Gene expression changes in an animal model of in utero irradiation-induced Cortical Dysplasia
Girish K Hiremath1, Cristiane Q Tilelli, Yaomin Xu
1Department of Neurosurgery, Cleveland Clinic, Cleveland, Ohio 44195, USA.
Purpose:
Cortical Dysplasia (CD) is the histopathological substrate in almost half of all drug-resistant focal epilepsies. Little is known about the gene expression profile of CD. As such information may help target therapeutics more effectively, our aim was to perform a gene expression analysis of an animal model of cortical dysplasia induced by in utero irradiation.
Methods:
Nine offspring from irradiated animals, and nine age-matched controls were sacrificed at post-natal day 60. Cortical and hippocampal regions were separated, and total ribonucleic acid (RNA) was extracted using a commercially available kit (Qiagen). RNA was then subjected to a gene expression analysis using an oligonucleotide microarray platform (Illumina). After statistical analysis, genes were considered differentially expressed when a p value less than 0.001 was observed. Real-time, quantitative polymerase chain reaction (RT-qPCR) was used to confirm microarray results for three genes via the Livak method.
Results:
Twenty three genes from cortical tissue met criteria for altered gene expression. Six genes from cortex seemed relevant to the pathogenesis of CD. Two genes that promoted cell survival (connective tissue growth factor and peroxiredoxin) were upregulated. One gene that promoted excitotoxic neurodegeneration (latrophilin-2) was downregulated. Two genes involved in glutamate (protein kinase C-alpha) and AMPA receptor recycling (NEEP-21) were downregulated. One gene, (Shank-1) involved in the control of dendritic maturation, was downregulated.
Conclusion:
Gene expression analysis in this animal model revealed some of the potential mechanisms by which CD may lead to the phenotype of intractable epilepsy. The downregulation of genes that are involved in glutamate and AMPA receptor recycling may lead to increased excitability. Disinhibition of aberrant dendritic branching, resulting from a downregulation of Shank-1, may also result in an increase in sprouting, excitation and/or hypersynchrony. Finally, genes promoting cell survival, either directly (connective tissue growth factor, peroxiredoxin) or indirectly (latrophilin-2) may allow CD tissue to survive the excitotoxic injury that it produces, thus allowing it to perpetuate the epileptic condition over time.
Insights
This study reveals gene expression changes in an animal model of cortical dysplasia (CD), a cause of drug-resistant epilepsy. Altered gene expression, particularly involving glutamate and cell survival, may explain how CD leads to intractable seizures.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Cortical dysplasia (CD) is a leading cause of drug-resistant focal epilepsies.
- Understanding the gene expression profile of CD is crucial for developing targeted therapies.
- Current knowledge regarding the molecular mechanisms underlying CD pathogenesis is limited.
Purpose of the Study:
- To investigate the gene expression profile of an animal model of cortical dysplasia (CD) induced by in utero irradiation.
- To identify genes and pathways involved in the development and progression of CD.
- To provide insights into potential therapeutic targets for drug-resistant epilepsy associated with CD.
Main Methods:
- Gene expression analysis was performed on cortical and hippocampal tissues from irradiated and control animal models at post-natal day 60.
- Oligonucleotide microarrays were used for high-throughput gene expression profiling.
- Real-time quantitative polymerase chain reaction (RT-qPCR) was employed to validate key gene expression changes.
Main Results:
- Twenty-three genes exhibited altered expression in the cortical tissue of the CD model.
- Upregulation of cell survival genes (connective tissue growth factor, peroxiredoxin) and downregulation of excitotoxicity-related genes (latrophilin-2, protein kinase C-alpha, NEEP-21, Shank-1) were observed.
- Specific downregulation of genes involved in glutamate and AMPA receptor recycling, and dendritic maturation was identified.
Conclusions:
- Gene expression alterations in this CD model provide potential mechanisms for intractable epilepsy.
- Downregulation of glutamate and AMPA receptor recycling genes may increase neuronal excitability.
- Aberrant dendritic branching and enhanced cell survival pathways may contribute to the perpetuation of the epileptic condition in CD.
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