| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Regular Article |
a Department of Pharmacology and Therapeutics and of Obstetrics and Gynecology, McGill University, Montréal, Québec, Canada H3G 1Y6
ABSTRACT
In the epididymis a series of complex, sequential events transform immature, spermatozoa into mature, motile sperm with fertilizing ability. These events are not intrinsic to germ cells but rather are a direct result of exposure to, and interaction with, the environment created by the epididymal epithelium. Regional differences along the epididymis are essential in the establishment of the environment required for sperm maturation. Although parts of this process have been identified, the molecular basis for the segment-specific differences and how they contribute to the process of sperm maturation, are not yet resolved. The identification of genes expressed in a region-specific manner will provide valuable insight into the functional differences between the regions. To characterize gene expression in the different regions of the epididymis, microarrays containing 1176 rat cDNAs were used to examine gene expression in the initial segment, caput, corpus, and cauda epididymidis of the adult Brown Norway rat. Overall, the cauda epididymidis expressed the most genes and the corpus epididymidis the fewest. A small percentage of genes (3%) were expressed highly (greater than fivefold the average expression on the array) along the tissue. Segment-specific gene expression for genes expressed at high levels was observed in all epididymal segments except the corpus epididymidis. Of the genes on the array, 36% were expressed in all four epididymal segments; expression changes that were a minimum of twofold in either direction between adjacent segments are discussed. The expression of cathepsins and oxidative stress-related genes was investigated. Six of the eight cathepsins on the array (B, C, E, H, L, and K) were expressed above twofold background and showed different levels of expression along the duct with cathepsin K showing the most dramatic change (i.e., a decrease of 87% between the initial segment and the corpus epididymidis). There was also differential expression along the epididymis of many genes associated with oxidative stress defenses. Using the power of expression array technology, we have identified novel transcripts expressed in a segment-specific manner and been able to assess how the expression of several selected gene families is modulated along the epididymis.
epididymis, gene regulation, sperm maturation
INTRODUCTION
The epididymis, a component of the testicular excurrent duct system, is a highly specialized tissue that functions in the transport, maturation, and storage of spermatozoa [1, 2]. The maturation of spermatozoa and the acquisition of motility and fertilizing ability do not occur as a function of the passage of time, but rather as a consequence of exposure to the luminal environment of the epididymis [3]. The composition of the luminal fluid that bathes spermatozoa as they transit through the epididymis is highly complex and changes progressively along the tissue [4, 5]. The secretory and absorptive activities of the epididymal epithelium mediate the changes in the luminal fluid and thus determine the microenvironment in which spermatozoa are able to become fully mature.
The epididymal epithelium is composed of four major epithelial cell types and can be divided anatomically into four segments: the initial segment, caput, corpus, and cauda epididymidis. Whereas the division between regions may be anatomical, it is now established that discrete functions take place in the various segments. On a physiological level, this is evidenced by studies of sperm populations taken from discrete regions of the adult epididymis in which developing spermatozoa exhibit segment-related acquisition of motility and fertilizing ability [6]. The increase in the concentration of spermatozoa occurs primarily between the rete testis and the proximal epididymis and, although the bulk of the fluid secreted by the rete testis is absorbed by the efferent ducts, the cells of the proximal epididymis play a role in the reabsorption of fluid and endocytosis of proteins [2]. The extensive modifications associated with sperm maturation occur while spermatozoa traverse the caput and corpus epididymidis, and are a result of the activities of the cells in these segments. Spermatozoal motility parameters change from immotile or vibratory to direct forward movements, and membranes are remodeled; the protein composition and location of specific proteins change, glycoproteins are acquired or altered, phospholipids are removed or used, and the lipid composition of the membrane changes [2, 7]. Spermatozoa are mature; that is, they are motile and able to fertilize upon reaching the cauda epididymidis, where the cells provide a milieu that is suitable for their maintenance and storage.
The functional segmentation of the epididymis is also represented at a molecular level by regional differences in gene expression [8, 9]. Moreover, the differential response of the segments to androgen withdrawal, aging, and stress indicates that each region represents discrete regulatory units [9]. The epididymis, therefore, provides a unique opportunity to study regionalized gene expression along a duct in which functional changes are occurring in germ cells.
