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Wolfram Eichler - One of the best experts on this subject based on the ideXlab platform.
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CD97 isoform expression in leukocytes
Journal of Leukocyte Biology, 2000Co-Authors: Wolfram EichlerAbstract:Different adhesive capacity in interactions with CD55 has been ascribed to the isoforms of the leukocyte CD97 Antigen, CD97 (EGF 1,2,5), CD97 (EGF 1,2,3,5), and CD97 (EGF 1,2,3,4,5). In the study, coexpression of the three CD97 isoforms and predominance of CD97 (EGF 1,2,5) transcripts in leukocytes are demonstrated. The contribution of CD97 (EGF 1,2,3,5) and CD97 (EGF 1,2,3,4,5) to total CD97 levels varied among most cell types only slightly, although relatively higher mRNA levels of both isoforms were detected in U 937 cells and monocytes. In peripheral blood lymphocytes, CD97 isoforms did not show clear variation after PMA stimulation and were down-regulated equally after CD97 crosslinking. Moreover, the CD97 isoform pattern was not altered in monocytes after interferon-g stimulation and in synovial T cells from patients with rheumatoid arthritis. CD97 mRNA levels did not necessarily correspond to CD97 surface density. The findings suggest that adhesive activity of CD97 toward CD55 is unlikely to be regulated by differential CD97 isoform expression. J. Leukoc. Biol. 68: 561–567; 2000.
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CD97 isoform expression in leukocytes.
Journal of leukocyte biology, 2000Co-Authors: Wolfram EichlerAbstract:Different adhesive capacity in interactions with CD55 has been ascribed to the isoforms of the leukocyte CD97 Antigen, CD97 (EGF 1,2,5), CD97 (EGF 1,2,3,5), and CD97 (EGF 1,2,3,4,5). In the study, coexpression of the three CD97 isoforms and predominance of CD97 (EGF 1,2,5) transcripts in leukocytes are demonstrated. The contribution of CD97 (EGF 1,2,3,5) and CD97 (EGF 1,2,3,4,5) to total CD97 levels varied among most cell types only slightly, although relatively higher mRNA levels of both isoforms were detected in U 937 cells and monocytes. In peripheral blood lymphocytes, CD97 isoforms did not show clear variation after PMA stimulation and were down-regulated equally after CD97 cross-linking. Moreover, the CD97 isoform pattern was not altered in monocytes after interferon-gamma stimulation and in synovial T cells from patients with rheumatoid arthritis. CD97 mRNA levels did not necessarily correspond to CD97 surface density. The findings suggest that adhesive activity of CD97 toward CD55 is unlikely to be regulated by differential CD97 isoform expression.
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expression characteristics of the human CD97 Antigen
Tissue Antigens, 1997Co-Authors: Wolfram Eichler, Jorg Hamann, Gabriela AustAbstract:Molecules whose expression is increased upon stimulation on leukocyte populations are of considerable interest because insights into their structure and function extend knowledge of the intracellular and intercellular events that accompany cellular activation. One such molecule is CD97, a cell surface Antigen that is rapidly upregulated upon activation on lymphocytes. Increasing CD97 levels on peripheral blood lymphocytes (PBL) induced by different stimuli were found to be largely independent on de novo RNA and protein synthesis during the early stage of activation. Thus, inhibition of CD97 surface expression by cycloheximide was not noticeable or insignificant for 15 min to 4 h after stimulation. Furthermore, a fraction of intracellular CD97 decreased within 2 h suggesting redistribution of CD97 protein. Later, de novo protein synthesis apparently contributes to the induction of high CD97 surface density and inhibition by cycloheximide was more pronounced. Upregulation of CD97 on PBL involves protein kinase C-, tyrosine protein kinase- and Ca2+-dependent intracellular pathways. The effect on CD97 surface expression of the phorbol ester, phorbol 12-myristate 13-acetate (PMA), is different in PBL and Jurkat T cells. Whereas it stimulated after 22 h strong CD97 increase on PBL it suppressed CD97 expression on Jurkat T cells. CD97 expression, which is strong and constitutive on myelo-monocytic cells, is shown to be not leukocyte-restricted. Thus, CD97 transcripts were found in most of the investigated nonhematopoietic cell types and CD97 protein was detected on the cell surface at low amount. In a previous report, sequence data of a CD97 cDNA suggested a protein homologous to the secretin receptor superfamily and consisting of 722 amino acids with 8 potential glycosylation sites. According to this finding, glycoproteins displaying apparent molecular weights in the region of 70–85 kDa were detected in all investigated cell types. These molecules may represent differentially glycosylated and sialylated molecular forms of the same polypeptide. The findings support the notion that CD97 is broadly distributed and possesses a differentially regulated expression behavior on leukocytes and non-hematopoietic cells.
