1
|
Yilmaz M, Yalcin E, Presumey J, Aw E, Ma M, Whelan CW, Stevens B, McCarroll SA, Carroll MC. Overexpression of schizophrenia susceptibility factor human complement C4A promotes excessive synaptic loss and behavioral changes in mice. Nat Neurosci 2021; 24:214-224. [PMID: 33353966 PMCID: PMC8086435 DOI: 10.1038/s41593-020-00763-8] [Citation(s) in RCA: 161] [Impact Index Per Article: 53.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 11/20/2020] [Indexed: 12/13/2022]
Abstract
The complement component 4 (C4) gene is linked to schizophrenia and synaptic refinement. In humans, greater expression of C4A in the brain is associated with an increased risk of schizophrenia. To investigate this genetic finding and address how C4A shapes brain circuits in vivo, here, we generated a mouse model with primate-lineage-specific isoforms of C4, human C4A and/or C4B. Human C4A bound synapses more efficiently than C4B. C4A (but not C4B) rescued the visual system synaptic refinement deficits of C4 knockout mice. Intriguingly, mice without C4 had normal numbers of cortical synapses, which suggests that complement is not required for normal developmental synaptic pruning. However, overexpressing C4A in mice reduced cortical synapse density, increased microglial engulfment of synapses and altered mouse behavior. These results suggest that increased C4A-mediated synaptic elimination results in abnormal brain circuits and behavior. Understanding pathological overpruning mechanisms has important therapeutic implications in disease conditions such as schizophrenia.
Collapse
Affiliation(s)
- Melis Yilmaz
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Esra Yalcin
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Jessy Presumey
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Ernest Aw
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Minghe Ma
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Christopher W Whelan
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Beth Stevens
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Steven A McCarroll
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Michael C Carroll
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
| |
Collapse
|
2
|
Varin-Blank N, Dondi E, Tosi M, Hernandez C, Boucontet L, Gotoh H, Shiroishi T, Moriwaki K, Meo T. Male-specific transcription initiation of the C4-Slp gene in mouse liver follows activation of STAT5. Proc Natl Acad Sci U S A 1998; 95:8750-5. [PMID: 9671750 PMCID: PMC21148 DOI: 10.1073/pnas.95.15.8750] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The mouse genes encoding the constitutively expressed complement component C4 and its closely related isoform C4-Slp (sex-limited protein), which is expressed only in male animals of several strains, provide a unique model to study sequence elements and trans-acting factors responsible for androgen responsiveness. Our previous studies have shown that hormonal induction of C4-Slp is mediated by a sex-specific pattern of growth hormone secretion. Promoter analyses in vitro have led to contradictory conclusions concerning the significance of C4-Slp-specific sequences in the 5' flanking region. Mutant mice carrying the H-2(aw18) haplotype, which is characterized by a large deletion in the S region covering the C4 and 21-OHase A genes, permit the direct in vivo analysis of C4-Slp transcription, unhindered by the presence of C4. Run-on analysis of transcription in liver nuclei of males and females of this strain demonstrated a 100-fold higher transcriptional activity in males, essentially determined at the transcription initiation level. The androgen dependence of transcription initiation was confirmed by run-on analysis of testosterone-treated females, where transcriptional activity started after 6 days of androgen treatment and reached male levels after 20 days. Conversely, the growth hormone-regulated activity of transcription factor STAT5 was already detected in liver nuclei after 48 hr of androgen treatment. Furthermore, we demonstrate that activated STAT5 recognizes in vitro two upstream gamma interferon-activated sequence (GAS) elements of the C4-Slp gene, centered at positions -1969 and -1831. We postulate that binding of STAT5 to these C4-Slp-specific GAS elements plays a crucial role in the chromatin remodelings that lead to transcriptional competence of the C4-Slp gene in the liver.
Collapse
Affiliation(s)
- N Varin-Blank
- Unité d'Immunogénétique et Institut National de la Santé et de la Recherche Médicale, U. 276, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Szalai AJ, van Ginkel FW, Dalrymple SA, Murray R, McGhee JR, Volanakis JE. Testosterone and IL-6 Requirements for Human C-Reactive Protein Gene Expression in Transgenic Mice. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.11.5294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
In vitro, IL-6 is the main inducer of the human C-reactive protein (CRP) gene, and IL-1 and steroids can enhance this effect. However, in mice, IL-6 is necessary but not sufficient for induction of the human CRP transgene, and testosterone is required for its constitutive expression by males. To examine the relative contributions of testosterone and IL-6 in the regulation of CRP gene expression, we produced CRP-transgenic (CRPtg), IL-6-deficient (IL-6−/−) mice. Male CRPtg/IL-6−/− mice expressed CRP constitutively, but CRP levels were not increased after injection of LPS. However, acute-phase CRP levels were attained after injection of IL-6. In contrast, female CRPtg/IL-6−/− mice did not express CRP constitutively or after administration of LPS, IL-6, IL-1, or IL-6 plus IL-1. Like males, testosterone-treated CRPtg/IL-6−/− females expressed CRP constitutively, and their transgene responded to injection of IL-6. The endogenous acute-phase protein serum amyloid P (SAP) was expressed constitutively equally by male and female IL-6−/− mice, responded minimally to LPS, and did not respond to either IL-6 or IL-1 alone. Acute-phase levels of SAP were induced in IL-6−/− mice by injection of IL-6 together with IL-1 or LPS. We conclude that in vivo, both constitutive and IL-6-dependent acute-phase expression of the CRP transgene require testosterone. In contrast, testosterone is not required for expression of the SAP gene, which requires IL-1 plus IL-6 for acute-phase induction.
