Boston-based Third Rock Ventures, a venture firm focused on life science companies, said this week that it has closed on Third Rock Fund II, a $426M fund focused on the life science area, and also opened up a San Francisco office. According to Third Rock, partner Craig Muir and principal Jake Bauer are relocating to San Francisco to better work with its West Coast based portfolio firms. The firm's first fund, Fund I, was established in 2007 with $378M. As part of the new fund, the venture firm said it has added Charles Homcy (formerly of Portola Pharmaceuticals) as a venture partner in the San Francisco office. The firm's current portfolio includes firms Ablexis, Afferent Pharmaceuticals, Agios Pharmaceuticals, Alnara Pharmaceuticals, bluebird bio, Constellation Pharmaceuticals, DC Devices, Edimer Pharmaceuticals, Eleven Biotherapeutics, Foundation Medicine, Nine Point Medical, Seventh Sense Biosystems and Zafgen.