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Functional monopolar spindles caused by mutation in mgr, a cell division gene of Drosophila melanogaster
C González1, J Casal, P Ripoll
1Centro de Biologia Molecular (CSIC-UAM), Universidad Autónoma de Madrid, Spain.
Abstract:
Mutation in the gene merry-go-round (mgr) of Drosophila causes a variety of phenotypic traits in somatic and germinal tissues, such as polyploid cells, metaphasic arrest, postmeiotic cysts with 16 nuclei, and spermatids with four times the normal chromosome content. The most characteristic phenotype is the appearance of mitotic and meiotic figures where all chromosomes are arranged in a circle. Treatment with anti-mitotic drugs and the phenotype of double mutants mgr asp (asp being a mutation altering the spindle) show that these circular figures need a functional spindle for their formation. These abnormal figures are caused by monopolar spindles similar to those observed after different treatments in several organisms. All mutant traits indicate that mgr performs a function necessary for the correct behaviour of centrosomes, thus opening this organelle to genetic analysis.
Insights
The Drosophila gene merry-go-round (mgr) mutation causes abnormal cell division, characterized by circular chromosome arrangements. This highlights mgr's crucial role in centrosome function and spindle organization.
Area of Science:
- * Developmental Biology
- * Cell Biology
- * Genetics
Background:
- * Mutations in the Drosophila gene merry-go-round (mgr) lead to diverse phenotypic abnormalities in somatic and germinal tissues.
- * Observed traits include polyploid cells, metaphase arrest, and abnormal chromosome content in gametes.
- * A hallmark phenotype is the circular arrangement of all chromosomes during mitosis and meiosis.
Purpose of the Study:
- * To investigate the function of the merry-go-round (mgr) gene in Drosophila melanogaster.
- * To elucidate the role of mgr in centrosome behavior and spindle formation.
- * To understand the genetic basis of abnormal chromosome segregation.
Main Methods:
- * Analysis of phenotypic traits in mgr mutant Drosophila.
- * Treatment with anti-mitotic drugs to assess the requirement of a functional spindle.
- * Examination of double mutants (mgr asp) to understand gene interactions in spindle formation.
Main Results:
- * The mgr mutation results in characteristic circular arrangements of chromosomes during cell division.
- * Formation of these circular figures requires a functional spindle, as evidenced by drug treatments and double mutant analysis.
- * The phenotype is attributed to monopolar spindles, similar to those seen in other organisms under various treatments.
Conclusions:
- * The merry-go-round (mgr) gene is essential for proper centrosome function.
- * The study demonstrates that mgr is necessary for correct centrosome behavior.
- * This research opens the centrosome, a critical organelle, to further genetic analysis.