Using microarray technology, it is feasible to examine the expression of multiple genes and gene families simultaneously, thus providing a comprehensive picture of the gene expression profile in a tissue or cell under a given condition [10]. Major advantages of microarray techniques over other available techniques for examining the transcriptional profile of a biological sample include the increased sensitivity of the arrays, the ability to work with smaller amounts of starting material, and the extended scale of gene expression analysis possible.
Elucidation of the transcriptional profiles of the different epididymal segments is a crucial step toward uncovering the regulatory and functional differences between them. To this end, we used gene array technology to analyze gene expression in the initial segment, caput, corpus, and cauda epididymidis of the rat. In addition, particular attention was paid to the expression of cathepsins and genes related to oxidative stress. Cathepsins are cysteine proteases that play a role in protein processing and intracellular protein degradation. The epididymal epithelium is highly active in the uptake, secretion, and processing of proteins and, although these processes are crucial to sperm maturation, the molecular players involved have not yet been fully characterized. Furthermore, given the susceptibility of spermatozoa to oxidative damage and the deleterious effects that this type of damage can have on fertilizing ability [11, 12], we examined epididymal expression of genes associated with oxidative stress defenses.
MATERIALS AND METHODS
Animals
Adult male Brown Norway rats (3 mo of age) were purchased from the National Institute on Aging (Bethesda, MD) and supplied by Harlan Sprague-Dawley Inc. (Indianapolis, IN). Rats were housed at the McIntyre Animal Resources Centre, McGill University, under controlled light (14L:10D) and temperature (22°C); animals had free access to food and water. All animal studies were conducted in accordance with the principles and procedures outlined in the Guide to the Care and Use of Experimental Animals prepared by the Canadian Council on Animal Care.
Rats were killed by decapitation. Epididymides were collected; sectioned into initial segment, caput, corpus, and cauda regions; immediately frozen in liquid nitrogen; and stored at -80°C until used for RNA extraction.
RNA Extraction
Total RNA was extracted with guanidine thiocyanate (Sigma, St. Louis, MO). Briefly, tissues were ground to a fine powder in prechilled (-80°C) ceramic mortars on dry ice and dissolved in 10 volumes (ml/g) of guanidine thiocyanate solution (4 M guanidine thiocyanate, 100 mM Tris-HCL pH 7.6, 0.5% sarcosyl, 0.1 M ß-mercaptoethanol, and 50 mM EDTA) to which 1 volume of saturated phenol (Sigma) and 0.1 volume of 2 M sodium acetate pH 4 had been added. The resulting dissoluate was placed in a 2.0-ml microfuge tube and 0.1 volume of chloroform:isoamyl alcohol (49:1) was added. Following vortexing, the tubes were left on ice for 20 min and then centrifuged for 20 min (16 100 x g, 4°C). The upper phase was transferred into a 1.5-ml microfuge tube to which an equal volume of isopropanol was added. After vortexing, tubes were placed at -20°C for 1 h and then centrifuged for 20 min (16 100 x g, 4°C). The resulting pellet was washed twice with 80% ethanol and resuspended in a minimal volume of double-distilled water (ddH2O). RNA samples were DNase-treated (refer to Atlas RNA Pure Isolation Kit user manual, section IV, Clontech, Palo Alto, CA) and the concentration determined by absorbance at 260 nm (Beckman DU7 spectrophotometer, Montreal, PQ, Canada). To verify the quality of the sample, 5 µg of RNA was run on a denaturing gel containing 1% agarose-formaldehyde. Each sample consisted of a single epididymal segment obtained from individual rats; no tissues were pooled.
