mortality/aging
• only 40% of homozygotes survive into adulthood
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• only 13.4% (versus expected 25%) of homozygotes are recovered from heterozygous breeding pairs at P0
• death is 3 times higher among pups from homozygous pairs; however, first litter homozygous mutant mothers show normal nesting, nursing, and pup retrieval behaviors relative to wild-type and heterozygous controls
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• only 50% of homozygotes are alive after 3 days of birth
• an additional 10% of homozygotes die between 3 days and 8 weeks of age
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growth/size/body
short snout
(
J:89882
)
• adult homozygotes display a short snout
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• at birth, homozygotes are 21% lighter than wild-type and heterozygous control littermates
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• at 1 week after birth, homozygotes are on average 45% lighter than wild-type and heterozygous control littermates
• adult homozygotes are about 40% lighter and never reach the size of their control littermates
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• adult homozygotes display a relatively small trunk
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• adult homozygotes exhibit a slightly disproportionate dwarfism, with a relatively small trunk and a short snout relative to control littermates
• however, at 2-3 weeks of age all major organs, including brain, liver, spleen, kidney, stomach, and intestine, are proportionally reduced to ~60% of control size
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• homozygotes display a progressive growth reduction from birth to weaning
• adult homozygotes are about 40% lighter and never reach the size of control littermates
• postnatal growth of female and male homozygotes is proportionally reduced to the same extent
• failure to thrive in the first days of life is highly variable ranging from complete exhaustion and early death to nearly normal appearance and activity
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• at E17.5, homozygous mutant embryos are 14% lighter than wild-type embryos
• however, no significant differences in body weight are observed at E12.5 and E14.5
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• homozygotes display a progressive fetal retardation from E17.5 to birth
• fetal growth retardation is associated with reduced Igf2 translation and a smaller placenta
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craniofacial
short snout
(
J:89882
)
• adult homozygotes display a short snout
|
limbs/digits/tail
kinked tail
(
J:89882
)
• some adult homozygotes exhibit tiny kinks on their tails
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behavior/neurological
• homozygotes that fail to thrive in the first days of life have trouble competing with littermates for feeding
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• a few homozygotes that survive early death display aggressive behavior
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• homozygotes that fail to thrive in the first days of life are inactive
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hyperactivity
(
J:89882
)
• a few homozygotes that survive early death display restlessness
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embryo
• at E17.5, mutant placentas are 18% lighter than wild-type placentas
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digestive/alimentary system
• severely affected homozygotes exhibit necrotic patches and adherences in the intestine
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• impaired intestinal development is associated with reduced postnatal expression of transcripts encoding extracellular matrix components, such as galectin- 1, lumican, tenascin-C, procollagen transcripts, and the Hsp47 procollagen chaperone
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• at 30 days of age, the mucosal thickness of the small intestine and colon is reduced by 54% and 67%, respectively
• at 30 days of age, the mucosal lining of the small intestine displays irregular misshapen villi and loss of mesenchyme
• at 30 days of age, the muscular wall of the colon is thinned to about one third of normal size
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• at 30 days of age, the average height of colonic crypts is reduced by 52%
• at 30 days of age, mutant colonic crypts appear twisted and deformed
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• at 30 days of age, the goblet cells in the colon are redistributed to the bottom of the crypts
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• at 30 days of age, the colonic muscular wall is thinned to about one third of normal size
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• dying and dehydrated mutant pups exhibit small intestine hypoplasia
• histological changes range from complete loss of villi to an almost normal appearance
• surviving adult homozygotes display a nearly normal small intestine histology
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• at E17.5, the small intestine of mutant mice displays irregularly-shaped villi
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• at E17.5, the size of small intestinal villi is reduced
• at 30 days of age, the average height and width of mutant villi is reduced by 62% and 49%, respectively; however, the number of villi remains unchanged
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renal/urinary system
• at 3-15 days of age, mutant collecting tubules appear irregular, with reduced lumen
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• at 3-15 days of age, mutant renal glomeruli are small and hypoplastic
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• at 3-15 days of age, homozygotes display immature kidney morphology
• histological changes are gradually normalized, indicating delayed kidney maturation
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• at 3-4 months of age, the wet weight, dry weight, and DNA content of mutant kidneys are proportionally reduced, indicating that reduced kidney size is mainly due to hypoplasia
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liver/biliary system
• at 3-15 days of age, mutant livers display subtle changes in the lobular structure
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• some severely affected adult homozygotes display hepatic steatosis
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hematopoietic system
skeleton
• at 3-15 days of age, homozygotes display a distinct loss of cartilage in the lower extremities and tail, the growth plate in the tibia, and on top of the blade of the scapula as well as in the mandible and the nasal bone, as shown by alcian blue staining
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homeostasis/metabolism
dehydration
(
J:89882
)
• homozygotes that fail to thrive in the first days of life are dehydrated
|
immune system
endocrine/exocrine glands
• at 30 days of age, the average height of colonic crypts is reduced by 52%
• at 30 days of age, mutant colonic crypts appear twisted and deformed
|
• at 30 days of age, the goblet cells in the colon are redistributed to the bottom of the crypts
|
cellular
• at 30 days of age, the goblet cells in the colon are redistributed to the bottom of the crypts
|
• at E17.5, the percentage of PCNA-positive cells in the liver and kidney is reduced from 33% +/- 4.9% to 23% +/- 4.8% and from 27% +/- 5.7% to 16% +/- 7.4%, respectively
• in the intestine, PCNA-positive cells are abnormally abundant all over the irregularly-shaped villi, whereas in the wild-type intestine PCNA-positive cells are primarily found at the root of the villi
• in vitro, mutant MEFs derived from E13.5 embryos show a 16% and 24% reduction in growth relative to wild-type MEFs after 24 hrs and 72 hrs of culture, respectively
• at E17.5, no significant increase in apoptosis is observed in liver or any other organ, as determined by TUNEL staining
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muscle
• at 30 days of age, the colonic muscular wall is thinned to about one third of normal size
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