Male Reproductive Tract

The Rat Epididymal Transcriptome: Comparison of Segmental Gene Expression in the Rat and Mouse Epididymides

Abstract
Regional differences along the epididymis are essential for the establishment of the luminal environment required for sperm maturation. In the current study, 19 morphologically distinct segments of the rat epididymis were identified by microdissection. Total RNA was isolated from each segment and subjected to microarray analysis. Segmental analysis of epididymal gene expression identified more than 16,000 expressed qualifiers, whereas profiling of RNA from whole rat epididymis identified approximately 12,000 expressed qualifiers. Screening a panel of normal rat tissues identified both epididymal-selective and epididymal-specific transcripts. In addition, more than 3,500 qualifiers were shown to be present and differentially expressed, up or down, by more than four-fold between any two segments. This current study complements our previous segment-dependent analysis of gene expression in the mouse epididymis and allows for comparative analyses between datasets. A total of 492 genes were shown to be present on both the MOE430 (mouse) and RAE230_2 (rat) microarrays, expressed in the epididymis of both species and differentially expressed in between segments in each species by more than 4-fold. Moreover, an in-depth qRT-PCR analysis of 36 members of the beta defensin gene family showed highly conserved patterns of expression along the length of both the mouse and rat epididymides. These analyses elucidate global gene expression patterns along the length of the rat epididymis and provide a novel evaluation of conserved and nonconserved gene expression patterns in the epididymides of the two species. Furthermore, these data provide a powerful resource for the research community in future studies of biological factors that mediate sperm maturation and storage.

Key words: Epididymis • Gene regulation

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