Natural variation in four human collagen genes across an ethnically diverse population

Collagens are members of one of the most important families of structural proteins in higher organisms. There are 28 types of collagens encoded by 43 genes in humans that fall into several different functional protein classes. Mutations in the major fibrillar collagen genes lead to osteogenesis imperfecta (COL1A1 and COL1A2 encoding the chains of Type I collagen), chondrodysplasias (COL2A1 encoding the chains of Type II collagen), and vascular Ehlers-Danlos syndrome (COL3A1 encoding the chains of Type III collagen). Over the past 2 decades, mutations in these collagen genes have been catalogued, in hopes of understanding the molecular etiology of diseases caused by these mutations, characterizing the genotype-phenotype relationships, and developing robust models predicting the molecular and clinical outcomes. To achieve these goals better, it is necessary to understand the natural patterns of variation in collagen genes in human populations. We screened exons, flanking intronic regions, and conserved noncoding regions for variations in COL1A1, COL1A2, COL2A1, and COL3A1 in 48 individuals from each of four ethnically diverse populations. We identified 459 single-nucleotide polymorphisms (SNPs), more than half of which were novel and not found in public databases. Of the 52 SNPs found in coding regions, 15 caused amino acid substitutions while 37 did not. Although the four collagens have similar gene and protein structures, they have different molecular evolutionary characteristics. For example, COL1A1 appears to have been under substantially stronger negative selection than the rest. Phylogenetic analysis also suggests that the four genes have very different evolutionary histories among the different ethnic groups. Our observations suggest that the study of collagen mutations and their relationships with disease phenotypes should be performed in the context of the genetic background of the subjects.     

Submitting articles to the BMJ

ObjectiveTo measure the effect of giving out free smoke alarms on rates of fires and rates of fire related injury in a deprived multiethnic urban population.DesignCluster randomised controlled trial.SettingForty electoral wards in two boroughs of inner London, United Kingdom.ParticipantsPrimarily households including elderly people or children and households that are in housing rented from the borough council.Intervention20 050 smoke alarms, fittings, and educational brochures distributed free and installed on request.ResultsGiving out free smoke alarms did not reduce injuries related to fire (rate ratio 1.3; 95% confidence interval 0.9 to 1.9), admissions to hospital and deaths (1.3; 0.7 to 2.3), or fires attended by the fire brigade (1.1; 0.96 to 1.3). Similar proportions of intervention and control households had installed alarms (36/119 (30%) v 35/109 (32%); odds ratio 0.9; 95% confidence interval 0.5 to 1.7) and working alarms (19/118 (16%) v 18/108 (17%); 0.9; 0.4 to 1.8).ConclusionsGiving out free smoke alarms in a deprived, multiethnic, urban community did not reduce injuries related to fire, mostly because few alarms had been installed or were maintained.

What is already known on this topic

In the United Kingdom, residential fires caused 466 deaths and 14 600 non-fatal injuries in 1999The risk of death from fire is associated with socioeconomic classOne study reported an 80% decline in hospitalisations and deaths from residential fires after free smoke alarms were distributed in an area at high risk, but these results may not apply in other settings, and evidence from randomised controlled trials is lacking

What this study adds

Giving out free smoke alarms in a multiethnic poor urban population did not reduce injuries related to fire or firesGiving smoke alarms away may be a waste of resources and of little benefit unless alarm installation and maintenance is assured     

Specific down-regulation of annexin II expression in human cells interferes with cell proliferation

The protein-tyrosine kinase substrate annexin II is a growth regulated gene whose expression is increased in several human cancers. While the precise function of this protein is not understood, annexin II is proposed to be involved in multiple physiological activities, including DNA synthesis and cell proliferation. Targeted disruption of the annexin II gene affects calcium signaling, tyrosine phosphorylation and apoptosis, indicating the important physiological role of this protein. We used a transient co-transfection assay to regulate annexin II expression in human HeLa, 293 and 293T cells, and measured the effects of annexin II down regulation on DNA synthesis and proliferation. Transfection of cells with an antisense annexin II vector results in inhibition of cell division and proliferation, with concomitant reduction in annexin II message and protein levels. Cellular DNA synthesis is significantly reduced in antisense transfected cells. Replication extracts made from antisense transfected cells have significantly reduced efficiency to support SV40 in vitro DNA replication, while the extracts made from sense transfected cells are fully capable of replication. Our results indicate an important role of annexin II in cellular DNA synthesis and cell proliferation.     

