title: Transcriptome analysis of bull semen with extreme nonreturn rate: use of suppression-subtractive hybridization to identify functional markers for fertility.
abstract: Spermatozoa are terminally differentiated cells produced during the complex process of spermatogenesis. Although the role of their residual RNA content is still being debated, this transcriptome may represent a fingerprint of spermatogenesis quality. In the present study, we undertook differential transcript profiling of spermatozoa from fertile bulls with extreme nonreturn rates (NRRs): a low-fertile group, and a high-fertile group. Using the suppression-subtractive hybridization technique in combination with macroarray analysis, we also identified novel genes. Both extreme NRR index groups retained redundant identity, such as ribosomal and mitochondrial sequences, at a statistically significant level. An elevated number of 12S, 18S, and Large Chain R rRNA gene copies were found in low-fertile bulls and validated in spermatozoa by quantitative RT-PCR for a small cohort of bulls with known fertility index. Whereas the high-NRR library exhibited a large proportion (29%) of transcripts associated with known functions (e.g., metabolism, signal transduction, translation, glycosylation, and protein degradation), only 10% of the low-NRR sequences did. This difference is also conveyed by two other categories: 17% Bovine Genome and 48% unknown in the high-NRR library, compared with 3% and 80%, respectively, in the low-NRR library. Some of the unknown transcripts are similar to expressed sequence tags detected in the male reproductive organ of certain plants and retain homology to a putative human protein. Whereas the individual transcriptome profiles may be useful in fertility assessment, these findings also suggest cross-species conservation, could contribute to a better understanding of spermatogenesis, and provide new insights regarding idiopathic infertility.
authors.affiliation: Dairy and Swine Research and Development Center, Agriculture and Agri-Food Canada, Sherbrooke, Quebec, Canada J1M 1Z3.
authors.forename: C
authors.initials: C
authors.lastname: Lalancette
authors.forename: C
authors.initials: C
authors.lastname: Thibault
authors.forename: I
authors.initials: I
authors.lastname: Bachand
authors.forename: N
authors.initials: N
authors.lastname: Caron
authors.forename: N
authors.initials: N
authors.lastname: Bissonnette
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000235:genetics; D005298:Fertility / Q000235:genetics*; D020869:Gene Expression Profiling; D015723:Gene Library; D007248:Infertility, Male / Q000235:genetics / Q000662:veterinary; D008297:Male; D009693:Nucleic Acid Hybridization / Q000379:methods*; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012661:Semen / Q000737:chemistry*
chemical_list: D012333:RNA, Messenger