| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Research Article |
Department of Life Science,3 Gwangju Institute of Science and Technology, Gwangju 500–712, Korea
Section of Molecular and Cellular Biology,4 University of California, Davis, California 95616
ABSTRACT
A number of a disintegrin and metalloprotease (ADAM) family members are expressed in mammalian male reproductive organs such as testis and epididymis. These reproductive ADAMs are divided phylogenically into three major groups: ADAMs 1, 4, 6, 20, 21, 24, 25, 26, 29, 30, and 34 (the first group); ADAMs 2, 3, 5, 27, and 32 (the second group); and ADAMs 7 and 28 (the third group). Previous mouse knockout studies indicate that ADAM1, ADAM2, and ADAM3 have intricate expressional relationships, playing critical roles in fertilization. In the present study, we analyzed processing, biochemical characteristics, localization, and expressional relationship of the previously-unexplored, second-group ADAMs (ADAM5, ADAM27, and ADAM32). We found that all of the three ADAMs are made as precursors in the testis and processed during epididymal maturation, and that ADAM5 and ADAM32, but not ADAM27, are located on the sperm surface. Using sperm from Adam2–/– and Adam3–/– mice, we found that, among the three ADAMs, the level of ADAM5 is modestly and severely reduced in Adam3 and Adam2 knockout sperm, respectively. Further, we analyzed ADAM7, an epididymis-derived sperm surface ADAM from the separate phylogenetic group, in the knockout sperm. We found that the level of ADAM7 is also significantly reduced in both Adam2 and Adam3-null sperm. Taken together, our results suggest a novel expressional relationship of ADAM5 and ADAM7 with ADAM2 and ADAM3, which play critical roles in fertilization.
epididymis, fertilization, gamete biology, sperm, testis
INTRODUCTION
The a disintegrin and metalloproteases (ADAMs) are a family of transmembrane proteins, sharing a conserved multidomain structure: an N-terminal signal sequence, pro-, metalloprotease, disintegrin, cysteine-rich, EGF-like, transmembrane and cytoplasmic domains. The ADAM family members have been discovered in a variety of tissues and species [1–5]. The family currently has at least 33 members, and 18 of them are expressed in the mammalian male reproductive organs, such as testis and epididymis [6]. Based on an ADAM phylogenetic tree, mammalian ADAMs with gene expression in the male reproductive organs are divided into three major groups: ADAMs 1, 4, 6, 20, 21, 24, 25, 26, 29, 30, and 34 (the first group); ADAMs 2, 3, 5, 27 and 32 (the second group); and ADAMs 7 and 28 (the third group) (Fig. 1A). Notable features of the first-group ADAMs are that all the genes are expressed specifically or predominantly in the testis and lack introns in their coding sequences, and many of them are present as multiple copies in the mouse genome [7]. The second-group ADAM genes are also expressed exclusively or predominantly in the testis. Unlike the first-group ADAM genes, they cover the large regions of the genome and consist of multiple small exons [8, 9]. The third-group ADAM genes are expressed abundantly in the epididymis, and their gene expression is regulated by androgen or testicular factors [10]. Among the ADAMs with testicular or epididymal gene expression, ADAM1a, ADAM1b, ADAM2, ADAM3, ADAM7, ADAM24, and ADAM28 have been studied at the protein level in mouse [10–24]. Most of these ADAM proteins are present in spermatogenic cells (ADAMs 1a, 1b, 2, 3, and 24) and/or sperm (ADAMs 1b, 2, 3, 7, and 24). Notably, ADAM1a or ADAM1b, two ADAM isoforms, form a heterodimer with ADAM2 in these cells.
|
Previous mouse knockout studies showed that male mice with deletion of the gene for ADAM1a, ADAM2, or ADAM3 are infertile and their sperm are defective in the fertilization process [14, 15, 17, 19, 20]. The intriguing feature of these knockouts is an intricate relationship between the fertilization phenotypes and protein expression phenotypes. Both Adam1a and Adam2 knockout sperm, but not Adam3-null sperm, are impaired in migration from the uterus to the oviduct. Common protein expression phenotypes between Adam1a and Adam2 knockouts are the absence of ADAM1a/2 heterodimer in testicular germ cells and severe loss of ADAM3 in epididymal sperm. Adam1a, Adam2, and Adam3 knockout sperm are all defective in binding to the egg zona pellucida and all commonly lack or barely contain ADAM3. From these results, it has been suggested that ADAM1a/2 heterodimer in testicular germ cells is implicated in the regulation or localization of sperm proteins, including ADAM3, involved in sperm migration in the female reproductive tracts and sperm-egg zona pellucida adhesion, thus playing a critical role in fertilization.
