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a Graduate Institute of Life Science,
b Department of Biology and Anatomy,
c Institute of Preventive Medicine, National Defense Medical Center, Taipei, Taiwan 114, Republic of China
d Division of Urology, Department of Surgery, Tri-Service General Hospital, Taipei, Taiwan 114, Republic of China
e Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 115, Republic of China
ABSTRACT
Mammalian spermatozoa interact with the proteins secreted by the epididymis to develop fertility. Transmembrane proteins that possess a disintegrin and metalloprotease (ADAM) domains are shown to be closely related to spermatogenesis and fertilization. Our previous study demonstrated that GP-83, a glycoprotein secreted by the epididymis, was conjugated to mature sperm. In this study, a 2.1-kilobase (kb) GP-83-expressing insert was isolated from a cDNA library of human epididymis by immunoscreening using GP-83-specific antiserum. The 5' end rapid amplification of cDNA ends (RACE) and 3'-RACE of the 2.1-kb insert elucidated two isoforms of GP-83-encoding cDNA sequences, an
-form of 3451 base pairs (bp) and ß-form of 2643 bp. Both forms exhibit the same open reading frame of 2262 bp predicting a peptide of 754 amino acid residues. Deduced amino acid sequence revealed signal sequence, prodomain, metalloproteinase, disintegrin, cysteine-rich, epidermal growth factor-like, transmembrane, and cytoplasmic domains. The GP-83-encoding sequence was recognized as human ADAM7 due to significant homology to other ADAM7s. According to the DNA sequences elucidated in the Human Genome Project, h-ADAM7 was located at chromosome 8p22. Ex vivo expression confirmed that h-ADAM7 cDNA did encode GP-83. Northern blot analysis revealed two transcripts of 4 kb and 3 kb in the epididymis, but not in testis or other major tissues. These results indicate that the GP-83-encoding gene is a human epididymis-associated ADAM7 gene (human ADAM7, h-ADAM7) and may be involved in the sperm-egg interaction.
epididymis, fertilization, gamete biology, sperm, sperm maturation
INTRODUCTION
In mammals, sperm are exposed to a microenvironment created by the absorptive and secretory activities of the epididymal epithelium cells [1]. Passing along the epididymal duct, sperm undergo morphological and functional modifications [2] that culminate in the acquisition of forward motility and the ability to recognize and penetrate the zona pellucida of an egg [3, 4]. Therefore, the interactions between epididymal secretary proteins and sperm membrane are essential for the mammalian sperm to develop fertility [1, 5]. However, the roles of epididymal secretory proteins in sperm maturation are not well defined [5,6].
A novel family of transmembrane proteins that contain a disintegrin and metalloprotease (ADAM) domain had been identified in a variety of tissues and species [7]. A total of 29 ADAM cDNAs have been cloned and sequenced [7, 8]. Although the biological functions are not well defined, ADAMs are involved in rather diverse biological processes, such as virus-cell fusion [9], neurogenesis [10], and fertilization [11, 12]. A full-length ADAM cDNA encodes a multidomain protein containing prodomain, metalloprotease, disintegrin, cysteine-rich, epidermal growth factor (EGF)-like, transmembrane, and cytoplasmic domains [7, 13, 14]. Among the 29 known ADAM cDNAs, 12 are testis specific and 3 are testis predominant [7]. These 15 ADAMs are proposed to play important roles in spermatogenesis and/or fertilization. The inhibition of sperm-egg fusion by fertilin ß (ADAM2)-specific monoclonal antibody [15] further substantiates the role of ADAM in fertilization. The ADAM7 molecules found in the rat, monkey [16], and mouse [17] are all epididymis-associated and proposed to be involved in sperm maturation. However, biological functions of ADAMs in sperm maturation and fertilization are not defined yet.
Our previous study demonstrated that GP-83, a glycoprotein secreted by human epididymis was located on the anterior acrosome of ejaculated spermatozoa [18]. In acrosome-reacted spermatozoa, GP-83 shifted from the anterior acrosome to the equatorial region [19], a region that the membrane participates in the early steps of sperm-egg fusion [20, 21]. These results strongly implicate the involvement of GP-83 in sperm-egg interaction. In order to elucidate the GP-83-encoding DNA sequence and predict the biological significance of GP-83, we cloned and analyzed a GP-83-encoding cDNA from a cDNA library of human epididymis.
