Transcriptional profile associated with human oocyte meiotic maturation

The transition from a transcriptionally active state (GV) to a transcriptionally inactive state (mature MII oocytes) is one of the requirements for the acquisition of oocyte developmental competence. After maturation, oocytes are mostly transcriptionally quiescent, and developmental competence prior to embryonic genome activation (EGA) relies on maternal RNA and proteins. The landscape of expressed genes at the MII stage could be mostly driven by post-transcriptional mechanisms, such as alternative splicing (AS). With the development of single cell transcriptome analysis, genome wide AS analysis becomes technically feasible and available to fully characterize the AS patterns in human oocytes. Profiling spliced mRNA isoforms might provide novel information on the molecular mechanisms driving early development, and might be a source of potential biomarkers of oocyte quality. The goal of the present study is to perform a transcriptomic analysis in oocytes at different stages of maturation, to identify the profiles of alternative spliced isoforms produced in both oocyte’ stages. A total of 12 in vivo matured (MII) and 4 non-matured (GV stage) oocytes from 16 women undergoing oocyte donation were included in this study, processed and analyzed individually. Average women age was 28 ± 4.7 years (range 21-34), with a mean antral follicle count (AFC) of 21 ± 10.7 follicles (range 5-43). Oocytes were divided in 4 experimental groups (4 oocytes in each group) according to their maturation stage, and the age and AFC of the women (mean ± SD): GV oocytes from women up to 30 years old with high AFC (GV group; 26±4.1 years old and 27±13 follicles), MII oocytes from women up to 30 years old with high AFC (H-MII group; 26±4.6 years old and 24±3 follicles), MII oocytes from women with low AFC (L-MII group; 27±5.4 years old and 7±1 follicles) and MII oocytes from women above 31 years old with high AFC (O-MII group; 32.8±1.5 years old and 27±6 follicles). Total RNA from each oocyte independently was isolated, amplified, labeled, and hybridized on HTA 2.0 arrays (Affymetrix).