X0306 4 2018-02-13 0 0001590750 MIRAGEN THERAPEUTICS, INC. MGEN 0001451612 Booth Bruce C/O MIRAGEN THERAPEUTICS, INC. 6200 LOOKOUT ROAD BOULDER CO 80301 1 0 0 0 Common Stock 2018-02-13 4 P 0 545454 5.50 A 1351090 I See Footnote Common Stock 3142580 I See Footnote Represents shares purchased through the Issuer's follow-on public offering. The shares are held by Atlas Venture Fund X, L.P. ("Atlas Venture X"). Atlas Venture Associates X, L.P. ("AVA X LP"), is the general partner of Atlas Venture X, and Atlas Venture Associates X, LLC ("AVA X LLC"), is the general partner of AVA X LP. Each of AVA X LP and AVA X LLC disclaims Section 16 beneficial ownership of the securities held by Atlas Venture X, except to the extent of its pecuniary interest therein, if any. The shares are held by Atlas Venture Fund VII, L.P. ("Atlas Venture VII"). Atlas Venture Associates VII, L.P. ("AVA VII LP") is the general partner of Atlas Venture VII, and Atlas Venture Associates VII, Inc. ("AVA VII Inc.") is the general partner of AVA VII LP. Each of AVA VII LP and AVA VII Inc. disclaims Section 16 beneficial ownership of the securities held by Atlas Venture VII, except to the extent of its pecuniary interest therein, if any. /s/ Bruce Booth 2018-02-13