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CD97 a dedifferentiation marker in human thyroid carcinomas
Cancer Research, 1997Co-Authors: Gabriela Aust, Nilserik Heldin, Oliver Lotz, Wolfram Eichler, Stephan Laue, Werner A Scherbaum, Irina Lehmann, Henning Dralle, Cuong HoangvuAbstract:Abstract CD97 is a dimeric glycoprotein of Mr 75,000–85,000 and 28,000 belonging to a novel subfamily of seven-span transmembrane region leukocyte cell surface molecules. It is expressed abundantly in cells of hematopoietic origin. This is the first report demonstrating the expression of CD97 outside the hematopoetic system. CD97 was studied in normal human and neoplastic follicular epithelium of the thyroid and anaplastic (n = 3) and papillary (n = 1) thyroid carcinoma cell lines. In normal thyroid tissue (n = 11), no immunoreactivity of CD97 could be found, whereas in differentiated thyroid carcinomas (n = 10), CD97 expression was either lacking or low. Eleven of 12 undifferentiated anaplastic carcinomas revealed high CD97 presentation. CD97 was absent or only weakly present in patients with postoperative T1 tumors but increased greatly with the progression to postoperative T4 tumors. CD97 is clearly present in thyroid carcinoma cell lines but only at a very low level in normal human thyrocytes. Quantitation of CD97 cell surface expression levels revealed that C 643 and SW 1736 cells showed a two to four times higher specific antibody-binding capacity than did 8505 C and HTh 74 cells and a nearly 20 times higher specific antibody-binding capacity than normal thyrocytes. Phorbol 12-myristate 13-acetate treatment progressively caused a decrease of CD97 Antigen expression in all cell lines to about 30% of their initial levels after 48 h. Immunohistochemical staining of SW 1736 cells revealed that CD97 is located in most of the cell compartments and suggested a CD97 internalization process after phorbol 12-myristate 13-acetate treatment. Semiquantitative reverse transcription-PCR showed a correlation of CD97 mRNA and cell surface CD97 expression level in the cell lines. SW 1736, HTh 74, and 8505 C cells apparently expressed CD97 with alternative glycosylation compared to peripheral lymphocytes, whereas most of the CD97 Antigen presented on thyrocytes and C 643 cells had glycosylation sites resembling those of lymphocytes. The data suggest that CD97 expression may be a sensitive marker of dedifferentiation and of lymph node involvement in human thyroid tumors.
Gabriela Aust - One of the best experts on this subject based on the ideXlab platform.
