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Zalewski CK, Sydlowski SA, King KA, Bianconi S, Dang Do A, Porter FD, Brewer CC. Auditory phenotype of Smith-Lemli-Opitz syndrome. Am J Med Genet A 2021; 185:1131-1141. [PMID: 33529473 DOI: 10.1002/ajmg.a.62087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/23/2020] [Accepted: 01/07/2021] [Indexed: 11/11/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive multiple congenital malformation and intellectual disability syndrome resulting from variants in DHCR7. Auditory characteristics of persons with SLOS have been described in limited case reports but have not been systematically evaluated. The objective of this study is to describe the auditory phenotype in SLOS. Age- and ability-appropriate hearing evaluations were conducted on 32 patients with SLOS. A subset of 21 had auditory brainstem response testing, from which an auditory neural phenotype is described. Peripheral or retrocochlear auditory dysfunction was observed in at least one ear of 65.6% (21) of the patients in our SLOS cohort. The audiometric phenotype was heterogeneous and included conductive, mixed, and sensorineural hearing loss. The most common presentation was a slight to mild conductive hearing loss, although profound sensorineural hearing loss was also observed. Abnormal auditory brainstem responses indicative of retrocochlear dysfunction were identified in 21.9% of the patients. Many were difficult to test behaviorally and required objective assessment methods to estimate hearing sensitivity. Individuals with SLOS are likely to have hearing loss that may impact communication, including speech and language development. Routine audiologic surveillance should be conducted to ensure prompt management of hearing loss.
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Affiliation(s)
| | - Sarah A Sydlowski
- NIDCD, National Institutes of Health, Bethesda, Maryland, USA.,Cleveland Clinic Head & Neck Institute, Cleveland, Ohio, USA
| | - Kelly A King
- NIDCD, National Institutes of Health, Bethesda, Maryland, USA
| | - Simona Bianconi
- NICHD, National Institutes of Health, Bethesda, Maryland, USA
| | - An Dang Do
- NICHD, National Institutes of Health, Bethesda, Maryland, USA
| | - Forbes D Porter
- NICHD, National Institutes of Health, Bethesda, Maryland, USA
| | - Carmen C Brewer
- NIDCD, National Institutes of Health, Bethesda, Maryland, USA
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Rohanizadegan M, Sacharow S. Desmosterolosis presenting with multiple congenital anomalies. Eur J Med Genet 2017; 61:152-156. [PMID: 29175559 DOI: 10.1016/j.ejmg.2017.11.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Revised: 10/26/2017] [Accepted: 11/21/2017] [Indexed: 12/30/2022]
Abstract
Desmosterolosis is a rare multiple congenital anomaly syndrome caused by a defect in the enzyme 3-beta-hydroxysterol delta-24-reductase (DHCR24) in the cholesterol biosynthesis pathway. Defects in this enzyme cause increased level of the cholesterol precursor desmosterol while disrupting development of cholesterol, impacting embryogenesis. A total of 9 cases of desmosterolosis have been reported to date. We report a 20-month-old male from consanguineous parents with multiple congenital anomalies including corpus callosum hypoplasia, facial dysmorphism, cleft palate, pectus deformity, short and wide neck and distal contractures. On analysis of the regions of homozygosity found by microarray, we identified DHCR24 as a candidate gene. Sterol quantitation showed a desmosterol level of 162 μg/mL (nl: 0.82 ± 0.48). Genetic testing confirmed the diagnosis with a homozygous likely pathogenic mutation (p.Glu191Lys) in the DHCR24 gene. Our case expands the known diagnostic spectrum for Desmosterolosis. We suggest considering Desmosterolosis in the differential diagnosis of patients who present with concurrent agenesis of the corpus callosum with white matter atrophy and ventriculomegaly, retromicrognathia with or without cleft palate, hand contractures, and delay of growth and development. Children of consanguineous mattings may be at higher risk for rare recessive disorders and testing for cholesterol synthesis defect should be a consideration for affected children. Initial evaluation can be performed using sterol quantitation, followed by genetic testing.
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Affiliation(s)
- Mersedeh Rohanizadegan
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| | - Stephanie Sacharow
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
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A placebo-controlled trial of simvastatin therapy in Smith-Lemli-Opitz syndrome. Genet Med 2016; 19:297-305. [PMID: 27513191 PMCID: PMC5303568 DOI: 10.1038/gim.2016.102] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 06/14/2016] [Indexed: 11/26/2022] Open
Abstract
Background Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation/cognitive impairment syndrome characterized by the accumulation of 7-dehydrocholesterol (7DHC), a precursor sterol of cholesterol. Simvastatin, an HMG-CoA reductase inhibitor that crosses the blood-brain-barrier, has been proposed for treatment of SLOS based on in vitro and in vivo studies suggesting that simvastatin increases expression of hypomorphic DHCR7 alleles. Methods Safety and efficacy of simvastatin therapy in 23 mild to typical SLOS patients was evaluated in a randomized, double-blind, placebo-controlled trial. The cross-over trial consisted of two 12 month treatment phases separated by a 2 month wash-out period. Results No safety issues were identified in this study. Plasma dehydrocholesterol levels decreased significantly 8.9 ± 8.4% on placebo to 6.1 ± 5.5% on simvastatin (p<0.005) and we observed a trend toward decreased cerebral spinal fluid dehydrocholesterol levels. A significant improvement (p=0.017, paired t-test) was observed in the Aberrant Behavior Checklist-C Irritability when subjects were on simvastatin. Conclusions This paper reports the first randomized, placebo-controlled trial designed to test the safety and efficacy of simvastatin therapy in SLOS. Simvastatin appears to be relatively safe in SLOS patients, improves the serum dehydrocholesterol/total sterol ratio, and significantly improves irritability symptoms in mild to classical SLOS patients.
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Kelly MN, Tuli SY, Tuli SS, Stern MA, Giordano BP. Brothers with Smith-Lemli-Opitz syndrome. J Pediatr Health Care 2015; 29:97-103. [PMID: 24954735 DOI: 10.1016/j.pedhc.2014.04.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 04/10/2014] [Accepted: 04/24/2014] [Indexed: 12/13/2022]
Abstract
Abnormal cholesterol metabolism is the cause of SLOS, with low cholesterol levels and elevated levels of cholesterol precursors thought to contribute to the clinical findings in this syndrome. Management of SLOS involves early intervention with appropriate therapies for identified disabilities, genetic counseling for families, nutritional consultations, educational interventions, and behavioral management. Although no randomized dietary studies have been conducted, cholesterol supplementation continues to be a common recommendation for persons with SLOS, because it may result in clinical improvement and has few adverse effects (Nowaczyk, 2013). Even with early detection and treatment (e.g., sibling B in this case report), persons with SLOS often have significant behavioral issues and cognitive and developmental delays that require a team approach by parents, educators, specialists, and primary care providers.