Collapse
Affiliation(s)
- Alexander J. Szalai
- *Division of Clinical Immunology and Rheumatology, Department of Medicine and
| | - Frederik W. van Ginkel
- †Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294; and
| | - Stacie A. Dalrymple
- ‡Department of Molecular Biology, DNAX Research Institute, Palo Alto, CA 94304
| | - Richard Murray
- ‡Department of Molecular Biology, DNAX Research Institute, Palo Alto, CA 94304
| | - Jerry R. McGhee
- †Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294; and
| | - John E. Volanakis
- *Division of Clinical Immunology and Rheumatology, Department of Medicine and
| |
Collapse
|
4
|
Jiang PP, Frederick K, Hansen TH, Miller RD. Localization of the mouse gene releasing sex-limited expression of Slp. Proc Natl Acad Sci U S A 1996; 93:913-7. [PMID: 8570659 PMCID: PMC40158 DOI: 10.1073/pnas.93.2.913] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
To probe genetic variation in the regulation of sexual dimorphism, we have characterized the mouse protein Slp, coded by the gene sex-limited protein (Slp). Slp expression in many strains is limited to males and is androgen-dependent. However, female expression is also observed in rare strains, due to nonlinked gene(s) termed regulator of sex-limitation (rsl). In this report we demonstrate that female expression of Slp results from homozygous recessive allele(s) at a single autosomal locus that maps to a 2.2-centimorgan interval on chromosome 13. This conclusion was supported by extensive genetic analyses including the use of polymorphic microsatellites to type numerous backcross progeny and a recombinant inbred series and to identify the congenic interval in three independently derived congenic strains. Four attractive candidate genes were identified by the localization of rsl. Interestingly, rsl was found not only to enable expression in females but to also increase expression in males. The findings suggest that the expression of Slp and perhaps other sexually dimorphic proteins is regulated by two pathways, one that is dependent upon rsl but not androgens and another that is rsl-independent but requires androgens.
Collapse
Affiliation(s)
- P P Jiang
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | | | | | | |
Collapse
|
5
|
Yokomori N, Kobayashi R, Moore R, Sueyoshi T, Negishi M. A DNA methylation site in the male-specific P450 (Cyp 2d-9) promoter and binding of the heteromeric transcription factor GABP. Mol Cell Biol 1995; 15:5355-62. [PMID: 7565685 PMCID: PMC230784 DOI: 10.1128/mcb.15.10.5355] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The Cyp 2d-9 gene encodes the male-specific steroid 16 alpha-hydroxylase in mouse liver and shares a conserved regulatory element (-100TTCCGGGC-93) with another male-specific Slp promoter. As shown with the Slp promoter (N. Yokomori, R. Moore, and M. Negishi, Proc. Natl. Acad. Sci. USA 92:1302-1306, 1995), the male-preferential demethylation also occurs at CpG/-97 in the Cyp 2d-9 promoter. The transcription factor which specifically binds to the demethylated element has been purified. The peptide sequences reveal that the factor consists of GABP alpha and GABP beta 1 with Ets and Notch motifs, respectively. Both DNase I footprinting and gel shift assays indicate that the bacterially expressed glutathione S-transferase-GABP fusion proteins bind to the regulatory element only when CpG/-97 is demethylated. Moreover, Cyp 2d-9 promoter is trans-activated by coexpression of GABP proteins in HepG2 cells. Given the additional results that CpG/-50 of the female-specific steroid 15 alpha-hydroxylase (Cyp 2a-4) promoter is preferentially demethylated in the females, the sex-specific expressions of the P450 genes correlate very well with DNA demethylation. We also conclude that GABP is a methylation-sensitive transcription factor and is a potential transcription activator of the male-specific Cyp 2d-9 promoter.
Collapse
Affiliation(s)
- N Yokomori
- Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
| | | | | | | | | |
Collapse
|
6
|
Vaishnaw AK, Hargreaves R, Campbell RD, Morley BJ, Walport MJ. DNase I hypersensitivity mapping and promoter polymorphism analysis of human C4. Immunogenetics 1995; 41:354-8. [PMID: 7759131 DOI: 10.1007/bf00163992] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Human complement component C4 is encoded by two structurally distinct loci in the major histocompatibility complex (MHC) class III region. The two isotypes, C4A and C4B, differ at only four residues in the C4d fragment, but C4 constitutes the most polymorphic of the complement components. It is not known, however, whether the regions involved in the regulation of C4 expression also display polymorphic variation. By using the technique of DNase I hypersensitivity mapping, we established that the only area of transcriptional activity for C4 in the hepatocyte cell line, HepG2, occurs approximately 500 base pairs upstream of the transcriptional start site. This region was found to be remarkably constant in sequence when analyzed in the context of differing MHC haplotypes including HLA B57, C4A6, C4B1, DR7, which has been correlated with reduced expression of the C4A isotype. Similarly, polymerase chain reaction followed by single-strand conformation polymorphism analysis failed to demonstrate any promoter polymorphisms in 103 individuals comprising 52 systemic lupus erythematosus patients and 51 healthy controls.
