Showing papers by "David A. Pearce published in 2004"

Targeted disruption of the protein kinase SGK3/CISK impairs postnatal hair follicle development.

Abstract: Members of the serum- and glucocorticoid-regulated kinase (SGK) family are important mediators of growth factor and hormone signaling that, like their close relatives in the Akt family, are regulated by lipid products of phosphatidylinositol-3-kinase. SGK3 has been implicated in the control of cell survival and regulation of ion channel activity in cultured cells. To begin to dissect the in vivo functions of SGK3, we generated and characterized Sgk3 null mice. These mice are viable and fertile, and in contrast to mice lacking SGK1 or Akt2, respectively, display normal sodium handling and glucose tolerance. However, although normal at birth, by postpartum day 4 they have begun to display an unexpected defect in hair follicle morphogenesis. The abnormality in hair follicle development is preceded by a defect in proliferation and nuclear accumulation of beta-catenin in hair bulb keratinocytes. Furthermore, in cultured keratinocytes, heterologous expression of SGK3 potently modulates activation of beta-catenin/Lef-1-mediated gene transcription. These data establish a role for SGK3 in normal postnatal hair follicle development, possibly involving effects on beta-catenin/Lef-1-mediated gene transcription.

A preliminary study of airborne microbial biodiversity over Peninsular Antarctica.

Abstract: This study used PCR-based molecular biological identification techniques to examine the biodiversity of air sampled over Rothera Point (Antarctic Peninsula). 16S rDNA fragments of 132 clones were sequenced and identified to reveal a range of microorganisms, including cyanobacteria, actinomycetes, diatom plastids and other uncultivated bacterial groups. Matches for microorganisms that would be considered evidence of human contamination were not found. The closest matches for many of the sequences were from Antarctic clones already in the databases or from other cold environments. Whilst the majority of the sequences are likely to be of local origin, back trajectory calculations showed that the sampled air may have travelled over the Antarctic Peninsula immediately prior to reaching the sample site. As a result, a proportion of the detected biota may be of non-local origin. Conventional identification methods based on propagule morphology or culture are often inadequate due to poor preservation of characteristic features or loss of viability during airborne transfer. The application of molecular biological techniques in describing airborne microbial biodiversity represents a major step forward in the study of airborne biota over Antarctica and in the distribution of microorganisms and propagules in the natural environment.

Mechanisms of mineralocorticoid action: determinants of receptor specificity and actions of regulated gene products.

Abstract: The mineralocorticoid receptor (MR) and its close cousin, the glucocorticoid receptor (GR), share considerable structural and functional similarity, including indistinguishable DNA binding properties, yet they mediate distinct physiological responses in some tissues. Specificity is determined by their distinct interactions with other protein factors and modification by peptides, including the small ubiquitin modifier SUMO1. Serum and glucocorticoid-regulated kinase 1 (sgk1) is one key target gene of both MR and GR, and encodes a serine-threonine kinase that stimulates the apical membrane localization of the epithelial sodium channel ENaC. Sgk1 exerts its effects, at least in part, by inhibiting an isoform of the ENaC inhibitory ubiquitin ligase Nedd4-2. This review briefly summarizes two areas of mineralocorticoid research: molecular determinants of MR specificity, and the role of Sgk1 in mediating the effects of aldosterone on epithelial Na(+) transport.

Glutamic acid decarboxylase autoimmunity in Batten disease and other disorders.

Abstract: Degenerative diseases of the CNS, such as stiff-person syndrome (SPS), progressive cerebellar ataxia, and Rasmussen encephalitis, have been characterized by the presence of autoantibodies. Recent findings in individuals with Batten disease and in animal models for the disorder indicate that this condition may be associated with autoantibodies against glutamic acid decarboxylase (GAD), an enzyme that converts the excitatory neurotransmitter glutamate to the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Anti-GAD autoantibodies could result in excess excitatory neurotransmitters, leading to the seizures and other symptoms observed in patients with Batten disease. The pathogenic potential of GAD autoantibodies is examined in light of what is known for other autoimmune disorders, such as multiple sclerosis, SPS, Rasmussen encephalitis, and type 1 diabetes, and may have radical implications for diagnosis and management of Batten disease.

Sgk1 mediates osmotic induction of NPR-A gene in rat inner medullary collecting duct cells.

