Exhibit 99.1

Signature of Reporting Persons:

This statement on Form 4 is filed by Versant Venture Capital III, L.P. and
Versant Side Fund III, L.P. The principal business address of each of the
reporting persons is 3000 Sand Hill Road, Bldg. 4, Ste. 210, Menlo Park,
California 94025. The reporting entities disclaim beneficial ownership of the
securities listed herein except to the extent of their ecuniary interest
therein.

Versant Venture Capital III, L.P.

By:  Versant Ventures III, LLC
     its General Partner

By:  /s/ Robin L. Prager, Attorney-in-Fact
     --------------------------------------
     Robin L. Prager, Attorney-in-Fact

Versant Side Fund III, L.P.

By:  Versant Ventures III, LLC
     its General Partner

By:  /s/ Robin L. Prager, Attorney-in-Fact
     -------------------------------------
     Robin L. Prager, Attorney-in-Fact