Mapping, sequence, and expression analysis of the human fertilin beta gene (FTNB)

Low levels of PRSS37 protein in sperm are associated with many cases of unexplained male infertility

PRSS37, a putative trypsin-like serine protease, is highly conserved during mammalian evolution as revealed by multiple sequence alignment. Mice deficient for Prss37 gene exhibit male infertility, but their mating behavior, spermatogenesis, sperm morphology, and motility remain unaffected, similar to a situation called unexplained male infertility (UMI) in men (human being). Here, we demonstrated that PRSS37 is restrictively expressed in human testis, where it is mainly located in the elongating and elongated spermatids during spermiogenesis as shown by immunohistochemical analysis of normal human testicular sections. In mature sperm, PRSS37 appears in the acrosome region and diminishes during acrosome reaction. Further examination reveals that PRSS37 contents in sperm from patients with UMI are dramatically lower than those in sperm from men with proven fertility or from sperm donors. Sperm with low PRSS37 contents exhibit abnormal activation of the proacrosin/acrosin system and premature proteolysis of ADAM2, which may impair the functional competence of human sperm in vivo However, the in vitro fertilization outcomes of sperm with low PRSS37 contents are not affected. Together, these data implicate an important role of PRSS37 for male fertility. PRSS37 can be used as a potential molecular biomarker for evaluating sperm fertilization capability in vivo but not in vitro.

Characterization of Mammalian ADAM2 and Its Absence from Human Sperm

The members of the ADAM (a disintegrin and metalloprotease) family are membrane-anchored multi-domain proteins that play prominent roles in male reproduction. ADAM2, which was one of the first identified ADAMs, is the best studied ADAM in reproduction. In the male germ cells of mice, ADAM2 and other ADAMs form complexes that contribute to sperm-sperm adhesion, sperm-egg interactions, and the migration of sperm in the female reproductive tract. Here, we generated specific antibodies against mouse and human ADAM2, and investigated various features of ADAM2 in mice, monkeys and humans. We found that the cytoplasmic domain of ADAM2 might enable the differential association of this protein with other ADAMs in mice. Western blot analysis with the anti-human ADAM2 antibodies showed that ADAM2 is present in the testis and sperm of monkeys. Monkey ADAM2 was found to associate with chaperone proteins in testis. In humans, we identified ADAM2 as a 100-kDa protein in the testis, but failed to detect it in sperm. This is surprising given the results in mice and monkeys, but it is consistent with the failure of ADAM2 identification in the previous proteomic analyses of human sperm. These findings suggest that the reproductive functions of ADAM2 differ between humans and mice. Our protein analysis showed the presence of potential ADAM2 complexes involving yet-unknown proteins in human testis. Taken together, our results provide new information regarding the characteristics of ADAM2 in mammalian species, including humans.

Characterization of Mammalian ADAM2 and Its Absence from Human Sperm

The members of the ADAM (a disintegrin and metalloprotease) family are membrane-anchored multi-domain proteins that play prominent roles in male reproduction. ADAM2, which was one of the first identified ADAMs, is the best studied ADAM in reproduction. In the male germ cells of mice, ADAM2 and other ADAMs form complexes that contribute to sperm-sperm adhesion, sperm-egg interactions, and the migration of sperm in the female reproductive tract. Here, we generated specific antibodies against mouse and human ADAM2, and investigated various features of ADAM2 in mice, monkeys and humans. We found that the cytoplasmic domain of ADAM2 might enable the differential association of this protein with other ADAMs in mice. Western blot analysis with the anti-human ADAM2 antibodies showed that ADAM2 is present in the testis and sperm of monkeys. Monkey ADAM2 was found to associate with chaperone proteins in testis. In humans, we identified ADAM2 as a 100-kDa protein in the testis, but failed to detect it in sperm. This is surprising given the results in mice and monkeys, but it is consistent with the failure of ADAM2 identification in the previous proteomic analyses of human sperm. These findings suggest that the reproductive functions of ADAM2 differ between humans and mice. Our protein analysis showed the presence of potential ADAM2 complexes involving yet-unknown proteins in human testis. Taken together, our results provide new information regarding the characteristics of ADAM2 in mammalian species, including humans.

Identification and characterization of promoter and regulatory regions for mouse Adam2 gene expression

ADAM2, a member of the 'a disintegrin and metalloprotease' (ADAM) family, is a key protein in mammalian fertilization that is specifically expressed in testicular germ cells. Here, we investigated the transcriptional regulation of the mouse Adam2 gene. An in silico analysis identified two conserved non-coding sequences located upstream of the mouse and human ADAM2 genes. The upstream region of the mouse Adam2 gene was found to lack typical TATA and CAAT boxes, and to have a high GC content. Our in vitro transient transfection-reporter analysis identified a promoter in this region of the mouse Adam2 gene, along with regulatory regions that inhibit the activity of this promoter in somatic cells. Site-directed mutagenesis revealed that the caudal-type homeobox 1 and CCTC-binding factor motifs are responsible for the inhibitory activities of the repressor regions. Finally, electrophoretic mobility shift assays showed putative transcription factor-promoter DNA complexes, and DNA-affinity chromatography and proteomic analyses identified myelin gene regulatory factor as a binding partner of the Adam2 promoter. This provides the first identification and characterization of promoter and repressor regions that regulate the transcription of the mouse Adam2 gene, and offers insights into the regulation of this germ-cell-specific gene.

