I enjoyed reading your input on our paper and you're absolutely right about the "blunt instrument" that DNMT inhibitors serve as. I'd love to have a way of specifically blocking the methylation of PP1, for example, during the consolidation period. (And I'm open to suggestions for how to achieve this...) Also, I can appreciate your concern that the DNMT inhibitor is damaging hippocampal neurons. I'm still pretty confident in the control where we re-trained the animals, but we also have the data where we infused the inhibitor 6 hours after training (outside the initial window of consolidation) and the animals showed normal memory the following day. That should partially speak to your concern, shouldn't it? Also, for what it's worth, there's unpublished data from another lab that neurons in culture show no sign of apoptosis or decrease in synapse number following extended exposure to 5-aza or zeb. But regardless, this is obviously just the tip of the iceberg--there are a ton of experiments that need to be done...

"I'd love to have a way of specifically blocking the methylation of PP1, for example, during the consolidation period. (And I'm open to suggestions for how to achieve this...)"

Idea: bond an appropriate zinc finger protein to a demethylator (or alternatively a methyltransferase antibody).

Miller: I'm excited to see the author of the paper commenting at GNXP! I hope that you can answer some questions for me:

1. Are you certain that the drug infusions only hit neurons in area CA1? Traditionally, investigators have focused on DNA methylation in (recently) mitotic cells. And the place where you find mitotic neurons is the dentate gyrus.

2. You probably don't have the data to answer this, but do you know how long after the training you can wait to admninister the DNMT inhibitor to get the memory impairment? I'm surprised that there's an effect even though the inhibitor is not pre-administered before training.

Newby: You, sir, are quite ambitious with your ideas. Why don't you go make me a customized zinc-finger protein? ^-^

2. You probably don't have the data to answer this, but do you know how long after the training you can wait to admninister the DNMT inhibitor to get the memory impairment? I'm surprised that there's an effect even though the inhibitor is not pre-administered before training.

Well in the paper they show that they wait six hours after training and the inhibitor has no effect. So the window is 6 hours. This is also a very nice control for the hippocampal lesions that I was concerned about. I too am excited about the authors commenting here. Thank you Courtney for raising the level. I'll try to answer how to more gene-specifically effect DNA methylation after a little more thought.