51
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Liu J, Yu S, Litman D, Chen W, Weinstein LS. Identification of a methylation imprint mark within the mouse Gnas locus. Mol Cell Biol 2000; 20:5808-17. [PMID: 10913164 PMCID: PMC86058 DOI: 10.1128/mcb.20.16.5808-5817.2000] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The imprinted mouse gene Gnas produces the G protein alpha-subunit G(S)alpha and several other gene products by using alternative promoters and first exons. G(S)alpha is maternally expressed in some tissues and biallelically expressed in most other tissues, while the gene products NESP55 and XLalphas are maternally and paternally expressed, respectively. We investigated the mechanisms of Gnas imprinting. The G(S)alpha promoter and first exon are not methylated on either allele. A further upstream region (approximately from positions -3400 to -939 relative to the G(S)alpha translational start site) is methylated only on the maternal allele in all adult somatic tissues and in early postimplantation development. Within this region lies a fourth promoter and first exon (exon 1A) that generates paternal-specific mRNAs of unknown function. Exon 1A and G(S)alpha mRNAs have similar expression patterns, making competition between their promoters unlikely. Differential methylation in this region is established during gametogenesis, being present in oocytes and absent in spermatozoa, and is maintained in preimplantation E3. 5d blastocysts. Therefore, this region is a methylation imprint mark. In contrast, differential methylation of the NESP55 and XLalphas promoter regions (Nesp and Gnasxl) is not established during gametogenesis. The methylation imprint mark that we identified may be important for the tissue-specific imprinting of G(S)alpha.
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Affiliation(s)
- J Liu
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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52
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Bastepe M, Jüppner H. Identification and characterization of two new, highly polymorphic loci adjacent to GNAS1 on chromosome 20q13.3. Mol Cell Probes 2000; 14:261-4. [PMID: 10970731 DOI: 10.1006/mcpr.2000.0308] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
GNAS1, which is located in the chromosomal region 20q13.3, gives rise to maternally, paternally or bi-allelically expressed transcripts including the one that encodes the alpha subunit of the stimulatory G protein. Numerous naturally occurring mutations of this gene have been identified in several different disorders including certain forms of pseudohypoparathyroidism, progressive osseous heteroplasia, McCune-Albright syndrome and acromegaly. Polymorphic markers currently employed in the genetic evaluation of these disorders frequently prove uninformative owing to a low heterozygosity value associated with each marker. We searched for potentially polymorphic tandem repeats close to the GNAS1 locus, and identified two new, highly polymorphic loci that are located within a;48-kb region immediately downstream of this gene. These new microsatellite markers, with their high polymorphism information content, may prove to be useful in genetic studies related to GNAS1 as well as to other genes located in the flanking genomic region.
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Affiliation(s)
- M Bastepe
- Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
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53
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Carel JC, Garabédian M, Mallet E, Chaussain JL. [Pseudohypoparathyroidism: new diagnostic and therapeutic approaches]. Arch Pediatr 2000; 4:86s-90s. [PMID: 9246311 DOI: 10.1016/s0929-693x(97)86469-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- J C Carel
- Service d'endocrinologie pédiatrique et Inserm U342, Paris, France
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54
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Weinstein LS, Yu S, Ecelbarger CA. Variable imprinting of the heterotrimeric G protein G(s) alpha-subunit within different segments of the nephron. Am J Physiol Renal Physiol 2000; 278:F507-14. [PMID: 10751211 DOI: 10.1152/ajprenal.2000.278.4.f507] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The heterotrimeric G protein G(s) is required for hormone-stimulated intracellular cAMP generation because it couples hormone receptors to the enzyme adenylyl cyclase. Hormones that activate G(s) in the kidney include parathyroid hormone, glucagon, calcitonin, and vasopressin. Recently, it has been demonstrated that the G(s)alpha gene is imprinted in a tissue-specific manner, leading to preferential expression of G(s)alpha from the maternal allele in some tissues. In the kidney, G(s)alpha is imprinted in the proximal tubule but not in more distal nephron segments, such as the thick ascending limb or collecting duct. This most likely explains why in both humans and mice heterozygous mutations in the maternal allele lead to parathyroid hormone resistance in the proximal tubule whereas mutations in the paternal allele do not. In contrast, heterozygous mutations have little effect on vasopressin action in the collecting ducts. In mice with heterozygous null G(s)alpha mutations (both those with mutations on the maternal or paternal allele), expression of the Na-K-2Cl cotransporter was decreased in the thick ascending limb, suggesting that its expression is regulated by cAMP. The G(s)alpha genes also generate alternative, oppositely imprinted transcripts encoding XLalphas, a G(s)alpha isoform with a long NH(2)-terminal extension, and NESP55, a chromogranin-like neurosecretory protein. The role, if any, of these proteins in renal physiology is unknown.
