Temperature dependence of cell division timing accounts for a shift in the thermal limits of <i>C.elegans</i> and <i>C.briggsae</i>

Cold-blooded animals, which cannot directly control their body temperatures, have adapted to function within specific temperature ranges that vary between species. However, little is known about what sets the limits of the viable temperature range. Here we show that the speed of the first cell division in C.elegans N2 varies with temperature according to the Arrhenius equation. However, it does so only within certain limits. Outside these limits we observe alterations inthe cell cycle. Interestingly, these temperature limits also correspond to the animal's fertile range. In C.briggsae AF16, isolated from a warmer climatic region, both the fertile range and the temperature range over which the speed of cell division follows the Arrhenius equation, are shifted toward higher temperatures. Our findings suggest that the viable range of an organism can be adapted in part to a different thermal range by adjusting the temperature tolerance of cell division.Facultad de Ciencias ExactasInstituto de Física de Líquidos y Sistemas Biológico

Temperature dependence of cell division timing accounts for a shift in the thermal limits of <i>C.elegans</i> and <i>C.briggsae</i>

Cold-blooded animals, which cannot directly control their body temperatures, have adapted to function within specific temperature ranges that vary between species. However, little is known about what sets the limits of the viable temperature range. Here we show that the speed of the first cell division in C.elegans N2 varies with temperature according to the Arrhenius equation. However, it does so only within certain limits. Outside these limits we observe alterations inthe cell cycle. Interestingly, these temperature limits also correspond to the animal's fertile range. In C.briggsae AF16, isolated from a warmer climatic region, both the fertile range and the temperature range over which the speed of cell division follows the Arrhenius equation, are shifted toward higher temperatures. Our findings suggest that the viable range of an organism can be adapted in part to a different thermal range by adjusting the temperature tolerance of cell division.Facultad de Ciencias ExactasInstituto de Física de Líquidos y Sistemas Biológico

Temperature dependence of cell division timing accounts for a shift in the thermal limits of <i>C.elegans</i> and <i>C.briggsae</i>

Cold-blooded animals, which cannot directly control their body temperatures, have adapted to function within specific temperature ranges that vary between species. However, little is known about what sets the limits of the viable temperature range. Here we show that the speed of the first cell division in C.elegans N2 varies with temperature according to the Arrhenius equation. However, it does so only within certain limits. Outside these limits we observe alterations inthe cell cycle. Interestingly, these temperature limits also correspond to the animal's fertile range. In C.briggsae AF16, isolated from a warmer climatic region, both the fertile range and the temperature range over which the speed of cell division follows the Arrhenius equation, are shifted toward higher temperatures. Our findings suggest that the viable range of an organism can be adapted in part to a different thermal range by adjusting the temperature tolerance of cell division.Facultad de Ciencias ExactasInstituto de Física de Líquidos y Sistemas Biológico

Supplemental Information 3: raw data

Embryonic cell division is a mechanical process which is predominantly driven by contraction of the cleavage furrow and response of the remaining cellular matter. While most previous studies focused on contractile ring mechanisms of cytokinesis, effects of environmental factors such as pericellular vitelline membrane and temperature on the mechanics of dividing cells were rarely studied. Here, we apply a model-based analysis to the time-lapse imaging data of two species (Saccoglossus kowalevskii and Xenopus laevis) with relatively large eggs, with the goal of revealing the effects of temperature and vitelline envelope on the mechanics of the first embryonic cell division. We constructed a numerical model of cytokinesis to estimate the effects of vitelline confinement on cellular deformation and to predict deformation of cellular contours. We used the deviations of our computational predictions from experimentally observed cell elongation to adjust variable parameters of the contractile ring model and to quantify the contribution of other factors (constitutive cell properties, spindle polarization) that may influence the mechanics and shape of dividing cells. We find that temperature affects the size and rate of dilatation of the vitelline membrane surrounding fertilized eggs and show that in native (not artificially devitellinized) egg cells the effects of temperature and vitelline envelope on mechanics of cell division are tightly interlinked. In particular, our results support the view that vitelline membrane fulfills an important role of micromechanical environment around the early embryo the absence or improper function of which under moderately elevated temperature impairs normal development. Furthermore, our findings suggest the existence of scale-dependent mechanisms that contribute to cytokinesis in species with different egg size, and challenge the view of mechanics of embryonic cell division as a scale-independent phenomenon

Molecular features of the UNC-45 chaperone critical for binding and folding muscle myosin

Myosin is a motor protein that is essential for a variety of processes ranging from intracellular transport to muscle contraction. Folding and assembly of myosin relies on a specific chaperone, UNC-45. To address its substrate-targeting mechanism, we reconstitute the interplay between Caenorhabditis elegans UNC-45 and muscle myosin MHC-B in insect cells. In addition to providing a cellular chaperone assay, the established system enabled us to produce large amounts of functional muscle myosin, as evidenced by a biochemical and structural characterization, and to directly monitor substrate binding to UNC-45. Data from in vitro and cellular chaperone assays, together with crystal structures of binding-deficient UNC-45 mutants, highlight the importance of utilizing a flexible myosin-binding domain. This so-called UCS domain can adopt discrete conformations to efficiently bind and fold substrate. Moreover, our data uncover the molecular basis of temperature-sensitive UNC-45 mutations underlying one of the most prominent motility defects in C. elegans

Voluntariado en La Ciudad de Los Niños de Granada - Volunteering at the “Ciudad de Los Niños” of Granada

Throughout the course of the semester, I had the opportunity to work at La Ciudad de Los Niños, a facility devoted to bettering the lives of children living in Granada, Spain. I chose to write about this topic because of the positive influence it had on my learning, both culturally and linguistically. I gathered the content of my paper solely through my experience working there, through formal and informal interviews with workers and students, and by using the facility’s website. In keeping a work journal, I was able to monitor my language growth and document different facts about the Ciudad de Los Niños, as well as the programs it offers to the students. Inside of my paper, one will find a general overview of the Ciudad de Los Niños, what it does, its history and more. Additionally, I have included a section that compares my work at the Ciudad de Los Niños to a previous volunteering experience I had at Nathan Bishop Middle School in Providence, RI. I did this to draw comparisons between some the programs being offered to the youth in both the United States and Spain. Upon concluding my work at the Ciudad de Los Niños, I can firmly say that my learning increased tenfold because of the relationships I developed with the children there. I began working there merely as a volunteer, yet left as a friend to 25 beautiful and intelligent girls. I feel that having this opportunity improved my ability to speak Spanish significantly, because as the semester came to a close, I was able to see how the language barrier that once existed between us is now gone. Working with the youth of Granada gave me insight to a different aspect of the culture that could not be learned in the classroom, as they carried on traditions and included me in their celebrations. Working in such a friendly and culturally rich environment made my educational experience abroad more valuable and one that I will never forget