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Freeman KA, Eagle R, Merkens LS, Sikora D, Pettit-Kekel K, Nguyen-Driver M, Steiner RD. Challenging behavior in Smith-Lemli-Opitz syndrome: initial test of biobehavioral influences. Cogn Behav Neurol 2013; 26:23-9. [PMID: 23538569 PMCID: PMC3684260 DOI: 10.1097/wnn.0b013e31828bf6d5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To study challenging behavior (destruction, aggression, self-injury, stereotypy) in children with Smith-Lemli-Opitz syndrome (SLOS) using a biobehavioral model that helps distinguish biological from socially mediated variables influencing the behavior. BACKGROUND SLOS is an autosomal-recessive syndrome of multiple malformations and intellectual disability resulting from a genetic error in cholesterol synthesis in all cells and tissues, including brain. The exact cause of the challenging behavior in SLOS is unclear, but defective brain cholesterol synthesis may contribute. Because the precise genetic and biochemical etiology of SLOS is known, this disorder is a good model for studying biological causes of challenging behavior. METHOD In a preliminary application of a biobehavioral model, we studied the association between cholesterol levels (as a biochemical indicator of disease severity) and behavior subtype ("biological" vs "learned") in 13 children with SLOS. Parents completed a questionnaire that categorized challenging behavior as influenced primarily by social or nonsocial (thus, presumably biological) factors. RESULTS The severity of the cholesterol synthesis defect correlated significantly with behavior subtype classification for 1 of 2 challenging behaviors. Greater severity of the cholesterol synthesis defect was associated with behavior being classified as primarily influenced by biological factors. CONCLUSION The interplay between challenging behavior and defective cholesterol synthesis in SLOS may help explain biological influences on the behavior. Our findings have implications for research on the effectiveness of behavioral and medical treatments for behavioral difficulties in SLOS and other neurodevelopmental disorders.
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Affiliation(s)
- Kurt A Freeman
- Division of Psychology, Institute on Development & Disability, Institute on Development & Disability, Oregon Health & Science University, Portland 97239, USA.
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Abstract
Smith-Lemli-Opitz syndrome is an autosomal recessively inherited disorder. A severe defect in cholesterol biosynthesis has been identified leading to abnormally low plasma cholesterol levels and elevated levels of the cholesterol precursor 7-dehydrocholesterol, the result of deficiency of 7-dehydrocholesterol reductase. We describe one such child with Smith-Lemli-Opitz syndrome. This child had clinical features similar to Smith-Lemli-Opitz syndrome like facial dysmorphism and cardiac and renal anomalies with failure to thrive.
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Affiliation(s)
- Rachana Gedam
- Department of Pediatrics, B. J. Wadia Hospital for Children, Parel, Mumbai, India
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Svoboda MD, Christie JM, Eroglu Y, Freeman KA, Steiner RD. Treatment of Smith-Lemli-Opitz syndrome and other sterol disorders. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2012; 160C:285-94. [PMID: 23042642 DOI: 10.1002/ajmg.c.31347] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive genetic condition with a broad phenotype that results from deficiency of the final enzyme of the cholesterol synthesis pathway. This defect causes low or low-normal plasma cholesterol levels and increased 7- and 8-dehydrocholesterol (DHC) levels. Many therapies for SLOS and other disorders of sterol metabolism have been proposed, and a few of them have been undertaken in selected patients, but robust prospective clinical trials with validated outcome measures are lacking. We review the current literature and expert opinion on treatments for SLOS and other selected sterol disorders, including dietary cholesterol therapy, statin treatment, bile acid supplementation, medical therapies, and surgical interventions, as well as directions for future therapies and treatment research.
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Affiliation(s)
- Melissa D Svoboda
- Oregon Health&Science University (OHSU), Portland, Oregon 97239, USA
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Xu L, Liu W, Sheflin LG, Fliesler SJ, Porter NA. Novel oxysterols observed in tissues and fluids of AY9944-treated rats: a model for Smith-Lemli-Opitz syndrome. J Lipid Res 2011; 52:1810-20. [PMID: 21817059 DOI: 10.1194/jlr.m018366] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Treatment of Sprague-Dawley rats with AY9944, an inhibitor of 3β-hydroxysterol-Δ(7)-reductase (Dhcr7), leads to elevated levels of 7-dehydrocholesterol (7-DHC) and reduced levels of cholesterol in all biological tissues, mimicking the key biochemical hallmark of Smith-Lemli-Opitz syndrome (SLOS). Fourteen 7-DHC-derived oxysterols previously have been identified as products of free radical oxidation in vitro; one of these oxysterols, 3β,5α-dihydroxycholest-7-en-6-one (DHCEO), was recently identified in Dhcr7-deficient cells and in brain tissues of Dhcr7-null mouse. We report here the isolation and characterization of three novel 7-DHC-derived oxysterols (4α- and 4β-hydroxy-7-DHC and 24-hydroxy-7-DHC) in addition to DHCEO and 7-ketocholesterol (7-kChol) from the brain tissues of AY9944-treated rats. The identities of these five oxysterols were elucidated by HPLC-ultraviolet (UV), HPLC-MS, and 1D- and 2D-NMR. Quantification of 4α- and 4β-hydroxy-7-DHC, DHCEO, and 7-kChol in rat brain, liver, and serum were carried out by HPLC-MS using d(7)-DHCEO as an internal standard. With the exception of 7-kChol, these oxysterols were present only in tissues of AY9944-treated, but not control rats, and 7-kChol levels were markedly (>10-fold) higher in treated versus control rats. These findings are discussed in the context of the potential involvement of 7-DHC-derived oxysterols in the pathogenesis of SLOS.
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Affiliation(s)
- Libin Xu
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN, USA
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Abstract
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive, multiple congenital malformation and intellectual disability syndrome, with clinical characteristics that encompass a wide spectrum and great variability. Elucidation of the biochemical and genetic basis for SLOS, specifically understanding SLOS as a cholesterol deficiency syndrome caused by mutation in DHCR7, opened up enormous possibilities for therapeutic intervention. When cholesterol was discovered to be the activator of sonic hedgehog, cholesterol deficiency with inactivation of this developmental patterning gene was thought to be the cause of SLOS malformations, yet this explanation is overly simplistic. Despite these important research breakthroughs, there is no proven treatment for SLOS. Better animal models are needed to allow potential treatment testing and the study of disease pathophysiology, which is incompletely understood. Creation of human cellular models, especially models of brain cells, would be useful, and in vivo human studies are also essential. Biomarker development will be crucial in facilitating clinical trials in this rare condition, because the clinical phenotype can change over many years. Additional research in these and other areas is critical if we are to make headway towards ameliorating the effects of this devastating condition.
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Zarowski M, Vendrame M, Irons M, Kothare SV. Prevalence of sleep problems in Smith-Lemli-Opitz syndrome. Am J Med Genet A 2011; 155A:1558-62. [DOI: 10.1002/ajmg.a.34021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 03/10/2011] [Indexed: 11/08/2022]
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Mendonca BB, Costa EMF, Belgorosky A, Rivarola MA, Domenice S. 46,XY DSD due to impaired androgen production. Best Pract Res Clin Endocrinol Metab 2010; 24:243-62. [PMID: 20541150 DOI: 10.1016/j.beem.2009.11.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Disorders of androgen production can occur in all steps of testosterone biosynthesis and secretion carried out by the foetal Leydig cells as well as in the conversion of testosterone into dihydrotestosterone (DHT). The differentiation of Leydig cells from mesenchymal cells is the first walk for testosterone production. In 46,XY disorders of sex development (DSDs) due to Leydig cell hypoplasia, there is a failure in intrauterine and postnatal virilisation due to the paucity of interstitial Leydig cells to secrete testosterone. Enzymatic defects which impair the normal synthesis of testosterone from cholesterol and the conversion of testosterone to its active metabolite DHT are other causes of DSD due to impaired androgen production. Mutations in the genes that codify the enzymes acting in the steps from cholesterol to DHT have been identified in affected patients. Patients with 46,XY DSD secondary to defects in androgen production show a variable phenotype, strongly depending of the specific mutated gene. Often, these conditions are detected at birth due to the ambiguity of external genitalia but, in several patients, the extremely undervirilised genitalia postpone the diagnosis until late childhood or even adulthood. These patients should receive long-term care provided by multidisciplinary teams with experience in this clinical management.
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Affiliation(s)
- Berenice B Mendonca
- Hospital das Clinicas, Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil.
