The second day of ISSCR 2016 started off with a great session on pluripotency and plasticity, and the first talk was by Shinya Yamanaka. He changed the title of his talk to “Reprogramming of Cells and Scientist”. As with my other posts on this meeting, this one is a stream of quotes and impressions from the talk. The beginning was more autobiographical on his part and then the second half was on basic science. I really enjoyed this talk overall.
It’s now been a decade since Shinya Yamanaka’s seminal paper on mouse IPS cells. Shinya started his talk going back in time to the early 1990s of his postdoc at the Gladstone. He cloned NAT1 as a postdoc (Yamanaka et al. Genes & Dev, 1997).
He found that NAT1 is required for early mouse development. He made NAT1 null mESCs and found that the NAT1 KO mESCs could not differentiate.
He got his own lab in 2000 and he and his group tried to induce pluripotency in somatic cells. It was 6 years later that they published the first IPS cell paper.
IPS cell technology has “reprogrammed me too” he said. One of the things I enjoy most about Shinya’s talks over the years (besides the wonderful science) is that he is very free with discussing what it means to be a scientist and how science effects scientists including on a personal level.
He noted that after human IPS cells, “I have been spending a lot of time in talking with people in government and industry and banks, and also spending a lot of time in fund raising.” I think this is what he meant by reprogramming of him by IPS cells.
“Some portion of myself is refractory to reprogramming. That part tells me I should enjoy basic research” and then he said that’s what my talk will be on: basic science.
He focused on NAT1 and its knockout in mESCs. Could NAT1 KO mESCs be in the ground state even without 2i treatment? NAT1-nulls even without 2i have the same morphology as WT cells in 2i. They did single cell RNA analysis. 2i makes WT mESCs more uniform in gene expression with higher Oct4 levels, etc. NAT1 nulls even without 2i are very similar to 2i WT cells. It seems NAT1 is an inhibitor of the ground state.
What about NAT1 in human ES cells?
Conventional gene targeting in human cells didn’t work. They could only get hets but no homozygous KOs (unpublished work of Kazu Takahashi). So it seems NAT1 is essential to human ES cells. Importantly, Kazu could get homozygous in the context of Dox NAT1 transgene. When you then remove Dox you get basically a complete NAT1 knockout. 2i LIF supports self-renewal of NAT1 null IPS cells. The NAT1 null IPS cell show higher than WT levels of OCT4 and NANOG as well as other pluripotency factors.
What does NAT1 do as a protein?
NAT1 is similar to eiF4G and it is known itself also as eiF4G2. They function in translational control. eiF4G is an essential linker in translational initiation. They searched for NAT1 binding proteins by doing flag tag IP. It binds to many translational proteins and many similar factors as eiF4G. There are a few things that eiF4G binds that NAT1 doesn’t.
Does NAT1 have general or specific translational regulatory functions? There might be some specific ones.
When NAT1 is turned off some specific proteins are elevated including KLF4 and PRDM14, two key TFs that are required for transition from primed to naive state. RNAs of these two are not changed so the change is at the translational level.
I can’t wait to hear more in the future about NAT1’s role in pluripotency.