Profilin binding to poly-L-proline and actin monomers along with ability to catalyze actin nucleotide exchange is required for viability of fission yeast

We tested the ability of 87 profilin point mutations to complement temperature-sensitive and null mutations of the single profilin gene of the fission yeast Schizosaccharomyces pombe. We compared the biochemical properties of 13 stable noncomplementing profilins with an equal number of complementing profilin mutants. A large quantitative database revealed the following: 1) in a profilin null background fission yeast grow normally with profilin mutations having >10% of wild-type affinity for actin or poly-L-proline, but lower affinity for either ligand is incompatible with life; 2) in the cdc3-124 profilin ts background, fission yeast function with profilin having only 2-5% wild-type affinity for actin or poly-L-proline; and 3) special mutations show that the ability of profilin to catalyze nucleotide exchange by actin is an essential function. Thus, poly-L-proline binding, actin binding, and actin nucleotide exchange are each independent requirements for profilin function in fission yeast.     

Evolution of research on cellular motility over five decades

This short review traces how our knowledge of the molecular mechanisms of cellular movements originated and developed over the past 50 years. Work on actin-based and microtubule-based movements developed in different ways, but in both fields, the discovery of the key proteins drove progress. Starting from an inventory of zero molecules in 1960, both fields matured spectacularly, so we now know the atomic structures of the important proteins, understand the kinetics and thermodynamics of their interactions, have documented how the molecules behave in cells, and can test theories with molecularly explicit computer simulations of cellular processes.     

Assembly of Acanthamoeba myosin-II minifilaments. Definition of C-terminal residues required to form coiled-coils, dimers, and octamers

Acanthamoeba myosin-II forms bipolar octamers by three successive steps of dimerization of the C-terminal, coiled-coil tail. In this study, we generated N-terminal and C-terminal truncation constructs and point mutants of the Acanthamoeba myosin-II tail to delineate the structural requirements for assembly of bipolar mini-filaments. By the use of light-scattering, CD spectroscopy, analytical ultracentrifugation, and tryptophan fluorescence experiments, we determined that: (1) the C-terminal 14 heptad repeats plus most of the tailpiece (residues 1381-1509) are required to form antiparallel dimers of coiled-coils; (2) amino acid residues within heptads 23-32 (residues 1254-1325) are required to form tetramers; (3) the C-terminal 32 heptad repeats suffice to assemble octameric minifilaments; (4) A1378 is outside of the interaction interface; (5) the mutation L1475W inhibits dimerization; and (6) F1443 is involved in the dimerization interface but is exposed to the solvent. We propose that the tailpiece (residues 1483-1509) interacts with two heptads (13 and 14, residues 1381-1393), which are important for dimerization and coiled-coil formation. These results support a model in which hydrophobic as well as electrostatic interactions control the register between myosin-II coiled-coils and guide sequential steps of dimerization that generate stable, octameric mini-filaments.     

Predictors of age at menarche in the newcastle thousand families study

Several studies have found relationships between early life factors (birth weight, length of gestation, height, weight, duration of breast-feeding, maternal age, social class, periods of infection, presence of adverse life events, and quality of housing conditions in childhood) and age at menarche but none has considered all of these factors in the same study. The follow-up study of the Newcastle Thousand Families birth cohort, established in 1947, provided age at menarche data collected retrospectively at age 50 from 276 women who returned self-completion questionnaires in 1997. Three main independent associations were observed: girls who experienced a shorter gestation, girls whose mothers were younger when they were born, and girls who were heavier at age 9 had earlier menarche. Birth weight, standardized for gestational age, was found to have different relationships with age at menarche depending upon how heavy or light a girl was at age 9. The results of this study support the hypotheses that conditions in fetal and early life are associated with the timing of menarche and that greater childhood growth is associated with earlier menarche. It is suggested that future work should focus on illuminating the mechanisms underlying these statistical relationships.     

