To study the nuclear dynamics during meiotic prophase in maize, we established a system to observe live meiocytes inside intact anthers. movement patterns differed dramatically between the two stages. Chromosome movements included rotations of the entire chromatin and movements of individual chromosome segments, which were mostly telomere-led. Chromosome motility was coincident with dynamic deformations of the nuclear envelope. Both, chromosome and nuclear envelope motility depended on actin microfilaments as well as tubulin. The complexity of the nuclear movements implies that several different mechanisms affect chromosome motility in early meiotic prophase in maize. We propose that the vigorous nuclear motility provides a mechanism for homologous loci Mps1-IN-1 to find each other during zygonema. Mouse monoclonal to CD22.K22 reacts with CD22, a 140 kDa B-cell specific molecule, expressed in the cytoplasm of all B lymphocytes and on the cell surface of only mature B cells. CD22 antigen is present in the most B-cell leukemias and lymphomas but not T-cell leukemias. In contrast with CD10, CD19 and CD20 antigen, CD22 antigen is still present on lymphoplasmacytoid cells but is dininished on the fully mature plasma cells. CD22 is an adhesion molecule and plays a role in B cell activation as a signaling molecule Keywords:chromosome dynamics, cytogenetics, meiosis, cell biology In early meiotic prophase, the nucleus undergoes a major spatial reorganization, which includes a general repositioning of chromatin and juxtaposition of homologous chromosomes (1). In many species, including maize, the nucleolus is located in the center of the nucleus during leptonema, and at the onset of zygonema, moves to a peripheral position (1,2). Concurrently with the nucleus migration, all chromosome ends attach to the nuclear envelope (NE) and cluster on a single site forming the telomere bouquet (3,4), which has been observed in most plants, animals, and fungi, including budding and fission yeasts, mouse, and maize. The telomeres remain clustered throughout zygonema. When the telomeres are clustered, centromeres are oriented in the opposite direction than the telomeres, resulting in a telomerecentromere polarization of the meiocyte nucleus. The presence of the bouquet coincides with pairing of homologous chromosomes (3,5). In plants, mammals, and fungi, chromosome pairing depends upon the progression of meiotic recombination (57). However, a recombination-driven homology recognition mechanism can only operate across a relatively short distance, probably 1.2 m (6). In large-genome species, such as maize, where the zygotene nucleus is 20 m Mps1-IN-1 in diameter, this mechanism may not be sufficient to reach across the chromatin mass in the nucleus, even when the chromosomes are brought together by the bouquet (6). These constraints suggest that homologous chromosome segments must first be positioned Mps1-IN-1 close to each other, before the homology search can take place. The ability of Mps1-IN-1 chromosomes to move across the nuclear space is essential for both the bouquet formation and chromosome pairing. Observations of live meiocytes in budding and fission yeasts have shown that during meiotic prophase chromosomes exhibit unexpectedly dynamic motility: the horse-tail chromosome movements in fission yeast and the rapid prophase movements (RPMs) in budding yeast (811). In fission yeast, these movements are particularly dramatic, with the entire nucleus moving violently back and forth (11,12). However, it has been unclear whether these dynamic motility patterns are specific to small-genome unicellular organisms where meiotic prophase is fairly short, or whether they are also present in species with large genomes and slowly progressing meiotic prophase. Until now, in-depth examinations of meiotic prophase dynamics in live meiocytes have not been performed in multicellular eukaryotes. Only fragmentary observations have been conducted in mouse and rats, and they have shown only limited extent of chromosome motility (13,14). In maize, efforts to culture isolated Mps1-IN-1 meiocytes to observe chromosome motility have been largely unsuccessful. Although metaphase I and later meiocytes develop properly in culture (15), attempts to culture isolated meiocytes in early stages of meiotic prophase have failed (16). To circumvent this problem, we developed a system to observe meiotic prophase in meiocytes inside intact live anthers, which, in contrast to isolated meiocytes, can be cultured in grasses during prophase I (17). Maize meiocytes develop in the center of the anther locule, which lies 70 to 100 m from the outside surface of the anther (Fig. S1). This depth is beyond the capabilities.