Abstract: We have shown previously that increased extracellular osmolality stimulates expression and promoter activity of the type A natriuretic peptide receptor (NPR-A) gene in rat inner medullary collecting duct (IMCD) cells through a mechanism that involves activation of p38 mitogen-activated protein kinase (MAPK). The serum and glucocorticoid inducible kinase (Sgk) is thought to participate in the regulation of sodium handling in distal tubular segments. We sought to determine whether this kinase might be involved in the osmotic stimulation of NPR-A gene promoter activity. Exposure of cultured IMCD cells to an additional 75 mmol/L NaCl in culture media (final osmolality 475 mosm/kg) resulted in an ≈4-fold increase in Sgk1 protein levels after 7 hours. The Sgk1 induction was almost completely inhibited by the p38 MAPK inhibitor SB203580, indicating that NaCl activates Sgk1 through the p38 MAPK pathway. Transient transfection of a mouse Sgk1 expression vector along with a −1590 NPR-A luciferase reporter resulted in an ≈3-fold increment in reporter activity, which was significantly reduced by cotransfection with a kinase-dead Sgk1 mutant. The NaCl-dependent induction was partially blocked (≈40% inhibition) by cotransfection of the kinase-dead Sgk1 mutant. Neither Sgk1 nor the kinase-dead mutant had any effect on endothelial nitric oxide synthase (eNOS) promoter activity, and the Sgk1 mutant and 8-bromo-cyclic guanosine monophosphate were, to some degree, additive in reducing osmotically stimulated NPR-A promoter activity. Collectively, these data imply that Sgk1 operates over an eNOS-independent, p38 MAPK-dependent pathway in mediating osmotic induction of the NPR-A gene promoter.

New approaches to improve the detection of eutrophication in UK coastal waters

Abstract: Robust assessments of eutrophication are necessary to meet the requirements of a range of international (OSPAR) and EU legislative drivers. To meet these needs EU states have developed marine monitoring programmes designed to allow the application of specified assessment procedures. The UK has reviewed its approach to monitoring eutrophication and has identified a range of future requirements to ensure the evidence base for assessment is robust and the underpinning science is in place. This paper describes the pilot application of in situ monitoring technology (SmartBuoy). Currently, two buoys are deployed in the southern North Sea and a third in Liverpool Bay (Irish Sea). The network of SmartBuoys returns data on physical, chemical and biological variables in near real-time (www.cefas.co.uk/monitoring). The rationale for system and network design will be described. Data from the multi-year time series will be presented and their subsequent use in assessments of eutrophication will be described.

Altered gene expression in the eye of a mouse model for batten disease.

Abstract: PURPOSE. Juvenile neuronal ceroid lipofuscinosis (JNCL or Batten Disease) is one of the most common progressive neurodegenerative disorders of childhood, resulting from autosomal recessive inheritance of mutations in the CLN3 gene. Pathologically, Batten disease is characterized by lysosomal storage of autofluorescent material in all tissue types. Although characterized by seizures, mental retardation, and loss of motor skills, the first presenting symptom of Batten disease is vision loss. METHODS. High-density oligonucleotide arrays were used to profile approximately 19,000 mRNAs in the eye of 10-week-old Cln3-knockout and normal mice, and the data were compared with that for the cerebellum in the same model as a means to identify gene expression changes that are specific to the eye. RESULTS. A detailed list was compiled of 285 functionally categorized genes that have altered expression in the eye of Cln3knockout mice before the appearance of the characteristic lysosomal storage material. Furthermore, 18 genes were identified and 6 validated by semiquantitative RT-PCR that have altered expression in the eye, but not in the cerebellum of Cln3-knockout mice. The genes that have altered expression specific to the eye of the Cln3-knockout mouse may be of importance in understanding the function of CLN3 in different tissues. CONCLUSIONS. Downregulation of genes associated with energy production in the mitochondria appears to be specific to the eye. The CLN3 defect may result in altered mitochondrial function in eye but not other tissue. More detailed experimentation is needed to understand the contribution of these changes in expression to disease state, and whether these changes are specific for certain cell types within the eye. (Invest Ophthalmol Vis Sci. 2004;45:2893‐2905) DOI: 10.1167/iovs.04-0143