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Strain-dependent embryonic lethality in mice lacking the retinoblastoma-related p130 gene
J E LeCouter1, B Kablar, P F Whyte
1Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
Abstract:
The retinoblastoma-related p130 protein is a member of a conserved family, consisting of Rb, p107 and p130, which are believed to play important roles in cell-cycle control and cellular differentiation. We have generated a null mutation in p130 by gene targeting and crossed the null allele into Balb/cJ and C57BL/6J strains of mice. In an enriched Balb/cJ genetic background, p130(-/-) embryos displayed arrested growth and died between embryonic days 11 and 13. Histological analysis revealed varying degrees of disorganization in neural and dermamyotomal structures. Immunohistochemistry with antibody reactive with Islet-1 indicated markedly reduced numbers of neurons in the spinal cord and dorsal root ganglia. Immunohistochemistry with antibody reactive with desmin indicated a similar reduction in the number of differentiated myocytes in the myotome. The myocardium of mutant embryos was abnormally thin and resembled an earlier staged two-chambered heart consisting of the bulbus cordis and the ventricular chamber. TUNEL analysis indicated the presence of extensive apoptosis in various tissues including the neural tube, the brain, the dermomyotome, but not the heart. Immunohistochemistry with antibody reactive with PCNA revealed increased cellular proliferation in the neural tube and the brain, and decreased proliferation in the heart. The placentas of p130(-/-) embryos did not display elevated apoptosis and were indistinguishable from wild type suggesting that the phenotype was not due to placental failure. Following a single cross with the C57BL/6 mice, p130(-/-) animals were derived that were viable and fertile. These results indicate that p130 in a Balb/cJ genetic background plays an essential role that is required for normal development. Moreover, our experiments establish that second-site modifier genes exist that have an epistatic relationship with p130.
Insights
The retinoblastoma-related p130 protein is crucial for embryonic development in mice. Loss of p130 function leads to developmental defects and embryonic lethality in certain genetic backgrounds.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- The retinoblastoma-related protein p130 is part of a family including Rb and p107.
- These proteins are known to be involved in cell-cycle control and differentiation.
Purpose of the Study:
- To investigate the role of p130 in embryonic development.
- To generate and characterize p130 knockout mice.
Main Methods:
- Gene targeting was used to create a p130 null mutation in mice.
- The null allele was crossed into Balb/cJ and C57BL/6J strains.
- Histological, immunohistochemical, and TUNEL analyses were performed on mutant embryos.
Main Results:
- p130(-/-) embryos on a Balb/cJ background exhibited growth arrest and died between embryonic days 11-13.
- Mutant embryos showed disorganization in neural and dermamyotomal structures, with reduced neuron and myocyte numbers.
- Abnormal heart development and increased apoptosis in neural tissues were observed, but not in the heart or placenta.
Conclusions:
- p130 plays an essential role in normal embryonic development within a Balb/cJ genetic background.
- The study identified second-site modifier genes that interact epistatically with p130, influencing developmental outcomes.