Collapse
Affiliation(s)
- A K Vaishnaw
- Dept. of Medicine, RPMS, Hammersmith Hospital, London, UK
| | | | | | | | | |
Collapse
|
7
|
Yokomori N, Moore R, Negishi M. Sexually dimorphic DNA demethylation in the promoter of the Slp (sex-limited protein) gene in mouse liver. Proc Natl Acad Sci U S A 1995; 92:1302-6. [PMID: 7877972 PMCID: PMC42507 DOI: 10.1073/pnas.92.5.1302] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Mouse Slp, a duplicate of the fourth complement component (C4) gene, exhibits EDTA-independent complement activity with a hepatic expression that is male specific. To provide an underlying mechanism for the male-specific expression, we have analyzed the promoter activity of the various 5'-flanking sequences and CpG demethylation of the Slp gene. Transient transfections using HepG2 cells indicate that the element TTCCGGGC (nt -124 to -117) regulates the promoter activity. Moreover, CpG at position -121 of this regulatory element is demethylated to a much higher degree in males than in females. This sexually dimorphic DNA demethylation is consistent with the male-specific expression of the Slp gene in DBA/2 males. The regulatory element binds to the different TTCCGGGC-specific nuclear proteins depending on the methylation of the CpG site. In contrast, the corresponding CpG at position -119 of the C4 gene, which is expressed in both males and females, is demethylated at equal and high levels in both sexes. We therefore propose that the DNA demethylation and methylation-sensitive transcription factors may be a part of the regulatory mechanism for the male-specific expression of the Slp gene.
Collapse
Affiliation(s)
- N Yokomori
- Pharmacogenetics Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709
| | | | | |
Collapse
|
8
|
Miyagoe Y, Galibert M, Georgatsou E, Fourel G, Meo T. Promoter elements of the mouse complement C4 gene critical for transcription activation and start site location. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37189-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
9
|
Miyagoe Y, Georgatsou E, Varin-Blank N, Meo T. The androgen-dependent C4-Slp gene is driven by a constitutively competent promoter. Proc Natl Acad Sci U S A 1993; 90:5786-90. [PMID: 8390682 PMCID: PMC46807 DOI: 10.1073/pnas.90.12.5786] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The androgen-dependent liver protein Slp, together with its constitutively expressed closely related isoform C4, provides a model to address the question of which minimal alteration in DNA can shut off the expression of a gene in a manner reversible by testosterone or by trans-acting mutations. Previous work indicated that sequences located at -1.9, -0.45, and -0.25 kb from the transcription start site of the C4-Slp gene played a critical role in determining its unusual functional divergence from C4. Now, using quantitatively and qualitatively controlled transfection assays in HepG2 human hepatoma cells and mouse L fibroblasts, we have observed that the C4-Slp promoter is fully effective and unhindered by upstream sequences and that the C4 promoter has a consistent albeit modest superiority. The determinant of this nearly 2-fold difference does not coincide with the sites highlighted in previous studies but lies within the most cap-site-proximal nucleotides, at positions -189 to +48. We have also established conditions for cell-free transcription of C4 and C4-Slp from plasmid and cosmid templates by using nuclear extracts from rat and mouse liver of both sexes as well as from L cells. At variance with the rat alpha 2u-globulin gene, C4-Slp transcription in vitro does not require male factors, for it is expressed as efficiently as C4 by all nuclear extracts. Further, the minimal promoter sequences required to direct accurate initiation extend not farther than the most proximal 19 nucleotides. Because L cells efficiently express transfected cosmids covering the whole C4 gene or C4/C4-Slp recombinants, as well as plasmids carrying the C4-Slp promoter, but fail to express the full C4-Slp gene, we favor a model in which the expression of the gene is modulated intragenically.
Collapse
Affiliation(s)
- Y Miyagoe
- Unité d'Immunogénétique, Institut Pasteur, Paris, France
| | | | | | | |
Collapse
|
10
|
Georgatsou E, Bourgarel P, Meo T. Male-specific expression of mouse sex-limited protein requires growth hormone, not testosterone. Proc Natl Acad Sci U S A 1993; 90:3626-30. [PMID: 8475111 PMCID: PMC46354 DOI: 10.1073/pnas.90.8.3626] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Sex-limited protein (Slp), an isoform of mouse complement component C4, is expressed predominantly in liver and nearly exclusively in sexually mature males or testosterone-treated females. It is encoded by a gene (C4-Slp) whose hormonal dependence has been attributed to an androgen-responsive transcriptional enhancer introduced accidentally, alongside the C4-Slp promoter, in the guise of the 5' long terminal repeat of an ancient retrovirus. We demonstrate that the pronounced rise of C4-Slp mRNA promoted by androgens in the liver is due to nuclear factors acting at a transcriptional stage. Curiously, hypophysectomized animals of either sex fail to express the gene and are refractory to testosterone. However, gene expression at male levels is restored even more promptly by injections of growth hormone alone. Additionally, animals carrying an ubiquitously expressed human growth hormone transgene lack C4-Slp mRNA and are insensitive to testosterone treatment. That growth hormone is sufficient to induce expression in a manner independent of androgen-receptor activity is shown by the hormonal treatment of Tfm mice. These androgen receptor-defective animals lack C4-Slp mRNA, which however can be fully induced by growth hormone injections. We conclude that the sexual dimorphism of C4-Slp expression employs liver nuclear mediators distinct from those directly instructed by androgens and is brought about by the intermittent rise of growth hormone, dictated by testosterone.