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expression characteristics of the human CD97 Antigen
Tissue Antigens, 1997Co-Authors: Wolfram Eichler, Jorg Hamann, Gabriela AustAbstract:Molecules whose expression is increased upon stimulation on leukocyte populations are of considerable interest because insights into their structure and function extend knowledge of the intracellular and intercellular events that accompany cellular activation. One such molecule is CD97, a cell surface Antigen that is rapidly upregulated upon activation on lymphocytes. Increasing CD97 levels on peripheral blood lymphocytes (PBL) induced by different stimuli were found to be largely independent on de novo RNA and protein synthesis during the early stage of activation. Thus, inhibition of CD97 surface expression by cycloheximide was not noticeable or insignificant for 15 min to 4 h after stimulation. Furthermore, a fraction of intracellular CD97 decreased within 2 h suggesting redistribution of CD97 protein. Later, de novo protein synthesis apparently contributes to the induction of high CD97 surface density and inhibition by cycloheximide was more pronounced. Upregulation of CD97 on PBL involves protein kinase C-, tyrosine protein kinase- and Ca2+-dependent intracellular pathways. The effect on CD97 surface expression of the phorbol ester, phorbol 12-myristate 13-acetate (PMA), is different in PBL and Jurkat T cells. Whereas it stimulated after 22 h strong CD97 increase on PBL it suppressed CD97 expression on Jurkat T cells. CD97 expression, which is strong and constitutive on myelo-monocytic cells, is shown to be not leukocyte-restricted. Thus, CD97 transcripts were found in most of the investigated nonhematopoietic cell types and CD97 protein was detected on the cell surface at low amount. In a previous report, sequence data of a CD97 cDNA suggested a protein homologous to the secretin receptor superfamily and consisting of 722 amino acids with 8 potential glycosylation sites. According to this finding, glycoproteins displaying apparent molecular weights in the region of 70–85 kDa were detected in all investigated cell types. These molecules may represent differentially glycosylated and sialylated molecular forms of the same polypeptide. The findings support the notion that CD97 is broadly distributed and possesses a differentially regulated expression behavior on leukocytes and non-hematopoietic cells.
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CD97 a dedifferentiation marker in human thyroid carcinomas
Cancer Research, 1997Co-Authors: Gabriela Aust, Nilserik Heldin, Oliver Lotz, Wolfram Eichler, Stephan Laue, Werner A Scherbaum, Irina Lehmann, Henning Dralle, Cuong HoangvuAbstract:Abstract CD97 is a dimeric glycoprotein of Mr 75,000–85,000 and 28,000 belonging to a novel subfamily of seven-span transmembrane region leukocyte cell surface molecules. It is expressed abundantly in cells of hematopoietic origin. This is the first report demonstrating the expression of CD97 outside the hematopoetic system. CD97 was studied in normal human and neoplastic follicular epithelium of the thyroid and anaplastic (n = 3) and papillary (n = 1) thyroid carcinoma cell lines. In normal thyroid tissue (n = 11), no immunoreactivity of CD97 could be found, whereas in differentiated thyroid carcinomas (n = 10), CD97 expression was either lacking or low. Eleven of 12 undifferentiated anaplastic carcinomas revealed high CD97 presentation. CD97 was absent or only weakly present in patients with postoperative T1 tumors but increased greatly with the progression to postoperative T4 tumors. CD97 is clearly present in thyroid carcinoma cell lines but only at a very low level in normal human thyrocytes. Quantitation of CD97 cell surface expression levels revealed that C 643 and SW 1736 cells showed a two to four times higher specific antibody-binding capacity than did 8505 C and HTh 74 cells and a nearly 20 times higher specific antibody-binding capacity than normal thyrocytes. Phorbol 12-myristate 13-acetate treatment progressively caused a decrease of CD97 Antigen expression in all cell lines to about 30% of their initial levels after 48 h. Immunohistochemical staining of SW 1736 cells revealed that CD97 is located in most of the cell compartments and suggested a CD97 internalization process after phorbol 12-myristate 13-acetate treatment. Semiquantitative reverse transcription-PCR showed a correlation of CD97 mRNA and cell surface CD97 expression level in the cell lines. SW 1736, HTh 74, and 8505 C cells apparently expressed CD97 with alternative glycosylation compared to peripheral lymphocytes, whereas most of the CD97 Antigen presented on thyrocytes and C 643 cells had glycosylation sites resembling those of lymphocytes. The data suggest that CD97 expression may be a sensitive marker of dedifferentiation and of lymph node involvement in human thyroid tumors.
Juan J Garrido - One of the best experts on this subject based on the ideXlab platform.
