Post-transcriptional gene regulation in ovarian granulosa cells

Abstract

High throughput gene expression analysis before and after the LH surge has provided insight into the diversity of ovarian genes involved in oocyte maturation, ovulation, and luteinization. However, steady state gene expression analysis is influenced by a number of post-transcriptional events that can impact the ability of an mRNA transcript to be translated, such as mRNA splicing, localization, degradation, and stability. To characterize LH-induced post-transcriptional gene regulation in ovarian cells, we analyzed mRNA associated with multiple ribosomes (i.e., polysomal RNA) by microarray. Polysomal RNA corresponds closely to protein synthesis. Polysomal RNA was collected by sucrose gradient fractionation. Both total and polysomal RNA samples were hybridized to 16 Affymetrix 430A gene array chips following two rounds of linear amplification. Of the genes expressed in granulosa cells, 21% exhibit a greater than 1-fold difference between their total and polysomal levels 1h after LH. This is the group of genes that exhibit some form of post-transcriptional gene regulation. Quantitative real-time RT-PCR was used to validate the arrays and examine the temporal changes of the genes. These results suggest that LH uniquely influences post-transcriptional gene regulation of a subset of genes to affect translation independent of transcription.