Dynamics of cohesin subunits in grasshopper meiotic divisions
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The cohesin complex plays a key role for the maintenance of sister chromatid cohesion and faithful chromosome segregation in both mitosis and meiosis. This complex is formed by two structural maintenance of chromosomes protein family (SMC) subunits and two non-SMC subunits: an α-kleisin subunit SCC1/RAD21/REC8 and an SCC3-like protein. Several studies carried out in different species have revealed that the distribution of the cohesin subunits along the chromosomes during meiotic prophase I is not regular and that some subunits are distinctly incorporated at different cell stages. However, the accurate distribution of the different cohesin subunits in condensed meiotic chromosomes is still controversial. Here, we describe the dynamics of the cohesin subunits SMC1α, SMC3, RAD21 and SA1 during both meiotic divisions in grasshoppers. Although these subunits show a similar patched labelling at the interchromatid domain of metaphase I bivalents, SMCs and non-SMCs subunits do not always colocalise. Indeed, SA1 is the only cohesin subunit accumulated at the centromeric region of all metaphase I chromosomes. Additionally, non-SMC subunits do not appear at the interchromatid domain in either single X or B chromosomes. These data suggest the existence of several cohesin complexes during metaphase I. The cohesin subunits analysed are released from chromosomes at the beginning of anaphase I, with the exception of SA1 which can be detected at the centromeres until telophase II. These observations indicate that the cohesin components may be differentially loaded and released from meiotic chromosomes during the first and second meiotic divisions. The roles of these cohesin complexes for the maintenance of chromosome structure and their involvement in homologous segregation at first meiotic division are proposed and discussed.
KeywordsSister Chromatid Meiotic Division Meiotic Prophase Sister Chromatid Cohesion Supplemental Movie
This work was supported by grants BFU2009-10987 and BFU2009-08975 from Ministerio de Ciencia e Innovación (Spain), and grant SAF2011-28842 from Ministerio de Economía y Competitividad (Spain). Adela Calvente had a pre-doctoral contract in Universidad Autónoma de Madrid financed by Consejería de Educación de la Comunidad de Madrid and Fondo Social Europeo during the development of the research. We would like to express our sincere gratitude to the anonymous reviewers for their suggestions.
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