Chromosomal mapping, sequence and transcription analysis of the porcine fertilin beta gene (ADAM2)

Fertilin beta (ADAM2) forms a part of the heterodimeric surface protein fertilin, found on the plasma membrane of mammalian sperm, and has been implicated in the process of sperm-egg fusion. Analysis of cDNA products obtained from adult porcine testis mRNA has presented a sequence corresponding to 2620 bp of the ADAM2 gene. This sequence contained an open reading frame encoding a 735-amino acid protein and homologous to ADAM2 genes known in other mammalian species. Polymerase chain reaction (PCR) analysis of genomic DNA showed that the 2620 bp of cDNA sequence comprises at least 21 exons and spans approximately 76 kb of genomic DNA, with its size and structure being relatively conserved between mouse, human and pig. Fluorescence in situ hybridization was used to map ADAM2 to chromosome 15 of the pig, using a bacterial artificial chromosome clone from the PigE BAC library. This finding is consistent with comparative mapping experiments performed between pig and human chromosomes. Analysis of nine mRNA samples, by reverse transcriptase-PCR, from different porcine tissues has also suggested that expression of ADAM2 is limited to the testis, a finding that is consistent with other mammalian species.

The identification of seven metalloproteinase-disintegrin (ADAM) genes from genomic libraries

Metalloproteinase-disintegrins (ADAMs) are membrane-spanning multi-domain proteins containing a zinc metalloproteinase domain and a disintegrin domain which may serve as an integrin ligand. Based on a conserved sequence within the disintegrin domain, GE(E/Q)CDCG, seven genes were isolated from a human genomic library. Two of these genes lack introns and show testis-specific expression (ADAM20 and ADAM21), while the other two genes contain introns (ADAM22 and ADAM23) and are expressed predominantly in the brain. In addition, three pseudogenes were isolated; one of which evolved from ADAM21. Human chromosomal mapping indicated that ADAM22 and ADAM23 mapped to chromosome 7q21 and 2q33, respectively, while the three pseudogenes 1-2, 3-3, and 1-32 mapped to chromosome 14q24.1, 8p23, and 14q24.1, respectively. An ancestral analysis of all known ADAMs indicates that the zinc-binding motif in the catalytic domain arose once in a common ancestor and was lost by those members lacking this motif.

Characterization of the cDNA and gene for mouse tumour necrosis factor alpha converting enzyme (TACE/ADAM17) and its location to mouse chromosome 12 and human chromosome 2p25

Numerous proteins are cleaved or "shed" from their membrane-bound form. One such protein, tumour necrosis factor alpha (TNF-alpha), is synthesized as a type 2 transmembrane protein. Recently, a human protease responsible for this shedding, the TNF-alpha converting enzyme (TACE/ADAM17), was isolated. TACE/ADAM17 is a member of the adamalysin class of zinc-binding metalloproteases or ADAM (a disintegrin and metalloprotease). We report the isolation and characterization of the mouse TACE/ADAM17 cDNA and gene. Mouse TACE/ADAM17 has a 92% amino-acid identity with the human protein and was ubiquitously expressed. A recombinant form of the protease is found to cleave a peptide representing the cleavage site of precursor mouse TNF-alpha. An alternatively spliced form of mouse TACE/ADAM17 was found that would produce a soluble protein. The gene for TACE/ADAM17 is approximately 50 kb and contains 19 exons. Chromosomal mapping places TACE/ADAM17 on mouse chromosome 12 and human chromosome 2p25.

Structure-function analysis of the ADAM family of disintegrin-like and metalloproteinase-containing proteins (review)

The ADAMs belong to a disintegrin-like and metalloproteinase-containing protein family that are zinc-dependent metalloproteinases. These proteins share all or some of the following domain structure: a signal peptide, a propeptide, a metalloproteinase, a disintegrin, a cysteine-rich, and an epidermal growth factor (EGF)-like domains, a transmembrane region, and a cytoplasmic tail. ADAMs are widely distributed in many organs, tissues, and cells, such as brain, testis, epididymis, ovary, breast, placenta, liver, heart, lung, bone, and muscle. These proteins are capable of four potential functions: proteolysis, adhesion, fusion, and intracellular signaling. Because the number of ADAM genes has grown rapidly and the biological functions of most members are unclear, this review analyzes the protein structures and functions, their activation and processing, their known and potential activities, and their evolutionary relationships. A sequence alignment of human ADAMs is compiled and their homology and physical data are calculated. The conceivable functions of ADAMs in reproduction, development, and diseases are also discussed.

A novel, secreted form of human ADAM 12 (meltrin alpha) provokes myogenesis in vivo

The ADAM (A Disintegrin And Metalloprotease) family of cell-surface proteins may have an important role in cellular interactions and in modulating cellular responses. In this report we describe a novel, secreted form of human ADAM 12 (meltrin alpha), designated ADAM 12-S (S for short), and a larger, membrane-bound form designated ADAM 12-L (L for long form). These two forms arise by alternative splicing of a single gene located on chromosome 10q26. Northern blotting demonstrated that mRNAs of both forms are abundant in human term placenta and are also present in some tumor cell lines. The ADAM 12-L transcript can also be detected in normal human adult skeletal, cardiac, and smooth muscle. Human A204 embryonal rhabdomyosarcoma cells that do not differentiate into muscle cells and do not express any form of ADAM 12 were stably transfected with an ADAM 12-S minigene encoding the disintegrin domain, the cysteine-rich domain, and the unique 34 amino acid carboxyl terminus. Nude mouse tumors derived from these transfected cells contained ectopic muscle cells of apparent mouse origin as shown by species-specific markers. These results may have potential applications in the development of muscle-directed gene and cell therapies.