Capturing chaotic chromosomes: Pairing in action

Accurate chromosome segregation is critical for the formation of haploid gametes, and therefore healthy offspring. Errors in segregation result in aneuploidy, which increases exponentially with maternal age (Hassold and Hunt, 2001). Maternally aged mouse oocytes were recently found to exhibit premature sister chromatid separation due to reduced levels of Securin, an essential regulator of sister chromatid cohesion (Nabti et al, 2017). This landmark finding was facilitated by using chromosome spreads that allow for the visualization of meiotic processes, such as recombination, synapsis, crossing over, and cohesion. This powerful technique is easy to perform and analyze, and allows for the identification of markers for different processes, including DNA damage and repair.Fil: Bertucci, Micka C.. University of Chicago; Estados UnidosFil: Das, Arunika. University of Chicago; Estados UnidosFil: Fitzgerald, Harriet C.. University of Chicago; Estados UnidosFil: Goszczynski, Daniel Estanislao. University of Chicago; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Kinesin 6 Regulation in Drosophila Female Meiosis by the Non-conserved N- and C- Terminal Domains

Bipolar spindle assembly occurs in the absence of centrosomes in the oocytes of most organisms. In the absence of centrosomes in Drosophila oocytes, we have proposed that the kinesin 6 Subito, a MKLP-2 homolog, is required for establishing spindle bipolarity and chromosome biorientation by assembling a robust central spindle during prometaphase I. Although the functions of the conserved motor domains of kinesins is well studied, less is known about the contribution of the poorly conserved N- and C- terminal domains to motor function. In this study, we have investigated the contribution of these domains to kinesin 6 functions in meiosis and early embryonic development. We found that the N-terminal domain has antagonistic elements that regulate localization of the motor to microtubules. Other parts of the N- and C-terminal domains are not required for microtubule localization but are required for motor function. Some of these elements of Subito are more important for either mitosis or meiosis, as revealed by separation-of-function mutants. One of the functions for both the N- and C-terminals domains is to restrict the CPC to the central spindle in a ring around the chromosomes. We also provide evidence that CDK1 phosphorylation of Subito regulates its activity associated with homolog bi-orientation. These results suggest the N- and C-terminal domains of Subito, while not required for localization to the central spindle microtubules, have important roles regulating Subito, by interacting with other spindle proteins and promoting activities such as bipolar spindle formation and homologous chromosome bi-orientation during meiosis

Supplemental Material for Das et al., 2018

Fertility and nondisjunction data for subito transgenes in a wild-type background are in Table S1 (in File S1). The percentages of oocytes in each category of spindle morphology determined cytologically is in Table S2 (in File S1). Examples of these spindle categories are in Figure S2. Western blots showing oocyte expression of each mutant transgene is shown in Figures S1, S3 and S5. Cytology of mutants not shown in Figures 1-7 are shown in Figures S4 and S5. <br