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Prasad AN, Malinger G, Lerman-Sagie T. Primary disorders of metabolism and disturbed fetal brain development. Clin Perinatol 2009; 36:621-38. [PMID: 19732617 DOI: 10.1016/j.clp.2009.06.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
There exists a link between the in utero metabolic environment and the development of the fetal nervous system. Prenatal neurosonography offers a unique, noninvasive tool in the detection of developmental brain malformations and the ability to monitor changes over time. This article explores the association of malformations of cerebral development reported in association with inborn errors of metabolism, and speculates on potential mechanisms by which such malformations arise. The detection of cerebral malformations prenatally should lead to a search for both genetic etiologies and inborn errors of metabolism in the fetus. Improving the changes of an early diagnosis provides for timely therapeutic interventions and it is hoped a brighter future for affected children and their families.
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Affiliation(s)
- Asuri N Prasad
- Section of Clinical Neurosciences, Department of Pediatrics and Child Health, Children's Hospital of Western Ontario, London Health Sciences Centre, University of Western Ontario, B-509, 800 Commissioners Road East, London, Ontario, N6C4G5, Canada
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Xie C, Turley SD, Dietschy JM. ABCA1 plays no role in the centripetal movement of cholesterol from peripheral tissues to the liver and intestine in the mouse. J Lipid Res 2009; 50:1316-29. [PMID: 19286647 DOI: 10.1194/jlr.m900024-jlr200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study uses the mouse to explore the role of ABCA1 in the movement of this cholesterol from the peripheral organs to the endocrine glands for hormone synthesis and liver for excretion. The sterol pool in all peripheral organs was constant and equaled 2,218 and 2,269 mg/kg, respectively, in abca1(+/+) and abca1(-/-) mice. Flux of cholesterol from these tissues equaled the rate of synthesis plus the rate of LDL-cholesterol uptake and was 49.9 mg/day/kg in control animals and 62.0 mg/day/kg in abca1(-/-) mice. In the abca1(+/+) animals, this amount of cholesterol moved from HDL into the liver for excretion. In the abca1(-/-) mice, the cholesterol from the periphery also reached the liver but did not use HDL. Fecal excretion of cholesterol was just as high in abac1(-/-) mice (198 mg/day/kg) as in the abac1(+/+) animals (163 mg/day/kg), although the abac1(-/-) mice excreted relatively more neutral than acidic sterols. This study established that ABCA1 plays essentially no role in the turnover of cholesterol in peripheral organs or in the centripetal movement of this sterol to the endocrine glands, liver, and intestinal tract for excretion.
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Affiliation(s)
- Chonglun Xie
- Department of Internal Medicine, University of Texas Southwestern Medical School, Dallas, TX 75390-9151, USA
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Ness GC, Chambers CM. Feedback and Hormonal Regulation of Hepatic 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase: The Concept of Cholesterol Buffering Capacity. ACTA ACUST UNITED AC 2008. [DOI: 10.1111/j.1525-1373.2000.22359.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Belgacem YH, Martin JR. Hmgcr in the corpus allatum controls sexual dimorphism of locomotor activity and body size via the insulin pathway in Drosophila. PLoS One 2007; 2:e187. [PMID: 17264888 PMCID: PMC1779623 DOI: 10.1371/journal.pone.0000187] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 01/02/2007] [Indexed: 01/10/2023] Open
Abstract
The insulin signaling pathway has been implicated in several physiological and developmental processes. In mammals, it controls expression of 3-Hydroxy-3-Methylglutaryl CoA Reductase (HMGCR), a key enzyme in cholesterol biosynthesis. In insects, which can not synthesize cholesterol de novo, the HMGCR is implicated in the biosynthesis of juvenile hormone (JH). However, the link between the insulin pathway and JH has not been established. In Drosophila, mutations in the insulin receptor (InR) decrease the rate of JH synthesis. It is also known that both the insulin pathway and JH play a role in the control of sexual dimorphism in locomotor activity. In studies here, to demonstrate that the insulin pathway and HMGCR are functionally linked in Drosophila, we first show that hmgcr mutation also disrupts the sexual dimorphism. Similarly to the InR, HMGCR is expressed in the corpus allatum (ca), which is the gland where JH biosynthesis occurs. Two p[hmgcr-GAL4] lines were therefore generated where RNAi was targeted specifically against the HMGCR or the InR in the ca. We found that RNAi-HMGCR blocked HMGCR expression, while the RNAi-InR blocked both InR and HMGCR expression. Each RNAi caused disruption of sexual dimorphism and produced dwarf flies at specific rearing temperatures. These results provide evidence: (i) that HMGCR expression is controlled by the InR and (ii) that InR and HMGCR specifically in the ca, are involved in the control of body size and sexual dimorphism of locomotor activity.
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Affiliation(s)
- Yesser Hadj Belgacem
- Laboratoire de Neurobiologie Cellulaire et Moléculaire (NBCM), Centre National de la Recherche Scientifique (CNRS), Unité UPR-9040, Gif-sur-Yvette, France
| | - Jean-René Martin
- Laboratoire de Neurobiologie Cellulaire et Moléculaire (NBCM), Centre National de la Recherche Scientifique (CNRS), Unité UPR-9040, Gif-sur-Yvette, France
- * To whom correspondence should be addressed. E-mail:
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Lachman RS. S. TAYBI AND LACHMAN'S RADIOLOGY OF SYNDROMES, METABOLIC DISORDERS AND SKELETAL DYSPLASIAS 2007. [PMCID: PMC7315357 DOI: 10.1016/b978-0-323-01931-6.50027-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Anstey A. School in photodermatology: Smith-Lemli-Opitz syndrome. PHOTODERMATOLOGY PHOTOIMMUNOLOGY & PHOTOMEDICINE 2006; 22:200-4. [PMID: 16869869 DOI: 10.1111/j.1600-0781.2006.00231.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The Smith-Lemli-Opitz syndrome has only recently been added to the small number of congenital disorders characterized by photosensitivity. The clinical features of this disorder are distinct from other photosensitivity syndromes. Details on the patho-mechanism of photosensitivity in the Smith-Lemli-Opitz syndrome have yet to be fully determined. However, preliminary evidence points to the deranged cholesterol metabolism that characterizes the syndrome as causal in this UVA-mediated photosensitivity disorder.
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Affiliation(s)
- Alex Anstey
- Academic Department of Dermatology, College of Medicine, Cardiff University, Cardiff, UK.
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Anstey AV, Azurdia RM, Rhodes LE, Pearse AD, Bowden PE. Photosensitive Smith-Lemli-Opitz syndrome is not caused by a single gene mutation: analysis of the gene encoding 7-dehydrocholesterol reductase in five U.K. families. Br J Dermatol 2005; 153:774-9. [PMID: 16181459 DOI: 10.1111/j.1365-2133.2005.06761.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive malformation syndrome characterized by a disorder in cholesterol metabolism. SLOS is caused by mutations in the DHCR7 gene which encodes 7-dehydrocholesterol reductase, an enzyme that catalyses the final step in cholesterol biosynthesis. We have previously established the clinical and photobiological features of the photosensitivity that is frequently a feature of SLOS. OBJECTIVES In this study, we have performed mutational analysis of the DHCR7 gene in individuals from five families with SLOS. In each family, one member was affected by severe photosensitivity as a manifestation of SLOS. METHODS Fifteen samples (including family controls) were screened using polymerase chain reaction amplification and direct automated sequencing. RESULTS Six different DHCR7 mutations were identified of which five were single point mutations that caused missense amino acid substitutions (P51H, T93M, L99P, E448K and R450L). The other was a splice site mutation (G-->C in splice acceptor site) affecting the intron 8-exon 9 splice junction (IVS8-1 G-->C). This splice site mutation and four of the five missense mutations have been previously published as causal in SLOS but the P51H is a novel mutation which has not previously been reported. CONCLUSIONS This is the first study in which DHCR7 gene mutational analysis has been performed on SLOS subjects with severe photosensitivity and indicates that no single mutation is responsible for the photosensitivity which characterizes this disorder.