MATERIALS AND METHODS
Construction of Epididymal cDNA Library
The cDNA expression library was constructed in 
ZAPII from human epididymis poly(A) RNA using a cDNA library synthesis kit (Stratagene, La Jolla, CA) according to the manufacturer's instructions. Briefly, total RNA was extracted from human corpus epididymis with Trizon (Gibco BRL, Rockville, MD). The poly(A)+ fraction was purified by oligo(dT)-cellulose column (Stratagene). Double-stranded cDNA was synthesized with 3–6 µg poly(A)+ RNA template, ligated to EcoRI/XhoI-digested ZAPII DNA, and subjected to in vitro packaging reaction. The packaged library was plated on Escherichia coli XL1-Blue MRF' and amplified as a plate lysate on agar plates [22]. The titer of this library was 107 plaque forming units (PFU).
Immunoscreening and Cloning of GP-83-Expressing cDNA Clones
The cDNA clones encoding GP-83 were identified by immunoscreening as described by Huynh et al. [23] with modifications. The cDNA library was plated on E. coli XL1-blue cells and grown at 37°C for 3–4 h. Recombinant protein expression was induced with 10 mM isopropyl-ß-D-thiogalactopyranoside (IPTG)-saturated nitrocellulose (Schleicher and Schuell, Dassel, Germany) at 37°C for 4–5 h. Filters were removed, soaked in blocking solution (5% low fat milk powder, 0.05% Tween 20 in PBS), and washed in washing buffer (0.1% Tween 20 in PBS, PBST). Filters were reacted with GP-83-specific antiserum for 3 h at 4°C, then washed in PBST three times, and incubated with peroxidase-conjugated goat anti-rabbit IgG (1:3000 dilution; Sigma, St. Louis, MO) at room temperature for 1 h. After washing, positive clones were revealed by a buffer containing 0.05 M Tris-HCl, 0.1% H2O2 and 0.05% diaminobenzidine tetrahydrochloride (DAB), pH 7.6.
The positive clones were subjected to further subcloning. The inserts of the positive clones recovered from the second subcloning were amplified by T3 primer (5'-AATTA ACCCT CACTA AAGGG-3') and T7 primer (5'-GTAAT ACGAC TCACT ATAGG GC-3') in Taq polymerase system (Gibco BRL). The 5' end and 3' end sequences of the inserts were further cloned by rapid amplification of cDNA ends (RACE).
Cloning of the 5' and 3' End of Human ADAM7
The 5' end of GP-83-expressing cDNA recovered as described above was further cloned according to the protocols of the 5' RACE System for rapid amplification of cDNA end (Gibco BRL). In brief, two primers, GPr160 (5'-TCGGT TCCTT AGTTT ATTGT G-3') and GPr50 (5'-TCCCT CATCT GAGTA TTTCA CTGGT TG-3') were designed from the 5' end of the 2.1-kilobase (kb) cDNA. GPr160 was annealed to human epididymis mRNA and cDNA was synthesized by SuperScript II reverse transcriptase (Gibco BRL). The mRNA template was degraded with RNase H. The single-stranded cDNA was purified with GlassMax Spin columns (Pharmacia, Piscataway, NJ) and tailed on the 3' end with the homopolymer cytosine (poly [C]) by terminal transferase. The tailed cDNA was amplified by polymerase chain reaction (PCR; Techne, FGENO2TP, Duxford, Cambridge, UK) with anchor primer (5'-CUACU ACUAC UAGGC CACGC GTCGA CTAGT ACGGG IIGGG IIGGG IIG 3') and GPr50 primer using the Taq polymerase system (Gibco BRL).
The Smart RACE cDNA Amplification Kit (Clontech, Palo Alto, CA) was used for 3'-RACE. In brief, cDNA was amplified by reverse transcriptase using 3'-RACE cDNA synthesis primer (5'-AAGCA GTGGT AACAA CGCAG AGTAC [T]30N-1N-3'). The 3' ends of h-ADAM7 were further amplified by specific primer of h-ADAM7, Ls1718 (5'-AGATT TCTTC CCTGT GAGGA GA-3'), and SMART II oligonucleotide (5'-AAGCA GTGGT AACAA CGCAG AGTAC GCGGG-3'), using the Taq polymerase system (Gibco BRL).