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molecular cloning and structural analysis of the porcine homologue to CD97 Antigen
Veterinary Immunology and Immunopathology, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, Juan J Garrido, D LlanesAbstract:Abstract CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF–TM7. We here report the cloning of cDNA encoding the pig homologue of CD97. A pig CD97 specific probe was generated by PCR amplification of pig leukocyte cDNA, using primers based on consensus regions among the known sequences of mouse and human CD97. Screening of a pig aorta smooth muscle cDNA library identified one clone containing an open reading frame (ORF) that encoded an 18 amino acid putative signal peptide, a 141 amino acid sequence consisting of three EGF domains, a mucin-like spacer region of 276 amino acid, containing a G-protein coupling motif of 52 amino acids, followed by a 250 amino acid region containing seven membrane spanning domains and a 47 amino acid cytoplasmic tail. The amino acid sequence of the clone was 75, 67 and 59% homologous to cattle, human and mouse CD97 Antigen, respectively. Therefore, it was termed pig CD97. Pig CD97 Antigen shares many structural features with human, cattle and mouse CD97. RT-PCR analysis of cDNA from different pig cells and tissues showed that CD97 was highly expressed in leukocytes and lymph node cells. This is the first report describing the identification of a member of the EGF–TM7 family in the pig.
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assignment of porcine CD97 gene to the 1 2q21 q22 region of the pig chromosome 2 with somatic cell hybrids
Cytogenetic and Genome Research, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, D Llanes, M Yerle, Juan J GarridoAbstract:CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF-TM7. To date, the EGF-TM7 group comprises CD97, EGF module-containing mucin-like hormone receptor (EMR) EMR1, EMR2, EMR3, and ETL in human, and CD97, F4/80 (EMR1) and EMR4 in the mouse (Kwakkenbos et al., 2002; McKnight et al., 1998; Stacey et al., 2002; Stacey et al., 2001). CD97 is induced rapidly on the surface of most leukocytes upon activation. So far, CD97 is the only EGF-TM7 family member of which a ligand has been identified. CD97 binds to its cellular ligand CD55 (decay accelerating factor), which protects several cell types from complement-mediated damage (Hannan et al., 1996). The functional consequences of CD97CD55 binding are largely unknown, but previous data imply that CD97-CD55 interactions play a role in cellular activation, migration, and adhesion under inflammatory conditions (Visser et al., 2002). The CD97 structural gene is mapped to the 19p13.2→ p13.12 region on human chromosome 19. We have recently cloned the pig homologue of the CD97 Antigen. Sequence comparison indicates that pig CD97 shares many structural features with human, cattle and mouse CD97 (Perez de la Lastra et al., 2003). To date, this is the first member of the EGF-TM7 family identified in the pig.
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Assignment of porcine CD97 gene to the 1/2q21-->q22 region of the pig chromosome 2 with somatic cell hybrids.
Cytogenetic and Genome Research, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, D Llanes, M Yerle, Juan J GarridoAbstract:CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF-TM7. To date, the EGF-TM7 group comprises CD97, EGF module-containing mucin-like hormone receptor (EMR) EMR1, EMR2, EMR3, and ETL in human, and CD97, F4/80 (EMR1) and EMR4 in the mouse (Kwakkenbos et al., 2002; McKnight et al., 1998; Stacey et al., 2002; Stacey et al., 2001). CD97 is induced rapidly on the surface of most leukocytes upon activation. So far, CD97 is the only EGF-TM7 family member of which a ligand has been identified. CD97 binds to its cellular ligand CD55 (decay accelerating factor), which protects several cell types from complement-mediated damage (Hannan et al., 1996). The functional consequences of CD97CD55 binding are largely unknown, but previous data imply that CD97-CD55 interactions play a role in cellular activation, migration, and adhesion under inflammatory conditions (Visser et al., 2002). The CD97 structural gene is mapped to the 19p13.2→ p13.12 region on human chromosome 19. We have recently cloned the pig homologue of the CD97 Antigen. Sequence comparison indicates that pig CD97 shares many structural features with human, cattle and mouse CD97 (Perez de la Lastra et al., 2003). To date, this is the first member of the EGF-TM7 family identified in the pig.
J Perez M De La Lastra - One of the best experts on this subject based on the ideXlab platform.
