February 19, 2018History of Medicine
The discovery of clustered DNA repeats began independently in three parts of the world. One of the first discoveries was in 1987 at Osaka University in Japan. Researcher Yoshizumi Ishino and colleagues published their findings on the sequence of a gene called iap and its relation to E. coli. Technological advances in the 1990s allowed them to continue their research and speed up their sequencing with a technique called metagenomics. They were able to collect seawater or soil samples and sequence the DNA in the sample. The first description of what would later be called CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats), occurred in 1987 when Yoshizumi Ishino accidentally cloned part of a CRISPR together with the iap gene, the target of interest. The organization of the repeats was unusual because repeated sequences are typically arranged consecutively along DNA. The function of the interrupted clustered repeats was not known at the time.
Ishino received his BS, MS and PhD degree in 1981, 1983 and 1986, respectively, from Osaka University. From 1987 to 1989, he was a post-doctoral fellow at Yale University (Dieter Soll's laboratory). In 2002, he became a professor at Kyushu University. Since October 2013, he is also a member of the NASA Astrobiology Institute, University of Illinois at Urbana-Champaign.
In 1993 researchers of Mycobacterium tuberculosis in the Netherlands published two articles about a cluster of interrupted direct repeats (DR) in this bacterium. These researchers recognized the diversity of the DR-intervening sequences among different strains of M. tuberculosis and used this property to design a typing method that was named spoligotyping, which is still in use today. At the same time, repeats were observed in the archaeal organisms of Haloferax and Haloarcula species, and their function was studied by Francisco Mojica at the University of Alicante in Spain. Although his hypothesis turned out to be wrong, Mojica surmised at the time that the clustered repeats had a role in correctly segregating replicated DNA into daughter cells during cell division because plasmids and chromosomes with identical repeat arrays could not coexist in Haloferax volcanii. Transcription of the interrupted repeats was also noted for the first time. Transcription of the interrupted repeats was also noted for the first time. In 2017 Mojica was a winner of the Albany Medical Center Prize.
The three articles below, are well written and informative regarding this new and exciting technology.