The products of 5' RACE and 3' RACE were purified by JET sorb Kit (Genomed, Bad Oeynhausen, Germany), subcloned into pGEM-T vector (Promega, Madison, WI) and transformed into competent Escherichia coli XL-I Blue cells. Colonies were selected in the presence of ampicillin and sequenced as described below.
Sequence Analysis of cDNA Clones
The cDNA inserts were subjected to sequencing reaction with Rhodamine Terminator Cycle Sequencing Ready Reaction Kit (PE Applied Biosystems, Foster City, CA) on an ABI Prism 377 autosequencer according to the dideoxy chain-termination method. The cDNA sequence encoding GP-83 and deduced amino acid sequence were analyzed by GenBank/EMBO databank using the GCG FASTA program [24].
Ex Vivo Expression of h-ADAM7
The h-ADAM7 cDNA (Fig. 1) was subcloned into a pRSET A vector (Invitrogen, San Diego, CA) at EcoRI restriction endonucleases sites to construct an expression plasmid. The resulting recombinant plasmid containing a 2.0-kb cDNA insert was designated as h-ADAM7p and transformed into competent E. coli BL21 (DE3) pLysS cells for protein expression. The h-ADAM7p-transformed cells were grown to a late log phase (A600 = 0.4
0.5) in 2x YT broth and induced to express proteins with 1 mM IPTG for 2 h. The cells were recovered and sonicated in a buffer containing 8 M urea, 0.1 M NaH2PO4, 10 mM Tris-HCl, pH 8.0 to extract proteins.
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Western Blot Analysis
The proteins expressed ex vivo were investigated for the presence of GP-83 by Western blotting using 5%/10% SDS-PAGE. The blots were incubated with GP-83 antiserum or poly-His (Santa Cruz Biotechnology, Santa Cruz, CA) antibody, followed by peroxidase-conjugated goat anti-rabbit IgG (Cappel, Turnhout, Belgium) and subsequently with enhanced luminol reagent (NEN, Boston, MA). Finally, the blots were exposed to x-ray film (X-Omat; Fuji, Japan) and the proteins that reacted with GP-83 antiserum or poly-His antibody were revealed by chemiluminescence.
High Stringency Northern Blot Analysis
Northern blot analysis for tissue specificity was performed on multiple tissue Northern blots (Clontech) and total RNA recovered from the testis and epididymis of five patients with prostate carcinoma who received orchidectomy before hormone therapy at Tri-Service General Hospital, Taipei, Taiwan. Total RNA (5 µg) from testis, caput, corpus, and cauda of epididymis were resolved on 1.2% formaldehyde-agarose gels and transferred onto Hybond-N filters [22]. The filters were prehybridized at 45°C for 1 h in a hybridization solution containing 50% deionized formamide, 5x SSC (1x SSC is 0.15 M CaCl plus 0.015 M sodium citrate), 0.1% (w/v) N-lauroylsarcosine, 0.02% (w/v) SDS, and 2% (w/v) blocking reagent (Boehringer Mannheim, Mannheim, Germany). The filters were then drained and replenished with fresh hybridization solution containing approximately 2.5 ng/ml probe, which was the 2.1-kb cDNA fragment labeled with digoxigenin using a random prime method (Boehringer Mannheim). The hybridization was allowed to proceed for 16–20 h at 45°C. Filters were washed in a buffer containing 0.1x SSC and 0.1% SDS at 68°C for 20 min twice, then blocked in blocking reagent for 30 min. The filters were incubated with anti-digoxigenin-alkaline phosphatase solution (1:5000 dilution; Boehringer Mannheim) for 1 h, and subsequently with enhanced luminol reagent (NEN). The filters were exposed to x-ray film (X-Omat; Fuji) and the transcripts reacted with the probe were revealed by chemiluminescence.
