Identification of novel target genes for the plasticity-related transcription factor Zif268

McDade, Donna Marie (2007) Identification of novel target genes for the plasticity-related transcription factor Zif268. PhD thesis, University of Glasgow.

Abstract

Activity based alterations in synaptic connectivity are thought to underlie the processes involved in learning and memory. Measurable changes in neuronal activation by long-term potentiation (LTP) are widely investigated as a possible cellular correlate of this phenomenon, as it can be induced quickly to elicit long-lasting modifications. These long-term changes in the activity of neuronal circuits are sustained by an altered pattern of gene expression and protein synthesis. The inducible transcription factor Zif268 has been implicated in almost all models of neuronal plasticity. Downstream targets of zif268 are widely believed to contribute to the duration and stabilisation of NMDA receptor dependent LTP which, in turn, can be linked to various models of learning and memory. However, these downstream targets are only just starting to receive attention.
By utilising a wide range of contemporary neuroscience techniques covering molecular & cell biology approaches, this thesis proposes two known proteins, gephyrin and ubiquilin, as well as a novel gene (urma), as potential downstream targets of Zif268. Both gephyrin and ubiquilin are associated with GABAA receptors at inhibitory synapses. Gephyrin is thought to cluster and anchor GABAA receptors at postsynaptic sites whilst ubiquilin is reported to regulate receptor surface expression. We found that gephyrin mRNA and protein expression levels were downregulated in response to increased levels of zif268 by transient transfection in PC-12 cells and NMDA stimulation in primary cultured cortical neurones. In addition, ubiquilin mRNA and protein levels were also downregulated within the same experimental paradigms, implying that both gephyrin and ubiquilin are downstream transcriptional targets of this plasticity-related gene.
A previously reported microarray experiment (James et al. 2005) contained 144 ESTs significantly affected by the transient transfection of Zif268 in PC-12 cells compared to control. Bioinformatic analyses of these tags revealed interesting genomic areas pertaining to little published information. After further investigation, EST AI169020 revealed a novel transcript that was downregulated in response to NMDA treatment of primary cortical neurones. Additional data mining suggests that urma may be a rarely expressed transcription factor. Basal levels of urma mRNA were also decreased in the Zif268 knockout mouse, as were ubiquilin mRNA levels.
Zif268 is a regulatory immediate early gene, activating or suppressing downstream targets that play a role in the duration and stabilisation of LTP. These results indicate that gephyrin and ubiquilin are potential mediators of NMDA receptor-dependent plasticity, by modifying inhibitory-signalling. In addition, Zif268 may actively suppress a novel plasticity-related transcription factor, urma. These findings may underlie important processes in learning and memory.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: LTP, Zif268, gephyrin, ubiquilin, plasticity.
• Subjects: R Medicine > RC Internal medicine > RC0254 Neoplasms. Tumors. Oncology (including Cancer); Q Science > QP Physiology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Supervisor's Name: Morris, Professor Brian
• Date of Award: 2007
• Depositing User: Ms DM McDade
• Unique ID: glathesis:2007-28
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 20 Nov 2007
• Last Modified: 10 Dec 2012 13:14
• URI: https://theses.gla.ac.uk/id/eprint/28