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Affiliation(s)
- L S Weinstein
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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55
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Yu S, Gavrilova O, Chen H, Lee R, Liu J, Pacak K, Parlow AF, Quon MJ, Reitman ML, Weinstein LS. Paternal versus maternal transmission of a stimulatory G-protein alpha subunit knockout produces opposite effects on energy metabolism. J Clin Invest 2000; 105:615-23. [PMID: 10712433 PMCID: PMC289181 DOI: 10.1172/jci8437] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Heterozygous disruption of Gnas, the gene encoding the stimulatory G-protein alpha subunit (G(s)alpha), leads to distinct phenotypes depending on whether the maternal (m-/+) or paternal (+/p-) allele is disrupted. G(s)alpha is imprinted, with the maternal allele preferentially expressed in adipose tissue. Hence, expression is decreased in m-/+ mice but normal in +/p- mice. M-/+ mice become obese, with increased lipid per cell in white and brown adipose tissue, whereas +/p- mice are thin, with decreased lipid in adipose tissue. These effects are not due to abnormalities in thyroid hormone status, food intake, or leptin secretion. +/p- mice are hypermetabolic at both ambient temperature (21 degrees C) and thermoneutrality (30 degrees C). In contrast, m-/+ mice are hypometabolic at ambient temperature and eumetabolic at thermoneutrality M-/+ and wild-type mice have similar dose-response curves for metabolic response to a beta(3)-adrenergic agonist, CL316243, indicating normal sensitivity of adipose tissue to sympathetic stimulation. Measurement of urinary catecholamines suggests that +/p- and m-/+ mice have increased and decreased activation of the sympathetic nervous system, respectively. This is to our knowledge the first animal model in which a single genetic defect leads to opposite effects on energy metabolism depending on parental inheritance. This probably results from deficiency of maternal- and paternal-specific Gnas gene products, respectively.
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Affiliation(s)
- S Yu
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institute of Health, Bethesda, MD 20892, USA
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56
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Ohyama K. Molecular Basis and Clinical Manifestation of McCune-Albright Syndrome. Clin Pediatr Endocrinol 2000. [DOI: 10.1297/cpe.9.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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57
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Kelsey G, Bodle D, Miller HJ, Beechey CV, Coombes C, Peters J, Williamson CM. Identification of imprinted loci by methylation-sensitive representational difference analysis: application to mouse distal chromosome 2. Genomics 1999; 62:129-38. [PMID: 10610704 DOI: 10.1006/geno.1999.6022] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Imprinted genes are distinguished by different patterns of methylation on their parental alleles, a property by which imprinted loci could be identified systematically. Here, representational difference analysis (RDA) is used to clone HpaII fragments with methylation differences on the maternal and paternal copies of distal chromosome (Chr) 2 in the mouse. Uniparental inheritance for this region causes imprinting phenotypes whose molecular basis is only partially understood. RDA led to the recovery of multiple differentially methylated HpaII fragments at two major sites of imprinted methylation: paternal-specific methylation at the Nesp locus and maternal-specific methylation at the Gnasxl locus. Nesp and Gnasxl represent oppositely imprinted promoters of the Gnas gene, which encodes the G-protein subunit, Gsalpha. The organization of the Nesp-Gnasxl-Gnas region was determined: Nesp and Gnasxl were found to be 15 kb apart, and Gnasxl was found to be 30 kb upstream of Gnas. Sites of imprinted methylation were also detected at the loci for neuronatin on Chr 2 and for M-cadherin on Chr 8. RDA was highly effective at identifying imprinted methylation, and its potential applications to imprinting studies are discussed.
