Unknown,Transcriptomics,Genomics,Proteomics

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Expression data from neurotrophin transgenic mice

ABSTRACT: A limited number of growth factors are capable of regulating numerous developmental processes, but how they accomplish this is unclear. In the gustatory system, brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT4) have different developmental roles but exert their effects through the same receptors (TrkB and p75). Using genome wide expression analysis, we determined that BDNF and NT4 also regulate the expression of different sets of genes downstream of receptor signaling in geniculate ganglion. These differences in gene expression likely determine their different roles. BDNF and NT4 could function differently because of temporal or spatial differences of expression or the activation of different signaling pathways. BDNF and NT4 regulate cell death, axonal growth and axonal guidance by altering gene expression. Because many of these functions of the two neurotrophins differ in taste development, each likely alters gene expression in a unique way. To determine if removal of BDNF and NT4 alters gene expression in different ways, I will compare microarray gene expression profiles in the geniculate ganglion among BDNF knockout, Nt4 knockout, and wild type mice during development.

ORGANISM(S): Mus musculus

SUBMITTER: Tao Huang

PROVIDER: E-GEOD-44734 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:To determine whether DGCR8 is required for maturation of all miRNAs, we performed miRNA microarray analysis. Using RNA from wild-type ES cells as our reference sample, we observed a global loss of miRNAs in DGCR8 knockout cells, but normal levels of expression in DGCR8 heterozygous cells. The similarity in expression levels between wild-type and heterozygous cells suggests that DGCR8 is not limiting in the maintenance of steady-state levels of miRNAs in ES cells. Of the eighty-nine miRNA array probes that showed significant signals with wild-type RNA, eighty-two were drastically reduced in the DGCR8 knockout cells. The remaining seven were not significantly altered in the DGCR8 knockout cells, but at least four of these seven miRNAs appear to be due to unavoidable contamination with RNA from the mouse embryonic fibroblast (MEF) feeder cells used for ES cell culture prior to the isolation of RNA. These miRNAs were highly expressed in the MEFs and decreased when the ES cells were temporarily passaged on gelatin-coated plates without feeders. The remaining three showed similar levels of expression in the heterozygous, knockout and MEF feeder cells. Therefore, these signals may be small RNAs that are not processed with the help of the microprocessor complex. Alternatively, these signals may result from unavoidable degradation products within the purified small RNA population. In either case, our results show that DGCR8 is broadly required for miRNA processing with little evidence for redundancy or bypass mechanisms. Keywords: cell type comparison, genetic modification MicroRNAs extracted from wild-type, DGCR8 heterozygous knockout and DGCR8 homozygous knockout were analyzed by microarray. In each array, wild-type samples serve as reference. Ratios were normalized based on positive control RNAs on the array. To determine if some of signals appeared in DGCR8 knockout ES cells are due to mice embryonic fibroblast (MEF) feeder cell contamination (this is unavoidable because these ES cells were grown on MEFs and passaged off MEF before RNA extraction). Two independent DGCR8 knockout ES cell lines were analyzed. For each cell line, array hybridization was done in duplicates. For DGCR8 heterozygous knockout ES cells, two independent batches of RNA samples were prepared and analyzed.

Project description:Treatment strategies of critical nerve injuries involving nerve gaps more than 3 cm are still not optimal. The need for an alternative to the standard autologous nerve grafts has led to the exploration of adipose derived stem cells (ASC) seeded in bioartificial nerve conduits for enhancement of peripheral nerve regeneration. ASC can be differentiated into Schwann cell like cells, which is believed to improve their neurotrophic potency. Nevertheless, the differentiation process requires several weeks and there is no evidence that the cells maintain their differentiated phenotype in vivo. Thus, the present study evaluated the synergistic effect of undifferentiated ASC with exogenously added growth factors in vitro with the aim to improve the neurotrophic potency of undifferentiated ASC through short ex-vivo stimulation with growth factors. The study furthermore provides a comparative in vitro assay of the six well-known neurotrophic factors NGF, GDNF, BDNF, CNTF, NT3 and NT4. ASC were cultured and thus stimulated in the presence of the respective exogenous growth factor for three days and resulting conditioned medium was evaluated in an in vitro axonal outgrowth assay. In addition, also unstimulated ASC’s conditioned medium was tested in combination with the respective exogenous growth factor for the same assay, which was perfomed on dorsal root ganglion (DRG) explants from 10 days old embryonic chicken. DRG explants from most promising conditions were further analyzed for upregulated STAT-3 and GAP-43 by qRT-PCR. Furthermore, also proteomics and phosphoproteomics were performed for ASC and DRG explants using mass spectrometry. The quantity of selected proteins contained in the ASC’s conditioned medium was investigated by ELISA. Combination of ASC’s conditioned medium with growth factors generally resulted in significantly enhanced axonal outgrowth when compared with their control of DRG explants cultured with the respective growth factor only. Specifically, conditioned medium derived from NT3-stimulated as well as ASC’s conditioned medium supplemented with NT3 or BDNF elicited significant axonal outgrowth from DRG explants in contrast to all other experimental conditions. Significant upregulation of STAT-3 and GAP-43 was evidenced for DRG explants grown in NT3-stimulated ASC’s conditioned medium and to a certain extent also for DRG cultured in ASC’s conditioned medium supplemented with NT3.

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Expression data from neurotrophin transgenic mice

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