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Affiliation(s)
- A V Anstey
- Department of Dermatology, Royal Liverpool University Hospital, Liverpool L7 8XP, U.K
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Abstract
The Smith-Lemli-Opitz syndrome (SLOS) is a disorder of impaired cholesterol biosynthesis because of a deficiency of the enzyme 7-dehydrocholesterol-Delta(7)-reductase, in the last step in cholesterol biosynthesis. Dietary cholesterol has been proposed as a potential therapy for SLOS and is being tested currently. Because there is no information on cholesterol absorption in SLOS, we recruited 12 SLOS patients into the General Clinical Research Center for 1-wk periods for administration of test meals and for blood and stool collections. A test breakfast that contained tracer cholesterol-4-C(14) with egg yolk or with crystalline cholesterol in suspension was given subsequently. Twenty-four and 48-h blood and 1-wk stool samples then were collected. The radioactivities in these samples were analyzed to determine the absorption of cholesterol by these patients. In 11 patients who were given egg yolk cholesterol, cholesterol absorption was 27.3 +/- 6.7%. The absorption was slightly less at 20.5 +/- 10.3% but not significantly different for the six patients who were given crystalline cholesterol. There was a positive correlation between the absorption of isotopic cholesterol as measured by determination of radioactive cholesterol in stool and the amount of isotopic cholesterol in the plasma at 24 and 48 h after the meal. Our data indicated that SLOS patients absorb cholesterol from the diet. However, the percentage of absorption is lower than reported values for normal adults and for hypercholesterolemic children. The absorption of crystalline cholesterol in suspension was slightly lower than the absorption of cholesterol in egg yolk cholesterol by these patients. The absorption of cholesterol may ameliorate some of the biochemical and developmental deficits in SLOS patients.
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Affiliation(s)
- Don S Lin
- Division of Endocrinology, Diabetes and Clinical Nutrition, Oregon Health & Science University, Portland, Oregon 97239, USA
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Merkens LS, Connor WE, Linck LM, Lin DS, Flavell DP, Steiner RD. Effects of dietary cholesterol on plasma lipoproteins in Smith-Lemli-Opitz syndrome. Pediatr Res 2004; 56:726-32. [PMID: 15319461 DOI: 10.1203/01.pdr.0000141522.14177.4f] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Smith-Lemli-Opitz syndrome is a condition of impaired cholesterol synthesis that is caused by mutations in DHCR7 encoding 7-dehydrocholesterol-Delta7 reductase. Birth defects and mental retardation are characteristic. Deficient plasma and tissue cholesterol and excess cholesterol precursors 7 and 8 dehydrocholesterol (7DHC and 8DHC) contribute to the pathogenesis. Cholesterol is transported to tissues via lipoproteins. We measured the effect of dietary cholesterol (egg yolk) on plasma lipoproteins to evaluate this potential treatment. We used the enzymatic method to measure total sterols in lipoproteins (n=12) and plasma (n=16). In addition, we analyzed individual plasma sterols by a gas chromatographic method. Samples were evaluated after 3 wk of a cholesterol-free diet and after 6-19 mo of dietary cholesterol. We also analyzed the distribution of sterols in lipoproteins and the apolipoprotein E genotype. Dietary cholesterol significantly increased the total sterols in plasma (2.22 +/- 0.13 to 3.10 +/- 0.22; mean +/- SEM; p < 0.002), in LDL (0.98 +/- 0.13 to 1.52 +/- 0.17 mM), and in HDL (0.72 +/- 0.04 to 0.92 +/- 0.07). Plasma cholesterol increased (1.78 +/- 0.16 to 2.67 +/- 0.25 mM; p < 0.007) and plasma 7DHC decreased in 10 children, but the mean decrease was not significant. The distribution of individual sterols in each lipoprotein fraction was similar to the distribution in plasma. The baseline cholesterol and the response to dietary cholesterol was the same in children with 3/3 and 3/4 apolipoprotein E genotypes. Dietary cholesterol increased total sterols in plasma, LDL, and HDL in children with Smith-Lemli-Opitz syndrome. These favorable increases in the lipoproteins are potentially therapeutic for this condition.
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Affiliation(s)
- Louise S Merkens
- Department of Pediatrics, Child Development and Rehabilitation Center, Doernbecher Children's Hospital, OR Health & Science University, CDRC-F, 707 SW Gaines, Portland, OR 97239, USA
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Goldenberg A, Wolf C, Chevy F, Benachi A, Dumez Y, Munnich A, Cormier-Daire V. Antenatal manifestations of Smith-Lemli-Opitz (RSH) syndrome: A retrospective survey of 30 cases. ACTA ACUST UNITED AC 2004; 124A:423-6. [PMID: 14735596 DOI: 10.1002/ajmg.a.20448] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Smith-Lemli-Opitz (SLO) syndrome or RSH syndrome is an autosomal recessive multiple malformation, and mental retardation syndrome ascribed to 7-dehydrocholesterol reductase deficiency, and usually diagnosed in the early postnatal period. Reviewing a series of 30 cases of SLO, we have investigated the variable antenatal expression of the disorder. Intrauterine growth retardation (IUGR) was the most frequent detectable trait (20/30). IUGR was either isolated (9/20) or associated with at least one other anomaly (11/20), including nuchal edema, renal, cardiac, cerebral malformations, genital anomalies, or polydactyly. In this last group, 3/11 presented with multiple malformations (> or =3 anomalies). In 5/30 cases, isolated nuchal edema (3/30), and isolated cardiac (1/30) or renal malformations (1/30) were the only detectable anomalies. Ultrasound findings were considered normal in 5/30 cases and were abnormal in 25/30 cases (83%), but early detection of multiple malformations was rare (3/30, 10%). We suggest giving consideration to a more systematic sterol analysis when dealing with IUGR, especially when associated anomalies are detected.
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Affiliation(s)
- Alice Goldenberg
- Department of Medical Genetics, Hôpital Necker-Enfants-Malades, 149 rue de Sèvres, 75043 Paris cedex 15, France
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Caruso PA, Poussaint TY, Tzika AA, Zurakowski D, Astrakas LG, Elias ER, Bay C, Irons MB. MRI and 1H MRS findings in Smith-Lemli-Opitz syndrome. Neuroradiology 2003; 46:3-14. [PMID: 14605787 DOI: 10.1007/s00234-003-1110-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2003] [Accepted: 07/29/2003] [Indexed: 04/13/2023]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder characterized by a defect in cholesterol biosynthesis, associated with mental retardation and multisystem structural abnormalities. This study investigated the prevalence of congenital CNS abnormalities by MRI in a large series of patients with SLOS and the correlation of the clinical and biochemical findings with the results of MRI and 1H MRS. Eighteen patients were studied; all underwent MRI of the brain, and 16 had 1H MRS of the cerebral white matter. The ratios choline:NAA, lipid:NAA, and lipid:choline metabolite were found to be correlated with the clinical degree of disease severity, serum total sterol ratios (cholesterol/cholesterol + 7-dehydrocholesterol + 8-dehydrocholesterol) and in two cases with the effect of cholesterol therapy. Abnormal CNS findings were noted in five patients, including callosal abnormalities (n = 4), Dandy-Walker variant (n = 1), and arachnoid cyst (n = 1). Holoprosencephaly was noted in one patient with a prevalence of 6%. Choline:NAA was elevated in seven patients. There was a statistically significant positive correlation between the lipid:choline ratio and the serum cholesterol precursor, 8-dehydrocholesterol. In two patients 1H MRS demonstrated abnormally elevated lipids prior to cholesterol therapy, which improved on therapy. The use of MRI and 1H MRS is an effective way to demonstrate brain structural abnormalities in patients with SLOS and may prove to be an effective method for the assessment of the effects of cholesterol replacement therapy in the brain.