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Affiliation(s)
- G Kelsey
- Developmental Genetics Programme, The Babraham Institute, Cambridge, United Kingdom.
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58
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Yu D, Yu S, Schuster V, Kruse K, Clericuzio CL, Weinstein LS. Identification of two novel deletion mutations within the Gs alpha gene (GNAS1) in Albright hereditary osteodystrophy. J Clin Endocrinol Metab 1999; 84:3254-9. [PMID: 10487696 DOI: 10.1210/jcem.84.9.5970] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Albright hereditary osteodystrophy (AHO) is a genetic disorder characterized by short stature, skeletal defects, and obesity. Within AHO kindreds, some affected family members have only the somatic features of AHO [pseudopseudohypoparathyroidism (PPHP)], whereas others have these features in association with resistance to multiple hormones that stimulate adenylyl cyclase within their target tissues [pseudohypoparathyroidism type Ia (PHP Ia)]. Affected members of most AHO kindreds (both those with PPHP and those with PHP Ia) have a partial deficiency of Gs alpha, the alpha-subunit of the G protein that couples receptors to adenylyl cyclase stimulation, and in a number of cases heterozygous loss of function mutations within the Gs alpha gene (GNAS1) have been identified. Using PCR with the attachment of a high melting domain (GC-clamp) and temperature gradient gel electrophoresis, two novel heterozygous frameshift mutations within GNAS1 were found in two AHO kindreds. In one kindred all affected members (both PHP Ia and PPHP) had a heterozygous 2-bp deletion in exon 8, whereas in the second kindred a heterozygous 2-bp deletion in exon 4 was identified in all affected members examined. In both cases the frameshift encoded a premature termination codon several codons downstream of the deletion. In the latter kindred affected members were previously shown to have decreased levels of GNAS1 messenger ribonucleic acid expression. These results further underscore the genetic heterogeneity of AHO and provides further evidence that PHP Ia and PPHP are two clinical presentations of a common genetic defect. Serial measurements of thyroid function in members of kindred 1 indicate that TSH resistance progresses with age and becomes more evident after the first year of life.
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Affiliation(s)
- D Yu
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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59
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Affiliation(s)
- M A Levine
- The Johns Hopkins University School of Medicine, Division of Pediatric Endocrinology, Department of Pediatrics, Baltimore, Maryland 21287, USA
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60
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The Role of Genomic Imprinting of Galpha in the Pathogenesis of Albright Hereditary Osteodystrophy. Trends Endocrinol Metab 1999; 10:81-85. [PMID: 10322399 DOI: 10.1016/s1043-2760(98)00124-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Albright hereditary osteodystrophy (AHO) is caused by heterozygous inactivating mutations of the gene encoding the alpha-subunit of the G protein Gs. The Gsalpha gene is a complex gene that uses various alternative promoters and produces various protein products. Recently, it has been shown that this gene is imprinted in a tissue-specific manner. The role of tissue-specific imprinting of Gsalpha in the pathogenesis of AHO is discussed.
