Biomedical subjects

Andrew R Cossins

Publications and source records attributed to Andrew R Cossins.

11 recordsLinked to original sources

PubMed2007

Beyond the lipid hypothesis: mechanisms underlying phenotypic plasticity in inducible cold tolerance.

The physiological adjustment of organisms in response to temperature variation is a crucial part of coping with environmental stress. An important component of the cold response is the increase in membrane lipid unsaturation, and this has been linked to an enhanced resistance to the debilitating or lethal effects of cold. Underpinning the lipid response is the upregulation of fatty acid desaturases (des), particularly those introducing double bonds at the 9-10 position of saturated fatty acids. For plants and microbes there is good genetic evidence that regulation of des genes, and the consequent changes in lipid saturation, are causally linked to generation of a cold-tolerant phenotype. In animals, however, supporting evidence is almost entirely limited to correlations of saturation with cold conditions. We describe our recent attempts to provide a direct test of this relationship by genetic manipulation of the nematode Caenorhabditis elegans. We show that this species displays a strong cold tolerant phenotype induced by prior conditioning to cold, and that this is directly linked to upregulated des activity. However, whilst genetic disruption of des activity and lipid unsaturation significantly reduced cold tolerance, animals retained a substantial component of their stress tolerant phenotype produced by cold conditioning. This indicates that mechanisms other than lipid unsaturation play an important role in cold adaptation.

Acclimatization↗

PubMed2006

Encoded microcarriers for high-throughput multiplexed detection.

Since the decoding of the human genome, the quest to obtain more and more molecular information from smaller and smaller samples is intensifying. Today the burden of this challenge is being borne by planar arrays, but the quality of the data provided by this approach is limited by variations in performance between different arrays. Suspension arrays of encoded microspheres provide higher quality data, but the amount of molecular information that can be acquired with them is limited by the number of codes that can be distinguished in the same sample. New methods of preparing encoded particles promise to alleviate this problem, but in the face of a growing number of new technologies it is sometimes difficult to decide which, if any, will succeed. Herein we appraise these new forms of encoded particle critically, and ask if they can deliver the necessary multiplexing power and whether they will perform well in multiplexed assays.

Humans↗

PubMed2006

Hypoxia-inducible myoglobin expression in nonmuscle tissues.

Myoglobin (Myg) is an oxygen-binding hemoprotein that is widely thought to be expressed exclusively in oxidative skeletal and cardiac myocytes, where it plays a key role in coping with chronic hypoxia. We now show in a hypoxia-tolerant fish model, that Myg is also expressed in a range of other tissues, including liver, gill, and brain. Moreover, expression of Myg transcript was substantially enhanced during chronic hypoxia, the fold-change induction being far greater in liver than muscle. By using 2D gel electrophoresis, we have confirmed that liver expresses a protein corresponding to the Myg-1 transcript and that it is significantly up-regulated during hypoxia. We have also discovered a second, unique Myg isoform, distinct from neuroglobin, which is expressed exclusively in the neural tissue but whose transcript expression was unaffected by environmental hypoxia. Both observations of nonmuscle expression and a brain-specific isoform are unprecedented, indicating that Myg may play a much wider role than previously understood and that Myg might function in the protection of tissues from deep hypoxia and ischemia as well as in reoxygenation and reperfusion injury.

Amino Acid Sequence↗

PubMed2005

Seasonally hibernating phenotype assessed through transcript screening.

