Live cell imaging reveals distinct roles in cell cycle regulation for Nek2A and Nek2B

Two splice variants of Nek2 kinase, a member of the NIMA-related family, have been identified as Nek2A and Nek2B. Nek2A regulates centrosome disjunction, spindle formation checkpoint signaling, and faithful chromosome segregation. A specific role for Nek2B has not yet been identified. Here, we have examined the distinct roles of Nek2A and Nek2B using timelapse video microscopy to follow the fate of cells progressing through the cell cycle in the absence of either Nek2A or Nek2B. We show that the down-regulation of Nek2B leads to a mitotic delay in the majority of cells. Upon exiting mitosis, cells exhibit mitotic defects such as the formation of multinucleated cells. Such phenotypes are not observed in cells that exit mitosis in the absence of Nek2A. These observations suggest that Nek2B may be required for the execution of mitotic exit.     

Testing for sex differences in biparental inbreeding and its consequences in a gynodioecious species

In many gynodioecious species cross-pollinated seeds from females outperform those from hermaphrodites. Using the gynodioecious alpine perennial Silene acaulis, I investigated whether this was the result of greater biparental inbreeding among hermaphrodites leading to greater biparental inbreeding depression. I also determined the influence of relatedness on progeny fitness. Experiments were performed using individuals from a site whose population structure and coefficient of inbreeding was known. In the first experiment, crosses were made on plants in the field to determine the effect of seven different crossing distances, plus selfing, on germination and early seedling survival and growth. Although selfed seeds died more often and grew slower than crossed seeds, the effect of crossing distance was negligible for all measured fitness traits, refuting the biparental inbreeding hypothesis as a mechanism to explain why seeds from hermaphrodites die more often than those from females. Nonetheless, cross-pollinated seeds from hermaphrodites did die more, indicating that another mechanism must be responsible. In the second experiment, the effect of different levels of inbreeding on germination and seedling survival was determined by growing seeds from experimental matings varying in relatedness. Inbreeding depression for a multiplicative fitness estimate was significant for all levels of inbreeding, suggesting that inbred individuals are unlikely to become established in the population and providing insight into the results of the first experiment. Alternative hypotheses are discussed to explain why seeds from hermaphrodites die more often, which together with the results of this study, suggest that the restoration of male function in hermaphrodites comes with a correlated cost to seedling survival.     

Phylogeny for species of Haemonchus (Nematoda: Trichostrongyloidea): considerations of their evolutionary history and global biogeography among Camelidae and Pecora (Artiodactyla)

Phylogenetic analysis of 25 morphological characters among the 12 species of Haemonchus resulted in 1 most parsimonious tree (60 steps; consistency index = 0.67, retention index = 0.80). Monophyly for Haemonchus was diagnosed by 3 unequivocal synapomorphies, including the asymmetric origin of the dorsal ray, relative size of the ventral rays, and the presence of a barb on each spicule tip. Species of Haemonchus have complex histories with respect to host and geographic associations: (1) origins in Africa with basal diversification in antelopes (H. krugeri, H. lawrencei, H. dinniki, H. horaki), (2) independent events of colonization for those species in Caprini and Bovinae (H. contortus, H. placei, H. bedfordi, H. similis), (3) colonization and development of core host associations within Camelidae (H. longistipes) and among Antilopinae, Tragelaphini, and Giraffidae (H. mitchelli, H. okapiae, H. vegliai), and (4) geographically widespread species that are represented only by those that have been translocated with domestic stock. The North American fauna is characterized by 3 introduced and exotic species, H. placei, H. contortus, H. similis, which emphasizes the importance of continued documentation of faunal diversity in the context of predictive foundations derived from phylogenetic studies. Satellite associations for species of Haemonchus, particularly among Cervidae and Camelidae in the Neotropics and Cervidae, Antilocapridae, and possibly wild Caprinae in the Nearctic, have been a consequence of introductions and exchange of parasites at historical interfaces for managed and natural ecosystems. Such distributions are emblematic of the overriding significance of anthropogenic factors as determinants of the global distributions for pathogenic parasites in domestic and wild ruminants.     

Sugar and alcohol molecules provide a therapeutic strategy for the serpinopathies that cause dementia and cirrhosis

Mutations in neuroserpin and alpha1-antitrypsin cause these proteins to form ordered polymers that are retained within the endoplasmic reticulum of neurones and hepatocytes, respectively. The resulting inclusions underlie the dementia familial encephalopathy with neuroserpin inclusion bodies (FENIB) and Z alpha1-antitrypsin-associated cirrhosis. Polymers form by a sequential linkage between the reactive centre loop of one molecule and beta-sheet A of another, and strategies that block polymer formation are likely to be successful in treating the associated disease. We show here that glycerol, the sugar alcohol erythritol, the disaccharide trehalose and its breakdown product glucose reduce the rate of polymerization of wild-type neuroserpin and the Ser49Pro mutant that causes dementia. They also attenuate the polymerization of the Z variant of alpha1-antitrypsin. The effect on polymerization was apparent even when these agents had been removed from the buffer. None of these agents had any detectable effect on the structure or inhibitory activity of neuroserpin or alpha1-antitrypsin. These data demonstrate that sugar and alcohol molecules can reduce the polymerization of serpin mutants that cause disease, possibly by binding to and stabilizing beta-sheet A.     

Trait selection in flowering plants: how does sexual selection contribute?