Complementary DNA Arrays and Hybridization
RNA samples were used to probe cDNA arrays (Clontech, Atlas Rat 1.2K) according to the manufacturer's instructions. Five arrays per epididymal segment per age group were probed and are referred to as replicates. Arrays were exposed to phosphorimager plates (Molecular Dynamics, Sunnyvale, CA) for 24 h before scanning (Storm; Molecular Dynamics). Analysis of array images with Atlas Image (Version 1.5, Clontech) was performed to quantify the intensity of each cDNA spot, which reflects the relative abundance of the RNA in the sample. The raw data for each gene (intensity of each spot on the array minus the background) were imported into Genespring (Silicon Genetics, Redwood, CA) for further analysis. In order to minimize experimental variation, data were normalized by defining the median level of expression on each array as 1 and normalizing the expression of each gene relative to 1; this value was calculated for all five replicates and averaged to generate the relative intensity for any given gene. A gene was considered as expressed if its intensity was at least twofold the average background of all the replicates in that experiment. The importance of replicates in gene array expression studies has been documented [13], therefore, changes in gene expression were considered only when they were consistent in at least three out of five replicate experiments. Moreover, gene expression changes between adjacent segments were discussed only when the difference in expression level was at least either doubled or suppressed by 50%.
Examination of the expression of genes that have a well-established expression profile along the epididymis provided a means to validate this approach. These genes were 5
-reductase type 2, a-raf, angiotensin-converting enzyme (ACE), clusterin, androgen receptor, and c-ros, and served as positive controls (Fig. 1). Clusterin and ACE had expression patterns that peaked dramatically in the caput epididymidis [14, 15]. The expression of 5-reductase type 2, a-raf, and c-ros decreased from the initial segment, reaching their lowest levels (undetectable in the case of c-ros) in the corpus and cauda epididymidis [16–18]; androgen receptor expression was unchanged along the duct [19]
|
RESULTS
The number of genes detected in each segment of the epididymis varied widely. Whereas 43% or 46% of the genes studied were expressed in the initial segment (517 out of 1176) and caput epididymidis (541 out of 1176), respectively, only 39% of the genes were expressed in the corpus epididymidis (463 out of 1176); the maximum number of genes expressed, 53%, was in the cauda epididymidis (626 out of 1176).
Of the 1176 genes on the array, approximately 3% (36) were highly expressed, at a relative intensity of five times or greater than the average expression of all genes, in all segments of the epididymis (Fig. 2). Not surprisingly, genes that code for cytoskeletal elements (cytoplasmic ß-actin, ezrin, and cofilin), protein translation (ribosomal proteins, elongation factor 2), glyceraldehyde 3-phosphate dehydrogenase, and polyubiquitin were included in this group. Other abundantly expressed genes included oxidative stress-related genes (glutathione S-transferase subunit 8, glutathione S-transferase subunit 4 mu, and copper-zinc superoxide dismutase 1), cytochrome oxidase subunit 1, cytochrome c oxidases (subunits IV, Vb, and VIa), cathepsin L, a-raf, macrophage migration inhibitory factor, ß2 microglobulin, heat stable antigen (CD24) and HSP90ß, a chaperone associated with steroid receptor function.
|
The initial segment, caput, and cauda epididymidis all showed segment specific expression of highly expressed genes. In the initial segment, the genes for c-K-ras 2b proto-oncogene, cathepsin K, proliferating cell nuclear antigen (PCNA), and sodium/dicarboxylate cotransporter are expressed exclusively and at high levels. The only gene expressed at high levels in the caput epididymidis alone was the gene for heat shock 70-kDa protein (HSP70). There were no genes expressed at high levels exclusively in the corpus epididymidis. In the cauda epididymidis, the genes that were highly expressed in a segment-specific manner were DNA binding protein inhibitor ID1, extracellular signal-regulated kinase 1 (ERK1), cyclin D2 (CCND2), I-kappa B -chain, insulin receptor-related receptor-, and STAT3.
Another subset of genes was highly expressed in more than one, but not in all, segments (Fig. 3). In the initial segment, caput, and cauda epididymidis, the genes for clusterin, DNA-binding protein inhibitor ID2, glutathione S-transferase (GST) subunit 7 pi, and an ATP synthase, were highly expressed. Insulin-like growth factor binding protein-6 (IGFBP-6) and microsomal GST were expressed above a relative intensity of five in the initial segment, corpus, and cauda epididymidis. One gene, fibroblast growth factor-activating protein, was expressed at high levels in the caput, corpus, and cauda epididymidis. Finally, in the corpus and cauda epididymidis, the genes for serotonin receptor subtype 5B (HTR5B), ATPase F, DNA-binding protein inhibitor ID3, sodium/potassium-transporting-ATPase ß1, ornithine decarboxylase, and platelet-derived growth factor-associated protein were highly expressed.