Hibernation is a seasonally entrained and profound phenotypic transition to conserve energy in winter. It involves significant biochemical reprogramming, although our understanding of the underpinning molecular events is fragmentary and selective. We have conducted a large-scale gene expression screen of the golden-mantled ground squirrel, Spermophilus lateralis, to identify transcriptional responses associated specifically with the summer-winter transition and the torpid-arousal transition in winter. We used 112 cDNA microarrays comprising 12,288 probes that cover at least 5,109 genes. In liver, the profiles of torpid and active states in the winter were almost identical, although we identified 102 cDNAs that were differentially expressed between winter and summer, 90% of which were downregulated in the winter states. By contrast, in cardiac tissue, 59 and 115 cDNAs were elevated in interbout arousal and torpor, respectively, relative to the summer active condition, but only 7 were common to both winter states, and during arousal none was downregulated. In brain, 78 cDNAs were found to change in winter, 44 of which were upregulated. Thus transcriptional changes associated with hibernation are qualitatively modest and, since these changes are generally less than twofold, also quantitatively modest. Unbiased Gene Ontology profiling of the transcripts suggests a winter switch to beta-oxidation of lipids in liver and heart, a reduction in metabolism of toxic compounds and the urea cycle in liver, and downregulated electron transport in the brain. We identified just one strongly winter-induced transcript common to all tissues, namely an RNA-binding protein, RBM3. This analysis clearly differentiates responses of the principal tissues, identifies a large number of new genes undergoing regulation, and broadens our understanding of affected cellular processes that, in part, account for the winter-adaptive hibernating phenotype.

Animals↗

PubMed2005

Microarray-based detection of protein binding and functionality by gold nanoparticle probes.

We report a microarray format for the detection of proteins and protein functionality (kinase activity) based on marking either specific antibody-protein binding or peptide phosphorylation events by attachment of gold nanoparticles followed by silver deposition for signal enhancement. The attachment of the gold nanoparticles is achieved by standard avidin-biotin chemistry. The detection principle is resonance light scattering. Highly selective recognition of standard proteins (proteins A and G) down to 1 pg/mL for proteins in solution and 10 fg for proteins on the microarray spots is demonstrated. Enzyme activity of the kinase (PKA) is detected with high specificity down to a limit of 1 fg for an established peptide substrate (kemptide) on the microarray spots. Kinase inhibition by the inhibitor (H89) is shown, demonstrating the potential for high-throughput screening for inhibitors.

Gold↗

PubMed2005

The use of transcriptomics to address questions in behaviour: production of a suppression subtractive hybridisation library from dominance hierarchies of rainbow trout.

Microarrays, or gene chips, are transforming the way that gene expression is measured by allowing us to determine the expression of thousands of genes from a sample. This gives immense power to examine gene expression on a global scale within individual animals and between animals. The scope for analysing complex animal functions at the molecular level is within our grasp. Relatively few studies have examined complex behaviours and correlated them with gene expression in the central nervous system. Here, we review the use of microarray technology in the dissection of behaviour and focus specifically on dominance status. A cDNA library using suppression subtraction hybridisation on rainbow trout Oncorhynchus mykiss of differing status has been produced to enrich the cDNA library for genes that are differentially expressed between individuals of different dominance status. A preliminary analysis demonstrated that there were 1,165 genes that differed between fish of different dominance status. Therefore, there is the potential of correlating gene expression profile with rank position within dominance hierarchies, thus identifying targets for candidate gene approaches.

Animals↗

PubMed2005

Evolution of oxygen secretion in fishes and the emergence of a complex physiological system.

We have reconstructed the events that led to the evolution of a key physiological innovation underpinning the large adaptive radiation of fishes, namely their unique ability to secrete molecular oxygen (O2). We show that O2 secretion into the swimbladder evolved some 100 million years after another O2-secreting system in the eye. We unravel the likely sequence in which the functional components of both systems evolved. These components include ocular and swimbladder countercurrent exchangers, the Bohr and Root effects, the buffering power and surface histidine content of hemoglobins, and red blood cell Na+/H+ exchange activity. Our synthesis reveals the dynamics of gains and losses of these multiple traits over time, accounting for part of the huge diversity of form and function in living fishes.

Adaptation, Physiological↗

PubMed2005

Fish as models for environmental genomics.