In this study, to explore other reproductive ADAMs in fertilization, we analyzed ADAM5, ADAM27, and ADAM32. They are closely related to ADAM2 and ADAM3 in the phylogenetic tree, but their protein characteristics are largely unknown. We provide new and comprehensive information on these ADAM proteins. In particular, using the Adam knockouts, we found that ADAM5 is related to ADAM2 and ADAM3. Additionally, we obtained new evidence that ADAM7, another reproductive ADAM expressed in the epididymis and transferred to the sperm surface, is affected by the loss of ADAM2 or ADAM3.
MATERIALS AND METHODS
Reverse Transcription-PCR
Tissue distribution and developmental expression patterns of Adam2, Adam3, Adam5, Adam27, and Adam32 were analyzed by RT-PCR. To investigate tissue distribution, cDNAs from multiple tissue cDNA panels (Clontech) were used as templates for PCR. To examine the developmental expression patterns in testis, total RNA from testes, harvested at 8–90 days after birth, was used for reverse transcription, and the products of reverse transcription were used as templates for PCR. The gene-specific primers used for PCR were forward primer, 5'-ATCGTCTCTCACTATTTGGAAATACAT-3', and reverse primer, 5'-TAAAATAATTGCAAGTGATTCCAGAGT-3', corresponding to nt 552–962 (411 bp) for Adam2; forward primer, 5'-TAACAAAGAGAATTCTGAGGATAAAGA-3', and reverse primer, 5'-AAAGCCCTCCACAGCTAACGTCTTTGG-3', corresponding to nt 630-1027 (398 bp) for Adam3; forward primer, 5'-CGATTCATTATGATGGATATCATCGTG-3', and reverse primer, 5'- CAGGACAATGACACTAAACGATTCTAA-3', corresponding to nt 592–987 (396 bp) for Adam5; forward primer, 5'-CATTCACAACTGTTACCTCAAAGTCTA-3', and reverse primer, 5'- TCCCTCCAAACCTATGTCTTCTGGATA-3', corresponding to nt 576–980 (405 bp) for Adam27; and forward primer, 5'-TTTAAAAACTTGTTTCCCCTCTATCTA-3', and reverse primer, 5'-GAGAATAACCGAAAAGGCCTCCAAGGT-3', corresponding to nt 533–952 (420 bp) for ADAM32. PCR reaction parameters were 94°C for 15 s, 55°C for 30 s, and 72°C for 30 s, for 32 cycles. The primers for glyceraldehyde 3-phosphate dehydrogenase (GPD1) as a control were forward primer, 5'-TGAAGGTCGGAGTCAACGGATTTGGT-3', and reverse primer, 5'-CATGTGGGCCATGAGGTC CACCAC-3'.
Antibodies
To produce polyclonal antibodies against mouse ADAM5, ADAM27, and ADAM32, glutathione S-transferase (GST) fusion proteins containing the disintegrin domains of mouse ADAM5 (amino acids 411–481), ADAM27 (amino acids 415–486), and ADAM32 (amino acids 397–471) were expressed in Escherichia coli BL21 and affinity-purified with glutathione Sepharose 4B. The recombinant proteins were used as antigen for producing rabbit polyclonal antisera. The antibodies were affinity-purified using corresponding proteins and the AminoLink Immobilization kit (Pierce). An antibody to ADAM7 was produced by immunizing rabbits with a GST fusion protein containing the cytoplasmic domain of mouse ADAM7 [10]. Monoclonal anti-mouse ADAM2 (9D2.2) and monoclonal anti-mouse ADAM3 (7C1.2) antibodies were purchased from Chemicon. Affinity-purified rabbit polyclonal antibody against SPAM1 (previously known as PH-20) was a generous gift from Dr. P. Primakoff (University of California at Davis) [25].
