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(82) COORDINATED REGULATION OF TRANSCRIPTS ENCODING ADAMTS-1 AND PROGESTERONE RECEPTOR IN EQUINE PREOVULATORY FOLLICLES. Boerboom, Derek1,2, Russell, Darryl1, Richards, JoAnne1, Sirois, Jean2, 1 Department of Molecular and Cellular Biology, Houston, TX2 Centre de Recherche en Reproduction Animale, St-Hyacinthe, Canada ABSTRACT- The localized breakdown of the connective tissues of the follicle wall that leads to ovulation is presumed to result from the LH-induced activation of specific proteolytic activities. However, despite intense efforts, the enzyme(s) involved in this process have yet to be unequivocally identified. Recently, a disintegrin and metalloproteinase with thrombospondin-like motifs-1 (ADAMTS-1) has been identified as a proteolytic enzyme that is transiently induced in the granulosa cell layer of rodent ovarian follicles following the LH surge. Subsequent pharmacological and genetic studies situated this ADAMTS-1 induction downstream of the induction of progesterone synthesis and progesterone receptor (PR) expression. Furthermore, the targeted disruption of ADAMTS-1 resulted in ovarian defects associated with severely impaired fertility. To elucidate the putative role for ADAMTS-1 in the ovulatory process of large monoovulatory species, a 3573 bp transcript was isolated from an equine follicular cDNA library, and was found to encode a nearly complete ADAMTS-1 homolog. When aligned, the region encompassing the catalytic domain, disintegrin-like domain, cystein-rich domain, spacer region and thrombospondin-1 motifs was found to be 95%, 92% and 92% identical to human, mouse and rat ADAMTS-1, respectively. The regulation of ADAMTS-1 and PR mRNAs in ovarian cells during the hCG-induced ovulatory process was then studied by real-time RT-PCR analysis using the LightCycler system. ADAMTS-1 was found to be markedly induced by 12 h post-hCG in granulosa cells (P < 0.01), followed by a 35-fold drop in expression by 30 h, and re-increased by 36 h (P < 0.05). Highest levels of ADAMTS-1 expression were identified in mature (day 8) corpora lutea (CL). A nearly identical pattern of expression was found for PR in granulosa cells, which also attained peak levels at 12 h and 36 h, with a minimum at 30 h. Unlike ADAMTS-1 however, no PR was detected in the CL. Together, these data suggest a tight coupling of ADAMTS-1 and PR expression in equine preovulatory follicles, consistent with genetic data that defined PR as an upstream regulator of ADAMTS-1 expression. Furthermore, this study provides an important model system for the future study of ovarian ADAMTS-1 function in monoovulatory species. KEY WORDS: granulosa cells, ovulation, ADAMTS-1, progesterone receptor |
