Thread by @CRISPRGuru

SEND is a novel concept of delivering mRNA into cells, published by @zhangf science.org/doi/abs/10.112…. In our @NatureProtocols article nature.com/articles/s4159…, we discuss conceptual ideas of testing & researching SEND system in mice.
A short tweetorial about SEND & our article 1/7

‘SEND’ (for ‘selective endogenous encapsidation for cellular delivery’) system packages an mRNA cargo into virus-like particles (VLPs) and delivers it to other cells. The SEND system has three components: two proteins (PEG10 & a fusogen) & Peg10 mRNA (cargo). 2/7

PEG10 protein forms a VLP like cage on its own mRNA. VLPs then exit the producer cell and attach to other cell (called recipient cell) via a fusogen and deliver the mRNA to the recipient cell. 3/7

Peg10 mRNA can be engineered to contain a different protein coding sequence; for e.g. Cas9. The modified mRNA gets packaged into VLPs, as long as it contains the untranslated (UTR) sequences of Peg10 mRNA. The modified mRNA (with Cas9 coding sequence) becomes the SEND cargo 4/7

In the pioneering work of @zhangf team science.org/doi/abs/10.112… SEND system was demonstrated in cell culture model. Plasmids of 3 SEND components (Peg10+cargo mRNA+fusogen) were transfected to cells. VLPs produced from those cells were added to other cells to deliver the cargo 5/7

While @zhangf team's work elegantly demonstrates SEND in cells, it is yet to be studied if SEND occurs in animals. Testing SEND in vivo requires careful designing of experiments including creating genetically engineered mice. We discuss 3 experimental strategies (A B & C). 6/7

Strategies: A) administering exogenously produced VLPs to mice B) administering SEND plasmids to produce VLPs in mice C) creating genetically engineered mice & leveraging mouse genetics tricks. Please see article for details nature.com/articles/s4159… Thank you for reading the🧵7/7

And our paper is a #Featured article at the journal website this week.
. Thank you @NatureProtocols!