Preparation of Cells and Protein Samples
Cells were collected from 10-wk-old male ICR mice and Adam2 (Adam2tm1Dgm/ Adam2tm1Dgm) and Adam3 (Adam3tm1Pmkf/Adam3tm1Pmkf) knockout mice [14, 19]. All animal investigations were carried out according to the guidelines of the Animal Care and Use Committee of Gwangju Institute of Science and Technology and the University of California at Davis. Testicular (spermatogenic) cells and testicular sperm were isolated using 52% isotonic Percoll (Amersham Bioscience) and resuspended in PBS. Sperm from the cauda epididymis and vas deferens were directly released into PBS. The collected cells and sperm were either directly resuspended in 1x SDS sample buffer (3% SDS), followed by boiling for 5 min, or lysed with a nonionic detergent (1% Triton X-100 in PBS) for 40 min on ice in the presence of 1x protease inhibitor cocktails (Calbiochem). The lysates were centrifuged for 10 min at 12000 x g. The supernatants from the lysates were mixed with 2x SDS sample buffer (6% SDS) and boiled for 5 min. The samples were either nonreduced or reduced with 5% ß-mercaptoethanol, as indicated in the text and figure legends.
Biotinylation and Trypsinization of Sperm Surface Proteins
Sperm from cauda epididymis and vas deferens were kept at room temperature for 30 min in PBS containing 1 mg/ml sulfo-NHS-LC-biotin (Pierce) or kept on ice for different periods of time in PBS containing 500 µg/ml trypsin (Sigma). The biotinylated sperm were washed three times with PBS. The trypsinized sperm were washed three times with PBS containing 1x protease inhibitor cocktails (Calbiochem) to block the protease activity. The biotinylated or trypsinized sperm were lysed with the lysis buffer. Proteins were boiled with 3% SDS and 5% ß-mercaptoethanol, run on SDS-PAGE, and analyzed by Western blot hybridization.
Western Blot Analysis
Samples were subjected to 10% or 12% SDS-PAGE. Following electrophoresis, proteins were transferred onto polyvinylidene difluoride membranes (0.2 µm; Bio-Rad Laboratories). The membranes were blocked with 5% nonfat dry milk in TBS containing 0.1% Tween 20 and incubated with primary antibodies, followed by incubation with alkaline phosphatase-conjugated secondary antibodies (Jackson Immunoresearch). Alkaline phosphatase activity was detected by NBT/BCIP (Promega Biotech). To determine the expression levels of proteins in Western blots, band intensity was quantified by Imaging Densitometer (Bio-Rad Laboratories). Expression data were statistically analyzed with the Student t-test.
RESULTS
ADAM Gene Expression in Mouse Testis
One of the main phylogenetic groups of ADAMs with testicular gene expression is composed of ADAMs 2, 3, 5, 27, and 32 (group II; Fig. 1A). To compare the gene expression pattern of these ADAMs, we carried out RT-PCR analysis using mouse cDNAs from various adult tissues and testes obtained at different days after birth. The mouse Adam genes were expressed exclusively (Adam2, Adam3, Adam27 and Adam32) or predominantly (Adam5) in the testis (Fig. 1B). The transcripts of these Adam genes were first detected in the testis at Day 14 (Adam2, and Adam5) or Day 16 (Adam3, Adam27, and Adam32) after birth (Fig. 1B).
Developmental, Biochemical, and Cellular Characteristics of the ADAM Proteins
To date, among the group-II ADAMs, only ADAM2 and ADAM3 have been studied at the protein level in mouse [11–17, 19, 20, 22, 23]. To investigate the characteristics of proteins encoded by the other Adam genes in the phylogenetic group II, we generated antibodies against the disintegrin domains of mouse ADAM5, ADAM27, and ADAM32. Each antibody was found to detect only the corresponding antigen by immunoblot analysis (data not shown), indicating the absence of antibody cross-reactivity among the ADAMs. To determine whether these ADAM proteins are present in testicular (spermatogenic) cells and sperm, and to further compare their characteristics to those of ADAM2 and ADAM3, we performed protein immunoblot analysis on cells from different stages during sperm development and maturation. Consistent with the previous findings, ADAM2 and ADAM3 were expressed as precursors in testicular cells and converted into processed forms in mature sperm (Fig. 2) [15, 19]. For ADAM5, ADAM27, and ADAM32, each antibody recognized a 98-kDa band in testicular cells and testicular sperm. In mature sperm from cauda epididymis and vas deferens, we observed a band with reduced molecular mass: 49 kDa for ADAM5, 42 kDa for ADAM27, and 44 kDa for ADAM32 (Fig. 2). Thus, this result indicates that ADAM5, ADAM27, and ADAM32, like ADAM2 and ADAM3, are made as precursors and processed to lower molecular-weight forms during sperm maturation in the epididymis.
