Ovarian follicular cysts are one of the most common causes of reproductive failure in mammals. A comparative gene expression approach may aid in elucidating the causes of ovarian cyst disease. In the present study, the differential display technique was used to identify mRNA sequences that accumulate preferentially in theca cells of bovine cystic follicles. Dedicator of cytokinesis 6 (Dock6) expression was observed in the theca cells of cystic follicles. Small interfering RNA (siRNA) knockdown of Dock6 increased progesterone (P4) production and StAR expression in theca cells of high-estrogen follicular cysts, but did not affect androstenedione (A4) production. We propose that Dock6 may be a marker associated with the development of follicular cysts. Additionally, Dock6 may be involved in the development of cystic follicles by suppressing P4 production rather than increasing A4 production in theca cells. (C) 2015 Elsevier Inc. All rights reserved.