By highlighting and merging the frameworks of sexual selectionenvisioned by Arnold (1994) and Murphy (1998), we discuss howsexual selection can occur in plants even though individualsdo not directly interact. We review studies on traits that influencepollen export and receipt in a variety of hermaphroditic andgynodioecious plants with the underlying premise that pollinationdynamics influences mate acquisition. Most of the studies reviewedfound that phenotypes that enhance pollen export are in harmonywith those that enhance pollen receipt suggesting that in manycases pollinator visitation rates limit both male and femalefunction. In contrast, fewer traits were under opposing selection;but when they were, the traits most often were associated withenhancing the specific aspects of a given sex function. Ourreview helps clarify and illustrate why sexual selection canbe a component of trait evolution in hermaphrodite plants.     

Evidence of a Male Sex Pheromone in the Round Goby (Neogobius melanostomus)

The reproductive success of the round goby (Neogobius melanostomus), an invasive fish, may be mediated by the use of pheromones. We hypothesized that reproductive male (RM) round gobies release sex pheromone to which reproductive females (RF) respond. In this study, we compared behavioural and electrophysiological responses of reproductive and non-reproductive female round gobies to conspeci fic males. Results of behavioural experiments in the laboratory showed that RF spent significantly more time near the source of the male odour compared with odours from control water. However, RF did not distinguish between odours from non-reproductive male (non-RM) water and control water. Non-reproductive females (non-RF) were not attracted to odours released from RM or non-RM water. Results of electro-olfactogram (EOG) responses showed that both RF and non-RF discriminated between HPLC fractionated RM and non-RM odours. However, the EOG responses of RF were about eight-fold higher than non-RF exposed to RM odours. These findings confirm that RM round gobies release a pheromone signal that attracts RF. The results of this research may be useful in developing control strategy using natural pheromones to disrupt the reproductive behaviour of the invasive round goby and to curtail its effects on native species. An erratum to this article is available at .     

The influence of climate variability on numbers of three waterbird species in Western Port, Victoria, 1973–2002

Seasonal and annual movements of Australian waterbirds are generally more complex than those of their Northern Hemisphere counterparts, and long-term data are needed to understand their relationships with climatic variables. This paper explores a long-term (1973–2002) set of waterbird counts from coastal Victoria and relates them to climatic data at local and continental scales. Three species (Black Swan Cygnus atratus, White-faced Heron Egretta novaehollandiae and Grey Teal Anas gracilis) were chosen for this analysis. Black Swans have large local breeding populations near the study region; White-faced Herons have smaller local breeding populations and Grey Teal breed extensively in ephemeral inland floodplains, such as those in the Murray-Darling Basin. All showed significant relationships with streamflow, regional rainfall and the Southern Oscillation Index (SOI) at appropriate scales and time-lags, with streamflow explaining the most variance. Black Swans showed a strong seasonal cycle in abundance and local climate variables had the greatest influence on the counts. Numbers were positively correlated with streamflow in southern Victoria three to six seasons before each count. Broader-scale climatic patterns were more important for the other two species. Numbers of White-faced Herons were positively correlated with streamflow or rainfall over various parts of Australia seven to nine seasons before each count. Numbers of Grey Teal showed weak seasonal cycles, and were negatively correlated with rainfall in Victoria or the Murray-Darling Basin in the seasons before or during each count, and positively with streamflow in the Murray-Darling Basin 15–18 months before each count.     

Slits contribute to the guidance of retinal ganglion cell axons in the mammalian optic tract

RGC axons extend in the optic tracts in a manner that correlates with the expression in the hypothalamus and epithalamus of a soluble factor inhibitory to RGC axon outgrowth. Additionally, although the RGC axons extend adjacent to the telencephalon, they do not normally grow into this tissue. Here, we show that slit1 and slit2, known chemorepellents for RGC axons expressed in specific regions of the diencephalon and telencephalon, help regulate optic tract development. In mice lacking slit1 and slit2, a subset of RGC axons extend into the telencephalon and grow along the pial surface but not more deeply into this tissue. Surprisingly, distinct guidance errors occur in the telencephalon of slit1 -/-; slit2 +/- and slit1/2 -/- embryos, suggesting that the precise level of Slits is critical for determining the path followed by individual axons. In mice lacking both slit1 and slit2, a subset of RGC axons also project aberrantly into the epithalamus, pineal and across the dorsal midline. However, many axons reach their primary target, the superior colliculus. This demonstrates that Slits play an important role in directing the guidance of post-crossing RGC axons within the optic tracts but are not required for target innervation.     

Isolation and culture of primary osteocytes from the long bones of skeletally mature and aged mice

The purpose of this work was to establish a methodology to enable the isolation and study of osteocytes from skeletally mature young (4-month-old) and old (22-month-old) mice. The location of osteocytes deep within bone is ideal for their function as mechanosensors. However, this location makes the observation and study of osteocytes in vivo technically difficult. Osteocytes were isolated from murine long bones through a process of extended collagenase digestions combined with EDTA-based decalcification. A tissue homogenizer was used to reduce the remaining bone fragments to a suspension of bone particles, which were placed in culture to yield an outgrowth of osteocyte-like cells. All of the cells obtained from this outgrowth that displayed an osteocyte-like morphology stained positive for the osteocyte marker E11/GP38. The osteocyte phenotype was further confirmed by a lack of staining for alkaline phosphatase and the absence of collagen1a1 expression. The outgrowth of osteocytes also expressed additional osteocyte-specific genes such as Sost and Mepe. This technique facilitates the isolation of osteocytes from skeletally mature bone. This novel enabling methodology should prove useful in advancing our understanding of the roles mature osteocytes play in bone health and disease.