Collapse
Affiliation(s)
- E Georgatsou
- Unité d'Immunogénétique et Institut National de la Santé et de la Recherche Médicale, Institut Pasteur, Paris, France
| | | | | |
Collapse
|
11
|
|
12
|
Zheng JH, Natsuume-Sakai S, Takahashi M, Nonaka M. Insertion of the B2 sequence into intron 13 is the only defect of the H-2k C4 gene which causes low C4 production. Nucleic Acids Res 1992; 20:4975-9. [PMID: 1329034 PMCID: PMC334272 DOI: 10.1093/nar/20.19.4975] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The serum level of the fourth component of complement (C4) in mice bearing H-2k haplotype is only 1/10 of that of non-H-2k mice. H-2k bearing mice, but not non-H-2k bearing mice, have an insertion of the B2 sequence into intron 13 of the C4 gene, and aberrant C4 mRNA in liver apparently generated by abnormal RNA splicing caused by the insertion of the B2 sequence. To test the possible causal relationship between the B2 insertion and low C4 production in H-2k mice directly, we constructed the H-2k C4 gene without the B2 insertion and the H-2w7 (non-H-2k) C4 gene with the B2 insertion by exchanging a part of intron 13 between these two genes. Transfection of the intact H-2w7 C4 gene or the chimeric H-2k gene without the B2 insertion into HepG2 cells resulted in the production of only normal C4 mRNA at the normal level. On the other hand, the intact H-2k C4 gene or the chimeric H-2w7 C4 gene with the B2 insertion directed production of both aberrant and a decreased amount of normal C4 mRNA. These results demonstrated that the insertion of B2 sequence into intron 13 of the C4 gene is the only determinant of low C4 production by H-2k mice through aberrant RNA processing.
Collapse
Affiliation(s)
- J H Zheng
- Department of Immunobiology, Kanazawa University, Japan
| | | | | | | |
Collapse
|
13
|
Abstract
The adjacent C4 and P450c21 genes encode the fourth component of serum complement and steroid 21-hydroxylase respectively, and are tandemly duplicated in the human, murine, and bovine genomes. We recently cloned a cDNA for another duplicated gene, operationally termed X, which overlaps the 3' end of human P450c21 and has the opposite transcriptional orientation. Thus, the organization of the locus is 5'-C4A-21A-XA-C4B-21B-XB-3' (Y. Morel, J. Bristow, S. E. Gitelman, and W. L. Miller, Proc. Natl. Acad. Sci. USA 86:6582-6586, 1989). To determine how this locus was duplicated, we sequenced the DNA at the duplication boundaries and the 7 kb between P450c21A and C4B comprising the XA locus. The sequences located the duplication boundaries precisely and indicate that the duplication occurred by nonhomologous recombination. The boundaries are substantially different from those of the corresponding duplication in the mouse genome, suggesting that similar gene duplications may have occurred independently in ancestors of rodents and primates after mammalian speciation. Compared with XB, the XA gene is truncated at its 5' end and bears a 121-bp intragenic deletion causing a frameshift and premature translational stop signal. Nevertheless, XA is transcribed into a stable 2.6-kb polyadenylated RNA that is expressed uniquely in the adrenal gland.
Collapse
|
14
|
Gitelman SE, Bristow J, Miller WL. Mechanism and consequences of the duplication of the human C4/P450c21/gene X locus. Mol Cell Biol 1992; 12:2124-34. [PMID: 1373808 PMCID: PMC364384 DOI: 10.1128/mcb.12.5.2124-2134.1992] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The adjacent C4 and P450c21 genes encode the fourth component of serum complement and steroid 21-hydroxylase respectively, and are tandemly duplicated in the human, murine, and bovine genomes. We recently cloned a cDNA for another duplicated gene, operationally termed X, which overlaps the 3' end of human P450c21 and has the opposite transcriptional orientation. Thus, the organization of the locus is 5'-C4A-21A-XA-C4B-21B-XB-3' (Y. Morel, J. Bristow, S. E. Gitelman, and W. L. Miller, Proc. Natl. Acad. Sci. USA 86:6582-6586, 1989). To determine how this locus was duplicated, we sequenced the DNA at the duplication boundaries and the 7 kb between P450c21A and C4B comprising the XA locus. The sequences located the duplication boundaries precisely and indicate that the duplication occurred by nonhomologous recombination. The boundaries are substantially different from those of the corresponding duplication in the mouse genome, suggesting that similar gene duplications may have occurred independently in ancestors of rodents and primates after mammalian speciation. Compared with XB, the XA gene is truncated at its 5' end and bears a 121-bp intragenic deletion causing a frameshift and premature translational stop signal. Nevertheless, XA is transcribed into a stable 2.6-kb polyadenylated RNA that is expressed uniquely in the adrenal gland.
