A single nucleotide polymorphism in the Bax gene promoter affects transcription and influences retinal ganglion cell death.
ASN Neuro 2010;
2:e00032. [PMID:
20360947 PMCID:
PMC2847828 DOI:
10.1042/an20100003]
[Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 02/24/2010] [Accepted: 03/02/2010] [Indexed: 11/17/2022] Open
Abstract
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/2JBax+/− mice exhibited complete resistance to nerve damage after 2 weeks
(similar to Bax−/− mice), but 129B6Bax+/− 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
analysis of the Bax promoters between these strains revealed a
single nucleotide polymorphism (T129B6 to CDBA/2J) at
position −515. A 1.5- to 2.5-fold increase in transcriptional
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
this polymorphism 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.
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