CAMBRIDGE, Mass.--(BUSINESS WIRE)--Dimension Therapeutics, Inc. ("Dimension" or the "Company"), a leading rare disease company advancing novel, liver-directed treatments for diverse genetic disorders, today announced that it has expanded its Board of Directors with the elections of Georges Gemayel, Ph.D., former Executive Vice President of Genzyme Corporation, and Arlene M. Morris, former CEO of Syndax Pharmaceuticals. Dimension also announced that Donald J. Hayden, Jr., is leaving his position as a member of the Company's Board of Directors.