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Mutational analyses of fs(1)Ya, an essential, developmentally regulated, nuclear envelope protein in Drosophila
1Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853-2703, USA.
Abstract:
The fs(1)Ya protein (YA) is an essential, maternally encoded, nuclear lamina protein that is under both developmental and cell cycle control. A strong Ya mutation results in early arrest of embryos. To define the function of YA in the nuclear envelope during early embryonic development, we characterized the phenotypes of four Ya mutants alleles and determined their molecular lesions. Ya mutant embryos arrest with abnormal nuclear envelopes prior to the first mitotic division; a proportion of embryos from two leaky Ya mutants proceed beyond this but arrest after several abnormal divisions. Ya unfertilized eggs contain nuclei of different sizes and condensation states, apparently due to abnormal fusion of the meiotic products immediately after meiosis. Lamin is localized at the periphery of the uncondensed nuclei in these eggs. These results suggest that YA function is required during and after egg maturation to facilitate proper chromatin condensation, rather than to allow a lamin-containing nuclear envelope to form. Two leaky Ya alleles that partially complement have lesions at opposite ends of the YA protein, suggesting that the N- and C-termini are important for YA function and that YA might interact with itself either directly or indirectly.
Insights
The fs(1)Ya protein (YA) is crucial for nuclear envelope formation and chromatin condensation during early embryonic development. Mutations in YA lead to abnormal nuclear envelopes and developmental arrest, highlighting its essential role.
Area of Science:
- Developmental Biology
- Cell Biology
- Genetics
Background:
- The fs(1)Ya protein (YA) is a maternally encoded nuclear lamina protein.
- YA is essential for embryonic development and is under developmental and cell cycle control.
- Strong Ya mutations cause early embryonic arrest.
Purpose of the Study:
- To define the function of the nuclear lamina protein YA in the nuclear envelope during early embryonic development.
- To characterize the phenotypes of four Ya mutant alleles and determine their molecular lesions.
Main Methods:
- Phenotypic characterization of four Ya mutant alleles.
- Determination of molecular lesions in Ya mutants.
- Analysis of unfertilized eggs and early embryos.
Main Results:
- Ya mutant embryos exhibit abnormal nuclear envelopes and arrest before the first mitotic division.
- Leaky Ya mutants show delayed arrest after several abnormal divisions.
- Unfertilized Ya eggs display nuclei with varying sizes and condensation states due to abnormal meiotic product fusion.
- Lamin localization occurs at the periphery of uncondensed nuclei in Ya eggs.
Conclusions:
- YA function is required during and after egg maturation for proper chromatin condensation, not solely for nuclear envelope formation.
- Lesions in partially complementing leaky Ya alleles at opposite protein ends suggest the importance of N- and C-termini.
- The findings imply potential self-interaction of the YA protein, either directly or indirectly.