The naive question: you keep seeing the word 'endonuclease' in gene-editing articles. What is it? The answer is refreshingly literal. 'Endo' means inside, 'nuclease' means a thing that cuts nucleic acid. An endonuclease is a protein that cuts DNA from the inside of a strand.
Think of it like scissors versus a paper-shredder that only feeds from the edge. An exonuclease trims from the ends; an endonuclease snips in the middle, wherever you steer it. For editing a gene buried in the middle of a chromosome, you need the middle-cutting kind.
On its own, an endonuclease cuts somewhat indiscriminately. The whole art of gene editing is making it cut only where you want. The General Hospital Corporation's grant US10544433B2 uses RNA-guided FokI nucleases — a design that requires two cutters to converge before anything is cut, sharply raising precision.
Researchers also repurpose the cutting machinery for things other than cutting. Gunma University's US10612044B2 covers a DNA methylation editing kit — using the targeting parts to change a chemical mark on DNA rather than break it. Same address system, different action.
Here's the 'so what.' When a patent says it covers an 'endonuclease-based' method — as Seattle Children's US10563226B2 does for editing primary cells — it's telling you the invention is built on a steered middle-cutting protein. That one word tells you the core mechanism.
The short version: an endonuclease is the scissors at the heart of gene editing. Everything clever in the patents is about aiming it — and, increasingly, about using its aim for jobs beyond cutting.