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Mutations affecting the meiotic and mitotic divisions of the early Caenorhabditis elegans embryo
P E Mains1, K J Kemphues, S A Sprunger
1Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309.
Abstract:
We describe interactions between maternal-effect lethal mutations in four genes of Caenorhabditis elegans whose products appear to be involved in the meiotic and mitotic divisions of the one-cell embryo. Mitosis is disrupted by two dominant temperature-sensitive gain-of-function maternal-effect lethal mutations, mei-1(ct46) and mel-26(ct61), and by recessive loss-of-function maternal-effect lethal mutations of zyg-9. The phenotypic defects resulting from these mutations are similar. Doubly mutant combinations show a strong enhancement of the maternal-effect lethality under semipermissive conditions, suggesting that the mutant gene products interact. We isolated 15 dominant suppressors of the gain-of-function mutation mei-1(ct46). Thirteen of these suppressors are apparently intragenic, but 11 of them suppress in trans as well as cis. Two extragenic suppressors define a new gene, mei-2. The suppressor mutations in these two genes also result in recessive maternal-effect lethality, but with meiotic rather than mitotic defects. Surprisingly, most of these suppressors are also able to suppress mel-26(ct61) in addition to mei-1(ct46). The products of the four genes mei-1, mei-2, zyg-9 and mel-26 could be responsible for some of the specialized features that distinguish the meiotic from the mitotic divisions in the one-cell embryo.
Insights
Mutations in four Caenorhabditis elegans genes disrupt cell division. These genes, mei-1, mei-2, zyg-9, and mel-26, are crucial for distinguishing meiotic from mitotic divisions in early embryos.
Area of Science:
- Developmental Biology
- Genetics
- Cell Biology
Background:
- Maternal-effect lethal mutations in Caenorhabditis elegans provide insights into early embryonic development.
- The meiotic and mitotic divisions of the one-cell embryo involve complex genetic regulation.
Purpose of the Study:
- To investigate the interactions between maternal-effect lethal mutations in four genes involved in early embryonic cell divisions.
- To identify genes and their products essential for distinguishing meiotic from mitotic processes.
Main Methods:
- Analysis of maternal-effect lethal mutations in four Caenorhabditis elegans genes: mei-1, mel-26, and zyg-9.
- Generation and characterization of dominant suppressors for the mei-1(ct46) gain-of-function mutation.
- Examination of phenotypic defects and lethality in single, double, and suppressor mutant combinations.
Main Results:
- Mutations in mei-1, mel-26, and zyg-9 disrupt mitotic divisions, causing enhanced lethality in double mutants.
- Isolation of 15 dominant suppressors of mei-1(ct46), including intragenic and extragenic mutations defining a new gene, mei-2.
- Suppressor mutations in mei-1 and mei-2 cause meiotic defects and can suppress mel-26(ct61) mutations.
Conclusions:
- The gene products of mei-1, mei-2, zyg-9, and mel-26 interact and are likely involved in specialized features differentiating meiotic and mitotic divisions.
- These genes play critical roles in ensuring the fidelity of chromosome segregation during early embryonic development in C. elegans.