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Affiliation(s)
- P A Caruso
- Department of Radiology, Massachusetts Eye and Ear Infirmary, Boston, USA
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23
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Muzzin KB, Harper LF. Smith-Lemli-Opitz syndrome: a review, case report and dental implications. SPECIAL CARE IN DENTISTRY 2003; 23:22-7. [PMID: 12887150 DOI: 10.1111/j.1754-4505.2003.tb00285.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive developmental disorder characterized by multiple congenital malformations, dysmorphic craniofacial features, and mental impairment. SLOS is caused by a deficiency of the enzyme 7-dehydrocholesterol delta7 reductase which converts 7-dehyrocholesterol to cholesterol. This error results in elevated serum levels of 7-dehydrocholesterol and decreased levels of serum cholesterol. This article describes the clinical features and medical treatment of SLOS. A case report is included, with recommended guidelines for providing safe and comprehensive dental care for individuals with SLOS.
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Affiliation(s)
- Kathleen B Muzzin
- Caruth School of Dental Hygiene, Baylor College of Dentistry, Texas A & M University Health Science Center, 3302 Gaston Avenue, Dallas, TX 75246, USA.
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Goldenberg A, Chevy F, Bernard C, Wolf C, Cormier-Daire V. [Clinical characteristics and diagnosis of Smith-Lemli-Opitz syndrome and tentative phenotype-genotype correlation: report of 45 cases]. Arch Pediatr 2003; 10:4-10. [PMID: 12818773 DOI: 10.1016/s0929-693x(03)00214-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
INTRODUCTION SLO (Smith-Lemli-Opitz) syndrome is an autosomal recessive multiple congenital malformations syndrome, including mental retardation, failure to thrive, craniofacial abnormalities, incomplete development of male genitalia, limb anomalies and various internal organ abnormalities. This syndrome is caused by a deficiency of cholesterol biosynthesis at the distal step of 7-dehydrocholesterol reductase (7DHCR). PATIENTS AND METHODS We have reviewed 45 cases of SLO syndrome and showed the large clinical spectrum of this syndrome. RESULTS The prenatal diagnosis should be considered when dealing with antenatal growth retardation and visceral malformations. At birth, a normal weight does not systematically exclude the diagnosis. Diagnosis was more difficult for older children especially for girls and should be suspected on the association of mental retardation, autism, short stature and microcephaly. We found a correlation between low plasmatic cholesterol measurement and clinical severity. Phenotype-genotype correlation was difficult to establish. However, homozygosity for IVS8-1G > C splice site mutation was associated with severe phenotype. CONCLUSION Better understanding of the 7DHCR gene regulation factors and of the compensatory mechanism of foeto-maternal cholesterol transfer are necessary to explain the wide clinical spectrum of the SLO syndrome.
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Affiliation(s)
- A Goldenberg
- Département de génétique médical, hôpital Necker-Enfants-Malades, assistance publique-hôpitaux de Paris, 149, rue de Sèvres, 75743 Paris, France
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25
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Affiliation(s)
- Bruce R Korf
- Department of Genetics, University of Alabama at Birmingham, Kaul Human Genetics Building Rm 230, 720 20th Street South, Birmingham, AL 35294-0024, USA.
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Wang L, Schuster GU, Hultenby K, Zhang Q, Andersson S, Gustafsson JA. Liver X receptors in the central nervous system: from lipid homeostasis to neuronal degeneration. Proc Natl Acad Sci U S A 2002; 99:13878-83. [PMID: 12368482 PMCID: PMC129791 DOI: 10.1073/pnas.172510899] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Liver X receptors (LXRalpha and -beta) are nuclear receptors abundant in the liver where they are regulators of lipid homeostasis. Both LXRs are also expressed in the brain, but their roles in this tissue remain to be clarified. We examined the brains of mice in which the genes of both LXRalpha and -beta have been disrupted and found several severe abnormalities. One of the most striking features is that the lateral ventricles are closed and lined with lipid-laden cells. In addition, there are enlarged brain blood vessels, especially in the pars reticularis of the substantia nigra and in the globus pallidus. Other features of the brains are excessive lipid deposits, proliferation of astrocytes, loss of neurons, and disorganized myelin sheaths. Electron micrographs revealed that, as mice aged, lipid vacuoles accumulated in astrocytes surrounding blood vessels. Comparison of mRNA profiles in LXR knockout mice and wild-type littermates showed that expression of several LXR target genes involved in cholesterol efflux from astrocytes was reduced. These findings show that LXRs have an important function in lipid homeostasis in the brain, and that loss of these receptors results in neurodegenerative diseases. Further characterization of the role of LXRs in the brain could lead to new insights into the etiology and treatment of some neurodegenerative disorders.
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MESH Headings
- Animals
- Astrocytes/metabolism
- Axons/pathology
- Biological Transport, Active/genetics
- Blood-Brain Barrier
- Brain/metabolism
- Brain/pathology
- Central Nervous System/metabolism
- Central Nervous System/pathology
- Cholesterol/metabolism
- DNA-Binding Proteins
- Gene Expression Regulation
- Homeostasis
- Lipid Metabolism
- Liver X Receptors
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microcirculation/pathology
- Microscopy, Electron
- Nerve Degeneration/genetics
- Nerve Degeneration/metabolism
- Nerve Degeneration/pathology
- Orphan Nuclear Receptors
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Cytoplasmic and Nuclear
- Receptors, Retinoic Acid/deficiency
- Receptors, Retinoic Acid/genetics
- Receptors, Retinoic Acid/metabolism
- Receptors, Thyroid Hormone/deficiency
- Receptors, Thyroid Hormone/genetics
- Receptors, Thyroid Hormone/metabolism
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Affiliation(s)
- Ling Wang
- Department of Medical Nutrition, NOVUM, Karolinska Institute, Huddinge University Hospital, S-141 86 Huddinge, Sweden
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27
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Starck L, Lövgren-Sandblom A, Björkhem I. Cholesterol treatment forever? The first Scandinavian trial of cholesterol supplementation in the cholesterol-synthesis defect Smith-Lemli-Opitz syndrome. J Intern Med 2002; 252:314-21. [PMID: 12366604 DOI: 10.1046/j.1365-2796.2002.01037.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To investigate if exogenous cholesterol affects sterol turnover in the cholesterol-synthesis defect Smith-Lemli-Opitz syndrome (SLOS) and if clinical effects justify long-time supplementation. The SLOS is caused by a deficiency of the enzyme 7-dehydrocholesterol-7-reductase with markedly reduced cholesterol levels and greatly increased levels of 7-dehydrocholesterol (7-DHC). DESIGN Treatment with dietary cholesterol in patients with SLOS in a case series study. SETTING All biochemical analyses were performed in one laboratory. The clinical follow-up was carried out by one of the authors (LS), a paediatric neurologist. SUBJECTS Seven patients with biochemically verified SLOS have been diagnosed in Sweden and all of them are included in the study. INTERVENTIONS Six patients were treated for 0.5-6 years orally with cholesterol and the bile acid taurocholate and one patient was supplemented with cholesterol only. MAIN OUTCOME MEASURES In addition to cholesterol, 7- and 8-DHC, lathosterol was used as a marker of endogenous cholesterol synthesis and the patients were followed clinically. Nerve conduction velocities (NCV) were measured before treatment in all patients and a UVA-light test was performed in one of them. RESULTS Lathosterol was initially increased by cholesterol supply in subjects with very low cholesterol levels with subsequent rise of 7- and 8-DHC. Photosensitivity clinically improved in all, verified by UVA-light testing in one. Progressive polyneuropathy improved, whilst stationary forms did not. CONCLUSION Dietary cholesterol can up-regulate sterol turnover in severely affected patients. Although some specific features are treatable and verifiable by objective methods, data supporting life-long treatment dietary cholesterol in all SLO patients are still lacking.
