|Cushman, Robert - Bob|
Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/29/2005
Publication Date: 7/20/2005
Citation: Cushman, R.A., Allan, M.F., Christenson, R., Echternkamp, S.E. 2005. Differential gene expression in the ovarian cortex of cows selected for multiple ovulations [abstract]. Biology of Reproduction. (Supplement):188. (Abstract #W483)
Technical Abstract: Cattle selected for multiple ovulations have greater numbers of growing preantral and antral follicles, and the current MARC herd has an ovulation rate of 1.81 +/ 0.02 follicles per estrous cycle. Anti-mullerian hormone (AMH) and growth differentiation factor-9 (GDF-9) are two members of the transforming growth factor-beta (TGF-beta) family of growth factors with known functions in follicular development. Both genes have been previously mapped to bovine chromosome 7 in the approximate region containing a QTL for ovulation rate. Therefore, we hypothesized that enhanced follicular development in selected cattle (Twinners) might be due to changes in mRNA expression for these factors. Total cellular RNA was extracted from 250 mg of ovarian cortex of Twinner (n = 37) and non-Twinner (n = 28) cows, treated with DNAse I, and was used for quantification by real-time RT-PCR using the SYBR Green reporter method. Specific primers were used for bovine AMH and GDF-9 with GAPDH as an internal control. AMH primers spanned the intron between exons 5 and 6, and visualization of amplicons on a 2% agarose gel confirmed efficacy of the DNAse digest. Relative levels were calculated by the delta-CT method and were analyzed for line effect using the MIXED procedure of SAS. AMH mRNA was significantly greater (P = 0.0018) in Twinner ovarian cortex as compared to ovarian cortex from non-Twinners (delta-CT = 2.06 +/ 0.48 vs. 0.01 +/ 0.41). However, there was no difference in levels of GDF-9 mRNA between Twinners and non-Twinners (delta-CT = 2.5 +/ 0.17 vs. 2.4 +/ 0.14). A study from another laboratory demonstrated that addition of AMH to cultures of isolated rat preantral follicles enhanced FSH-stimulated growth in 2- and 4-day cultures. Therefore, the increased expression of AMH in the ovarian cortex of Twinners may result in enhanced follicular development, possibly by increasing responsiveness to FSH.