Expression of the thymosin beta10 gene in normal and kainic acid-treated rat forebrain

Regeneration of chronic myocardial infarction by injectable hydrogels containing stem cell homing factor SDF-1 and angiogenic peptide Ac-SDKP

Regeneration of chronic myocardial infarction (CMI) is one of the challenging issues due to its limited regeneration activity compared to acute or sub-acute stage. In this study, we examined whether combination of stem cell homing factor (SDF-1) and angiogenic peptides (Ac-SDKP) injected with biomimetic hydrogels promote regeneration of cardiac function in a CMI model. We evaluated the regeneration of chronically infarcted myocardium using injectable biomimetic hydrogels containing two therapeutic factors; stromal-derived factor-1 (SDF-1) and Ac-SDKP for stem cell homing and angiogenesis, respectively. Injection of the two therapeutic factors into the infarct region of the left ventricle showed that the biomimetic hydrogels containing two therapeutic factor exhibited significantly improved left ventricle function, increased angiogenesis, decreased infarct size and greatest wall thickness within the infarct region at 4 weeks post-treatment. From these results, it is clear that hydrogels containing two therapeutic factors showed synergistic effects on regeneration in the chronic heart failure model. In conclusion, these results suggest that combination of stem cell homing factor with angiogenic peptides recruit stem cells to the microenvironments, increase the expression of angiogenic genes, enhance the matured vessel formation and improve the cardiac function in chronic MI.

Reduced myelin basic protein and actin-related gene expression in visual cortex in schizophrenia

Most brain gene expression studies of schizophrenia have been conducted in the frontal cortex or hippocampus. The extent to which alterations occur in other cortical regions is not well established. We investigated primary visual cortex (Brodmann area 17) from the Stanley Neuropathology Consortium collection of tissue from 60 subjects with schizophrenia, bipolar disorder, major depression, or controls. We first carried out a preliminary array screen of pooled RNA, and then used RT-PCR to quantify five mRNAs which the array identified as differentially expressed in schizophrenia (myelin basic protein [MBP], myelin-oligodendrocyte glycoprotein [MOG], β-actin [ACTB], thymosin β-10 [TB10], and superior cervical ganglion-10 [SCG10]). Reduced mRNA levels were confirmed by RT-PCR for MBP, ACTB and TB10. The MBP reduction was limited to transcripts containing exon 2. ACTB and TB10 mRNAs were also decreased in bipolar disorder. None of the transcripts were altered in subjects with major depression. Reduced MBP mRNA in schizophrenia replicates findings in other brain regions and is consistent with oligodendrocyte involvement in the disorder. The decreases in expression of ACTB, and the actin-binding protein gene TB10, suggest changes in cytoskeletal organisation. The findings confirm that the primary visual cortex shows molecular alterations in schizophrenia and extend the evidence for a widespread, rather than focal, cortical pathophysiology.

Using evolutionary conserved modules in gene networks as a strategy to leverage high throughput gene expression queries

BACKGROUND

Large-scale gene expression studies have not yielded the expected insight into genetic networks that control complex processes. These anticipated discoveries have been limited not by technology, but by a lack of effective strategies to investigate the data in a manageable and meaningful way. Previous work suggests that using a pre-determined seed-network of gene relationships to query large-scale expression datasets is an effective way to generate candidate genes for further study and network expansion or enrichment. Based on the evolutionary conservation of gene relationships, we test the hypothesis that a seed network derived from studies of retinal cell determination in the fly, Drosophila melanogaster, will be an effective way to identify novel candidate genes for their role in mouse retinal development.

METHODOLOGY/PRINCIPAL FINDINGS

Our results demonstrate that a number of gene relationships regulating retinal cell differentiation in the fly are identifiable as pairwise correlations between genes from developing mouse retina. In addition, we demonstrate that our extracted seed-network of correlated mouse genes is an effective tool for querying datasets and provides a context to generate hypotheses. Our query identified 46 genes correlated with our extracted seed-network members. Approximately 54% of these candidates had been previously linked to the developing brain and 33% had been previously linked to the developing retina. Five of six candidate genes investigated further were validated by experiments examining spatial and temporal protein expression in the developing retina.

CONCLUSIONS/SIGNIFICANCE

We present an effective strategy for pursuing a systems biology approach that utilizes an evolutionary comparative framework between two model organisms, fly and mouse. Future implementation of this strategy will be useful to determine the extent of network conservation, not just gene conservation, between species and will facilitate the use of prior biological knowledge to develop rational systems-based hypotheses.