|
To investigate the biochemical and cellular properties of the ADAMs in sperm, various characteristics of the processed ADAMs from mature sperm were determined and compared. Under nonreducing conditions, the molecular sizes of all five ADAM proteins were decreased (Fig. 3A), consistent with the typical characteristics of ADAMs with considerable numbers of cysteine residues [15]. Treatment of sperm with a nonionic detergent led to complete solubilization of ADAM5, ADAM27, and ADAM32 as well as ADAM2 and ADAM3, indicating the similar biochemical characteristics among the ADAMs in mature sperm (Fig. 3B). It is notable that the ADAM27 antibody detects a minor band above the 42-kDa protein. This protein could be an additional form of ADAM27 or a different member of the ADAM family with some cross-reactivity with the ADAM27 antibody. Nonetheless, the protein is dissimilar to the other ADAMs because it is not solubilized by the nonionic detergent. Previously, ADAM2 and ADAM3 have been found to be present on the sperm surface [15, 22]. To investigate the subcellular localization of ADAM5, ADAM27, and ADAM32, we performed cell surface labeling and trypsinization experiments. Sperm surface labeling with biotin resulted in increases in the molecular sizes of ADAM5 and ADAM32. However, the molecular size of ADAM27 was unchanged (Fig. 4A). Similarly, ADAM5 and ADAM32, but not ADAM27, were affected by sperm surface trypsinization (Fig. 4B). These results suggest that ADAM5 and ADAM32, like ADAM2 and ADAM3, are localized on the cell surface of mature sperm, but ADAM27 may be an exception to this localization pattern.
|
|
Expression of ADAMs in Adam2 and Adam3 Knockout Mice
Previous studies on mouse knockouts of Adam1a, Adam2, and Adam3 indicate the presence of an apparent relationship among the levels of expression of these proteins during sperm development [14, 15, 19, 20]. To investigate whether these ADAMs are further related to ADAM5, ADAM27, and ADAM32, we examined the expression levels of the ADAMs in testicular cells and mature sperm from wild-type, Adam2–/–, and Adam3–/– mice. Consistent with previous findings, ADAM2 and ADAM3 were normally expressed in ADAM3- and ADAM2-deficient testicular cells, respectively (Fig. 5A) [19, 20]. Similarly, the amounts of ADAM5, ADAM27, and ADAM32 were normal in both of Adam3 and Adam2 knockout testicular cells. It had previously been found that the level of ADAM2 is weakly reduced in Adam3–/– sperm, and Adam2-null sperm barely contain ADAM3 [19, 20] and that result was confirmed here (Fig. 5A). We found for the first time that the level of ADAM5, but not that of ADAM27 or ADAM32, is significantly changed in both Adam2 and Adam3 knockout sperm relative to wild-type sperm. The loss of ADAM2 resulted in the severe reduction of ADAM5 in mature sperm (22% of wild-type sperm), and Adam3-null sperm contained moderately, but significantly, reduced amounts of ADAM5 (59% of wild-type sperm; Fig. 5, A and B). This result suggests that ADAM5 is synthesized normally and is maintained during spermatogenesis, but that it is lost during sperm differentiation and/or maturation in Adam2 and Adam3-null mice.
|
Because multiple sperm surface ADAMs are related to each other, we asked whether another sperm surface ADAM, not synthesized in testicular germ cells, might be affected by the loss of ADAM2 or ADAM3. Such an ADAM is ADAM7. We recently found that mouse ADAM7 is expressed in the epididymis and secreted and transferred to the plasma membrane over the entire sperm head during epididymal transit [10]. We examined the level of ADAM7 in testicular cells and mature sperm from wild-type, Adam2–/–, and Adam3–/– mice. ADAM7 was absent from testicular cells, but was detected as a single band of 108 kDa in mature sperm, regardless of the genotypes, confirming the previous finding on the synthesis and relocation of ADAM7 (Fig. 5A) [10]. We found significant reduction of ADAM7 to 37% and 48% of the wild-type level in Adam2 and Adam3 knockout sperm, respectively (Fig. 5B). This indicates that sperm are defective in association with ADAM7 in the absence of ADAM2 or ADAM3 during epididymal transit. Taken together, our findings on a number of ADAMs present in mouse sperm suggest that the protein expression or integrity of the two sperm surface ADAMs (ADAM5 and ADAM7) is regulated by ADAM2 and ADAM3 with critical roles in the process of fertilization (see Discussion).