|
Segment Specificity of Gene Expression
Genes that were expressed above twofold background in all four segments of the epididymis make up approximately 36% (425 out of 1176) of all the genes on the array. In order to provide more insight into the selective regional gene expression along the epididymis, genes that were expressed at least twice or at half the levels in one segment as compared to the adjacent segment, are discussed (Fig. 4).
|
Initial Segment and Caput Epididymidis
Between the initial segment and the caput epididymidis, more genes decreased in expression than increased (21 and 11, respectively). It is interesting that transcripts for three genes involved in glutathione metabolism (epididymal secretory glutathione peroxidase, glutathione synthetase, and glutathione S-transferase subunit 7 pi) decreased between these two regions. The expression of 3ß-hydroxysteroid dehydrogenase (3ßHSD), an essential enzyme in androgen biosynthesis, and cytochrome P450 IB1, an enzyme that catalyzes the 4-hydroxylation of 17ß-estradiol, also decreased in the caput epididymidis. Other genes that decreased in expression included cysteine-rich protein 2 (CRP2), neuropeptide Y5 receptor, and cyclin D1 (CCND1). The genes that increased in the caput epididymidis from the initial segment included clusterin, a well-characterized glycoprotein; angiotensin converting enzyme (ACE), an enzyme that plays a role in the regulation of ion flux in the epididymis; HSP70; and the adenosine A1 receptor.
Caput and Corpus Epididymidis
Between the caput and corpus epididymidis, a similar number of genes increased (15) and decreased (13) in expression. In the caput, the genes for steroid 5-reductase 2, cathepsin K, HSP70, prostaglandin F2 receptor, and the DNA-binding protein inhibitor ID2 were expressed at greater levels than they were in the corpus. In contrast, expression of c-neu, cysteine rich protein 2, and ornithine decarboxylase, a rate limiting enzyme in polyamine synthesis, increased between these two regions.
Corpus and Cauda Epididymidis
The vast majority of genes that changed by twofold or more between the corpus and cauda epididymidis increased in expression (37 increased, 5 decreased). The genes expressed at higher levels in the corpus epididymidis were the cAMP-dependent protein kinase inhibitor (testis form), ACE, glycerol kinase, and the interleukin receptor 2A alpha chain. It is interesting that all of the DNA binding protein inhibitors on the array (ID1, ID2, and ID3) and many of the insulin-like growth factor-binding proteins (IGFBP-1, IGFBP-3, IGFBP-5, and IGFBP-6) had increased expression in the cauda epididymidis. Other genes that had increased expression in the cauda epididymidis were ornithine decarboxylase, cyclin D2, and the receptors for 5-hydroxytryptamine (serotonin receptor 5B) and neuropeptide Y (NPY receptor 5Y).
Gene Families
Besides revealing the expression of novel genes, microarray technology can add to our understanding of the expression of gene families that are known to be important in the epididymis. Specifically, we examined the expression of cathepsins and genes involved in oxidative stress defenses.
Cathepsins
Of the eight cathepsins on the array (cathepsins B, C, D, E, H, L, K, and S), all but cathepsins D and S were expressed above twofold background in all four segments of the epididymis (Fig. 5). Cathepsin E expression increased (1.9-fold) between the initial segment and the caput epididymidis and was relatively unchanged (less than a 1.5-fold change) along the rest of the tissue. Cathepsin C expression decreased (slightly less than 50%) between these two regions but increased by twofold between the corpus and cauda epididymidis. Cathepsin H expression increased by 1.5-fold between the caput and the corpus epididymidis. Cathepsin K expression decreased dramatically (87%) between the initial segment and corpus epididymidis and remained constant in the cauda. Expression levels of cathepsins L and B changed by less than 1.5-fold along the epididymis.