RESULTS
Cloning of GP-83-Encoding cDNA
To gain an insight into the biological functions of GP-83 in sperm-egg interaction, GP-83-encoding cDNA was cloned from the cDNA library of human epididymis that was constructed in the ZAP II expression vector. GP-83-expressing clones were identified by immunoscreening with GP-83-specific antiserum that was raised with purified GP-83 protein, and recognized a major molecule of 83 kDa in human epididymis and seminal fluid [19]. The inserts of the positive clones from the second subcloning were amplified by T3 primer and T7 primer in Taq polymerase system that revealed inserts of 0.7–2.1 kb. On Southern blots, the 2.1-kb insert hybridized with all other inserts, which indicated that these inserts were the partial sequences of a same gene. The 2.1-kb insert was isolated and sequenced in both directions (Fig. 1). A further 583 (1–583) base pairs (bp) extending from the 5' end of the 2.1-kb insert were elucidated by 5' RACE. In addition, two 3' end-cDNA sequences were identified by 3' RACE; one is the same as that of the 2.1-kb clone (1714–2643 bp) and the other with 1742 bp (1714–3451) (Fig. 1). Therefore, there are two isoforms of GP-83-encoding cDNA sequences; one is 3451 bp (-form) and the other is 2643 bp (ß-form) including the poly(A) tail. Because the segment of 2411–3451 bp in -form was an untranslated region, both the cDNA sequences exhibit an open reading frame of 2262 bp, predicting a peptide of 754 amino acid residues (Fig. 1B).
Sequence Analysis and Comparisons of h-ADAM7
The identity of GP-83-encoding cDNA was determined by searching the GenBank and EMBL Data Banks, which revealed sequence homology to the metalloprotease and disintegrin domains of ADAM molecules [13, 14]. The cDNA sequence of GP-83 exhibited significant sequence homology to EAP-1 of the monkey and rat [16] and ADAM7 of mouse [17] (Fig. 2). Therefore, these molecules are referred to as ADAM7 of human, monkey, rat, and mouse, respectively [8, 25]. Blasting in NCBI, h-ADAM7 was mapped to chromosome 8p22 according to the DNA sequences elucidated in the Human Genome Project.
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Sequence analysis of GP-83, i.e., human ADAM7 (h-ADAM7) cDNA revealed a protein containing a prodomain (169 residues in all four species of ADAM7), metalloprotease domain (204 residues in human and monkey, 203 in mouse and rat), disintegrin domain (91 residues in all four species), cysteine-rich domain (141 residues), EGF-like domain (29 residues), transmembrane domain (64 residues in human, 68 residues in monkey, mouse, and rat), and cytoplasmic domain (39 residues in human, 40 in monkey, 37 in mouse and rat) (Fig. 2).
Deduced amino acid sequence of GP-83 is 93.3%, 68.4%, and 68% identical to those of ADAM7 proteins of the monkey, mouse, and rat, respectively. There are seven potential N-linked glycosylation sites in h-ADAM7. The metalloproteinase domain of h-ADAM7 shares significant sequence similarity with those of monkey (95%), mouse (73%), and rat (70%) ADAM7. The metalloprotease domain of h-ADAM7 exhibits an active site sequence, 
QLGNLGMQD. According to Hite and his colleagues [26], three histidine residues (H, underlined) bind zinc, and the glycine residue (G, italicized) allows a turn. However, a glutamine (Q, bold) replaced the glutamate residue (E) in the catalytic site of h-ADAM7 as in those of the monkey, mouse, and rat ADAM7 proteins (Fig. 2).
The disintegrin domain of h-ADAM7 shares 86% identity with that of monkey ADAM7 and 75% identity with those of mouse and rat. Although the binding motif of disintegrins in most snake venoms is RGD (Arg-Gly-Asp), the putative integrin-binding sequence of h-ADAM7 is KDE(CD) as retrieved from homologous domains of other disintegrins (Fig. 2) that also contain a negative charged residue at the carboxyl end of the binding domain.
The intracellular domain of h-ADAM7 is the same as those of other species that contain SH3 consensus sequences, RTEPILP [25, 27]. Although the natural ligands for ADAM tails have not yet been identified, it is likely that some of these tails have signaling potential.
Identification of GP-83 Proteins Expressed by h-ADAM7
To examine if the h-ADAM7 cDNA sequence encoded GP-83, h-ADAM7 cDNA was subcloned into the pRSET A vector. The proteins expressed in h-ADAM7-transformed competent E. coli BL21 (DE3) pLysS cells were examined on Western blots probed with GP-83-specific antiserum [19]. Among newly expressed proteins that reacted with His-specific antibody, GP-83 was identified by specific antibody (Fig. 3). This result indicated that h-ADAM7 cDNA is GP-83-encoded cDNA.
