Differential gene expression profiles of human efferent ducts and epididymis

Mammalian spermatozoa acquire their fertilizing ability during epididymal transit. Gene expression patterns along the epididymis are established by specific transcription factor networks that coordinate region-specific functions. The epididymis is usually divided into 3 segments: caput, corpus, and cauda. The human epididymis anatomy does not allow clear distinction between these three segments. To determine to which extent gene expression is segmented along the human epididymis, transcriptome profiling was performed on 8 distinct epididymal regions from 3 donors. Microarray analysis was performed on a Gene Chip Human Clariom S (Affymetrix®) array representing 337 100 transcriptional variants encoded by 20 800 genes. Proximal segments 1 to 3 were distinguishable from the distal epididymal segments (4 to 8) as shown by unsupervised Principal Component Analysis. Transcripts from each segment with differentially expressed genes (DEGs) > 2-fold change and FDR < 0.05 were clustered in relation to their intensity profiles. While no DEGs were detected between segments 1–3 corresponding to the efferent ducts, 1140 DEGs were detected between efferent ducts (1–3) and the epididymis (4–8), 400 between caput (4–6) vs. corpus/cauda (7–8) and none between corpus (7) and cauda (8). Gene Ontology annotation revealed that up-regulated DEGs in the efferent ducts (1–3) were predominantly related to cilium assembly/movement and cell differentiation. The biological process terms fertilization, defense and immune responses were associated with caput epididymis (4–6) while spermatogenesis and protein binding were found all along the epididymis (4–8). In conclusion, the proximal human epididymis is exclusively occupied by efferent ducts with a distinct DEG profile compared with the downstream epididymal segments. Moreover, gene expression profiling revealed two regions in the human epididymis; the caput and the distal corpus/cauda region. Taken together, analysis of the human epididymal transcriptome reveals a limited DEG profile. Human epididymides were obtained through our local organ transplantation program after obtaining written consent from the families as previously described. Donors were 37, 50 and 52 years of age with no known medical pathologies that could affect reproductive function. Epididymides anatomically defined as an organ found on the surface of the testis, were dissected into 8 sections as illustrated in Figure 1A. According to human epididymal histology, sections 1–3 correspond to efferent ducts. The caput, corpus and cauda segments are less well defined and are referred to sections 4–6, 7 and 8, respectively. Each section was dissected into small tissue pieces that were snap-frozen in liquid nitrogen and stored at −80°C until use.