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61
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Falls JG, Pulford DJ, Wylie AA, Jirtle RL. Genomic imprinting: implications for human disease. THE AMERICAN JOURNAL OF PATHOLOGY 1999; 154:635-47. [PMID: 10079240 PMCID: PMC1866410 DOI: 10.1016/s0002-9440(10)65309-6] [Citation(s) in RCA: 269] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/06/1999] [Indexed: 01/14/2023]
Abstract
Genomic imprinting refers to an epigenetic marking of genes that results in monoallelic expression. This parent-of-origin dependent phenomenon is a notable exception to the laws of Mendelian genetics. Imprinted genes are intricately involved in fetal and behavioral development. Consequently, abnormal expression of these genes results in numerous human genetic disorders including carcinogenesis. This paper reviews genomic imprinting and its role in human disease. Additional information about imprinted genes can be found on the Genomic Imprinting Website at http://www.geneimprint.com.
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Affiliation(s)
- J G Falls
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina27710, USA
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62
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Hayward BE, Moran V, Strain L, Bonthron DT. Bidirectional imprinting of a single gene: GNAS1 encodes maternally, paternally, and biallelically derived proteins. Proc Natl Acad Sci U S A 1998; 95:15475-80. [PMID: 9860993 PMCID: PMC28067 DOI: 10.1073/pnas.95.26.15475] [Citation(s) in RCA: 206] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/1998] [Indexed: 11/18/2022] Open
Abstract
The GNAS1 gene encodes the alpha subunit of the guanine nucleotide-binding protein Gs, which couples signaling through peptide hormone receptors to cAMP generation. GNAS1 mutations underlie the hormone resistance syndrome pseudohypoparathyroidism type Ia (PHP-Ia), so the maternal inheritance displayed by PHP-Ia has raised suspicions that GNAS1 is imprinted. Despite this suggestion, in most tissues Gsalpha is biallelically encoded. In contrast, the large G protein XLalphas, also encoded by GNAS1, is paternally derived. Because the inheritance of PHP-Ia predicts the existence of maternally, rather than paternally, expressed transcripts, we have investigated the allelic origin of other mRNAs derived from GNAS1. We find this gene to be remarkable in the complexity of its allele-specific regulation. Two upstream promoters, each associated with a large coding exon, lie only 11 kb apart, yet show opposite patterns of allele-specific methylation and monoallelic transcription. The more 5' of these exons encodes the neuroendocrine secretory protein NESP55, which is expressed exclusively from the maternal allele. The NESP55 exon is 11 kb 5' to the paternally expressed XLalphas exon. The transcripts from these two promoters both splice onto GNAS1 exon 2, yet share no coding sequences. Despite their structural unrelatedness, the encoded proteins, of opposite allelic origin, both have been implicated in regulated secretion in neuroendocrine tissues. Remarkably, maternally (NESP55), paternally (XLalphas), and biallelically (Gsalpha) derived proteins all are produced by different patterns of promoter use and alternative splicing of GNAS1, a gene showing simultaneous imprinting in both the paternal and maternal directions.
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Affiliation(s)
- B E Hayward
- Human Genetics Unit, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
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63
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Hayward BE, Kamiya M, Strain L, Moran V, Campbell R, Hayashizaki Y, Bonthron DT. The human GNAS1 gene is imprinted and encodes distinct paternally and biallelically expressed G proteins. Proc Natl Acad Sci U S A 1998; 95:10038-43. [PMID: 9707596 PMCID: PMC21457 DOI: 10.1073/pnas.95.17.10038] [Citation(s) in RCA: 192] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/1998] [Indexed: 01/27/2023] Open
Abstract
The GNAS1 gene encodes the alpha subunit of the G protein Gs, which couples receptor binding by several hormones to activation of adenylate cyclase. Null mutations of GNAS1 cause pseudohypoparathyroidism (PHP) type Ia, in which hormone resistance occurs in association with a characteristic osteodystrophy. The observation that PHP Ia almost always is inherited maternally has led to the suggestion that GNAS1 may be an imprinted gene. Here, we show that, although Gsalpha expression (directed by the promoter upstream of exon 1) is biallelic, GNAS1 is indeed imprinted in a promoter-specific fashion. We used parthenogenetic lymphocyte DNA to screen by restriction landmark genomic scanning for loci showing differential methylation between paternal and maternal alleles. This screen identified a region that was found to be methylated exclusively on a maternal allele and was located approximately 35 kb upstream of GNAS1 exon 1. This region contains three novel exons that are spliced into alternative GNAS1 mRNA species, including one exon that encodes the human homologue of the large G protein XLalphas. Transcription of these novel mRNAs is exclusively from the paternal allele in all tissues examined. The differential imprinting of separate protein products of GNAS1 therefore may contribute to the anomalous inheritance of PHP Ia.
