For all the myriad genome-editing tricks of the CRISPR/Cas9 system, slipping into cells by way of viral vector was previously not one of them. The gene for the large Cas9 enzyme—which originated from the Streptococcus pyogenes bacterium—maxed out the carrying capacity of vectors’ genomes. Researchers from the Broad Institute and MIT and their colleagues have now found that a smaller Cas9 from a different bacterium can do the job with ease. They described their modified approach in Nature.

This discovery expands the potential CRISPR toolbox for treating genetic diseases in humans.

This was a big obstacle than can now be overcome:

http://www.genengnews.com/gen-news-highlights/crispr-clears-major-obstacle-impeding-its-therapeutic-use/81251106/

Scientific American has a good explanation of how this moves CRISPR closer to clinical use:

http://www.scientificamerican.com/article/new-discovery-moves-gene-editing-closer-to-use-in-humans/

Researchers describe a technique for creating mutations that invade the genome and transmit themselves across to the next generation with near 100% success, defying the classic laws of Mendelian genetics. It is the latest—and some say, most impressive—example of gene drive: biasing inheritance to spread a gene rapidly through a population, or even an entire species. At this level of efficiency, a single mosquito equipped with a parasite-blocking (it blocks transmission, doesn't kill the parasites) gene could in theory spread malaria resistance through an entire breeding population in a single season. A collaboration is under way, based on this study, to do just that.

Reddit comments:

http://reddit.com/r/science/comments/2zs7qr/genetic_modification_chain_reaction_has_been_made/

Science has compiled some of its recent research papers, commentaries, and news articles on CRISPR and its implications in a special collection.