Collapse
Affiliation(s)
- S E Gitelman
- Department of Pediatrics, University of California, San Francisco 94143
| | | | | |
Collapse
|
15
|
Abstract
Transposable elements, and retroviral-like elements in particular, are a rich potential source of genetic variation within a host's genome. Many mutations of endogenous genes in phylogenetically diverse organisms are due to insertion of elements that affect gene expression by altering the normal pattern of regulation. While few such associations are known to have been maintained over time, two recently elucidated examples suggest transposable elements may have a significant impact in evolution of gene expression. The first example, concerning the mouse sex-limited protein (Slp), clearly establishes that ancient retroviral enhancer sequences now confer hormonal dependence on the adjacent gene. The second example shows that within the human amylase gene family, salivary specific expression has arisen due to inserted sequences, deriving perhaps from a conjunction of two retrotransposable elements.
Collapse
Affiliation(s)
- D M Robins
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor 48109
| | | |
Collapse
|
16
|
Huang ZM, Takahashi M, Nonaka M. Differential expression of the five C4-related genes of H-2w7 mice. Immunogenetics 1991; 33:361-6. [PMID: 2050390 DOI: 10.1007/bf00216695] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Mice bearing the H-2w7 haplotype have five C4-related genes, one C4, one Slp, and three C4/Slp hybrid genes. The expression of these five genes in the liver of H-2w7 mice was estimated at the steady state level of their respective mRNA. We have amplified by the polymerase chain reaction (PCR) three regions of the C4/Slp mRNA where some of these five genes show nucleotide substitution. A relative amount of each gene product was estimated by single-strand conformation polymorphism (SSCP) analysis or by direct counting of the number of respective clones after subcloning into a plasmid vector. A steady state level of the C4 mRNA was most abundant among C4-related gene transcripts. The hybrid 1 and 3 genes were expressed at a similar level which is about 1/2-1/3 of the C4 level. The hybrid 2 gene was expressed at about 1/5 of the hybrid 1 or 3 level. Neither male nor female H-2w7 mice expressed the Slp gene. These results showed that the expression of the five C4-related genes of H-2w7 mice is differentially regulated in spite of the close similarity in the nucleotide sequences in both the 5' flanking and coding regions of these genes.
Collapse
Affiliation(s)
- Z M Huang
- Department of Immunobiology, Kanazawa University, Japan
| | | | | |
Collapse
|
17
|
Interleukin-1-mediated enhancement of mouse factor B gene expression via NF kappa B-like hepatoma nuclear factor. Mol Cell Biol 1991. [PMID: 2174104 DOI: 10.1128/mcb.10.12.6283] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Complement factor B, a serine protease playing a pivotal role in alternative pathway activation, is an acute-phase plasma protein. Previous studies have revealed that interleukin-1 (IL-1) mediates, at least in part, the acute-phase induction of factor B expression and that the IL-1-responsive element resides in the region between -553 and -478 relative to the transcription initiation site of the mouse factor B gene. In this paper, we demonstrate a specific binding site for a nuclear factor of human hepatoma HepG2 cells in this region of the factor B gene, using gel shift and methylation interference analysis. The nucleotide sequence of the binding site is closely similar to the NF kappa B or H2TF1 binding motif. The binding activity of HepG2 showed very similar specificity to that of NF kappa B or H2TF1, as shown by a competition binding assay, and was induced by IL-1 alpha treatment. A synthetic oligonucleotide corresponding to this binding site, as well as a similar sequence found in another class III complement C4 gene, conferred IL-1 responsiveness on the minimal factor B promoter. In contrast, a mutated oligonucleotide that could not bind to the HepG2 nuclear factor did not confer IL-1 responsiveness. These results suggest that IL-1 induces factor B expression via NF kappa B or a closely related factor in hepatocyte nuclei.
Collapse
|
18
|
Pattanakitsakul S, Nakayama K, Takahashi M, Nonaka M. Three extra copies of a C4-related gene in H-2w7 mice are C4/Slp hybrid genes generated by multiple recombinational events. Immunogenetics 1990; 32:431-9. [PMID: 2272665 DOI: 10.1007/bf00241638] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mice bearing the H-2w7 haplotype have five C4-related genes and constitutively express the Slp antigen. To understand the structure and evolution of the five C4-related genes of the C3H.W7 mouse, we have determined nucleotide sequences of the 5' end region of these genes. A C4/Slp hybrid nature was confirmed for three of five C4-related genes as predicted previously by restriction enzyme analysis. The nucleotide sequences of the 5' flanking regions of these three hybrid genes showed close similarity to that of the C4 gene, while the 3' side of the ninth exon of the three hybrid genes showed close similarity to that of the Slp gene. In contrast, the regions between the first exon and the middle of the ninth exon of the three hybrid genes showed a mosaic structure of C4-like and Slp-like sequences. Moreover, the boundaries of the C4-like and Slp-like sequences were quite different among the three hybrid genes. The pattern of nucleotide sequence diversity in this region among the five C4-related sequences could be mainly explained not by point mutations but by gene conversions or unequal crossovers. These results suggest that multiple genetic recombinational events between two homologous sequences played an important role in the generation and diversification of the extra copies of the C4/Slp gene in the H-2w7 mouse.