|
Oxidative Stress-Related Genes
The expression of glutathione synthetase (GSH synthetase), one of the enzymes involved in glutathione biosynthesis, decreased dramatically (71%) between the initial segment and the caput epididymidis and increased (1.5-fold) between the corpus and the cauda epididymidis. Epididymal secretory glutathione peroxidase (GPX5) was expressed in the initial segment of the epididymis but decreased to very low levels in the caput epididymidis and along the rest of the tissue. Phospholipid hydroperoxide glutathione peroxidase (GPX4) was also expressed along the epididymis; its expression did not change by more than 1.2-fold in the proximal regions of the tissue but increased by 1.8-fold between the corpus and cauda epididymidis. Another peroxidase, thioredoxin peroxidase, which in its monomeric form will scavenge oxidants to protect cellular components, was expressed at very low, invariant levels (less than a 1.5-fold change) along the epididymis. Copper-zinc superoxide dismutase (CuZn-SOD) was expressed at very high levels that did not vary by more than 1.2-fold along the epididymis (Fig. 6). Eight glutathione S-transferases (GSTs) were present on the array, five of which were expressed above background along the epididymis (Fig. 7). GST subunit 13 expression changed only between the corpus and cauda epididymidis, where it increased by 2.3-fold. The expression of GST subunit 7 pi (GST7-7) decreased by 82% between the initial segment and corpus epididymidis, then increased by 1.7-fold in the cauda epididymidis. Similarly, microsomal GST (GST12; MGST1) expression decreased (37%) between the initial segment and caput, then increased by 1.7-fold in the corpus and cauda epididymidis. The expression of GST subunit 4 mu (GSTM2) and GST subunit 8 changed by less than 1.4-fold throughout the length of the tissue.
|
|
DISCUSSION
Microarray technology is a powerful and efficient way to investigate region-specific gene expression along the epididymis. Many genes have been reported to be expressed exclusively, or at their highest levels, in the proximal epididymis [8, 9]. By comparison, few examples of regional specificity have been described in the distal epididymis [8, 9], thus leaving gene expression in the cauda region relatively unexplored. Based on histological evidence, one would expect the caput epididymidis, the segment that has a very extensive supranuclear Golgi complex and endoplasmic reticulum [2] to be the most active segment in terms of protein synthesis; yet studies in which total protein synthesis was assessed by 35S-methionine incorporation along the epididymis [20, 21] have suggested that the highest rate of protein synthesis was in the cauda epididymidis. Our results are consistent with the protein synthesis studies in that the cauda epididymidis expressed more genes overall, and more genes at high levels, than the caput epididymidis. It is interesting that in the corpus epididymidis, the adjacent segment, gene expression was lower in both proportion and level than in any other epididymal region.
Highly Expressed Genes
Genes expressed at high levels in the epididymis, particularly in a segment-specific manner, were of particular interest. In the initial segment, cathepsin K was one such gene. Several members of the cathepsin family of lysosomal cysteine proteases have been localized in the rat epididymis. Cathepsins are known to be involved in intracellular protein degradation [22]; however, the discovery of new family members with tissue-specific expression has led to the speculation that certain cathepsins have more specialized functions than simple housekeeping enzymes [23]. Cathepsin K, one of the more recently discovered cathepsins, plays a central role in bone reabsorption and acts extracellularly in both osteoclasts [24] and thyrocytes [25]. The identification of transcripts for proteases such as cathepsin K that are expressed in a segment-specific manner supports the hypothesis that proprotein processing is an important event in sperm maturation and that different proteins may be processed in different epididymal regions [7, 26]. In addition to the modification of sperm plasma membrane proteins, the uptake of secreted epididymal proteins is another facet of epididymal sperm maturation [27, 28]. Interestingly, the transcript for hsp70, a sperm plasma membrane protein [29], is expressed at high levels exclusively in the caput epididymidis. Segment-specific gene expression such as this may provide insight into genes involved in sperm maturation.
Twofold or Greater Changes in Gene Expression Between Adjacent Segments
Analysis of those genes that changed by a minimum of twofold between adjacent segments is one way to highlight the relative importance of different genes in different regions. The initial segment, when compared with the caput epididymidis, expressed higher levels of cytochrome P450 IB1 and 3ß-HSD, genes involved in steroid metabolism [30, 31]. The initial segment is the first epididymal segment exposed to testicular factors and hormones via the luminal fluid and is the most dramatically affected by their withdrawal [32, 33]. The activity and the messages for 5-reductases, enzymes that metabolize testosterone to dihydrotestosterone, the active androgen in the epididymis, are most abundant in the proximal epididymis [16]. Aside from endocrine factors and direct testicular input, factors that act in a paracrine manner are also believed to play a role in regulating epididymal epithelial function [34–36]. Neuropeptide Y, a peptide that modulates the central gonadotropic axis via the Y5 receptor subtype in the rat hypothalamus [37], is expressed in the epididymis [38] and may be one such factor. We found it interesting that NPY Y5 receptor expression also decreased from the initial segment to the caput epididymidis.