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Affiliation(s)
- B E Hayward
- Human Genetics Unit, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
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64
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Yu S, Yu D, Lee E, Eckhaus M, Lee R, Corria Z, Accili D, Westphal H, Weinstein LS. Variable and tissue-specific hormone resistance in heterotrimeric Gs protein alpha-subunit (Gsalpha) knockout mice is due to tissue-specific imprinting of the gsalpha gene. Proc Natl Acad Sci U S A 1998; 95:8715-20. [PMID: 9671744 PMCID: PMC21142 DOI: 10.1073/pnas.95.15.8715] [Citation(s) in RCA: 288] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Albright hereditary osteodystrophy (AHO), an autosomal dominant disorder characterized by short stature, obesity, and skeletal defects, is associated with heterozygous inactivating mutations of GNAS1, the gene encoding the heterotrimeric G protein alpha-subunit (Gsalpha) that couples multiple receptors to the stimulation of adenylyl cyclase. It has remained unclear why only some AHO patients present with multihormone resistance and why AHO patients demonstrate resistance to some hormones [e.g., parathyroid hormone (PTH)] but not to others (e.g., vasopressin), even though all activate adenylyl cyclase. We generated mice with a null allele of the mouse homolog Gnas. Homozygous Gs deficiency is embryonically lethal. Heterozygotes with maternal (m-/+) and paternal (+/p-) inheritance of the Gnas null allele have distinct phenotypes, suggesting that Gnas is an imprinted gene. PTH resistance is present in m-/+, but not +/p-, mice. Gsalpha expression in the renal cortex (the site of PTH action) is markedly reduced in m-/+ but not in +/p- mice, demonstrating that the Gnas paternal allele is imprinted in this tissue. Gnas is also imprinted in brown and white adipose tissue. The maximal physiological response to vasopressin (urinary concentrating ability) is normal in both m-/+ and +/p- mice and Gnas is not imprinted in the renal inner medulla (the site of vasopressin action). Tissue-specific imprinting of Gnas is likely the mechanism for variable and tissue-specific hormone resistance in these mice and a similar mechanism might explain the variable phenotype in AHO.
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Affiliation(s)
- S Yu
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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65
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Nakamoto JM, Sandstrom AT, Brickman AS, Christenson RA, Van Dop C. Pseudohypoparathyroidism type Ia from maternal but not paternal transmission of a Gs? gene mutation. ACTA ACUST UNITED AC 1998. [DOI: 10.1002/(sici)1096-8628(19980526)77:4<261::aid-ajmg2>3.0.co;2-q] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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66
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Namnoum AB, Merriam GR, Moses AM, Levine MA. Reproductive dysfunction in women with Albright's hereditary osteodystrophy. J Clin Endocrinol Metab 1998; 83:824-9. [PMID: 9506735 DOI: 10.1210/jcem.83.3.4652] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Most individuals with Albright's hereditary osteodystrophy (AHO) have deficient expression or function of G(s alpha), the alpha subunit of the guanine nucleotide binding protein that stimulates adenylyl cyclase, and are resistant to parathyroid hormone (PTH) and other hormones that act via stimulation of adenylyl cyclase. To determine the incidence and etiology of ovarian dysfunction in women with AHO, we examined the reproductive history and hypothalamic-pituitary-ovarian axis in 17 affected women aged 17-43 yr. All patients had typical PTH resistance and an approximately 50% reduction in erythrocyte G(s alpha) activity, (0.43 +/- 0.03 vs. 0.92 +/- 0.08 for normal control subjects, P < 0.001). Fourteen of the 17 patients (76%) were oligomenorrheic or amenorrheic, more than half had delayed or incomplete sexual development, and only two had a history of earlier pregnancy. Most women were mildly hypoestrogenic, with normal to slightly elevated serum gonadotropin levels. Computer analysis of 24 hour LH measurement showed that the frequency of LH peaks/24 h in AHO women varied widely, but as a group they were not statistically different from a group of normal women studied in the early follicular phase. Administration of 100 microg synthetic GnRH produced normal FSH and LH responses. We conclude that reproductive dysfunction is common in women with AHO and probably represents partial resistance to gonadotropins.
