Cytoplasmic division cycles without the nucleus and mitotic CDK/cyclin complexes.

Cytoplasmic divisions are thought to rely on nuclear divisions and mitotic signals. We demonstrate in Drosophila embryos that cytoplasm can divide repeatedly without nuclei and mitotic CDK/cyclin complexes. Cdk1 normally slows an otherwise faster cytoplasmic division cycle, coupling it with nuclear divisions, and when uncoupled, cytoplasm starts dividing before mitosis. In developing embryos where CDK/cyclin activity can license mitotic microtubule (MT) organizers like the spindle, cytoplasmic divisions can occur without the centrosome, a principal organizer of interphase MTs. However, centrosomes become essential in the absence of CDK/cyclin activity, implying that the cytoplasm can employ either the centrosome-based interphase or CDK/cyclin-dependent mitotic MTs to facilitate its divisions. Finally, we present evidence that autonomous cytoplasmic divisions occur during unperturbed fly embryogenesis and that they may help extrude mitotically stalled nuclei during blastoderm formation. We postulate that cytoplasmic divisions occur in cycles governed by a yet-to-be-uncovered clock mechanism autonomous from CDK/cyclin complexes.

Autonomous clocks that regulate organelle biogenesis, cytoskeletal organization, and intracellular dynamics.

How do cells perceive time? Do cells use temporal information to regulate the production/degradation of their enzymes, membranes, and organelles? Does controlling biological time influence cytoskeletal organization and cellular architecture in ways that confer evolutionary and physiological advantages? Potential answers to these fundamental questions of cell biology have historically revolved around the discussion of 'master' temporal programs, such as the principal cyclin-dependent kinase/cyclin cell division oscillator and the circadian clock. In this review, we provide an overview of the recent evidence supporting an emerging concept of 'autonomous clocks,' which under normal conditions can be entrained by the cell cycle and/or the circadian clock to run at their pace, but can also run independently to serve their functions if/when these major temporal programs are halted/abrupted. We begin the discussion by introducing recent developments in the study of such clocks and their roles at different scales and complexities. We then use current advances to elucidate the logic and molecular architecture of temporal networks that comprise autonomous clocks, providing important clues as to how these clocks may have evolved to run independently and, sometimes at the cost of redundancy, have strongly coupled to run under the full command of the cell cycle and/or the circadian clock. Next, we review a list of important recent findings that have shed new light onto potential hallmarks of autonomous clocks, suggestive of prospective theoretical and experimental approaches to further accelerate their discovery. Finally, we discuss their roles in health and disease, as well as possible therapeutic opportunities that targeting the autonomous clocks may offer.

Inducing systemic and mucosal immune responses to B-T construct of F1 antigen of Yersinia pestis in microsphere delivery.

Plague is a zoonotic disease caused by Yersinia pestis, an etiological agent of pneumonic and bubonic plague. There is a need for an improved plague vaccine that may overcome the limitation of presently available whole cell vaccine. An alternative approach described here, is the use of protective epitopes from immunodominant antigen of Y. pestis. One such antigen is the F1 antigen, a major envelope and virulent protein that possess antiphagocytic and anti-microbial properties. The present study was aimed to develop a peptide-based vaccine, based upon the constructs made between B and T cell epitopes of F1 antigen of Y. pestis. The immunogenicity, IgG subclass pattern, affinity, avidity and in vivo protective efficacy of the antibodies generated for different B-T constructs were studied in murine model using microsphere as the delivery vehicle. The mode of immunization was both intranasal and intramuscular, with single and multiple doses of immunization, respectively. Intranasal immunization generated consistent high titre and long lasting immune response both for IgG and IgA in sera and sIgA in washes while intramuscular route generated peak IgG levels in sera only. The IgG isotypic levels pattern showed higher IgG2a/IgG2b levels in intranasal route while mixed isotypic levels of IgG1, IgG2a/IgG2b were observed in intramuscular route. The affinity and relative avidity of antibodies showed best results with intranasal route as compared to the intramuscular route. The specific activity measurement (IgG/IgA content) in sera and washes were well correlated with the antibody levels. Finally, in vivo protective studies showed that B1T1 and B2T1 conjugates protected the mice till day 15 while rest of the conjugates showed poor protection.