Differential effects of ecosystem engineering by the superb lyrebird Menura novaehollandiae and herbivory by large mammals on floristic regeneration and structure in wet eucalypt forests

Ecosystem engineers that modify the soil and ground‐layer properties exert a strong influence on vegetation communities in ecosystems worldwide. Understanding the interactions between animal engineers and vegetation is challenging when in the presence of large herbivores, as many vegetation communities are simultaneously affected by both engineering and herbivory. The superb lyrebird Menura novaehollandiae, an ecosystem engineer in wet forests of south‐eastern Australia, extensively modifies litter and soil on the forest floor. The aim of this study was to disentangle the impacts of engineering by lyrebirds and herbivory by large mammals on the composition and structure of ground‐layer vegetation. We carried out a 2‐year, manipulative exclusion experiment in the Central Highlands of Victoria, Australia. We compared three treatments: fenced plots with simulated lyrebird foraging; fenced plots excluding herbivores and lyrebirds; and open controls. This design allowed assessment of the relative impacts of engineering and herbivory on germination rates, seedling density, vegetation cover and structure, and community composition. Engineering by lyrebirds enhanced the germination of seeds in the litter layer. After 2 years, more than double the number of germinants were present in “engineered” than “non‐engineered” plots. Engineering did not affect the density of seedlings, but herbivory had strong detrimental effects. Herbivory also reduced the floristic richness and structural complexity (<0.5 m) of forest vegetation, including the cover of herbs. Neither process altered the floristic composition of the vegetation within the 2‐year study period. Ecosystem engineering by lyrebirds and herbivory by large mammals both influence the structure of forest‐floor vegetation. The twofold increase in seeds stimulated to germinate by engineering may contribute to the evolutionary adaptation of plants by allowing greater phenotypic expression and selection than would otherwise occur. Over long timescales, engineering and herbivory likely combine to maintain a more‐open forest floor conducive to ongoing ecosystem engineering by lyrebirds.     

Fibroblast growth factor complexed to the cytotoxin saporin is growth inhibitory but not cytotoxic for embryonal carcinoma cells

Fibroblast growth factors (FGFs) have been implicated in a number of proliferative lesions, including malignant tumor growth and vascularization. As a result, cytotoxic agents that target cell surface FGF receptors are currently under investigation. Previous reports have shown that conjugation of basic FGF with the ribosome inactivator, saporin, results in a potent cytotoxin specific for cells bearing high-affinity FGF receptors. In this report, we have used this FGF receptor-dependent cytotoxin to study receptor interactions at the surface of embryonal carcinoma cells, which express low numbers of high-affinity FGF receptors. The growth of three embryonal carcinoma cell lines and one embryonic stem cell line was shown to be inhibited by bFGF-saporin, suggesting that these cells are able to bind and internalize FGF through high-affinity FGF receptors. In addition, we determined that the responses of these cells to bFGF-saporin are qualitatively different than the responses of CHO-KI cells, which also exhibit low numbers of high-affinity FGF receptors. Specifically, pretreatment with bFGF-saporin reduces the cloning efficiency of CHO-KI cells 8- to 10-fold, whereas bFGF-saporin has little or no effect on the cloning efficiency of embryonal carcinoma cells. This finding suggests that bFGF-saporin is cytotoxic for CHO-KI cells, but not for embryonal carcinoma cells. Thus, our findings argue strongly that other factors, in addition to high-affinity FGF receptor number, are important in determining sensitivity of cells of bFGF-saporin.     

Two multipotent embryonal carcinoma cell lines irreversibly differentiate in defined media

Two unrelated multipotent embryonal carcinoma cell lines, OC-15S1 and 1003, have been cultured in hormone-supplemented defined media in order to identify the signals that influence their differentiation. Previous studies have shown that F9 embryonal carcinoma cells can be grown for many generations in the defined medium, EM-3, which contains fibronectin, insulin, and transferrin in place of serum. F9 cells, which only differentiate into a few cell types, undergo little or no differentiation in EM-3 unless an inducer is present (A. Rizzino and C. Crowley, 1980, Proc. Natl. Acad. Sci. USA77, 457–461). This report demonstrates that, in contrast to F9, OC-15S1 and 1003 embryonal carcinoma cells do not proliferate in EM-3. Instead, the cells differentiate. However, the differentiated cells do not survive in EM-3 unless it is supplemented with factors such as purified serum lipoproteins. In EM-3 containing high-density lipoprotein, a population of differentiated cells, devoid of embryonal carcinoma cells, is formed. The differentiated cells that appear exhibit an epithelioid morphology throughout the culture. These cells also secrete plasminogen activator and two different criteria argue that it is the type released by parietal endoderm. This suggests that, under the influence of the defined medium, both multipotent embryonal carcinoma cell lines differentiate at high frequency into parietal endoderm. It was also determined that fibronectin promotes the differentiation of OC-15S1 and 1003 in serum-containing media, and this suggests that fibronectin is at least partly responsible for the differentiation observed in EM-3 plus high-density lipoprotein. In light of these findings, it is suggested that fibronectin may directly influence cellular differentiation during early mammalian development.