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Affiliation(s)
- A B Namnoum
- Department of Gynecology and Obstetrics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA
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67
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Ringel MD, Schwindinger WF, Levine MA. Clinical implications of genetic defects in G proteins. The molecular basis of McCune-Albright syndrome and Albright hereditary osteodystrophy. Medicine (Baltimore) 1996; 75:171-84. [PMID: 8699958 DOI: 10.1097/00005792-199607000-00001] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Inactivating and activating mutations in the gene encoding G alpha s (GNAS1) are known to be the basis for 2 well-described contrasting clinical disorders, Albright hereditary osteodystrophy (AHO) and McCune-Albright syndrome (MAS). AHO is an autosomal dominant disorder due to germline mutations in GNAS1 that decrease expression or function of G alpha s protein. Loss of G alpha s function leads to tissue resistance to multiple hormones whose receptors couple to G alpha s. By contrast, MAS results from postzygotic somatic mutations in GNAS1 that lead to enhanced function of G alpha s protein. Acquisition of the activating mutation early in life leads to a more generalized distribution of the mosaicism and is associated with the classic clinical triad of polyostotic fibrous dysplasia, endocrine hyperfunction, and café au lait skin lesions described in MAS. Acquisition of a similar activating mutation in GNAS1 later in life presumably accounts for the restricted distribution of the gsp oncogene, and is associated with the development of isolated lesions (for example, fibrous dysplasia, pituitary or thyroid tumors) without other manifestations of MAS. Tissues that are affected by loss of G alpha s function in AHO are also affected by gain of G alpha s function in MAS, thus identifying specific tissues in which the second messenger cAMP plays a dominant role in cell growth, proliferation, or function. Further investigations of the functions of G alpha s and other members of the GTPase binding protein family will provide more insight into the pathogenesis and clinical manifestations of human disease.
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Affiliation(s)
- M D Ringel
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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68
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Brinkman BM, Huizinga TW, Breedveld FC, Verweij CL. Allele-specific quantification of TNFA transcripts in rheumatoid arthritis. Hum Genet 1996; 97:813-8. [PMID: 8641702 DOI: 10.1007/bf02346195] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Clinical and laboratory studies have suggested a pivotal role for tumor necrosis factor alpha (TNFA) in the pathogenesis of rheumatoid arthritis (RA). Interindividual variation in the expression of TNFA indicates the existence of functionally distinct TNFA alleles that could play a role in susceptibility to TNFA-associated diseases such as RA. In order to determine whether differential TNFA gene expression is present in RA, we studied the relative contribution of TNFA alleles to the total amount of steady-state mRNA in peripheral blood mononuclear cells of RA patients and healthy individuals. Moreover, allelic TNFA mRNA expression was analyzed in synovial biopsy material of RA patients. For this purpose, we used the recently identified C-insertion polymorphism located in the 5' untranslated region of the first exon. The location of this polymorphism within a part of the gene that is transcribed into mRNA allowed us to discriminate between the contribution of each allele to the total amount of TNFA mRNA in heterozygous individuals. The results of this study do not indicate the existence of variation at the level of mRNA transcribed from each TNFA allele by in vitro and physiological stimulation conditions in RA patients. Therefore, our data do not suggest a role for transcriptionally distinct TNFA alleles in the susceptibility to RA.