Nano-bio-chips for high performance multiplexed protein detection: Determinations of cancer biomarkers in serum and saliva using quantum dot bioconjugate labels

The integration of semiconductor nanoparticle quantum dots (QDs) into a modular, microfluidic biosensor for the multiplexed quantitation of three important cancer markers, carcinoembryonic antigen (CEA), cancer antigen 125 (CA125), and Her-2/Neu (C-erbB-2) was achieved. The functionality of the integrated sample processing, analyte capture and detection modalities was demonstrated using both serum and whole saliva specimens. Here, nano-bio-chips that employed a fluorescence transduction signal with QD-labeled detecting antibody were used in combination with antigen capture by a microporous agarose bead array supported within a microfluidics ensemble so as to complete the sandwich-type immunoassay. The utilization of QD probes in this miniaturized biosensor format resulted in signal amplification 30 times relative to that of standard molecular fluorophores as well as affording a reduction in observed limits of detection by nearly 2 orders of magnitude (0.02 ng/mL CEA; 0.11 pM CEA) relative to enzyme-linked immunosorbent assay (ELISA). Assay validation studies indicate that measurements by the nano-bio-chip system correlate to standard methods at R² = 0.94 and R² = 0.95 for saliva and serum, respectively. This integrated nano-bio-chip assay system, in tandem with next-generation fluorophores, promises to be a sensitive, multiplexed tool for important diagnostic and prognostic applications.     

Zimbabwe Culture before Mapungubwe: New Evidence from Mapela Hill,South-Western Zimbabwe

Across the globe, the emergence of complex societies excites intense academic debate in archaeology and allied disciplines. Not surprisingly, in southern Africa the traditional assumption that the evolution of socio-political complexity began with ideological transformations from K2 to Mapungubwe between CE1200 and 1220 is clouded in controversy. It is believed that the K2−Mapungubwe transitions crystallised class distinction and sacred leadership, thought to be the key elements of the Zimbabwe culture on Mapungubwe Hill long before they emerged anywhere else. From Mapungubwe (CE1220–1290), the Zimbabwe culture was expressed at Great Zimbabwe (CE1300–1450) and eventually Khami (CE1450–1820). However, new fieldwork at Mapela Hill, when coupled with a Bayesian chronology, offers tremendous fresh insights which refute this orthodoxy. Firstly, Mapela possesses enormous prestige stone-walled terraces whose initial construction date from the 11^th century CE, almost two hundred years earlier than Mapungubwe. Secondly, the basal levels of the Mapela terraces and hilltop contain élite solid dhaka (adobe) floors associated with K2 pottery and glass beads. Thirdly, with a hilltop and flat area occupation since the 11^th century CE, Mapela exhibits evidence of class distinction and sacred leadership earlier than K2 and Mapungubwe, the supposed propagators of the Zimbabwe culture. Fourthly, Mapungubwe material culture only appeared later in the Mapela sequence and therefore post-dates the earliest appearance of stone walling and dhaka floors at the site. Since stone walls, dhaka floors and class distinction are the essence of the Zimbabwe culture, their earlier appearance at Mapela suggests that Mapungubwe can no longer be regarded as the sole cradle of the Zimbabwe culture. This demands not just fresh ways of accounting for the rise of socio-political complexity in southern Africa, but also significant adjustments to existing models.     

Fertilizing capacity of bovine sperm may be maintained by binding of oviductal epithelial cells

The ability of the bovine oviduct to maintain the motility and fertilizing capacity of bovine sperm was investigated by incubating frozen-thawed sperm with endosalpingeal epithelial cells cultured on either tissue culture plastic (nonpolarizing) or Matrigel-coated Millicell (polarizing) substrata. Sperm were also incubated in medium alone or with cultured bovine tracheal epithelial cells. Motility was determined at 6-h intervals over a 48-h period. The fertilizing capacity of sperm was evaluated after 0, 24, and 30 h of incubation by adding oocytes to the culture and determining the incidences of fertilization and polyspermy. Motility was maintained for 48 h in sperm that bound to endosalpingeal epithelial cells, but to a greater extent with polarized cells (38.4% motile) than with nonpolarized cells (0.8%). Fertilizing capacity was maintained for 30 h in sperm incubated with endosalpingeal epithelial cells on Matrigel/Millicell, but not in sperm incubated in medium alone or with tracheal cells. Only sperm incubated with oviductal cells developed hyperactivated motility. Scanning electron micrographs revealed that sperm were bound by the rostral portion of the intact acrosome to the apical surface of polarized endosalpingeal cells. These results suggest that the oviduct may not only store sperm but may also maintain sperm viability and fertilizing capacity during the preovulatory period.