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Expression of h-ADAM7 mRNA in Human Tissue
Northern blot analysis revealed two transcripts of h-ADAM7, approximately 4 kb and 3 kb in caput, corpus, and cauda of the epididymis (Fig. 4). The h-ADAM7 mRNA was not found in testis, heart, brain (whole), placenta, lung, liver, skeletal muscle, kidney, pancreas, spleen, thymus, prostate, uterus (no endometrium), small intestine, colon (no mucosa), or peripheral blood leukocytes.
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DISCUSSION
In this study, we present the complementary DNA and deduced amino acid sequence of GP-83 (Fig. 1), which contains signal sequence, prodomain, metalloproteinase, disintegrin, cysteine-rich, EGF-like, transmembrane, and cytoplasmic domains (Fig. 1). Both nucleotide sequence and deduced amino acid sequence of GP-83 revealed significant homology to EAP-1 of the monkey and rat [16] and ADAM7 of mouse [17] (Fig. 2). Based on the sequence homology and phylogenetic analysis, EAP-1 of monkey and rat was referred as monkey and rat ADAM7 [25] and GP-83 as h-ADAM7 [8]. Both Northern blotting (Fig. 4) and immunoblotting [19] demonstrated that GP-83 was expressed in human epididymis but not in testis. These results further indicate that all ADAM7 proteins identified to date are expressed by epididymal epithelial cells [25]. Although the biological roles of ADAM7 proteins are not defined yet, putative protease and adhesion domains imply roles in cell-cell interaction, protein processing, and cell signaling [17].
In most ADAMs, the proprotein domain is cleaved off to activate the protease domain. The regulation mechanism, as found in the soluble matrix metalloprotease (MMPs) and crotalid snake venom metalloprotease (SVMPs), is referred as a cysteine switch [28, 29]. Due to the presence of an unpaired cysteine, the cysteine switch is thought to interact with Zn2+ in the catalytic domain. However, within the metalloproteinase catalytic residue, the glutamate (E) is replaced by a glutamine (Q) in h-ADAM7 and other ADAM7 proteins. Thus, the h-ADAM7 protein may not have protease activity as Cornwall and Hsia [17] proposed for other ADAM proteins.
ADAMs display structural homology to SVMPs and are postulated to function as adhesive protein ligands such as fibronectin, vitronectin, and fibrinogen [30]. After proteolytic processing, the disintegrins of SVMPs are integrin ligands of 50–80 amino acids. These disintegrins interact with integrins through a 13-amino acid motif that contains an integrin-binding sequence, RGD (Arg-Gly-Asp). The disintegrin-like domains of the ADAMs are likely ligands for integrins or other receptors [25], but RGD is found only in ADAM 15 (metargidin) [31, 32]. Although the counterpart of RGD in h-ADAM7 was KDE, the integrin-binding domain of ADAM7 is proposed to be ECD [33]. Because ECD is the consensus sequence of the ADAM7, we wonder if adjacent amino acids such as KDE(CD) in h-ADAM7 and EDE(CD) in monkey ADAM7 (EAP-I) [16] may mediate the species-specific integrin-disintegrin interactions.
Cytoplasmic tails of the ADAMs, ranging from 11 to 176 amino acids in length, do not share significant sequence similarity with each other or with other proteins. Several ADAM tails are rich in proline, which suggests that they may contain binding sites for cytoskeleton-associated proteins or SH3 domain-containing proteins, a large group of molecules involving cell signaling [25, 27, 34]. The intracellular domain of h-ADAM7 contains SH3 consensus sequences, RTEPILP [25], which suggests that h-ADAM7 (GP-83) may be involved in a signal transduction pathway.
Our previous studies demonstrated that GP-83 was secreted by human epididymis and conjugated to sperm in the corpus [18]. GP-83 found on the anterior acrosome of ejaculated sperm was shifted to the equatorial region after the acrosome reaction [19]. In this study, transmembrane and cytoplasmic domains suggest GP-83 to be a membrane protein that may mediate a signal transduction pathway. In addition, the rather long extracellular portion of GP-83 contains a disintegrin domain (Fig. 1) that may be involved in specific integrin-disintegrin interactions. Because the equatorial region is the region that sperm binds egg [20, 21], the disintegrin domain of sperm is proposed to mediate specific binding to integrin on the egg surface [33]. These findings indicate that GP-83 (h-ADAM7) is a membrane protein of sperm that may play important roles in sperm-egg recognition and interaction. However, how a membrane protein-like GP-83 to be secreted by epididymis and conjugated to sperm need to be elucidated.
