid is detected; however, a patchy calcification of cartilaginous tissue matrix is noted in the femur, tibia, and vertebrae, resulting in a reticulated pattern in the diaphyseal regions
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• at 17.5 dpc, homozygotes display an almost complete absence of ossification of the entire skeleton; in contrast, cartilage formation appears unaffected
• at birth, homozygotes exhibit small areas of mineralization; however, these areas do not correspond to any ossification
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• at 19.5 dpc, the cellular mesenchymal layer that gives rise to intramembranous ossification is absent in mutant skulls
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craniofacial
• at 19.5 dpc, mutant skulls have thinner cartilaginous plates than wild-type skulls
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• in homozygotes, the tooth primordia are severely hypoplastic; however, differentiation into the different layers proceeds normally
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• from ~E16.5 dpc onwards, homozygotes display a foreshortened nose
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respiratory system
• live-born homozygotes exhibit vascular congestion of the lungs
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• from ~E16.5 dpc onwards, homozygotes display a foreshortened nose
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• in live-born homozygotes, lungs appear underinflated despite normal bronchio-alveolar development; lung morphology is consistent with death due to asphyxia
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• most homozygotes delivered by Caesarean section at 18.5 or 19.5 dpc live; however, some pups occasionally gasp for air at irregular intervals, and show no signs of life after 20 minutes
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hematopoietic system
• newborn homozygotes display no formation of marrow cavities: vascularization and population of the marrow by hematopoetic cells fails
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• at 16.5 dpc, homozygotes display a 10- to 100-fold rise in primitive nucleated erythrocytes relative to wild-type mice
• the increase in primitive nucleated erythrocytes is likely to be a secondary effect of absence of hemotopoietic marrow development
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growth/size/body
• in homozygotes, the tooth primordia are severely hypoplastic; however, differentiation into the different layers proceeds normally
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• from ~E16.5 dpc onwards, homozygotes display a foreshortened nose
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• homozygotes are small relative to wild-type mice
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• the weight of homozygous mutant mice is reduced by approximately one-third relative to the weight of wild-type mice
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cardiovascular system
• live-born homozygotes exhibit vascular congestion of the lungs
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