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Affiliation(s)
- L Starck
- Sachs' Children's Hospital, S-11883 Stockholm, Sweden.
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28
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Anstey A. Photomedicine: lessons from the Smith-Lemli-Opitz syndrome. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2001; 62:123-7. [PMID: 11566274 DOI: 10.1016/s1011-1344(01)00171-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder caused by a discrete block in the cholesterol biosynthetic pathway. Recognition of the metabolic basis of this condition has bought into focus knowledge from fields as diverse as clinical genetics, sterol biochemistry, foetal nutrition, and experimental teratology, resulting in a rush of new insights in these fields. Unfortunately, late recognition of photosensitivity as part of this syndrome has largely excluded photodermatologists and photobiologists from the recent frenzy of research in this disorder. However, clinical features of this new inherited photosensitivity syndrome have now been established, and monochromator light testing has confirmed it to be a UVA-mediated condition. Current knowledge concerning photosensitivity in SLOS is reviewed and future research into the pathogenesis of this disorder is discussed.
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Affiliation(s)
- A Anstey
- Photodermatology Unit, Department of Dermatology, University of Wales College of Medicine, Cardiff, CF4 4XN, UK.
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29
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Witsch-Baumgartner M, Loeffler J, Menzel HJ, Utermann G, Neuhaus C. Mutation screening in the DHCR7 gene of patients with attention deficit and hyperactivity disorder. AMERICAN JOURNAL OF MEDICAL GENETICS 2001; 102:106-7. [PMID: 11471183 DOI: 10.1002/1096-8628(20010722)102:1<106::aid-ajmg1417>3.0.co;2-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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30
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Kim JH, Lee JN, Paik YK. Cholesterol biosynthesis from lanosterol. A concerted role for Sp1 and NF-Y-binding sites for sterol-mediated regulation of rat 7-dehydrocholesterol reductase gene expression. J Biol Chem 2001; 276:18153-60. [PMID: 11279217 DOI: 10.1074/jbc.m101661200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 7-dehydrocholesterol reductase (Dhcr7) is the terminal enzyme in the pathway of cholesterol biosynthesis. We have previously reported that sterol depletion in vivo caused a significant induction of both liver mRNA and enzyme activity of Dhcr7 (Bae, S.-H., Lee, J. N., Fitzky, B. U., Seong, J., and Paik, Y.-K. (1999) J. Biol. Chem. 274, 14624-14631). In this paper, we also observed liver cell-specific sterol-mediated Dhcr7 gene induction in vitro by sterol depletion in rat hepatoma cells, suggesting the presence of sterol-mediated regulatory elements in the Dhcr7 gene. To understand the mechanisms responsible for regulating Dhcr7 expression, we have isolated the 5'-flanking region of the gene encoding rat Dhcr7 and have characterized the potential regulatory elements of the gene that are responsible for sterol-mediated regulation. The Dhcr7 promoter contains binding sites for Sp1 (at -177, -172, -125, and -20), NF-Y (at -88 and -51), and SREBP-1 or ADD1 (at -33). Deletion analysis of the Dhcr7 gene promoter (-1053/+31), employing a nested series of Dhcr7-luciferase constructs, demonstrated that the -179 upstream region of the gene is necessary and sufficient for optimal efficient sterol-regulated transcription. DNase I footprinting and electrophoretic mobility shift assay showed that the SRE1/E box (-33/-22) involved in sterol response of many sterol-related enzyme genes was protected specifically by the overexpressed recombinant ADD1. Mutational analysis for the functional relationship between the identified cis-elements in this region indicate that one of the binding sites for Sp1 (GC box at -125) and NF-Y (CCAAT box at -88) plays a cooperative role in the sterol-mediated activation, in which the latter site also acts as a co-regulator for SREBP-activated Dhcr7 promoter activity. We believe that Dhcr7 is the first enzyme characterized with a sterol-regulatory function in the post-lanosterol pathway. This may be important for understanding the coordinated control of cholesterol biosynthesis as well as the molecular mechanism of Smith-Lemli-Opitz syndrome-related protein in mammals.
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Affiliation(s)
- J H Kim
- Department of Biochemistry, Bioproducts Research Center and Yonsei Proteome Research Center, Yonsei University, 134 Shinchon-dong, Sudaemoon-ku, Seoul 120-749, Korea
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Abstract
The central nervous system accounts for only 2% of the whole body mass but contains almost a quarter of the unesterified cholesterol present in the whole individual. This sterol is largely present in two pools comprised of the cholesterol in the plasma membranes of glial cells and neurons and the cholesterol present in the specialized membranes of myelin. From 0.02% (human) to 0.4% (mouse) of the cholesterol in these pools turns over each day so that the absolute flux of sterol across the brain is only approximately 0.9% as rapid as the turnover of cholesterol in the whole body of these respective species. The input of cholesterol into the central nervous system comes almost entirely from in situ synthesis, and there is currently little evidence for the net transfer of sterol from the plasma into the brain of the fetus, newborn or adult. In the steady state in the adult, an equivalent amount of cholesterol must move out of the brain and this output is partly accounted for by the formation and excretion of 24S-hydroxycholesterol. This cholesterol turnover across the brain is increased in neurodegenerative disorders such as Alzheimer's disease and Niemann-Pick type C disease. Indirect evidence suggests that large amounts of cholesterol also turn over among the glial cells and neurons within the central nervous system during brain growth and neuron repair and remodelling. This internal recycling of sterol may involve ligands such as apolipoproteins E and AI, and one or more membrane transport proteins such as members of the low density lipoprotein receptor family. Changes in cholesterol balance across the whole body may, in some way, cause alterations in sterol recycling and apolipoprotein E expression within the central nervous system, which, in turn, may affect neuron and myelin integrity. Further elucidation of the processes controlling these events is very important to understand a variety of neurodegenerative disorders.
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Affiliation(s)
- J M Dietschy
- Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8887, USA.
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Abstract
The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive metabolic disorder characterized by variable congenital malformations, facial dysmorphism, and mental retardation. Mutations in the DHCR7 gene have been identified in SLOS patients. This gene encodes for the enzyme Delta7-sterol reductase which catalyses the last step of cholesterol biosynthesis. Among the 73 different mutations observed so far, including 10 novel mutations reported in this review, the majority are missense mutations (65) which cluster in three domains of the protein: in the transmembrane domain (TM mutations), in the fourth cytoplasmic loop (4L mutations), and at the C-terminus (CT mutations). Two nonsense mutations, one splice site mutation, two single nucleotide insertions, and three deletions which likely all represent null mutations were also described. Expression studies have demonstrated a decreased protein stability for all analyzed missense mutations. By comparing clinical severity scores, biochemical data, and mutations in SLOS patients a genotype-phenotype correlation has been established. The null and 4L mutations are associated with a severe clinical phenotype, and TM and CT mutations are associated with a mild clinical phenotype. DHCR7 mutational spectra in SLOS patients of British, German, Italian, and Polish origin demonstrate significant geographic frequency differences of common DHCR7 mutations.