In the caput epididymidis, the gene for ACE was expressed at a higher level than in the adjacent segments. The regulation of fluid and ion secretion is crucial in order to develop the optimal environment for sperm maturation and storage [2, 4]. Several humoral factors, including angiotensins and prostaglandins, are believed to act locally in the epididymis to regulate anion secretion [39]. It is interesting that prostaglandin F2 receptor expression, like that of ACE, decreased between the caput and the corpus epididymidis.
Only a few genes, such as ornithine decarboxylase (ODC), for example, were expressed at twofold higher levels in the corpus epididymidis than in the caput epididymidis. ODC is a rate-limiting enzyme in the biosynthesis of polymines, such as spermine, spermidine, and putrescine [40].
In the cauda epididymidis, two groups of genes, insulin-like growth factor binding proteins (IGFBPs) and DNA binding protein inhibitors (IDs), were expressed at twofold or greater levels than in the corpus epididymidis. Insulin-like growth factors, small peptides that regulate cellular growth, differentiation, and metabolism, act by binding to high-affinity cell surface receptors. IGF-I is known to modulate Leydig and Sertoli cell function and IGF-I null mutant mice are infertile [41]. IGF-I has been localized in the caput and cauda epididymal regions of the postnatal epididymis [42]. IGFs are bound in serum and other biological fluids by binding proteins (IGFBPs) that compete with binding of IGF receptors and thus modulate IGF action [43]. That four of the six known IGFBPs were expressed in the cauda epididymidis at levels twofold higher than those observed in the corpus indicates that IGFs may play a role in the cauda epididymidis.
ID proteins, members of the basic helix-loop-helix (bHLH) family of transcription factors that lack DNA binding domains [44], were expressed at at least twofold greater levels in the cauda than any other epididymal region. These proteins act as dominant negative regulators of bHLH transcription factors by forming inactive heterodimers with them and inhibiting their DNA-binding and transcriptional activities [44]. Whereas the profile of transcriptional activators expressed in the cauda epididymidis is relatively unknown, the expression of such high levels of transcriptional repressors is suggestive of bHLH activity in this epididymal segment.
Gene Families
Cathepsins are cysteine proteases that play a role in the degradation and processing of proteins [22]. One of the primary activities of the epididymal epithelium is the endocytosis and degradation of luminal contents [2, 45]. In addition, it is now believed that the epididymis produces proteases that participate in propeptide processing and sperm maturation [7, 26]. Cathepsins A, B, D, H, and L have been localized immunohistochemically in the rat epididymis [46–48] and enzyme assays have been performed for cathepsins B, H, and L [48]. In addition to cathepsin B, H, and L, which were detected along the entire tissue, cathepsins E, C, and K were expressed in all four segments of the epididymis. Cathepsin L expression was much higher than the other cathepsins, however, expression did not fluctuate much between the different epididymal regions. In contrast, cathepsin K was expressed highly in a segment-specific manner; between the initial segment and corpus epididymidis its expression decreased by almost 90%. Because cathepsins have different substrate specificities, mechanisms of activation and endogenous inhibitors and are regulated differently by pH [23], it is thus not surprising to observe that most cathepsin transcripts had different expression patterns along the epididymis and, in any given segment, were expressed in varied abundance.
It is widely recognized that epididymal spermatozoa are highly susceptible to damage resulting from reactive oxygen species (ROS) [11, 12]. Spermatozoa have little in the way of intracellular antioxidant enzymes and high concentrations of membrane lipids (polyunsaturated fatty acids) that are particularly vulnerable to peroxidative damage [49]. Spermatozoa also produce ROS (hydrogen peroxide and superoxide) that are essential for capacitation and chromatin condensation [49]. Thus the epididymal epithelium must be able to protect spermatozoa and itself from oxidative damage. The epididymis is a rich source of antioxidant enzymes [50, 51]. Several of the antioxidant-related genes on the array we used were expressed along the tissue with relatively little regional differences. Strikingly, the expression of GSTpi, a class of GST that has been immunolocalized in the epididymis of the rat [52], decreased remarkably (82%) between the initial segment and the corpus epididymidis. GSTpi functions in the metabolism of xenobiotics and has been implicated in carcinogenesis and the acquisition of antineoplastic drug resistance [53]. Such high expression in the initial segment of the epididymis may indicate the presence of a preferred substrate in the proximal epididymis.
