Jeanne Pawitan • 4 years ago In my opinion, the success of Obokata is not due to the acid bath only, as the source of the cells she reprogrammed might play a role. She used cells from a transgenic mice, which bears a special Oct4/GFP construct that contains promoter and enhancers.1, 2 other researchers have tried to replicate her success using other kinds of cells, and they failed.3 Prof. Lee and his team tried to use transgenic mice bearing Oct4/GFP as Obokata et al used, and carefully followed the protocol, but failed.4 In technical tips for STAP cell conversion, which was published on 5 March 2014, Obokata et al gave some tips to reproduce their work, including a statement that they used an ?Oct3/4-EGFP transgenic mouse line?, 5 while Prof. Lee used CBA-Tg(Pou5f1-EGFP)2Mnn/j transgenic mice from the Jackson Laboratory,4 thus not precisely the same and I supposed the promoter/enhancers in these two kinds of mice are different. In my opinion, the promoter/enhancer in Obokata et al’s transgenic mouse derived cells can be induced by low pH to cause gene expression, thus the expression of Oct4/GFP, while those of others can not. Therefore, in the conclusion of Obokata?s et al?s work should be emphasized that stimulus-triggered acquired pluripotency was only tested in Oct3/4-EGFP transgenic mouse line derived cells,and whether the technique works on other types of cells need further confirmation.
別の方のコメントです。 Alexandra Iché • 4 years ago I have not followed closely the whole STAP ?story?, but I totally agree with the comment from Jeanne Pawitan. As a non-specialist, I was stricken by the fact that transgenic mice used in this work carry a construct containing the whole OCT4 gene. Indeed, the GOF18 construct encompass the OCT4 coding sequence, which is located downstream of GFP and SV40 polyA signal sequences. In my opinion, one hypothesis may be that acidic conditions allow a low activation of the promoter, as well as a reduction of polyA signal efficacy, leading to OCT4 protein expression, which in turn could trigger cell reprogramming. Polyadenylation modulation in stress conditions was recently described (Graber JH et al., Genome Res., 2013), as well as modulation of translation initiation (Komar and Hatzoglou, Cell cycle, 2013) in such conditions. Obviously, this explanation is not valid for experiments performed using CAG-GFP mice ?