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Affiliation(s)
- M Witsch-Baumgartner
- Institute of Medical Biology and Human Genetics, University of Innsbruck, Innsbruck, Austria
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34
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Battaile KP, Battaile BC, Merkens LS, Maslen CL, Steiner RD. Carrier frequency of the common mutation IVS8-1G>C in DHCR7 and estimate of the expected incidence of Smith-Lemli-Opitz syndrome. Mol Genet Metab 2001; 72:67-71. [PMID: 11161831 DOI: 10.1006/mgme.2000.3103] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is a multiple congenital anomaly/mental retardation syndrome of variable severity with an incidence previously estimated at 1 in 20,000-60,000 based on case frequency surveys. Identification of the gene defect in SLOS has made it possible to calculate the carrier frequency and estimate disease incidence using molecular methods to identify carriers. Using a previously described PCR-RFLP assay we screened 1503 anonymous blood samples from random newborn screening blood spot cards for the presence of the common SLOS mutation IVS8-1G>C in order to determine the carrier frequency. Sixteen carriers were identified in the 1503 samples. Since the frequency of the IVS8-1G>C mutation among all SLOS gene mutations is known, the overall carrier frequency for all mutations can be calculated. The calculated carrier frequency for all mutations based on this result is 1 in 30, predicting an SLOS incidence of 1 in 1590 to 1 in 13,500. The current incidence estimate may, therefore, significantly underestimate the true incidence of SLOS. This discrepancy between calculated and observed incidence could be due to undiagnosed mild cases, misdiagnosed severe cases, death prior to diagnosis, or fetal loss. More comprehensive incidence studies are needed to determine if SLOS is as common as predicted by the very high (1 in 30) carrier frequency determined in this study.
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Affiliation(s)
- K P Battaile
- Department of Pediatrics, Oregon Health Sciences University, Portland, OR 97201, USA
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35
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Nissinen MJ, Gylling H, Kaski M, Tammisto P, Mieskonen S, Ignatius J, Miettinen TA. Smith-Lemli-Opitz syndrome and other sterol disorders among Finns with developmental disabilities. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 2000; 136:457-67. [PMID: 11128747 DOI: 10.1067/mlc.2000.110607] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is an inherited disorder of cholesterol metabolism in which 7- and 8-dehydrocholesterols are accumulated in blood and tissues. Diagnosis of SLOS and other disorders in cholesterol metabolism (eg, cerebrotendinous xanthomatosis, phytosterolemia, desmosterolosis, and X-linked dominant Conradi-Hünermann-Happle syndrome) can be performed by gas-liquid chromatographic analysis of serum sterols. To elucidate their involvement in developmental disability, we evaluated serum sterols in two study groups: developmentally disabled subjects in long-term care (N = 322) and newborns and young children (N = 49) with features of SLOS in the Finnish population of 5 million. Only 1 SLOS case (type II) was found from among the 49 children. Seven additional adult cases (type I) with a wide range of clinical features and the serum sterol abnormalities characteristic of SLOS were detected from among the developmentally disabled subjects. The frequency of SLOS in the latter group was relatively high (7 in 322). No other hereditary sterol disorders were found, but two subgroups with low serum cholesterol precursor sterols and high serum plant sterols were identified. Several subjects, including the 7 SLOS patients, used ample medication and had abnormalities in serum sterol concentrations. Thus, among the subjects taking melperone, a high serum delta8-cholestenol level suggests an interference by the drug with cholesterol synthesis. Our results emphasize the importance of analyzing the serum sterols of developmentally disabled subjects to diagnose SLOS and of finding putative undiagnosed disorders in sterol metabolism associated with these clinical conditions.
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Affiliation(s)
- M J Nissinen
- Department of Medicine, University of Helsinki, Finland
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36
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Steiner RD, Linck LM, Flavell DP, Lin DS, Connor WE. Sterol balance in the Smith-Lemli-Opitz syndrome: reduction in whole body cholesterol synthesis and normal bile acid production. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)33456-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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37
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Battaile KP, Steiner RD. Smith-Lemli-Opitz syndrome: the first malformation syndrome associated with defective cholesterol synthesis. Mol Genet Metab 2000; 71:154-62. [PMID: 11001806 DOI: 10.1006/mgme.2000.3020] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive condition with multiple malformations, mental retardation, and growth failure, results from markedly reduced activity of the final enzyme in the cholesterol biosynthetic pathway, 7-dehydrocholesterol reductase (DHCR7). Clinical signs vary in severity, ranging from fetal loss to holoprosencephaly with multiple malformations to isolated syndactyly. The biochemical defect in SLOS is a deficiency of DHCR7, which results in an abnormally low cholesterol level, and increased amounts of intermediates of sterol biosynthesis. Animal models currently exist through the use of cholesterol biosynthesis inhibitors, from which a great deal has been learned. Pregnant rats treated with inhibitors of DHCR7 yield pups that have abnormal sterol profiles and craniofacial abnormalities characteristic of severe SLOS. Biochemical testing of human patients can be performed using gas chromatography/mass spectroscopy (GC/MS) to analyze the sterol content of tissues, amniotic fluid, or cell culture lysate. Numerous mutations have been identified in DHCR7 but seven individual mutations account for 67% of the total mutations reported in the literature. Clinical trials with SLOS are underway, with the goal of increasing the cholesterol concentration in the plasma and tissues through the administration of dietary cholesterol. Thus far, this approach has shown limited efficacy. Nevertheless, the recent identification of the biochemical and molecular genetic basis for SLOS is reason for optimism that the condition may one day yield to treatment.
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Affiliation(s)
- K P Battaile
- Department of Pediatrics, Oregon Health Sciences University, Portland, Oregon 97201, USA
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38
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Ness GC, Chambers CM. Feedback and hormonal regulation of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase: the concept of cholesterol buffering capacity. PROCEEDINGS OF THE SOCIETY FOR EXPERIMENTAL BIOLOGY AND MEDICINE. SOCIETY FOR EXPERIMENTAL BIOLOGY AND MEDICINE (NEW YORK, N.Y.) 2000; 224:8-19. [PMID: 10782041 DOI: 10.1046/j.1525-1373.2000.22359.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Regulation of the expression of hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase by the major end product of the biosynthetic pathway, cholesterol, and by various hormones is critical to maintaining constant serum and tissue cholesterol levels in the face of an ever-changing external environment. The ability to downregulate this enzyme provides a means to buffer the body against the serum cholesterol-raising action of dietary cholesterol. The higher the basal expression of hepatic HMG-CoA reductase, the greater the "cholesterol buffering capacity" and the greater the resistance to dietary cholesterol. This review focuses on the mechanisms of feedback and hormonal regulation of HMG-CoA reductase in intact animals rather than in cultured cells and presents the evidence that leads to the proposal that regulation of hepatic HMG-CoA reductase acts as a cholesterol buffer. Recent studies with animals have shown that feedback regulation of hepatic HMG-CoA reductase occurs at the level of translation in addition to transcription. The translational efficiency of HMG-CoA reductase mRNA is diminished through the action of dietary cholesterol. Oxylanosterols appear to be involved in this translational regulation. Feedback regulation by dietary cholesterol does not appear to involve changes in the state of phosphorylation of hepatic HMG-CoA reductase or in the rate of degradation of this enzyme. Several hormones act to alter the expression of hepatic HMG-CoA reductase in animals. These include insulin, glucagon, glucocorticoids, thyroid hormone and estrogen. Insulin stimulates HMG-CoA reductase activity likely by increasing the rate of transcription, whereas glucagon acts by opposing this effect. Hepatic HMG-CoA reductase activity undergoes a significant diurnal variation due to changes in the level of immunoreactive protein primarily mediated by changes in insulin and glucagon levels. Thyroid hormone increases hepatic HMG-CoA reductase levels by acting to increase both transcription and stability of the mRNA. Glucocorticoids act to decrease hepatic HMG-CoA reductase expression by destabilizing reductase mRNA. Estrogen acts to increase hepatic HMG-CoA reductase activity primarily by stabilizing the mRNA. Deficiencies in those hormones that act to increase hepatic HMG-CoA reductase gene expression lead to elevations in serum cholesterol levels. High basal expression of hepatic HMG-CoA reductase, whether due to genetic or hormonal factors, appears to result in greater cholesterol buffering capacity and thus increased resistance to dietary cholesterol.
