DeNA (pronounced DNA) is a Japanese based mobile gaming company that in 2015, Nintendo partnered with for their mobile expeditions
The company formed in 1999 to launch an online auction service, but has since then, moved mainly towards games. They were a major developer on "dumb" mobile phones when they were popular in Japan. In 2010, they launched their Mobage service, one of the largest mobile game service in Japan. Disney partnered with them to create mobile games in 2012.
The partnership was formally announced in a press conference on March 17, 2015. Under this partnership DeNA would produce mobile games using Nintendo IPs and help create a membership program that substitutes for Club Nintendo. They have also exchanged stock with DeNA getting 1% of Nintendo's stock and Nintendo owns 10% of DeNA. This puts Nintendo as the second biggest
No games related to Nintendo have been released as of this point but, they should arrive in Fall 2015.