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molecular cloning and structural analysis of the porcine homologue to CD97 Antigen
Veterinary Immunology and Immunopathology, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, Juan J Garrido, D LlanesAbstract:Abstract CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF–TM7. We here report the cloning of cDNA encoding the pig homologue of CD97. A pig CD97 specific probe was generated by PCR amplification of pig leukocyte cDNA, using primers based on consensus regions among the known sequences of mouse and human CD97. Screening of a pig aorta smooth muscle cDNA library identified one clone containing an open reading frame (ORF) that encoded an 18 amino acid putative signal peptide, a 141 amino acid sequence consisting of three EGF domains, a mucin-like spacer region of 276 amino acid, containing a G-protein coupling motif of 52 amino acids, followed by a 250 amino acid region containing seven membrane spanning domains and a 47 amino acid cytoplasmic tail. The amino acid sequence of the clone was 75, 67 and 59% homologous to cattle, human and mouse CD97 Antigen, respectively. Therefore, it was termed pig CD97. Pig CD97 Antigen shares many structural features with human, cattle and mouse CD97. RT-PCR analysis of cDNA from different pig cells and tissues showed that CD97 was highly expressed in leukocytes and lymph node cells. This is the first report describing the identification of a member of the EGF–TM7 family in the pig.
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assignment of porcine CD97 gene to the 1 2q21 q22 region of the pig chromosome 2 with somatic cell hybrids
Cytogenetic and Genome Research, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, D Llanes, M Yerle, Juan J GarridoAbstract:CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF-TM7. To date, the EGF-TM7 group comprises CD97, EGF module-containing mucin-like hormone receptor (EMR) EMR1, EMR2, EMR3, and ETL in human, and CD97, F4/80 (EMR1) and EMR4 in the mouse (Kwakkenbos et al., 2002; McKnight et al., 1998; Stacey et al., 2002; Stacey et al., 2001). CD97 is induced rapidly on the surface of most leukocytes upon activation. So far, CD97 is the only EGF-TM7 family member of which a ligand has been identified. CD97 binds to its cellular ligand CD55 (decay accelerating factor), which protects several cell types from complement-mediated damage (Hannan et al., 1996). The functional consequences of CD97CD55 binding are largely unknown, but previous data imply that CD97-CD55 interactions play a role in cellular activation, migration, and adhesion under inflammatory conditions (Visser et al., 2002). The CD97 structural gene is mapped to the 19p13.2→ p13.12 region on human chromosome 19. We have recently cloned the pig homologue of the CD97 Antigen. Sequence comparison indicates that pig CD97 shares many structural features with human, cattle and mouse CD97 (Perez de la Lastra et al., 2003). To date, this is the first member of the EGF-TM7 family identified in the pig.
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Assignment of porcine CD97 gene to the 1/2q21-->q22 region of the pig chromosome 2 with somatic cell hybrids.
Cytogenetic and Genome Research, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, D Llanes, M Yerle, Juan J GarridoAbstract:CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF-TM7. To date, the EGF-TM7 group comprises CD97, EGF module-containing mucin-like hormone receptor (EMR) EMR1, EMR2, EMR3, and ETL in human, and CD97, F4/80 (EMR1) and EMR4 in the mouse (Kwakkenbos et al., 2002; McKnight et al., 1998; Stacey et al., 2002; Stacey et al., 2001). CD97 is induced rapidly on the surface of most leukocytes upon activation. So far, CD97 is the only EGF-TM7 family member of which a ligand has been identified. CD97 binds to its cellular ligand CD55 (decay accelerating factor), which protects several cell types from complement-mediated damage (Hannan et al., 1996). The functional consequences of CD97CD55 binding are largely unknown, but previous data imply that CD97-CD55 interactions play a role in cellular activation, migration, and adhesion under inflammatory conditions (Visser et al., 2002). The CD97 structural gene is mapped to the 19p13.2→ p13.12 region on human chromosome 19. We have recently cloned the pig homologue of the CD97 Antigen. Sequence comparison indicates that pig CD97 shares many structural features with human, cattle and mouse CD97 (Perez de la Lastra et al., 2003). To date, this is the first member of the EGF-TM7 family identified in the pig.
D Llanes - One of the best experts on this subject based on the ideXlab platform.