Neurotrophic roles of the beta-thymosins in the development and regeneration of the nervous system

Beta-thymosins (Tbetas) are polypeptides abundant in the cytosol, nucleus, and extracellular space of many cell types. In the nervous system, the expression of Tbetas is regulated during the development of the central nervous system and following neuronal insults in cell-type and brain-region dependent manners, which may be related to the function of Tbetas in the growth and regeneration of the nervous system. Supporting such a proposition, overexpression of Tbetas in neurons has been shown to modify the axonal branches in vivo and neurite branches in vitro. These neurite-modifying functions have been suggested to be due to the activity of Tbetas to bind actin. In addition, we recently observed that Tbetas suppressed the apoptotic neuronal death in chick embryos, and these functions might be mediated by the extracellularly secreted form(s) of Tbetas. These results suggest that Tbetas play neurotrophic roles in the neuroprotection and neuronal growth/regeneration via their cytosolic actin-remodeling activity and extracellular antiapoptotic activity. Even though further verification is required, we also observed that Tbeta15 was translocated into the injured neuronal nuclei, and this event appeared to be an eliminatory process of the injured cells. Therefore, treatment with Tbetas or their related peptides appear to be beneficial for neuronal diseases by preventing neuronal death or promoting neuronal regeneration.

Anti-apoptotic function of thymosin-β in developing chick spinal motoneurons

Thymosin-betas (Tbetas) are water-soluble peptides abundantly present in the cytoplasm and extracellular compartment. The functions of Tbetas appear to be pleiotrophic, including actin-remodeling, wound healing, angiogenesis, etc. In the present study, we present the evidence that Tbetas have anti-apoptotic activity on developing chick motoneurons (MNs) in vivo. Using in ovo electroporation, we introduced three isoforms of Tbeta (Tbeta4, Tbeta10, and Tbeta15) and found the significantly diminished normal and limb bud removal (LBR)-induced programmed cell death. Such anti-apoptotic activity is independent of Tbeta's actin remodeling activity. On the other hand, overexpression of Tbetas substantially reduced early cell death initiation signal, such as phosphorylation of c-Jun. Collectively, these results suggest that Tbetas may prevent apoptosis of neurons via blockade of early apoptogenic signals independent of actin remodeling action.

Expression of thymosin beta in the rat brain following transient global ischemia

Thymosin beta (Tbeta) isoforms play an important role in the organization of the cytoskeleton by sequestering G-actin during development of the mammalian brain. In this study, we examined changes in the expression of Tbeta4 and Tbeta15 after transient global ischemia. Tbeta15 mRNA increased gradually in the dentate gyrus (DG) of the hippocampal formation from 3 h after reperfusion and peaked 9 h later. Similarly, a significant increase in Tbeta4 mRNA level was observed in the DG 12 h after reperfusion. Tbeta4 and Tbeta15 proteins were found in different cell types in control brains; Tbeta15 was expressed in a subset of doublecortin (DCX)-positive cells in the DG, whereas Tbeta4-IR was observed in DG neurons and nearby microglial cells. After ischemia, Tbeta15-IR was found in DG neurons and Tbeta4-IR in the reactivated microglial cells. Interestingly, Tbeta15-IR accumulated in the nuclei of CA1 neurons, which are vulnerable to ischemic insults. These results suggest that Tbeta4 and Tbeta15 function in different cellular contexts during ischemia-induced responses.

Hippocampal gene expression is modulated by hypergravity

We used the cDNA microarray technique to monitor simultaneously possible changes induced by hypergravity in the expression level of thousands of hippocampal genes. We tested the mRNA level of about 5000 genes in the hippocampus of mice subjected to 1.09 g (1g) or to 1.85 g (2g) for five repeated 1-h daily rotations in a centrifuge (g = 9.81 m/s2). Data were compared with those obtained for mice kept stationary (C). The ratios 1g/C and 2g/C identified genes affected by rotation and rotation + hypergravity, respectively, whereas 2g/1g ratio identified those affected by hypergravity. We found that about 200 genes were affected by rotation and/or rotation + hypergravity. Almost all the genes affected by rotation + hypergravity were up-regulated, only five being down-regulated. The modulated genes code for proteins involved in a wide range of cellular functions (DNA/RNA metabolism, protein processing, intermediate metabolism, cytoskeleton and motility, cell cycle and apoptosis, signal transduction, neuronal structure/function), suggesting that rotation + hypergravity may affect several aspects of the hippocampal function in order to compensate for environmental changes. Six genes directly or indirectly involved in synaptic transmission and plasticity (proSAAS, neuroblastoma ras oncogene, ESTs moderately similar to thymosin beta-10, syndet, inhibin beta E and Ngfi-A binding protein 2) were found to be significantly modulated by hypergravity and unaffected or only slightly affected by rotation. The modulation by hypergravity of these genes suggests that this stimulus might induce plastic remodelling of the hippocampal circuits, possibly both at structural and functional level.

