Transcriptional analysis of apoptotic cerebellar granule neurons following rescue by gastric inhibitory polypeptide

Abstract

Apoptosis triggered by exogenous or endogenous stimuli is a crucial phenomenon to determine the fate of neurons, both in physiological and in pathological conditions. Our previous study established that gastric inhibitory polypeptide (Gip) is a neurotrophic factor capable of preventing apoptosis of cerebellar granule neurons (CGNs), during its pre-commitment phase. In the present study, we conducted whole-genome expression profiling to obtain a comprehensive view of the transcriptional program underlying the rescue effect of Gip in CGNs. By using DNA microarray technology, we identified 65 genes, we named survival related genes, whose expression is significantly de-regulated following Gip treatment. The expression levels of six transcripts were confirmed by real-time quantitative polymerase chain reaction. The proteins encoded by the survival related genes are functionally grouped in the following categories: signal transduction, transcription, cell cycle, chromatin remodeling, cell death, antioxidant activity, ubiquitination, metabolism and cytoskeletal organization. Our data outline that Gip supports CGNs rescue via a molecular framework, orchestrated by a wide spectrum of gene actors, which propagate survival signals and support neuronal viability.

Figure 1.

Hierarchical clustering of genes differently expressed in CGNs treated with Gip, during the pre-commitment of apoptosis. Sixty-five rescue genes (differentially expressed in K5 vs. K5 + Gip); were named using their UniGene symbol and were ordered into a dendrogram, whose length of the branches represents the relatedness of the expression levels in different experimental conditions. Data are presented in a matrix format: each row is equivalent to a single gene and each column is equivalent to one of the three different experimental conditions (K25, K5, K5 + Gip). The color of the corresponding cell in the matrix indicates the averaged normalized intensity from replicates. Red, blue and white respectively represent transcript levels below, equal or above the median abundance across all conditions. Color intensity reflects the magnitude of the deviation from the median (see scale below). Rescue genes differently expressed also following induction of apoptosis (K25 vs. K5) are indicated by *.

Figure 2.

A comprehensive picture showing expression changes associated with CGNs rescue by Gip treatment. Fifty out of sixty-five “Survival related genes” (SGRs) encode proteins with a known function. This figure represents the sub-cellular compartments and molecular processes of these proteins. Each encoded protein is labeled with a thermometer that indicates gene expression changes: downward thermometers have a blue color and indicate down-regulated expression, whereas upward thermometers have a red color and indicate up-regulated expression. In addition to the SRGs, this Figure includes other genes (without a thermometer), which are part of a specific pathway. The figure legend below shows the set of symbols whereby network objects and interactions between objects are indicated in the figure. Mechanism of physical interactions between objects is indicated as follows: (B), binding; (+P), phosphorylation; (Z), catalysis; (T), transformation; (TR), transcription; (CM), covalent modifications; (IE), influence on expression; and (?), unspecified.

Figure 2.

A comprehensive picture showing expression changes associated with CGNs rescue by Gip treatment. Fifty out of sixty-five “Survival related genes” (SGRs) encode proteins with a known function. This figure represents the sub-cellular compartments and molecular processes of these proteins. Each encoded protein is labeled with a thermometer that indicates gene expression changes: downward thermometers have a blue color and indicate down-regulated expression, whereas upward thermometers have a red color and indicate up-regulated expression. In addition to the SRGs, this Figure includes other genes (without a thermometer), which are part of a specific pathway. The figure legend below shows the set of symbols whereby network objects and interactions between objects are indicated in the figure. Mechanism of physical interactions between objects is indicated as follows: (B), binding; (+P), phosphorylation; (Z), catalysis; (T), transformation; (TR), transcription; (CM), covalent modifications; (IE), influence on expression; and (?), unspecified.