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molecular cloning and structural analysis of the porcine homologue to CD97 Antigen
Veterinary Immunology and Immunopathology, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, Juan J Garrido, D LlanesAbstract:Abstract CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF–TM7. We here report the cloning of cDNA encoding the pig homologue of CD97. A pig CD97 specific probe was generated by PCR amplification of pig leukocyte cDNA, using primers based on consensus regions among the known sequences of mouse and human CD97. Screening of a pig aorta smooth muscle cDNA library identified one clone containing an open reading frame (ORF) that encoded an 18 amino acid putative signal peptide, a 141 amino acid sequence consisting of three EGF domains, a mucin-like spacer region of 276 amino acid, containing a G-protein coupling motif of 52 amino acids, followed by a 250 amino acid region containing seven membrane spanning domains and a 47 amino acid cytoplasmic tail. The amino acid sequence of the clone was 75, 67 and 59% homologous to cattle, human and mouse CD97 Antigen, respectively. Therefore, it was termed pig CD97. Pig CD97 Antigen shares many structural features with human, cattle and mouse CD97. RT-PCR analysis of cDNA from different pig cells and tissues showed that CD97 was highly expressed in leukocytes and lymph node cells. This is the first report describing the identification of a member of the EGF–TM7 family in the pig.
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assignment of porcine CD97 gene to the 1 2q21 q22 region of the pig chromosome 2 with somatic cell hybrids
Cytogenetic and Genome Research, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, D Llanes, M Yerle, Juan J GarridoAbstract:CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF-TM7. To date, the EGF-TM7 group comprises CD97, EGF module-containing mucin-like hormone receptor (EMR) EMR1, EMR2, EMR3, and ETL in human, and CD97, F4/80 (EMR1) and EMR4 in the mouse (Kwakkenbos et al., 2002; McKnight et al., 1998; Stacey et al., 2002; Stacey et al., 2001). CD97 is induced rapidly on the surface of most leukocytes upon activation. So far, CD97 is the only EGF-TM7 family member of which a ligand has been identified. CD97 binds to its cellular ligand CD55 (decay accelerating factor), which protects several cell types from complement-mediated damage (Hannan et al., 1996). The functional consequences of CD97CD55 binding are largely unknown, but previous data imply that CD97-CD55 interactions play a role in cellular activation, migration, and adhesion under inflammatory conditions (Visser et al., 2002). The CD97 structural gene is mapped to the 19p13.2→ p13.12 region on human chromosome 19. We have recently cloned the pig homologue of the CD97 Antigen. Sequence comparison indicates that pig CD97 shares many structural features with human, cattle and mouse CD97 (Perez de la Lastra et al., 2003). To date, this is the first member of the EGF-TM7 family identified in the pig.
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Assignment of porcine CD97 gene to the 1/2q21-->q22 region of the pig chromosome 2 with somatic cell hybrids.
Cytogenetic and Genome Research, 2003Co-Authors: J Perez M De La Lastra, Yasser E A Shahein, D Llanes, M Yerle, Juan J GarridoAbstract:CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF-TM7. To date, the EGF-TM7 group comprises CD97, EGF module-containing mucin-like hormone receptor (EMR) EMR1, EMR2, EMR3, and ETL in human, and CD97, F4/80 (EMR1) and EMR4 in the mouse (Kwakkenbos et al., 2002; McKnight et al., 1998; Stacey et al., 2002; Stacey et al., 2001). CD97 is induced rapidly on the surface of most leukocytes upon activation. So far, CD97 is the only EGF-TM7 family member of which a ligand has been identified. CD97 binds to its cellular ligand CD55 (decay accelerating factor), which protects several cell types from complement-mediated damage (Hannan et al., 1996). The functional consequences of CD97CD55 binding are largely unknown, but previous data imply that CD97-CD55 interactions play a role in cellular activation, migration, and adhesion under inflammatory conditions (Visser et al., 2002). The CD97 structural gene is mapped to the 19p13.2→ p13.12 region on human chromosome 19. We have recently cloned the pig homologue of the CD97 Antigen. Sequence comparison indicates that pig CD97 shares many structural features with human, cattle and mouse CD97 (Perez de la Lastra et al., 2003). To date, this is the first member of the EGF-TM7 family identified in the pig.