Collapse
|
19
|
Nonaka M, Huang ZM. Interleukin-1-mediated enhancement of mouse factor B gene expression via NF kappa B-like hepatoma nuclear factor. Mol Cell Biol 1990; 10:6283-9. [PMID: 2174104 PMCID: PMC362903 DOI: 10.1128/mcb.10.12.6283-6289.1990] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Complement factor B, a serine protease playing a pivotal role in alternative pathway activation, is an acute-phase plasma protein. Previous studies have revealed that interleukin-1 (IL-1) mediates, at least in part, the acute-phase induction of factor B expression and that the IL-1-responsive element resides in the region between -553 and -478 relative to the transcription initiation site of the mouse factor B gene. In this paper, we demonstrate a specific binding site for a nuclear factor of human hepatoma HepG2 cells in this region of the factor B gene, using gel shift and methylation interference analysis. The nucleotide sequence of the binding site is closely similar to the NF kappa B or H2TF1 binding motif. The binding activity of HepG2 showed very similar specificity to that of NF kappa B or H2TF1, as shown by a competition binding assay, and was induced by IL-1 alpha treatment. A synthetic oligonucleotide corresponding to this binding site, as well as a similar sequence found in another class III complement C4 gene, conferred IL-1 responsiveness on the minimal factor B promoter. In contrast, a mutated oligonucleotide that could not bind to the HepG2 nuclear factor did not confer IL-1 responsiveness. These results suggest that IL-1 induces factor B expression via NF kappa B or a closely related factor in hepatocyte nuclei.
Collapse
Affiliation(s)
- M Nonaka
- Department of Immunobiology, Kanazawa University, Japan
| | | |
Collapse
|
20
|
Nakayama K, Pattanakitsakul S, Yokoyama S, Kimura H, Nonaka M, Takahashi M. Post-transcriptional regulation of complement C4 in low C4-producing strain of mouse. Immunogenetics 1990; 31:361-7. [PMID: 2370081 DOI: 10.1007/bf02115011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The expression of the fourth component of complement (C4) of the mouse can differ 20-fold and is determined by C4-high (C4h) or C4-low (C4l) alleles. To investigate the molecular mechanisms underlying the differences in C4 expression, we compared the transcriptional activity of the C4 genes between high and low C4-producer strains of mice (B10 and FM vs B10.BR) using nuclear transcriptional and chloramphenicol acetyltransferase (CAT) assays. We also compared the level of C4-specific RNA in total and nuclear RNA of the liver. The results revealed no significant difference in transcriptional activity between C4h and C4l genes. However, the steady-state levels of C4 mRNA are ten times lower in C4l strains than in C4h strains, suggesting that the major regulation of C4 plasma levels occurs at the post-transcriptional level.
Collapse
Affiliation(s)
- K Nakayama
- Department of Immunobiology, Kanazawa University, Japan
| | | | | | | | | | | |
Collapse
|
21
|
Bruisten SM, Skamene E, Demant P. Haplotype-specific interactions of non-H-2-linked genetic factors controlling the mouse C4 and Slp protein levels. Genetics 1989; 121:795-801. [PMID: 2566557 PMCID: PMC1203662 DOI: 10.1093/genetics/121.4.795] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The influence of non-H-2 linked genes on the plasma levels of the H-2 S-region encoded proteins C4, Slp, and factor B was tested in Recombinant Inbred (RI) strains. The A X B and B X A RI strains exhibit a continuous range of C4 and Slp levels from very high to very low which reach beyond the levels of their parental strains, C57BL/6J and A/J, indicating involvement of several trans-regulatory (non-H-2-linked) genes. Only limited variation in levels of factor B has been found. No linkage relationship could be established for the trans-regulatory genes, because more than one gene is involved. A complex interaction of H-2 haplotype, genetic background, sex, and possibly maternal effect in determining the C4 and Slp protein plasma levels has been observed. The H-2-dependent sex effect is evident, because males have higher C4 levels than females in RI strains with H-2b but not with H-2a haplotype. This sex effect is also background dependent, because it is present in the H-2b congenic strain on A background (A.BY) but not in C57BL/10 and C57BL/6 (both H-2b). Mice from RI strains with H-2b haplotype have in general higher C4 levels than mice with H-2a haplotype.
Collapse
Affiliation(s)
- S M Bruisten
- Division of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam
| | | | | |
Collapse
|
22
|
Demant P, Oomen LC, Oudshoorn-Snoek M. Genetics of tumor susceptibility in the mouse: MHC and non-MHC genes. Adv Cancer Res 1989; 53:117-79. [PMID: 2678946 DOI: 10.1016/s0065-230x(08)60281-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- P Demant
- Division of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam
| | | | | |
Collapse
|
23
|
A complex androgen-responsive enhancer resides 2 kilobases upstream of the mouse Slp gene. Mol Cell Biol 1988. [PMID: 3165490 DOI: 10.1128/mcb.8.6.2350] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neighboring genes encoding the mouse sex-limited protein (Slp) and fourth component of complement (C4) show extensive homology. In contrast to C4, however, Slp is regulated by androgen. One region of the Slp gene capable of hormonal response following transfection was located about 2 kilobases upstream of the transcription start site, where the C4 and Slp sequences diverge. This region, delimited here to a 0.75-kilobase fragment, showed cryptic promoter activity as well as androgen responsiveness in either orientation in front of the bacterial chloramphenicol acetyltransferase coding region. When this fragment was placed upstream of a viral long terminal repeat, increased chloramphenicol acetyltransferase expression derived from the viral promoter. Proteins from nuclear extracts specifically bound to four sequences within the region, near sites that are DNase I hypersensitive in vivo and reflect the hormonal and developmental regulation of Slp. Like several other cellular enhancers, this androgen-responsive element seems to be modular in nature and complex in its function.
