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Abstract #26063 Published in IGR 12-2
A single nucleotide polymorphism in the bax gene promoter affects transcription and influences retinal ganglion cell death
Semaan SJ; Li Y; Nickells RWASN Neuro 2010; 2: 87-101
Pro-apoptotic Bax is essential for RGC (retinal ganglion cell) death. Gene dosage experiments in mice, yielding a single wild-type Bax allele, indicated that genetic background was able to influence the cell death phenotype. DBA/2J(Bax+/-) mice exhibited complete resistance to nerve damage after 2 weeks (similar to Bax(-/-) mice), but 129B6(Bax+/-) mice exhibited significant cell loss (similar to wild-type mice). The different cell death phenotype was associated with the level of Bax expression, where 129B6 neurons had twice the level of endogenous Bax mRNA and protein as DBA/2J neurons. Sequence analysisof the Bax promotersbetween these strains revealed a single nucleotide polymorphism (T(129B6) to C(DBA/2J)) at position -515. A 1.5- to 2.5-fold increase intranscriptional activity was observed from the 129B6 promoter in transient transfection assays in a variety of cell types, including RGC5 cells derived from rat RGCs. Since thispolymorphism occurred in a p53 half-site, we investigated the requirement of p53 for the differential transcriptional activity. Differential transcriptional activity from either 129B6 or DBA/2J Bax promoters were unaffected in p53-(/-) cells, and addition of exogenous p53 had no further effect on this difference, thus a role for p53 was excluded. Competitive electrophoretic mobility-shift assays identified two DNA-protein complexes that interacted with the polymorphic region. Those forming Complex 1 bound with higher affinity to the 129B6 polymorphic site, suggesting that these proteins probably comprised a transcriptional activator complex. These studies implicated quantitative expression of the Bax gene as playing a possible role in neuronal susceptibility to damaging stimuli.
R. W. Nickells. Department of Opthalmology and Visual Sciences, University of Wisconsin, School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, United States. nickells@wisc.edu
Classification:
2.13 Retina and retinal nerve fibre layer (Part of: 2 Anatomical structures in glaucoma)
11.8 Neuroprotection (Part of: 11 Medical treatment)
3.5 Molecular biology incl. SiRNA (Part of: 3 Laboratory methods)
3.6 Cellular biology (Part of: 3 Laboratory methods)