In this study, we have exploited the power of microarray technology to investigate region-specific gene expression along the epididymis. We have identified the segment-specific expression of several genes never before described in the epididymis. Moreover, we describe the expression of new members of gene families that are known to be important in epididymal physiology.
FOOTNOTES
First decision: 26 March 2001.
1 Supported by grants from CIHR and the National Institutes of Health (NIA-AG08321). 
2 Correspondence: B. Robaire, Department of Pharmacology and Therapeutics,
McGill University, 3655 Promenade Sir-William-Osler, Montréal,
PQ, Canada H3G 1Y6. FAX: 514 398 7120;brobaire{at}pharma.mcgill.ca
Accepted: April 10, 2001.
Received: February 27, 2001.
REFERENCES
This article has been cited by other articles:
|
|
 |
|
  V. Thimon, E. Calvo, O. Koukoui, C. Legare, and R. Sullivan Effects of Vasectomy on Gene Expression Profiling along the Human Epididymis Biol Reprod, August 1, 2008; 79(2): 262 - 273. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Dube, L. Hermo, P. T.K Chan, and D. G Cyr Alterations in Gene Expression in the Caput Epididymides of Nonobstructive Azoospermic Men Biol Reprod, February 1, 2008; 78(2): 342 - 351. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. Thimon, O. Koukoui, E. Calvo, and R. Sullivan Region-specific gene expression profiling along the human epididymis Mol. Hum. Reprod., October 1, 2007; 13(10): 691 - 704. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Prabagaran, U. C. Hegde, S. B. Moodbidri, A. H. Bandivdekar, and V. P. Raghavan Postnatal Expression and Androgen Regulation of HOXBES2 Homeoprotein in Rat Epididymis J Androl, September 1, 2007; 28(5): 755 - 771. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Dube, P. T.K. Chan, L. Hermo, and D. G. Cyr Gene Expression Profiling and Its Relevance to the Blood-Epididymal Barrier in the Human Epididymis Biol Reprod, June 1, 2007; 76(6): 1034 - 1044. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Jelinsky, T. T. Turner, H. J. Bang, J. N. Finger, M. K. Solarz, E. Wilson, E. L. Brown, G. S. Kopf, and D. S. Johnston The Rat Epididymal Transcriptome: Comparison of Segmental Gene Expression in the Rat and Mouse Epididymides Biol Reprod, April 1, 2007; 76(4): 561 - 570. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Prabagaran, A.H. Bandivdekar, V. Dighe, and V.P. Raghavan HOXBES2: A Novel Epididymal HOXB2 Homeoprotein and Its Domain-Specific Association with Spermatozoa Biol Reprod, February 1, 2007; 76(2): 314 - 326. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Seenundun and B. Robaire Time-Dependent Rescue of Gene Expression by Androgens in the Mouse Proximal Caput Epididymidis-1 Cell Line after Androgen Withdrawal Endocrinology, January 1, 2007; 148(1): 173 - 188. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. A. Henderson, G. M Cooke, and B. Robaire Region-specific expression of androgen and growth factor pathway genes in the rat epididymis and the effects of dual 5{alpha}-reductase inhibition. J. Endocrinol., September 1, 2006; 190(3): 779 - 791. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A Glover and S J Assinder Acute exposure of adult male rats to dietary phytoestrogens reduces fecundity and alters epididymal steroid hormone receptor expression. J. Endocrinol., June 1, 2006; 189(3): 565 - 573. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Carroll, M. Hamzeh, and B. Robaire Expression, Localization, and Regulation of Inhibitor of DNA Binding (Id) Proteins in the Rat Epididymis J Androl, March 1, 2006; 27(2): 212 - 224. