Stage-specific gene expression in early differentiating oligodendrocytes

Transcriptome profiling of wheat differentially expressed genes exposed to different chemotypes of Fusarium graminearum

The study is an overview of the behavior of the wheat transcriptome to the Fusarium graminearum fungus using two different chemotypes. The transcriptome profiles of seven putative differentially expressed defense-related genes were identified by SSH and further examined using qPCR. Fusarium head blight (FHB) of wheat (Triticum aestivum L.), caused by several species of the fungus fusarium, is important in all wheat growing regions worldwide. The most dominant species in Canada is Fusarium graminearum (Fg). F. graminearum isolates producing mycotoxins such as 3-acetyl-deoxynivalenol (3ADON) and 15-acetyl-deoxynivalenol (15ADON). The objective of this study was to investigate the effect of the different chemotypes of Fg on the transcriptome pattern of expressed wheat genes. A cDNA library was constructed from infected "Sumai 3" spikes harvested at different times after inoculation with a macroconidia suspension. Employing suppression subtractive hybridization (SSH), the subtracted cDNA library was differentially screened by dot-blot hybridization. Thirty-one clones were identified; one was isolated and characterized, and transcriptome profiling of seven up-regulated putative defense-related genes was performed using quantitative real-time reverse-transcriptase PCR. These genes may be involved in the wheat-pathogen interactions revealing transcript accumulation differences between the non-diseased, 3ADON-, and 15ADON-infected plants. Additionally, significant differences in gene expression were observed between 3ADON- and 15ADON-infected plants which highlight the significance of a particular chemotype in FHB disease.

Neonatal and adult O4(+) oligodendrocyte lineage cells display different growth factor responses and different gene expression patterns

Oligodendrocytes are the myelinating cells of the central nervous system. Although the CNS possesses the ability to repair demyelinating insults, in certain cases, such as the chronic lesions found in multiple sclerosis, remyelination fails. Cycling cells capable of becoming oligodendrocytes have been identified in both the developing and the adult mammalian forebrain. Many studies have focused on differences in gene expression profiles as oligodendrocyte progenitors differentiate into myelinating oligodendrocytes by isolating cells at different developmental stages from animals at a single age. However, few have studied the differences that exist between the progenitors of the neonatal CNS and those of the adult CNS. This study examined the response of neonatal and adult O4(+) cells to platelet-derived growth factor-AA, basic fibroblast growth factor, and insulin-like growth factor-1 and revealed marked differences. Whereas adult cells readily differentiated in vitro, the majority of neonatal progenitors remained immature. Microarray analysis was used to examine differences between acutely isolated neonatal and adult progenitors further. Gene expression profiles showed that the adult O4(+) cells are more developmentally mature than neonatal cells. Neonatal cells expressed higher levels of genes involved in proliferation. Adult O4(+) cells expressed higher levels of transcripts for genes involved in cell death and survival. Therefore, O4(+) cells from the adult differ greatly from those of the neonate, and the developmental stage of the animal models utilized must be taken into consideration when applying principles from neonatal systems to the adult.

Conformational and biochemical characterization of a biologically active rat recombinant Protease Nexin-1 expressed in E. coli

Protease Nexin-1, a 43-kDa glycoprotein, is a major physiological thrombin inhibitor involved in the modulation of nerve cell plasticity. Recombinant rat Protease Nexin-1 (rPN-1) was efficiently produced in Escherichia coli using a T7 RNA polymerase based expression system and purified by heparin-sepharose affinity chromatography yielding 3 mg of protein per liter of cell culture. The purity and chemical identity of rPN-1 were assessed by SDS-PAGE, Reverse Phase- High Performance Liquid Chromatography, mass spectrometry and two-dimensional-gel electrophoresis. Conformational analysis by circular dichroism and fluorescence spectroscopy revealed the presence of mixed alpha/beta secondary structure and the prevailing localization of Trp-residues in rather polar environments. Fluorescence titration of rPN-1 with heparin indicated that rPN-1 binds heparin with high affinity. Furthermore, the formation of a SDS-stable 1:1 thrombin-rPN-1 complex, monitored by SDS-PAGE, confirmed the native-like structure of rPN-1. Finally, the cellular effects of rPN-1, such as its ability to promote neurite outgrowth in neuroblastoma cells, were found to be very similar to those elicited by natural PN-1. Altogether, our results demonstrate that glycosylation does not alter neither structure nor function of PN-1 and that E. coli is a suitable expression system for obtaining milligram quantities of pure and fully active rPN-1 for structural and functional studies.

Expression profiling of salinity-alkali stress responses by large-scale expressed sequence tag analysis in Tamarix hispid

Tamarix hispida, a woody halophyte, thrives in saline and saline-alkali soil. To better understand the gene expression profiles that manifest in response to saline-alkali stress, three cDNA libraries were constructed from leaf tissue of T. hispida plants that were well watered and exposed to NaHCO3 for 24 and 52 h. A total of 9,447 high quality expressed sequence tags (ESTs) were obtained from the three libraries. These ESTs represent 3,945 unigenes, including 986 contigs and 2,959 singlets. The numbers of unigenes obtained from the three libraries were 1,752, 1,558 and 1,675, respectively. The EST analysis was performed to compare gene expression in the three cDNA libraries; the transcripts responsive to NaHCO3 were identified. The differentially expressed transcripts were identified. The up-regulation genes were involved in a variety function areas, such as stress-related proteins, hormone signaling transduction, antioxidative response, transcriptional regulators, protein synthesis and destination, ion homeostasis, photosynthesis and metabolism. The results indicated that the response to NaHCO3 in T. hispida is a complex one, involving multiple physiological and metabolic pathways. Nine gene expression patterns were compared in response to NaHCO3 and NaCl using real time reverse transcription-polymerase chain reaction (RT-PCR). Gene expression trends were similar after a 24-h exposure to either NaCl or NaHCO3, however, great variability was found after a 52-h exposure, indicating that short-term responses to either salt may not be obviously different.

Tissue plasminogen activator and glial function

Tissue plasminogen activator (tPA) is the only FDA-approved treatment of thrombotic stroke and is a major parenchymal serine protease in the brain. However, it has been implicated in a plethora of brain pathologies, raising concern about its use as a safe therapeutic. tPA is thought to regulate physiological processes that entail tissue remodeling and plasticity, purportedly due to its ability to initiate the degradation of extracellular matrix proteins and possibly other substrates. Understanding the physiological role(s) of tPA promises to both elucidate important aspects of brain function and improve the available therapies for neurological disease. In this context, the effects of tPA on glial cells, mainly microglial cells, but also astrocytes and Schwann cells, appear to be of particular importance, given the increasing awareness of the significance of glia in brain physiology and pathology