Thymosin alpha-1 modulates excitatory synaptic transmission in cultured hippocampal neurons in rats

Thymosin alpha-1 (Talpha1) not only possesses immunoregulatory properties in periphery but also is expressed in the central nervous system (CNS) and affects the function of the CNS. To further elucidate the role of Talpha1 in the CNS, the whole-cell recording technique was used to observe the effect of Talpha1 on the spontaneous excitatory synaptic transmission in cultured rat hippocampal neurons. The results showed that acute treatment with Talpha1 significantly enhanced the frequency of AMPA-mediated spontaneous excitatory postsynaptic current (sEPSC) at the concentrations of 1 and 10 microg/ml and also enhanced the frequency of AMPA-mediated miniature excitatory postsynaptic current (mEPSC) at 10 microg/ml. However, the amplitude of both sEPSC and mEPSC were not changed by Talpha1. Those results suggested that Talpha1 involves in the regulation of excitatory synaptic transmission in hippocampal neurons, which contribute to its neurophysiological function in the CNS.

The beta-thymosins, small actin-binding peptides widely expressed in the developing and adult cerebellum

The beta-thymosins are a highly conserved family of small polar peptides known to bind monomeric actin and inhibit its polymerization. The beta-thymosins show a high degree of sequence conservation among all vertebrate classes and they have been also identified in some invertebrate phyla. The most abundant beta-thymosins in mammals are thymosin beta4 (Tbeta4) and thymosin beta10 (Tbeta10), two ubiquitous small (43 amino acids) peptides sharing a high degree of sequence homology. Both beta-thymosins are present in virtually all mammalian tissues and cells studied, showing distinct patterns of expression in several tissues. The beta-thymosins are expressed in the developing and mature nervous system, indicating their participation with other actin-binding peptides in the control of actin polymerization. In the rat cerebellum the temporal and cellular patterns of expression of Tbeta4 and Tbeta10 are different, suggesting that each beta-thymosin could play a specific physiological function during cerebellum development. The possible roles of beta-thymosins in the developing mammalian cerebellum are discussed.

Transcriptional profiling reveals strict boundaries between hippocampal subregions

The hippocampus consists of distinct anatomic regions that have been demonstrated to have different biological functions. To explore the molecular differences between hippocampal subregions, we performed transcriptional profiling analysis by using DNA microarray technology. The cRNA derived from the CA1, CA3, and dentate gyrus regions of the hippocampus and from spinal cord was hybridized to Affymetrix high-density oligo arrays. This systematic approach revealed sets of genes that were expressed specifically in subregions of the hippocampus corresponding to predefined cytoarchitectural boundaries, which could be confirmed by in situ hybridization and Real Time quantitative polymerase chain reaction. The relative enrichment and absence of genes in the hippocampal subregions support the conclusion that there is a molecular basis for the previously defined anatomic subregions of the hippocampus and also reveal genes that could be important in defining the unique functions of the hippocampal subfields.

Kainate-induced genes in the hippocampus: lessons from expression patterns

Kainate, the analog of the excitatory amino acid L-glutamate, upon binding to non-NMDA glutamate receptors, causes depolarization of neurons followed by severe status epilepticus, neurodegeneration, plasticity and gliosis. These events are best observed in hippocampus, the limbic structure implicated in learning and long-term memory formation. Neurons in all hippocampal structures undergo hyper-activation, however, whereas the cells in the CA subfields degenerate within 2--3 days following the application of kainate, the granule cells of the dentate gyrus are resistant to any form of neurodegeneration and even initiate new synaptic contacts. These physiological and histological changes are modulated by short-term and long-term alterations in gene expression. Perhaps close examination of the changing spatio-temporal patterns of mRNAs of various genes may help in generating a clearer picture of the molecular events leading to complex cognitive functions.

Differential expression of thymosins beta(4) and beta(10) during rat cerebellum postnatal development

The beta-thymosins are a family of actin monomer-sequestering proteins widely distributed among vertebrate classes. The most abundant beta-thymosins in mammalian species are thymosin beta(4) (Tbeta(4)) and thymosin beta(10) (Tbeta(10)), two small peptides (43 amino acids) sharing a high degree of sequence homology. In the present work, we have analyzed the distribution of Tbeta(4) and Tbeta(10) in the developing and adult rat cerebellum using in situ hybridization and immunohistochemistry techniques. Our results show that the temporal and cellular patterns of expression of both beta-thymosins are different. In the young (7 and 18 postnatal days) and adult (1 and 4 months old) rat cerebellum, Tbeta(4) was mainly expressed in the glia (microglia, Golgi epithelial cells and oligodendrocytes), neurons (granule cells and Purkinje cells), and in the capillaries. In 14-month-old rats, the Tbeta(4) immunoreactivity was only detected in some microglia cells. In young and adult animals, most of the Tbeta(10) immunoreactivity was localized in several types of neuronal cells including granule cells, Golgi neurons and Purkinje cells. In old animals, a faint Tbeta(10) signal could be detected in a few Purkinje cells. Our results suggest that each beta-thymosin could play a different function in the control of actin dynamics.