Analysis Tools
mortality/aging
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• homozygotes are obtained at the expected Mendelian frequency at E15.0-E16.0; however, a significant number of homozygotes are found dead at E16.5-E17.5
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• no live-born mice Lig4-null mice are generated from Lig4tm1Fwa/+, Xrcc5+/+ crosses (0/153 total offspring)
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growth/size/body
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• at E13.5-E14.5, mutant embryos are ~12% smaller than wild-type embryos
• by E15.0-E16.0, mutant embryos are ~25% smaller than wild-type embryos
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cellular
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• in culture, mutant MEFs show defective repair of ionizing radiation-induced DNA damage
• in culture, mutant MEFs show impaired V(D)J recombination, as shown by both recombination signal sequence (RSS) and coding-joining deficiencies
• impaired V(D)J recombination accounts for the blocked lymphopoiesis observed in older mutant embryos
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• mutant MEFs show significantly increased sensitivity to ionizing radiation relative to wild-type MEFs
• in contrast, sensitivity to ultraviolet irradiation remains unaffected
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• in culture, MEFs isolated from E13.5 homozygotes display significantly increased doubling times (55 hrs) relative to heterozygous (24 hrs) or wild-type MEFs (27 hrs)
• BrdU-labeling indicates a 23-34% reduction in the number of mutant MEFs found in the S phase of the cell cycle
• continuous BrdU-labeling of day 10 mutant MEFs and subsequent replating at low density shows impaired proliferative capacity and premature senescence
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• cultured fibroblasts display chromosomal instability at a level of ~55%
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immune system
small thymus
(
J:50865
)
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• at E15.0-E16.0, homozygotes exhibit a small thymus relative to wild-type embryos
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• total thymocyte cellularity is reduced ~100-fold compared to wild-type
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• in culture, fetal liver cells from E15-E17.5 mutant embryos show a significant reduction in IgM+ B220+ B cells, indicating defective B-cell development
• nucleotide sequencing of potential rearrangements in DNA from mutant B-cell cultures revealed grossly abnormal DJ and V(D)J joins, with large deletions extending from one or both sides of the recombining segment
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• B cell development is arrested at the B220+ D43+ progenitor stage
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• T lymphocyte development is arrested at the double negative (DN) stage
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• at E16.5-E17.5, mutant embryos exhibit an arrest of thymocyte development at the CD4-CD8-CD25+ stage, indicating a defect in productive rearrangement of T-cell antigen receptor beta genes
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hematopoietic system
| N |
• at E15.0-E16.0, homozygotes appear grossly normal with no apparent anemia
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small thymus
(
J:50865
)
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• at E15.0-E16.0, homozygotes exhibit a small thymus relative to wild-type embryos
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• total thymocyte cellularity is reduced ~100-fold compared to wild-type
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• in culture, fetal liver cells from E15-E17.5 mutant embryos show a significant reduction in IgM+ B220+ B cells, indicating defective B-cell development
• nucleotide sequencing of potential rearrangements in DNA from mutant B-cell cultures revealed grossly abnormal DJ and V(D)J joins, with large deletions extending from one or both sides of the recombining segment
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• B cell development is arrested at the B220+ D43+ progenitor stage
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• T lymphocyte development is arrested at the double negative (DN) stage
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• at E16.5-E17.5, mutant embryos exhibit an arrest of thymocyte development at the CD4-CD8-CD25+ stage, indicating a defect in productive rearrangement of T-cell antigen receptor beta genes
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endocrine/exocrine glands
small thymus
(
J:50865
)
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• at E15.0-E16.0, homozygotes exhibit a small thymus relative to wild-type embryos
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• total thymocyte cellularity is reduced ~100-fold compared to wild-type
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