Wounding induces motility in sheets of corneal epithelial cells through loss of spatial constraints: role of heparin-binding epidermal growth factor-like growth factor signaling

Cellular responses to wounding have often been studied at a molecular level after disrupting cell layers by mechanical means. This invariably results in damage to cells at the edges of the wounds, which has been suggested to be instrumental for initiating wound healing. To test this, we devised an alternative procedure to introduce gaps in layers of corneal epithelial cells by casting agarose strips on tissue culture plates. In contrast to mechanical wounding, removal of the strips did not lead to detectable membrane leakage or to activation of the stress-activated kinase JNK. Nonetheless, cells at the edge underwent the typical morphological transition to a highly motile phenotype, and the gaps closed at rates similar to those of mechanically induced wounds. To allow biochemical analysis of cell extracts, a procedure was devised that makes cell-free surface area acutely available to a large proportion of cells in culture. Rapid activation of the epidermal growth factor receptor (EGFR) was detected by immunoblotting, and the addition of an EGFR-blocking antibody completely abolished wound healing. In addition, wound healing was inhibited by agents that block signaling by the heparin-binding epidermal growth factor-like growth factor (HB-EGF). Cells stimulated with cell-free tissue culture surface released a soluble factor that induced activation of the EGFR, which was distinct from HB-EGF. These studies suggest that the triggering event for the induction of motility in corneal epithelial cells is related to the sudden availability of permissive surface area rather than to mechanical damage, and they demonstrate a central role of signaling through HB-EGF.     

The chaperone Chs7 forms a stable complex with Chs3 and promotes its activity at the cell surface

The polytopic yeast protein Chs3 (chitin synthase III) relies on a dedicated membrane‐localized chaperone, Chs7, for its folding and expression at the cell surface. In the absence of Chs7, Chs3 forms high molecular weight aggregates and is retained in the endoplasmic reticulum (ER). Chs7 was reported to be an ER resident protein, but its role in Chs3 folding and transport was not well characterized. Here, we show that Chs7 itself exits the ER and localizes with Chs3 at the bud neck and intracellular compartments. We identified mutations in the Chs7 C‐terminal cytosolic domain that do not affect its chaperone function, but cause it to dissociate from Chs3 at a post‐ER transport step. Mutations that prevent the continued association of Chs7 with Chs3 do not block delivery of Chs3 to the cell surface, but dramatically reduce its catalytic activity. This suggests that Chs7 engages in functionally distinct interactions with Chs3 to first promote its folding and ER exit, and subsequently to regulate its activity at the plasma membrane.      

Exploiting the wild crucifer <Emphasis Type="Italic">Thlaspi arvense</Emphasis> to identify conserved and novel genes expressed during a plant’s response to cold stress

Thlaspi arvense, a wild species from the Brassicaceae family, was shown to have a higher level of freezing tolerance than either of its close relatives, the model plant Arabidopsis thaliana or the crop Brassica napus (canola). Over 600 clones were sequenced from a subtractive cDNA library generated from cold treated T. arvense tissue, establishing that T. arvense shared significant sequence identity with both A. thaliana and B. napus (90–92%). In light of the strong sequence similarity between T. arvense and A. thaliana and to exploit the available genomics resources for Arabidopsis, the efficacy of using long 70 mer oligonucleotide whole genome Arabidopsis microarrays was tested for T. arvense. Gene expression in T. arvense leaf tissue during the very early stages of cold acclimation (or cold stress) was assayed at three time points and compared to an untreated control. This analysis highlights some of the difficulties and benefits of using cross-species microarray analysis. The data suggested that T. arvense responds in a similar fashion to cold stress as the model plant A. thaliana. However, for a number of genes quantitative differences in the level and timing of expression were identified. One of the most notable differences suggested that sulphur assimilation leading to the increased production of the methyl donor S-adenosyl-methionine was playing a role in the response of T. arvense to cold stress. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

ER-to-Golgi protein delivery through an interwoven,tubular network extending from ER

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A New Freshwater Biodiversity Indicator Based on Fish Community Assemblages

Biodiversity has reached a critical state. In this context, stakeholders need indicators that both provide a synthetic view of the state of biodiversity and can be used as communication tools. Using river fishes as model, we developed community indicators that aim at integrating various components of biodiversity including interactions between species and ultimately the processes influencing ecosystem functions. We developed indices at the species level based on (i) the concept of specialization directly linked to the niche theory and (ii) the concept of originality measuring the overall degree of differences between a species and all other species in the same clade. Five major types of originality indices, based on phylogeny, habitat-linked and diet-linked morphology, life history traits, and ecological niche were analyzed. In a second step, we tested the relationship between all biodiversity indices and land use as a proxy of human pressures. Fish communities showed no significant temporal trend for most of these indices, but both originality indices based on diet- and habitat- linked morphology showed a significant increase through time. From a spatial point of view, all indices clearly singled out Corsica Island as having higher average originality and specialization. Finally, we observed that the originality index based on niche traits might be used as an informative biodiversity indicator because we showed it is sensitive to different land use classes along a landscape artificialization gradient. Moreover, its response remained unchanged over two other land use classifications at the global scale and also at the regional scale.     

Ethnicity Is an Independent Determinant of Age-Specific PSA Level: Findings from a Multiethnic Asian Setting

Objectives

To study the baseline PSA profile and determine the factors influencing the PSA levels within a multiethnic Asian setting.

Materials and Methods

We conducted a cross-sectional study of 1054 men with no clinical evidence of prostate cancer, prostate surgery or 5α-reductase inhibitor treatment of known prostate conditions. The serum PSA concentration of each subject was assayed. Potential factors associated with PSA level including age, ethnicity, height, weight, family history of prostate cancer, lower urinary tract voiding symptoms (LUTS), prostate volume and digital rectal examination (DRE) were evaluated using univariable and multivariable analysis.

Results

There were 38 men (3.6%) found to have a PSA level above 4 ng/ml and 1016 (96.4%) with a healthy PSA (≤4 ng/ml). The median PSA level of Malay, Chinese and Indian men was 1.00 ng/ml, 1.16 ng/ml and 0.83 ng/ml, respectively. Indians had a relatively lower median PSA level and prostate volume than Malays and Chinese, who shared a comparable median PSA value across all 10-years age groups. The PSA density was fairly similar amongst all ethnicities. Further analysis showed that ethnicity, weight and prostate volume were independent factors associated with age specific PSA level in the multivariable analysis (p<0.05).

Conclusion

These findings support the concept that the baseline PSA level varies between different ethnicities across all age groups. In addition to age and prostate volume, ethnicity may also need to be taken into account when investigating serum PSA concentrations in the multiethnic Asian population.     

Hormonal regulation of gluconeogenic gene transcription in the liver

Glucose homeostasis in mammals is achieved by the actions of counterregulatory hormones, namely insulin, glucagon and glucocorticoids. Glucose levels in the circulation are regulated by the liver, the metabolic centre which produces glucose when it is scarce in the blood. This process is catalysed by two rate-limiting enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) whose gene expression is regulated by hormones. Hormone response units (HRUs) present in the two genes integrate signals from various signalling pathways triggered by hormones. How such domains are arranged in the regulatory region of these two genes, how this complex regulation is accomplished and the latest advancements in the field are discussed in this review.