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Affiliation(s)
- B M Brinkman
- Department of Rheumatology, University Hospital Leiden, The Netherlands
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69
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Yokoyama M, Takeda K, Iyota K, Okabayashi T, Hashimoto K. A 4-base pair deletion mutation of Gs alpha gene in a Japanese patient with pseudohypoparathyroidism. J Endocrinol Invest 1996; 19:236-41. [PMID: 8862504 DOI: 10.1007/bf03349874] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Mutations in the guanine nucleotide binding protein alpha subunit (Gs alpha) have been found in patients with pseudohypoparathyroidism (PHP). We have screened the Gs alpha gene for mutations in a Japanese patient with this disorder and identified a novel 4-base pair deletion in exon 7 in codons 189-190. This deletion causes a frameshift and if synthesis of a truncated form of Gs alpha occurred, it would likely be biologically inactive. The patient was heterozygous for this deletion. The patient's mother and an unaffected brother were tested for the presence of this mutation. His mother had the same mutation, and although her serum calcium and parathyroid hormone levels were within the normal range, she had subcutaneous calcifications. Thus, this mutation appears to be necessary but not sufficient to cause the complete pseudohypoparathyroidism phenotype and thus, other unknown factors, either genetic or acquired, may be necessary for the full syndrome to occur.
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Affiliation(s)
- M Yokoyama
- Second Department of Internal Medicine, Kochi Medical School, Japan
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Williamson CM, Dutton ER, Abbott CM, Beechey CV, Ball ST, Peters J. Thirteen genes (Cebpb, E2f1, Tcf4, Cyp24, Pck1, Acra4, Edn3, Kcnb1, Mc3r, Ntsr, Cd40, Plcg1 and Rcad) that probably lie in the distal imprinting region of mouse chromosome 2 are not monoallelically expressed. Genet Res (Camb) 1995; 65:83-93. [PMID: 7781998 DOI: 10.1017/s0016672300033103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Seven imprinted genes are currently known in the mouse but none have been identified yet in the distal imprinting region of mouse Chromosome (Chr) 2, a region which shows striking linkage conservation with human chromosome 20q13. Both maternal duplication/paternal deficiency and its reciprocal for distal Chr 2 lead to mice with abnormal body shapes and behavioural abnormalities. We have tested a number of candidate genes, that are either likely or known to lie within the distal imprinting region, for monoallelic expression. These included 3 genes (Cebpb, E2f1 and Tcf4) that express transcription factors, 2 genes (Cyp24 and Pck1) that are involved in growth, 5 genes (Acra4, Edn3, Kcnb1, Mc3r and Ntsr) where a defect could lead to neurological and probably behavioural problems, and 3 genes (Cd40, Plcg1 and Rcad) that are less obvious candidates but sequence information was available for designing primers to test their expression. On/off expression of each gene was tested by reverse transcription-polymerase chain reaction (RT-PCR) analysis of RNA extracted from tissues of mice with maternal duplication/paternal deficiency and its reciprocal for the distal region of Chr 2. None of the 13 genes is monoallelically expressed in the appropriate tissues before and shortly after birth which suggests that these genes are not imprinted later in development. This study has narrowed down the search for imprinted genes, and valuable information on which genes have been tested for on/off expression is provided. Since there is considerable evidence of conservation of imprinting between mouse and human, we would predict that the 13 genes are not imprinted in human. Five of the genes: E2f1, Tcf4, Kcnb1, Cd40 and Rcad, have not yet been mapped in human. However, because of the striking linkage conservation observed between mouse Chr 2 and human chromosome 20, we would expect these genes to map on human chromosome 20q13.
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