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. S. Johnston, S. A. Jelinsky, H. J. Bang, P. DiCandeloro, E. Wilson, G. S. Kopf, and T. T. Turner The Mouse Epididymal Transcriptome: Transcriptional Profiling of Segmental Gene Expression in the Epididymis Biol Reprod, September 1, 2005; 73(3): 404 - 413. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. E. Olson, V. P. Winfrey, S. K. NagDas, and M. H. Melner Region-specific Expression and Secretion of the Fibrinogen-related Protein, fgl2, by Epithelial Cells of the Hamster Epididymis and Its Role in Disposal of Defective Spermatozoa J. Biol. Chem., December 3, 2004; 279(49): 51266 - 51274. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Davies, C. Baumann, C. Kirchhoff, R. Ivell, R. Nubbemeyer, U.-F. Habenicht, F. Theuring, and U. Gottwald Targeted Deletion of the Epididymal Receptor HE6 Results in Fluid Dysregulation and Male Infertility Mol. Cell. Biol., October 1, 2004; 24(19): 8642 - 8648. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. M. Jervis and B. Robaire The Effects of Long-Term Vitamin E Treatment on Gene Expression and Oxidative Stress Damage in the Aging Brown Norway Rat Epididymis Biol Reprod, October 1, 2004; 71(4): 1088 - 1095. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Saez, C. Legare, J. Laflamme, and R. Sullivan Vasectomy-Dependent Dysregulation of a Local Renin-Angiotensin System in the Epididymis of the Cynomolgus Monkey (Macaca fascicularis) J Androl, September 1, 2004; 25(5): 784 - 796. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Sutovsky, R. Hauser, and M. Sutovsky Increased levels of sperm ubiquitin correlate with semen quality in men from an andrology laboratory clinic population Hum. Reprod., March 1, 2004; 19(3): 628 - 638. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Hsia and G. A. Cornwall DNA Microarray Analysis of Region-Specific Gene Expression in the Mouse Epididymis Biol Reprod, February 1, 2004; 70(2): 448 - 457. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Chen, P. H. Chow, S. K. Cheng, A. L. M. Cheung, L. Y. L. Cheng, and W.-S. O Male Genital Tract Antioxidant Enzymes: Their Source, Function in the Female, and Ability to Preserve Sperm DNA Integrity in the Golden Hamster J Androl, September 1, 2003; 24(5): 704 - 711. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Hu, Z. Zhou, C. Xu, Q. Shang, Y.-D. Zhang, and Y.-L. Zhang Androgen Down-Regulated and Region-Specific Expression of Germ Cell Nuclear Factor in Mouse Epididymis Endocrinology, April 1, 2003; 144(4): 1612 - 1619. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Shariatmadari, P. Sipila, M. Vierula, K. Tornquist, I. Huhtaniemi, and M. Poutanen Adenosine Triphosphate Induces Ca2+ Signal in Epithelial Cells of the Mouse Caput Epididymis Through Activation of P2X and P2Y Purinergic Receptors Biol Reprod, April 1, 2003; 68(4): 1185 - 1192. [Abstract] [Full Text] [PDF]
|
|
|
|
Only reported in murine epididymis. Both italicized and underlined genes are genes that have not been reported previously in the epididymis; the former are those that were expected due to their ubiquitous distribution, whereas the latter have not been previously described in the epididymis and are not ubiquitous. Ribosomal proteins, ribosomal protein L11, L12, L13; 40S ribosomal protein, S11, S12, S3A; 60S ribosomal protein, L19, L21, L44. GAPDH, glyceraldehyde 3-phosphate dehydrogenase; GST, glutathione S-transferase; Cu-Zn SOD1, copper-zinc superoxide dismutase 1; cytochrome oxidase, subunit I; cytochrome c oxidases, subunits IV, Vb, and VIa; MIF, macrophage migration inhibitory factor; HSP, heat shock protein; ANT2, adenine nucleotide translocator 2; CABP2, calcium binding protein 2; PCNA, proliferating nuclear cell antigen; Na+/dicarbox. cotransporter, sodium/dicarboxylate cotransporter; ID1, DNA binding protein inhibitor 1; ERK1, extracellular signal-regulated kinase 1; IRR
