The EMBO Meeting 2013

Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden

Liquid-like states of cytoplasm

Contemporary biology has identified many proteins involved in different cellular processes, but we are far from understanding how they perform the tasks that cell functions require. How do collections of proteins and other molecules come together to form compartments containing large numbers of macromolecular machines that execute specific and complex reactions? The search for underlying principles has been reinvigorated recently in part by insights into the role of phase transitions in organizing cellular compartments. I will illustrate these ideas using experiments that examine the nature and formation of P granules, which are collections for RNA and protein involved in specifying the germ line in C.elegans.

Biography

Prof. Dr. Anthony Hyman is Director and Group Leader at the Max Planck Institute of Molecular Cell Biology and Genetics. 1984 he received his BSc first class in Zoology from the University College in London, where he had also been working as research Assistant in 1981. From 1985 to 1987 he wrote his PhD about "The establishment of division axes in early C.elegans embryos" under the supervision of Dr. John White at the Laboratory of Molecular Biology, MRC in Cambridge, England. After that he moved to San Francisco where he did his postdoctoral research in the lab of Prof. Tim Mitchison at the University of California investigating the mechanism of chromosome movement studied in vitro. 1993 he became Group Leader at the European Molecular Biology Laboratory in Heidelberg, before he moved to Dresden in 1999 as one of the founding directors of the Max Planck Institute of Molecular Cell Biology and Genetics. 2002 he was named honorary Professor of Molecular Cell Biology at the Technical University Dresden. The year after he was awarded the EMBO Gold Medal. In 2007 he was elected as a Fellow of the Royal Society and was awarded the Leibniz Prize in 2011.

His research covers the mitotic spindle assembly and function, focusing on centrosomes; distribution of force generating mechanisms necessary for the first asymmetric division; establishment of cortical polarity. He primarily works in C.elegans embryos, but is also studying aspects of these problems in Human cells using the emerging techniques of BAC transgenesis.

HHMI & UT Southwestern, Dallas

Physical Mechanisms of Cell Organization on Micron Length Scales

Cells are organized on length scales from Angstroms to microns. However, the mechanisms by which Angstrom-scale molecular properties are translated to micron-scale macroscopic properties are not well understood. We have shown that interactions between multivalent proteins and multivalent ligands can cause liquid-liquid demixing phase transitions, resulting in formation of micron-sized liquid droplets in aqueous solution and micron-sized puncta on membranes. These transitions appear to occur concomitantly with sol-gel transitions to form large, dynamic polymers within the droplets/puncta. I will discuss how such transitions might control the spatial organization and biochemical activity of actin regulatory signaling pathways, and contribute to formation of PML nuclear bodies in the mammalian nucleus. Our data suggest a general mechanism by which cells might achieve micron-scale organization based on interactions between multivalent macromolecules.

Biography

Dr. Rosen is the Chair of the Department of Biophysics at UT Southwestern and an Investigator of the Howard Hughes Medical Institute.  Prior to moving to UT Southwestern in 2001 he was a member of the Cellular Biochemistry and Biophysics Program at the Memorial Sloan-Kettering Cancer Center in New York City.  He received undergraduate degrees in chemistry and in chemical engineering from the University of Michigan in 1987, and then spent a year in Alan Battersby's lab in the Department of Chemistry at the University of Cambridge as a Winston Churchill Foundation Scholar.  He received his Ph.D. in chemistry from Harvard University in 1993 under the direction of Stuart Schreiber, where he studied the structure and function of the FK506 binding protein, FKBP12.  He was a Damon Runyon-Walter Winchell post-doctoral fellow in the laboratories of Tony Pawson and Lewis Kay at the University of Toronto, where he studied regulation of the signaling adaptor protein, Crk, and developed methods of selective methyl group labeling of proteins for NMR spectroscopy.

Harvard Medical School, Cambridge

Spatial Organization of Very Large Cells

One of the big challenges in biology is to understand how cells physically self-organize using molecules that are much smaller than the cell. This challenge is epitomized by frog eggs and early embryos, where cell are hundreds of microns in diameter. After fertilization frog eggs cleave in the middle, and then cleave again at right angles, on their way to becoming embryos. The question of how these cleavage planes are accurately positioned has interested biologists for centuries. We have studied this problem using microscopy and biochemistry in frog and fish eggs, and in cell free extracts made from frog eggs. The answers lie in the behavior of starburst-like arrays of microtubules called asters that grow out of centrosomes, and in how these asters grow and interact inside the egg. I will describe our progress in understanding how large asters grow to fill the cell, what happens when two asters meet, how asters move within the cell, and how these processes together determine cleavage plane geometry.

Biography to follow