DISCUSSION
In the present study, we analyzed various characteristics of testicular ADAMs (ADAM5, ADAM27, and ADAM32). The timing of transcription of these Adam genes was found to correlate with that of the first appearance of pachytene spermatocytes. This indicates germ cell-specific expression of the Adam genes in the mouse testis, thus corroborating the previous studies [9, 26, 27]. We found for the first time that these ADAM proteins are the same in their developmental timing, nature of processing, and biochemical characteristics. All of the ADAMs are present as large precursors (98 kDa) in the testis and processed to 44- to 49-kDa proteins between the stages of testicular sperm and cauda epididymal sperm. It is likely that the processing of these ADAM precursors removes the pro- and metalloprotease domains, leaving N-terminal disintegrin domains in the processed forms, because the antibodies used in the immunoblot analysis were directed against the disintegrin domains. Previous studies on primate ADAMs also have shown the similar processing pattern of ADAM5 (in macaque) and ADAM27 (in macaque and human) [28, 29]. The ADAM5, ADAM27, and ADAM32 proteins in mouse sperm all decrease in their apparent molecular sizes under nonreducing conditions and are well solubilized by the nonionic detergent. In subcellular localization, however, not all the ADAM proteins are the same: ADAM5 and ADAM32, but not ADAM27, were shown to be present on the sperm surface.
ADAM5, ADAM27, and ADAM32, together with ADAM2 and ADAM3, belong to one main branch in the ADAM phylogenetic tree (Fig. 1A). Both ADAM2 and ADAM3 are synthesized as the precursors in testicular cells and converted to the processed forms containing the disintegrin domains at N-termini during sperm maturation in the epididymis. The processed ADAM2 and ADAM3 proteins are present on the surface of mature sperm (Figs. 2 and 4) [13–15, 19, 20, 22, 23]. In this regard, the characteristics of ADAM5 and ADAM32 analyzed in the present study are identical to those of ADAM2 and ADAM3. Thus, these four ADAMs might share a common mechanism for proteolytic processing and secretory pathway. Nonetheless, our additional findings suggest that these ADAMs are different in the regulation and maintenance of their expressional patterns (see below).
One of the remarkable features of the testicular ADAMs is that a number of the ADAMs have intricate expressional relationships, based on protein expression phenotypes in the mouse knockouts of Adam1a, Adam2, and Adam3. In relation to this, it should be noted that each of the ADAM1 isoforms is complexed with ADAM2, but not with ADAM3, to form a heterodimer. Table 1 shows the summary of protein expression in the Adam knockouts. Common protein expression phenotypes between Adam1a and Adam2 knockouts are the absence of the ADAM1a/2 heterodimer in testicular cells and severe loss of ADAM3 in epididymal sperm. From these knockout studies, it has been suggested that the ADAM1a/2 complex, potentially having a chaperone-like activity, is implicated in the intracellular transport or in maintaining the integrity of sperm proteins including ADAM3 (Fig. 6) [20, 23]. In the present study, we found for the first time that most ADAM5 protein (78%), like ADAM3, is lost in Adam2-null sperm. Because the amount of ADAM5 is reduced also in Adam3-null sperm, it is possible that the loss of ADAM5 in Adam2 knockout sperm is a direct consequence of the severe reduction of ADAM3 in the sperm. However, the extent of the loss of ADAM5 in Adam3 knockout sperm (41%) is not as dramatic as in Adam2 knockout sperm (78%; Table 1). Thus, the loss of ADAM5 in Adam2 knockout sperm results, at least in part, directly from the lack of ADAM2. This suggests that the expression or integrity of ADAM5 might be regulated by the ADAM1a/2 heterodimer in testicular cells (like ADAM3) or the ADAM1b/2 complex in mature sperm (Fig. 6).
|
|
Our previous study indicates that ADAM7 residing in an intracellular compartment of epididymal cells is transferred, with the intact transmembrane domain, to the plasma membrane over the entire sperm head during epididymal transit [10]. The unusual secretory characteristics of ADAM7 suggest that epididymal cells with membrane-bound ADAM7 form vesicles in the epididymal lumen and that the vesicles fuse with sperm. In the present study, we found that the more than half of the ADAM7 amount is lost in Adam2 and Adam3-null sperm, providing new evidence for the implication of ADAM7 in ADAM2- and ADAM3-dependent association with sperm during the posttesticular stage (Fig. 6).
