Sherman DJ, Xie R, Taylor RJ, George AH, Okuda S, Foster PJ, Needleman DJ, Kahne D. Lipopolysaccharide is transported to the cell surface by a membrane-to-membrane protein bridge. Science [Internet]. 2018;359 (6377) :798–801. Publisher's VersionAbstract
The outer membrane of Gram-negative bacteria is composed of lipopolysaccharide, a large glycolipid that prevents drugs from entering the cells. Disrupting lipopolysaccharide assembly hypersensitizes bacteria to antibiotics. Sherman et al. used biochemical tools to observe lipopolysaccharide transport. Seven proteins, which are conserved in all Gram-negative bacteria, appear to form a protein bridge that uses adenosine triphosphate to power transport of lipopolysaccharide from one membrane to another. The ability to monitor intermembrane transport of lipopolysaccharide will help in efforts to develop and characterize inhibitors.Science, this issue p. 798Gram-negative bacteria have an outer membrane that serves as a barrier to noxious agents in the environment. This protective function is dependent on lipopolysaccharide, a large glycolipid located in the outer leaflet of the outer membrane. Lipopolysaccharide is synthesized at the cytoplasmic membrane and must be transported to the cell surface. To understand this transport process, we reconstituted membrane-to-membrane movement of lipopolysaccharide by incorporating purified inner and outer membrane transport complexes into separate proteoliposomes. Transport involved stable association between the inner and outer membrane proteoliposomes. Our results support a model in which lipopolysaccharide molecules are pushed one after the other in a PEZ dispenser–like manner across a protein bridge that connects the inner and outer membranes.
Download Paper
Tan R, Foster PJ, Needleman DJ, McKenney RJ. Cooperative accumulation of dynein-dynactin at microtubule minus-ends drives microtubule network reorganization. Developmental Cell. 2018;44 (2) :233–247. Download Paper
Foster PJ, Yan W, Fürthauer S, Shelley M, Needleman DJ. Connecting macroscopic dynamics with microscopic properties in active microtubule network contraction. New Journal of Physics. 2017. Download Paper
Sanchez T, Seidler EA, Gardner DK, Needleman D, Sakkas D. Will noninvasive methods surpass invasive for assessing gametes and embryos?. Fertility and Sterility. 2017;108 (5) :730–737. Download Paper
Nazockdast E, Rahimian A, Needleman D, Shelley M. Cytoplasmic flows as signatures for the mechanics of mitotic positioning. Molecular Biology of the Cell. 2017 :mbc–E16. Download Paper
Needleman D, Dogic Z. Active matter at the interface between materials science and cell biology. [Internet]. 2017;2 :17048 EP -. Publisher's Version Download Paper
Lewis E, Farhadifar R, Farland LV, Needleman DJ, Missmer SA, Racowsky C. Use of imaging software for assessment of the associations among zona pellucida thickness variation, assisted hatching, and implantation of day 3 embryos. Journal of Assisted Reproduction and Genetics. 2017 :1-9. Download Paper
Hanley ML, Yoo TY, Sonnett M, Needleman DJ, Mitchison TJ. Chromosomal passenger complex hydrodynamics suggests chaperoning of the inactive state by nucleoplasmin/nucleophosmin. Molecular Biology of the Cell. 2017 :mbc–E16. Download Paper
Kaye B, Yoo TY, Foster PJ, Yu C-H, Needleman DJ. Bridging length scales to measure polymer assembly. Mol. Biol. Cell. 2017;28 :1379-1388. Download Paper
Kaye B, Foster PJ, Yoo TY, Needleman DJ. Developing and Testing a Bayesian Analysis of Fluorescence Lifetime Measurements. PLoS ONE. 2017;12 (1) :e0169337. doi:10.1371/journal.pone.0169337. Download Paper
Wu H-Y, Nazockdast E, Shelley MJ, Needleman DJ. Forces positioning the mitotic spindle: Theories, and now experiments. BioEssays [Internet]. 2016 :1600212–n/a. Publisher's Version Download Paper
Oh D, Yu C-H, Needleman D. Spatial organization of the Ran pathway by microtubules in mitosis. Proceedings of the National Academy of Sciences. 2016. Download
Farhadifar R, Ponciano JM, Andersen EC, Needleman DJ, Baer CF. Mutation Is a Sufficient and Robust Predictor of Genetic Variation for Mitotic Spindle Traits in Caenorhabditis elegans. Genetics [Internet]. 2016. Publisher's VersionAbstract

Different types of phenotypic traits consistently exhibit different levels of genetic variation in natural populations. There are two potential explanations: either mutation produces genetic variation at different rates, or natural selection removes or promotes genetic variation at different rates. Whether mutation or selection is of greater general importance is a longstanding unresolved question in evolutionary genetics. We report mutational variances (VM) for 19 traits related to the first mitotic cell division in C. elegans, and compare them to the standing genetic variances (VG) for the same suite of traits in a worldwide collection C. elegans. Two robust conclusions emerge. First, the mutational process is highly repeatable: the correlation between VM in two independent sets of mutation accumulation lines is  0.9. Second, VM for a trait is a good predictor of VG for that trait: the correlation between VM and VG is  0.9. This result is predicted for a population at mutation-selection balance; it is not predicted if balancing selection plays a primary role in maintaining genetic variation.

Download Paper
Yoo TY, Needleman DJ. Studying Kinetochores In Vivo Using FLIM-FRET. The Mitotic Spindle: Methods and Protocols. 2016 :169–186. Download Paper
Hu H, Juvekar A, Lyssiotis CA, Lien EC, Albeck JG, Oh D, Varma G, Hung YP, Ullas S, Lauring J, et al. Phosphoinositide 3-Kinase Regulates Glycolysis through Mobilization of Aldolase from the Actin Cytoskeleton. Cell. 2016;164 :433-446. Download Paper
Foster PJ, Fürthauer S, Shelley MJ, Needleman DJ. Active contraction of microtubule networks. eLife. 2015 :10.7554/eLife.10837. Download Paper
Needleman D. The Material Basis of Life. Trends in cell biology. 2015. Download Paper
Farhadifar R, Baer CF, Valfort A-C, Andersen EC, Müller-Reichert T, Delattre M, Needleman DJ. Scaling, selection, and evolutionary dynamics of the mitotic spindle. Current Biology. 2015;25 :732–740. Download Paper
Sazer S, Lynch M, Needleman D. Deciphering the Evolutionary History of Open and Closed Mitosis. Current Biology. 2014;24 :R1099–R1103. Download Paper
Needleman D, Brugues J. Determining physical principles of subcellular organization. Developmental cell. 2014;29 :135–138. Download Paper