In this study, h-ADAM7 cDNA was inserted into the pRSET A vector and expressed in competent E. coli BL21 (DE3) pLysS cells. The recombinant protein of h-ADAM7 was identified on Western blots with GP-83-specific antibody (Fig. 3). This result confirms that h-ADAM7 elucidated from the positive clones selected from immunoscreening is the GP-83-encoded cDNA.
The genomic organization of the ADAMs is complicated, and the encoding genes are dispersed on separate chromosomes [25, 35]. The genes for mouse ADAMs 1–5 locate on four different chromosomes [36, 37]. Some ADAMs may be encoded by more than one genomic segment, e.g., two isoforms of monkey ADAM6 cDNA encode the full-length protein [38]. Because the sequence differences between these 2 cDNAs are spread through the entire length, they are very likely two different genes. In this study, 5' RACE and 3' RACE of a 2.1-kb insert elucidated two isoforms of h-ADAM7 cDNA sequences, the -form of 3451 bp and the ß-form of 2643 bp (Fig. 1). This result was consistent with that of Northern blot analysis that identified two transcripts of approximately 4 kb and 3 kb in the epididymis (Fig. 4). Although the longer segment in the -form contains a longer untranslated region (Fig. 1), both cDNAs exhibit the same open reading frame of 2262 bases. In addition, h-ADAM7 is located at chromosome 8p22 according to the DNA sequence elucidated in the Human Genome Project. These findings indicate that both the -form and ß-form are encoded by the same gene. However, the biological significance of these two transcripts needs to be determined.
In addition to ADAM7, 12 testis-specific and 3 testis-predominant ADAMs are proposed to play important roles in spermatogenesis and fertilization [7, 25] and are referred to as ADAM1–6 [25]. Altogether, 19 among 29 known ADAMs are related to spermatogenesis and fertilization. However, none of known ADAMs is related to oogenesis.
In conclusion, the h-ADAM7 cDNA sequence encoding GP-83 is a human epididymis-associated ADAM7 containing signal sequence, prodomain, metalloprotease, disintegrin, cysteine-rich, EGF-like, transmembrane, and cytoplasmic domains and may play important roles in the sperm-egg interaction.
ACKNOWLEDGMENTS
The authors are grateful to Professor Ming-Ching Kao of the Department of Biochemistry, National Defense Medical Center, for his valuable advice in preparing this paper.
FOOTNOTES
First decision: 18 April 2001.
1 This study was supported in part by grants from the National Science Council, Republic of China (NSC 85-2331-B016-097 and NSC 86-2314-B016-064). 
2 Correspondence: Hwan-Wun Liu, Institute of Preventive Medicine, National
Defense Medical Center, 161, Sect. 6, Minchuan E. Rd., Taipei,
Taiwan 114, ROC. FAX: 886 2 87923159; hwanliu{at}ndmctsgh.edu.tw
Accepted: May 3, 2001.
Received: March 22, 2001.
REFERENCES
gt10 and gt11. In: Glover DM (ed.), DNA Cloning: A Practical Approach, vol. 1. Oxford: IRL Press; 1985: 49–78 This article has been cited by other articles:
|
|
 |
|
  V. Thimon, G. Frenette, F. Saez, M. Thabet, and R. Sullivan Protein composition of human epididymosomes collected during surgical vasectomy reversal: a proteomic and genomic approach Hum. Reprod., August 1, 2008; 23(8): 1698 - 1707. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 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]
|
|
|
|
 |
|
 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]
|
|
|
|
|
|
T. G. Cooper, A. Wagenfeld, G. A. Cornwall, N. Hsia, S. T. Chu, M.-C. Orgebin-Crist, J. Drevet, P. Vernet, C. Avram, E. Nieschlag, et al. Gene and Protein Expression in the Epididymis of Infertile c-ros Receptor Tyrosine Kinase-Deficient Mice Biol Reprod, November 1, 2003; 69(5): 1750 - 1762. [Abstract] [Full Text] [PDF]
|
|
|
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 |
|
 D. F. Seals and S. A. Courtneidge The ADAMs family of metalloproteases: multidomain proteins with multiple functions Genes & Dev., January 1, 2003; 17(1): 7 - 30. [Full Text] [PDF]
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