Collapse
|
24
|
Affiliation(s)
- D C Shreffler
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110
| |
Collapse
|
25
|
Abstract
C4 and Slp are highly homologous mouse genes that differ in function and regulation. Allelic variants exist in quantitative regulation of C4 and in hormonal regulation of Slp. We have examined expression in several tissues, including liver and peritoneal macrophages which are the major sites of synthesis, using a probe that allows direct comparison of C4 and Slp mRNAs. Correctly-sized and initiated RNA, within an order of magnitude of liver levels, is found in mammary gland, lung, spleen, and kidney; lower levels are detectable in testis, brain, heart and submaxillary gland. By comparing expression in congenic mouse strains differing in C4 and Slp loci, regulation of these genes is seen to vary in different tissues. This provides a well-defined genetic system in which to examine cis-acting sequences and trans-acting factors that result in tissue-specific patterns of gene regulation.
Collapse
Affiliation(s)
- B J Cox
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | | |
Collapse
|
26
|
Loreni F, Stavenhagen J, Kalff M, Robins DM. A complex androgen-responsive enhancer resides 2 kilobases upstream of the mouse Slp gene. Mol Cell Biol 1988; 8:2350-60. [PMID: 3165490 PMCID: PMC363433 DOI: 10.1128/mcb.8.6.2350-2360.1988] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Neighboring genes encoding the mouse sex-limited protein (Slp) and fourth component of complement (C4) show extensive homology. In contrast to C4, however, Slp is regulated by androgen. One region of the Slp gene capable of hormonal response following transfection was located about 2 kilobases upstream of the transcription start site, where the C4 and Slp sequences diverge. This region, delimited here to a 0.75-kilobase fragment, showed cryptic promoter activity as well as androgen responsiveness in either orientation in front of the bacterial chloramphenicol acetyltransferase coding region. When this fragment was placed upstream of a viral long terminal repeat, increased chloramphenicol acetyltransferase expression derived from the viral promoter. Proteins from nuclear extracts specifically bound to four sequences within the region, near sites that are DNase I hypersensitive in vivo and reflect the hormonal and developmental regulation of Slp. Like several other cellular enhancers, this androgen-responsive element seems to be modular in nature and complex in its function.
Collapse
Affiliation(s)
- F Loreni
- Department of Biological Sciences, Columbia University, New York, New York 10027
| | | | | | | |
Collapse
|
27
|
Nakanishi T, Kohno K, Ishiura M, Ohashi H, Uchida T. Complete nucleotide sequence and characterization of the 5'-flanking region of mammalian elongation factor 2 gene. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68797-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
28
|
Identification and characterization of functional genes encoding the mouse major urinary proteins. Mol Cell Biol 1988. [PMID: 2824995 DOI: 10.1128/mcb.7.10.3705] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mouse Ltk- cells were stably transfected with cloned genes encoding the mouse major urinary proteins (MUPs). C57BL/6J MUP genomic clones encoding MUP 2 (BL6-25 and BL6-51), MUP 3 (BL6-11 and BL6-3), and MUP 4 (BL6-42) have been identified. In C57BL/6J mice, MUP 2 and MUP 4 are known to be synthesized in male, but not female, liver, and MUP 3 is known to be synthesized in both male and female liver and mammary gland. A BALB/c genomic clone (BJ-31) was shown to encode a MUP that is slightly more basic than MUP 2 and was previously shown to be synthesized in both male and female liver of BALB/c but not C57BL/6 mice. Comigration on two-dimensional polyacrylamide gels of the MUPs encoded by the transfecting gene provides a basis for tentative identification of the tissue specificity and mode of regulation of each gene. DNA sequence analysis of the 5' flanking region indicates that the different MUP genes are highly homologous (0.20 to 2.40% divergence) within the 879 base pairs analyzed. The most prominent differences in sequence occur within an A-rich region just 5' of the TATA box. This region (from -47 to -93) contains primarily A or C(A)N nucleotides and varies from 15 to 46 nucleotides in length in the different clones.
Collapse
|
29
|
Held WA, Gallagher JF, Hohman CM, Kuhn NJ, Sampsell BM, Hughes RG. Identification and characterization of functional genes encoding the mouse major urinary proteins. Mol Cell Biol 1987; 7:3705-12. [PMID: 2824995 PMCID: PMC368026 DOI: 10.1128/mcb.7.10.3705-3712.1987] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Mouse Ltk- cells were stably transfected with cloned genes encoding the mouse major urinary proteins (MUPs). C57BL/6J MUP genomic clones encoding MUP 2 (BL6-25 and BL6-51), MUP 3 (BL6-11 and BL6-3), and MUP 4 (BL6-42) have been identified. In C57BL/6J mice, MUP 2 and MUP 4 are known to be synthesized in male, but not female, liver, and MUP 3 is known to be synthesized in both male and female liver and mammary gland. A BALB/c genomic clone (BJ-31) was shown to encode a MUP that is slightly more basic than MUP 2 and was previously shown to be synthesized in both male and female liver of BALB/c but not C57BL/6 mice. Comigration on two-dimensional polyacrylamide gels of the MUPs encoded by the transfecting gene provides a basis for tentative identification of the tissue specificity and mode of regulation of each gene. DNA sequence analysis of the 5' flanking region indicates that the different MUP genes are highly homologous (0.20 to 2.40% divergence) within the 879 base pairs analyzed. The most prominent differences in sequence occur within an A-rich region just 5' of the TATA box. This region (from -47 to -93) contains primarily A or C(A)N nucleotides and varies from 15 to 46 nucleotides in length in the different clones.
