Examination of D-TACC's role in chromosome segregation. J.J. Kramer 1, W.E. Theurkauf 2, R.S. Hawley 1. 1) Dept Molecular and Cellular Biology, University of California at Davis, Davis, CA. 95616; 2) Program in Molecular Medicine University of Massachusetts Medical Center 373 Plantation Street Worcester, MA 01605.
The Drosophila TACC gene, D-TACC, has recently been shown to encode a microtubule-associated protein, which localizes to the spindle pole and spindle microtubules. D-TACC is required for completion of the syncytial mitoses, as ablation of D-TACC function results in the formation of abnormally short mitotic spindles and, leads to mitotic catastrophe (Gergley et al., 2000). We independently identified a P-element induced allele of D-TACC in a cytological screen for mitotic mutants. This allele was used to generate a null allele of D-TACC. This allele is fully female sterile. Analysis of this allele indicates that D-TACC mutant embryos exhibit abherrent centrosomal behavior during centrosome separation. In mutant embryos, centrosomes exhibit a defect in separation during interphase while maintaining the ability to organize microtubules.
In a separate study, we have investigated D-TACCs role in chromosome segregation during both meiosis and mitosis. Changes in TACC ploidy have been shown to be associated with a number of mammalian tumor cell lines. In addition, overexpression of murineTACC1 results in transformation (Still et al. 1999). We have utilized standard genetic tests in order to investigate the chromosome transmission defects exhibited both in the absence of D-TACC function as well as in the presence of increased D-TACC dosage. In addition, we will correlate these defects with cytological observation of the meiotic figures in mutant oocytes. As seen in mitosis. D-TACC is present on the meiotic spindle.in vivo imaging indicates that this localization is dynamic and undergoes discrete changes in accordance with meiotic progression. We will attempt to interpret these changes based upon the information obtained from analysis of chromosome behavior in the absence of d-TACC function.