In a previous study using lymphoblast cell lines, Hu et al. [2005, 2006] reported that aA –G polymorphism in the l variant strongly altered the effects of this 5HTTLPR allele on mRNA expression. In addition, others have shown an effect of the Long G variant in the etiology in MD [Hu et al., 2007]. In the current study, we did not find an effect of the “Long G” allele on mRNA levels. We also examined the effect of this allele on expression in the 89 cell lines used in our prior study and did not find an effect in the cell lines either (unpublished data). Using publicly available data, Martin et al. [2007] also did not find an effect of the Long G variant on gene expression either but suggested that the role of genetic variation at this locus in regulating mRNA may be very complex. We agree and taken in total, these findings suggest that the effect size of the “long G” variant on mRNA transcription may be smaller than originally posited but suggest caution is in order.