One intriguing feature of the ADAM knockouts is the tangled relationship between protein expression phenotypes and fertilization phenotypes. Both Adam1a and Adam2 knockout sperm are defective in migration from the uterus to the oviduct [14, 20]. As described above, both knockout mice lack ADAM1a/2 heterodimer in testicular cells and have ADAM3 with severely reduced levels in mature sperm. Because Adam3 knockout sperm are normal in progression into the oviduct [19], ADAM1a/2 heterodimer, but not ADAM3, is implicated in sperm migration. Considering lack of the ADAM1a/2 complex in wild-type sperm, the function of this complex in sperm transport into the oviduct is indirect, indicating the presence of other sperm protein(s) directly responsible for this fertilization process. Our finding for ADAM5 raises the possibility that the protein, downstream of ADAM1a/2, is active during the process of sperm migration from the uterus to the oviduct. Another apparent fertilization phenotype of the Adam knockouts is the impaired binding of sperm to the egg zona pellucida. All Adam1a, Adam2, and Adam3-null sperm are defective in this fertilization process and contain in common no or a very low level of ADAM3 in mature sperm. Thus, ADAM3 appears to have a part in sperm binding to the egg zona pellucida. As found for ADAM7, of which the level is reduced in both Adam2 and Adam3-null sperm, the ADAM7 protein also might be related to this fertilization process. To determine whether ADAM5 and ADAM7 indeed function in the fertilization process will require the production and analysis of mutant mice with deletion of the genes encoding these proteins.
In summary, we have analyzed ADAM5, ADAM27, and ADAM32 with testicular gene expression, providing new information on the various protein characteristics, such as the nature of processing, biochemical properties, and subcellular localization. Using the Adam knockouts, we uncovered a relationship of expression levels of ADAM5 with ADAM2 and ADAM3 in mature sperm. In addition, the level of nontesticular, epididymal ADAM7 on sperm was revealed to be dependent on ADAM2 and ADAM3 expression. Thus, our study provides a new perspective for the relationship and regulation of the reproductive ADAM proteins with a potential role in fertilization.
ACKNOWLEDGMENTS
We thank Drs. Paul Primakoff, Diana Myles, and Kathryn Stein for valuable comments on the manuscript and for protein samples from the knockout mice.
FOOTNOTES
1 Supported by Korea Research Foundation Grant (KRF-2002-070-C007) to C.C. 
2 Correspondence. FAX: 82 62 970 2484; choch{at}gist.ac.kr
Received: 23 October 2005.
First decision: 16 November 2005.
Accepted: 22 December 2005.
REFERENCES
/ß dimerization, and lack of essential role of fertilin in sperm-egg fusion. Dev Biol 2000 222:289-295[CrossRef][Medline]This article has been cited by other articles:
|
|
 |
|
  R. Yamaguchi, K. Yamagata, H. Hasuwa, E. Inano, M. Ikawa, and M. Okabe Cd52, known as a major maturation-associated sperm membrane antigen secreted from the epididymis, is not required for fertilization in the mouse. Genes Cells, August 1, 2008; 13(8): 851 - 861. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Nishimura, D. G. Myles, and P. Primakoff Identification of an ADAM2-ADAM3 Complex on the Surface of Mouse Testicular Germ Cells and Cauda Epididymal Sperm J. Biol. Chem., June 15, 2007; 282(24): 17900 - 17907. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P.-L. Yao, Y.-C. Lin, P. Sawhney, and J. H. Richburg Transcriptional Regulation of FasL Expression and Participation of sTNF-{alpha} in Response to Sertoli Cell Injury J. Biol. Chem., February 23, 2007; 282(8): 5420 - 5431. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Yamaguchi, K. Yamagata, M. Ikawa, S. B. Moss, and M. Okabe Aberrant Distribution of ADAM3 in Sperm from Both Angiotensin-Converting Enzyme (Ace)- and Calmegin (Clgn)-Deficient Mice Biol Reprod, November 1, 2006; 75(5): 760 - 766. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
