Related Experiment Video
Updated: Aug 8, 2026
Studying Mitotic Checkpoint by Illustrating Dynamic Kinetochore Protein Behavior and Chromosome Motion in Living Drosophila Syncytial Embryos
Published on: June 14, 2012
CSN5/Jab1 mutations affect axis formation in the Drosophila oocyte by activating a meiotic checkpoint
Sergey Doronkin1, Inna Djagaeva, Steven K Beckendorf
1Department of Molecular and Cell Biology, 401 Barker Hall, University of California, Berkeley 94720, USA.
Abstract:
The COP9 signalosome (CSN) is linked to signaling pathways and ubiquitin-dependent protein degradation in yeast, plant and mammalian cells, but its roles in Drosophila development are just beginning to be understood. We show that during oogenesis CSN5/JAB1, one subunit of the CSN, is required for meiotic progression and for establishment of both the AP and DV axes of the Drosophila oocyte. The EGFR ligand Gurken is essential for both axes, and our results show that CSN5 mutations block the accumulation of Gurken protein in the oocyte. CSN5 mutations also cause the modification of Vasa, which is known to be required for Gurken translation. This CSN5 phenotype - defective axis formation, reduced Gurken accumulation and modification of Vasa - is very similar to the phenotype of the spindle-class genes that are required for the repair of meiotic recombination-induced, DNA double-strand breaks. When these breaks are not repaired, a DNA damage checkpoint mediated by mei-41 is activated. Accordingly, the CSN5 phenotype is suppressed by mutations in mei-41 or by mutations in mei-W68, which is required for double strand break formation. These results suggest that, like the spindle-class genes, CSN5 regulates axis formation by checkpoint-dependent, translational control of Gurken. They also reveal a link between DNA repair, axis formation and the COP9 signalosome, a protein complex that acts in multiple signaling pathways by regulating protein stability.
Insights
The COP9 signalosome subunit CSN5 is crucial for Drosophila oocyte development, regulating meiotic progression and axis formation by controlling Gurken protein translation via a DNA repair checkpoint.
Area of Science:
- Developmental Biology
- Cell Signaling
- Molecular Genetics
Background:
- The COP9 signalosome (CSN) complex regulates diverse cellular processes, including protein degradation and signaling pathways, across various organisms.
- While CSN's roles are established in yeast, plants, and mammals, its specific functions in Drosophila development are less understood.
Purpose of the Study:
- To investigate the role of CSN5/JAB1, a CSN subunit, in Drosophila oogenesis and early development.
- To elucidate the molecular mechanisms by which CSN5 influences meiotic progression and axis patterning in the oocyte.
Main Methods:
- Analysis of CSN5/JAB1 mutant phenotypes during Drosophila oogenesis.
- Investigating the impact of CSN5 mutations on the accumulation and translation of the EGFR ligand Gurken.
- Examining the modification status of Vasa protein in CSN5 mutants.
- Genetic interaction studies with genes involved in DNA repair checkpoints (mei-41) and double-strand break formation (mei-W68).
Main Results:
- CSN5 is essential for meiotic progression and the establishment of anterior-posterior (AP) and dorsal-ventral (DV) axes in the Drosophila oocyte.
- CSN5 mutations lead to reduced Gurken protein accumulation and aberrant modification of Vasa, a key regulator of Gurken translation.
- The CSN5 phenotype is suppressed by mutations in mei-41 (DNA damage checkpoint) and mei-W68 (double-strand break formation), indicating a link to DNA repair pathways.
Conclusions:
- CSN5 regulates Drosophila oocyte axis formation through checkpoint-dependent translational control of Gurken, similar to spindle-class genes.
- This study reveals a novel connection between DNA repair mechanisms, axis formation, and the COP9 signalosome in Drosophila development.
Related Concept Videos
01:57Meiosis II
02:19The Spindle Assembly Checkpoint
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
03:09Meiosis I
Prophase I is the most extended and complex step of meiosis I characterized by synapsis, chromosome pairing, and recombination of the homologous chromosomes. This process is facilitated by a proteinaceous structure called the...
02:02Meiosis II
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...
02:02Meiosis II
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...
01:21Nondisjunction