Fish offer important advantages for defining the organism-environment interface and responses to natural or anthropogenic stressors. Genomic approaches using fish promise increased investigative power, and have already provided insights into the mechanisms that underlie short-term and long-term environmental adaptations. The range of fish species for which genomic resources are available is increasing, but will require significant further expansion for the optimal application of fish environmental genomics.

Adaptation, Physiological↗

PubMed2004

Coping with cold: An integrative, multitissue analysis of the transcriptome of a poikilothermic vertebrate.

How do organisms respond adaptively to environmental stress? Although some gene-specific responses have been explored, others remain to be identified, and there is a very poor understanding of the system-wide integration of response, particularly in complex, multitissue animals. Here, we adopt a transcript screening approach to explore the mechanisms underpinning a major, whole-body phenotypic transition in a vertebrate animal that naturally experiences extreme environmental stress. Carp were exposed to increasing levels of cold, and responses across seven tissues were assessed by using a microarray composed of 13,440 cDNA probes. A large set of unique cDNAs (approximately 3,400) were affected by cold. These cDNAs included an expression signature common to all tissues of 252 up-regulated genes involved in RNA processing, translation initiation, mitochondrial metabolism, proteasomal function, and modification of higher-order structures of lipid membranes and chromosomes. Also identified were large numbers of transcripts with highly tissue-specific patterns of regulation. By unbiased profiling of gene ontologies, we have identified the distinctive functional features of each tissue's response and integrate them into a comprehensive view of the whole-body transition from one strongly adaptive phenotype to another. This approach revealed an expression signature suggestive of atrophy in cooled skeletal muscle. This environmental genomics approach by using a well studied but nongenomic species has identified a range of candidate genes endowing thermotolerance and reveals a previously unrecognized scale and complexity of responses that impacts at the level of cellular and tissue function.

Adaptation, Physiological↗

PubMed2004

Discovering genes: the use of microarrays and laser capture microdissection in pain research.

The DNA microarray is a powerful, high throughput technique for assessing gene expression on a system-wide genomic scale. It has great potential in pain research for determining the network of gene regulation in different pain conditions, and also for producing detailed gene expression maps in anatomical areas that process nociceptive stimuli. However, for the potential of this high throughput technology to be realised in pain research, microarrays need to be combined with other technologies. Laser capture microdissection is capable of isolating small populations of homogenous cells, allowing distinct areas involved in nociceptive processing to be examined. In combination with sophisticated PCR-based amplification protocols this technique provides sufficient amounts of messenger RNA (mRNA) for application to microarrays. Aside from the technological issues, a difficult task in any microarray study is the analysis of the resulting enormous data set to reveal the key genes, whose regulation is central to the phenotypic changes observed. For this to be achieved, the methods of data analysis, pattern searching and feature recognition, and bioinformatics have to be properly deployed all within the context of an appropriate statistical design. These issues are especially relevant to pain research where interindividual and interpopulation variation is likely to be high, and where polymorphisms can greatly affect nociceptive sensitivity and susceptibility to pain conditions. Methods for assessing the function of new candidate genes identified in microarray screening experiments are also discussed.

Animals↗

PubMed2002

Application of microarray technology in environmental and comparative physiology.

DNA microarray technology is revolutionizing many aspects of biological research, allowing the expression of many thousands of gene transcripts to be monitored simultaneously. This provides powerful tools for the genome-wide correlation of gene transcript levels with physiological responses and alterations in physiological states. To date, microarray analyses have been applied almost exclusively to a few model species for which the abundant gene sequence data permit the fabrication of whole-genome microarrays. However, many interesting physiological traits and responses are poorly expressed or absent in model species and may be better illustrated in nonmodel organisms. Comparative approaches to understanding function traditionally focus on species that by virtue of their unusual adaptations, lifestyles, and phylogeny are particularly suited to address a specific biological process or problem. In this review, we show that microarray technology can be successfully applied to these nonmodel species and used to generate new insights of comparative and evolutionary significance into animal function.

Acclimatization↗