Analysis Tools
mortality/aging
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• Background Sensitivity: fewer mutants are born than expected and there is a high number of stillborn; this is more severe on the A/Fa background than when outcrossed to CBA/Gr
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• syndactylous pups have a greatly increased mortality in the first few days after birth compared with non-syndactylous siblings
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skeleton
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• some homozygotes show fusion between the naviculare and cuboideum
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• the vertebrae of the distal tail can be normal, slightly shortened, or very small and wedge-shaped
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limbs/digits/tail
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• at embryonic day 11 there is hindlimb bud hyperplasia affecting only the preaxial half of the apical ectodermal ridge with an increased number of cells in both the superficial and basal layers; the underlying basement membrane has an irregular preaxial outline which becomes more conspicuous with age; from embryonic day 11 to 13 the developing footplate undergoes deformation modifying its external shape, the ectodermal cells lying close to the preaxial extremity of the hyperplastic apical ectodermal ridge are curved, and the fourth, third, and second mesodermal column each form in a deviated manner
(J:5107)
• at embryonic day 12 the limb buds appear bloated with the dorsal surfaces curved more than in normal embryos and the planar and plantar surfaces flattened, resulting in the free edge of the foot plates bending over in a planar and plantar direction and shortening the length of the circumference
(J:12940)
• at embryonic day 13 the palma and planta are concave and the middle digits are significantly crowded together
(J:12940)
• the limbs are narrower from side to side but thicker in a dorso-ventral direction at embryonic day 12 and 13 and this returns to a more normal form in later stages of development
(J:12940)
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• hyperplasia of the apical ectodermal ridge of the forelimbs is found by embryonic day 10.5 and of the hindlimbs by embryonic day 11 and this persists into embryonic day 13 when the apical ectodermal ridge has nearly disappeared in controls
• at embryonic day 12 and 13 the apical ectodermal ridge is pulled in a palmar or plantar direction rather than being on the edge of the foot plate
• from embryonic day 13 on there are roundish areas of the apical ectodermal ridge that separate from the underlying epidermis and form bodies that have dense nuclei and are presumed to slough off during development
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syndactyly
(
J:13049
)
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• all 4 feet are affected, digits 3 and 4 are always syndactylous, digit 2 is often syndactylous, digit 1 is sometimes syndactylous, and the hindfeet usually have digits joined via fused bones while the forefeet usually have the digits joined by soft tissue
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• some homozygotes show fusion between the naviculare and cuboideum
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• at embryonic day 14 the footplate outline has 4 projections instead of 5, and metatarsalia 3 and 4 converge and have a common basal phalanx
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• approximately 40% of syndactylism homozygotes have tail anomalies, such as a complete twist of the tail or one or two kinks, always in the distal half of the tail and most commonly in the third quarter of the tail in caudal vertebrae 16 to 21
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• the vertebrae of the distal tail can be normal, slightly shortened, or very small and wedge-shaped
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kinked tail
(
J:13049
)
reproductive system
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• although males that survive through wean age are usually normal breeders, female homozygotes are poor breeders
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embryo
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• at embryonic day 11 there is hindlimb bud hyperplasia affecting only the preaxial half of the apical ectodermal ridge with an increased number of cells in both the superficial and basal layers; the underlying basement membrane has an irregular preaxial outline which becomes more conspicuous with age; from embryonic day 11 to 13 the developing footplate undergoes deformation modifying its external shape, the ectodermal cells lying close to the preaxial extremity of the hyperplastic apical ectodermal ridge are curved, and the fourth, third, and second mesodermal column each form in a deviated manner
(J:5107)
• at embryonic day 12 the limb buds appear bloated with the dorsal surfaces curved more than in normal embryos and the planar and plantar surfaces flattened, resulting in the free edge of the foot plates bending over in a planar and plantar direction and shortening the length of the circumference
(J:12940)
• at embryonic day 13 the palma and planta are concave and the middle digits are significantly crowded together
(J:12940)
• the limbs are narrower from side to side but thicker in a dorso-ventral direction at embryonic day 12 and 13 and this returns to a more normal form in later stages of development
(J:12940)
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• hyperplasia of the apical ectodermal ridge of the forelimbs is found by embryonic day 10.5 and of the hindlimbs by embryonic day 11 and this persists into embryonic day 13 when the apical ectodermal ridge has nearly disappeared in controls
• at embryonic day 12 and 13 the apical ectodermal ridge is pulled in a palmar or plantar direction rather than being on the edge of the foot plate
• from embryonic day 13 on there are roundish areas of the apical ectodermal ridge that separate from the underlying epidermis and form bodies that have dense nuclei and are presumed to slough off during development
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integument
parakeratosis
(
J:12940
)
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• premature keratinization, in which the keratin formed retains nuclei, occurs from embryonic day 13 onwards in areas where epidermal hyperplasia has produced excessive thickness of epidermal cells, particularly the apical ectodermal ridge and hyperplastic patches of the limb epidermis
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• epidermal hyperplasia is found in sharply circumscribed areas of the limb epidermis by embryonic day 10.5
• hyperplasia of the distal tail epidermis is found by embryonic day 11, with thickening dorsally on either side of the neural tube
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