Collapse
Affiliation(s)
- W A Held
- Department of Molecular and Cellular Biology, Roswell Park Memorial Institute, Buffalo, New York 14263
| | | | | | | | | | | |
Collapse
|
30
|
Molecular genetics of androgen-dependent and -independent expression of mouse sex-limited protein. Mol Cell Biol 1987. [PMID: 3037333 DOI: 10.1128/mcb.7.5.1716] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genes of the mouse S locus encoding C4 (the fourth component complement) and Slp (sex-limited protein) show extensive homology but are distinct in their function and regulation. In some mouse strains, such as B10.D2, Slp is androgen regulated, whereas in others, such as B10.W7R, expression of Slp is constitutive. We have previously shown that the B10.W7R strain has multiple Slp genes. In this report, we present the structure of the single C4 and four Slp genes of the B10.W7R S locus and compare the upstream flanking regions by partial sequence analysis and function in transfection assays. Of the four Slp genes, three (Slpw7.A, Slpw7.B, and Slpw7.C) have upstream and promoter regions very similar to those of C4. The fourth Slp gene (Slpw7.D) is instead virtually identical to the androgen-regulated allele (Slpd from the B10.D2 mouse) in upstream regions. In particular, far-upstream sequences from both Slpd and Slpw7.D render the bacterial chloramphenicol acetyltransferase gene hormonally responsive upon transfection into mammary carcinoma cell lines. The upstream sequences between 2 to 3 kilobases of the Slp promoter initiate transcription from multiple sites when fused proximal to the chloramphenicol acetyltransferase gene, and these transcripts are threefold more abundant in the presence of androgen. This behavior is similar for Slpd and Slpw7.D, which suggests that Slpw7.D may be androgen regulated but that this is masked in vivo by constitutive expression of the other Slp genes. Nonhomologous recombination is implicated not only in expanding the copy number of C4 and Slp genes in the B10.W7R mouse but also in creating hybrid genes with regulatory features of C4 and structural features of Slp.
Collapse
|
31
|
Hemenway C, Robins DM. DNase I-hypersensitive sites associated with expression and hormonal regulation of mouse C4 and Slp genes. Proc Natl Acad Sci U S A 1987; 84:4816-20. [PMID: 3474627 PMCID: PMC305196 DOI: 10.1073/pnas.84.14.4816] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
There are four major regions of DNase I hypersensitivity in the 5' regions of the genes for the murine fourth component of complement (C4) and its homologous neighbor, Slp (sex-limited protein). Hypersensitivity around the start site of transcription and approximately equal to 0.5 kilobases upstream correlates qualitatively with expression of these genes. Two hypersensitive sites, at -2.3 and -2.0 kilobases, map specifically to the Slp gene and correlate with its hormonal regulation. That is, these sites are more prominent in male liver chromatin and become more apparent in chromatin from females treated with testosterone. Further, these sites are established in males to a greater extent than in females prior to expression of Slp and may reflect gene-commitment events. Comparison of chromatin from mouse strains differing in C4 and Slp alleles indicates that the four regions of hypersensitivity may be necessary but are not sufficient for high levels of expression.
Collapse
|
32
|
Stavenhagen J, Loreni F, Hemenway C, Kalff M, Robins DM. Molecular genetics of androgen-dependent and -independent expression of mouse sex-limited protein. Mol Cell Biol 1987; 7:1716-24. [PMID: 3037333 PMCID: PMC365272 DOI: 10.1128/mcb.7.5.1716-1724.1987] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Genes of the mouse S locus encoding C4 (the fourth component complement) and Slp (sex-limited protein) show extensive homology but are distinct in their function and regulation. In some mouse strains, such as B10.D2, Slp is androgen regulated, whereas in others, such as B10.W7R, expression of Slp is constitutive. We have previously shown that the B10.W7R strain has multiple Slp genes. In this report, we present the structure of the single C4 and four Slp genes of the B10.W7R S locus and compare the upstream flanking regions by partial sequence analysis and function in transfection assays. Of the four Slp genes, three (Slpw7.A, Slpw7.B, and Slpw7.C) have upstream and promoter regions very similar to those of C4. The fourth Slp gene (Slpw7.D) is instead virtually identical to the androgen-regulated allele (Slpd from the B10.D2 mouse) in upstream regions. In particular, far-upstream sequences from both Slpd and Slpw7.D render the bacterial chloramphenicol acetyltransferase gene hormonally responsive upon transfection into mammary carcinoma cell lines. The upstream sequences between 2 to 3 kilobases of the Slp promoter initiate transcription from multiple sites when fused proximal to the chloramphenicol acetyltransferase gene, and these transcripts are threefold more abundant in the presence of androgen. This behavior is similar for Slpd and Slpw7.D, which suggests that Slpw7.D may be androgen regulated but that this is masked in vivo by constitutive expression of the other Slp genes. Nonhomologous recombination is implicated not only in expanding the copy number of C4 and Slp genes in the B10.W7R mouse but also in creating hybrid genes with regulatory features of C4 and structural features of Slp.
Collapse
|