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Affiliation(s)
- G C Ness
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612, USA.
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Abstract
The Smith-Lemli-Opitz syndrome (SLOS) is one of the archetypical multiple congenital malformation syndromes. The recent discovery of the biochemical cause of SLOS and the subsequent redefinition of SLOS as an inborn error of cholesterol metabolism have led to important new treatment possibilities for affected patients. Moreover, the recent recognition of the important role of cholesterol in vertebrate embryogenesis, especially with regard to the hedgehog embryonic signalling pathway and its effects on the expression of homeobox genes, has provided an explanation for the abnormal morphogenesis in the syndrome. The well known role of cholesterol in the formation of steroid hormones has also provided a possible explanation for the abnormal behavioural characteristics of SLOS.
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Affiliation(s)
- R I Kelley
- The Johns Hopkins University, Kennedy Krieger Institute, 707 North Broadway, Baltimore, Maryland 21205, USA
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40
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Witsch-Baumgartner M, Fitzky BU, Ogorelkova M, Kraft HG, Moebius FF, Glossmann H, Seedorf U, Gillessen-Kaesbach G, Hoffmann GF, Clayton P, Kelley RI, Utermann G. Mutational spectrum in the Delta7-sterol reductase gene and genotype-phenotype correlation in 84 patients with Smith-Lemli-Opitz syndrome. Am J Hum Genet 2000; 66:402-12. [PMID: 10677299 PMCID: PMC1288092 DOI: 10.1086/302760] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive malformation syndrome, ranges in clinical severity from mild dysmorphism and moderate mental retardation to severe congenital malformation and intrauterine lethality. Mutations in the gene for Delta7-sterol reductase (DHCR7), which catalyzes the final step in cholesterol biosynthesis in the endoplasmic reticulum (ER), cause SLOS. We have determined, in 84 patients with clinically and biochemically characterized SLOS (detection rate 96%), the mutational spectrum in the DHCR7 gene. Forty different SLOS mutations, some frequent, were identified. On the basis of mutation type and expression studies in the HEK293-derived cell line tsA-201, we grouped mutations into four classes: nonsense and splice-site mutations resulting in putative null alleles, missense mutations in the transmembrane domains (TM), mutations in the 4th cytoplasmic loop (4L), and mutations in the C-terminal ER domain (CT). All but one of the tested missense mutations reduced protein stability. Concentrations of the cholesterol precursor 7-dehydrocholesterol and clinical severity scores correlated with mutation classes. The mildest clinical phenotypes were associated with TM and CT mutations, and the most severe types were associated with 0 and 4L mutations. Most homozygotes for null alleles had severe SLOS; one patient had a moderate phenotype. Homozygosity for 0 mutations in DHCR7 appears compatible with life, suggesting that cholesterol may be synthesized in the absence of this enzyme or that exogenous sources of cholesterol can be used.
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Affiliation(s)
- M Witsch-Baumgartner
- Institute of Medical Biology and Human Genetics, Schoepfstrasse 41, 6020 Innsbruck, Austria
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41
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Rizzo C, Dionisi-Vici C, D'Ippoliti M, Fina F, Sabetta G, Federici G. A simple and rapid HPLC method for simultaneous determination of plasma 7-dehydrocholesterol and vitamin E: its application in Smith-Lemli-Opitz patients. Clin Chim Acta 2000; 291:97-102. [PMID: 10612721 DOI: 10.1016/s0009-8981(99)00197-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- C Rizzo
- Department of Metabolism, IRCCS 'Bambino Gesù' Children's Research Hospital, Piazza S. Onofrio 4, 00165, Rome, Italy.
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Battaile KP, Maslen CL, Wassif CA, Krakowiak P, Porter FD, Steiner RD. A simple PCR-based assay allows detection of a common mutation, IVS8-1G-->C, in DHCR7 in Smith-Lemli-Opitz syndrome. GENETIC TESTING 2000; 3:361-3. [PMID: 10627944 DOI: 10.1089/gte.1999.3.361] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive multiple malformation disorder. A deficiency of the enzyme 7-dehydrocholesterol delta 7-reductase (DHCR7) is the primary abnormality in SLOS. The gene encoding DHCR7 has been cloned, and we have identified a mutation affecting the splice acceptor site 5' of exon 9 that occurs frequently in affected individuals. We developed a novel PCR-based assay to detect this common mutation in DHCR7. Using this assay, heterozygosity was detected for this mutation in 18 of 26 and homozygosity in 1 of 26 unrelated affected individuals. The high frequency of this mutation is suggestive of either a founder effect in our group of patients or a mutational hotspot. The simplicity and reliability of this assay will allow it to be used as a clinical test to aid in diagnosis of atypical cases, in carrier testing, in prediction of prognosis based on genotype, and in prenatal molecular genetic diagnostic testing.
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Affiliation(s)
- K P Battaile
- Department of Pediatrics, Oregon Health Sciences University, Portland 97201, USA
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Diagnóstico bioquímico del síndrome de Smith-Lemli-Opitz en un paciente con hiperplasia adrenal congénita. An Pediatr (Barc) 2000. [DOI: 10.1016/s1695-4033(00)78633-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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44
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Anstey AV. Photosensitivity in the Smith-Lemli-Opitz syndrome. PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE 1999; 15:217-8. [PMID: 10599969 DOI: 10.1111/j.1600-0781.1999.tb00091.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- A V Anstey
- Photodermatology Unit, University of Wales College of Medicine, Cardiff, United Kingdom
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Anstey AV, Ryan A, Rhodes LE, Charman CR, Arlett CF, Tyrrell RM, Taylor CR, Pearse AD. Characterization of photosensitivity in the Smith-Lemli-Opitz syndrome: a new congenital photosensitivity syndrome. Br J Dermatol 1999; 141:406-14. [PMID: 10583043 DOI: 10.1046/j.1365-2133.1999.03032.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Photosensitivity has recently been reported as a feature of the Smith-Lemli-Opitz syndrome (SLO). The aim of this study was to establish the photobiological features of this disorder and to examine the hypothesis that the photosensitivity is caused by the high levels of 7-dehydrocholesterol found in SLO. All known cases of SLO in the U.K. were reviewed and clinical details of photosensitivity were recorded in detail. The action spectrum of the photosensitive eruption was defined by monochromator light testing. Thirteen of the 23 subjects (57%) had severe photosensitivity, and in 10 there was no photosensitivity. No correlation was identified between levels of 7-dehydrocholesterol and severity of photosensitivity, suggesting that the photosensitivity in SLO is not caused by a direct phototoxic effect mediated by 7-dehydrocholesterol. A novel pattern of photosensitivity was observed, with onset of a sunburn-like erythema on sun-exposed skin within minutes of sun exposure, which persisted in most cases for up to 24-48 h before fading. Monochromator light testing in three subjects showed an ultraviolet (UV) A-mediated photosensitivity eruption with greatest photosensitivity at 350 nm. Photosensitivity is a common and prominent feature of SLO and appears to be UVA-mediated. Elucidation of its biochemical basis may provide insight into normal cutaneous protective mechanisms against UVA-induced photodamage, and also sun sensitivity in general.
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Affiliation(s)
- A V Anstey
- Photodermatology Unit, University of Wales College of Medicine, University Hospital of Wales, Cardiff CF4 4XN, U.K
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46
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Honda A, Salen G, Shefer S, Batta AK, Honda M, Xu G, Tint GS, Matsuzaki Y, Shoda J, Tanaka N. Bile acid synthesis in the Smith-Lemli-Opitz syndrome: effects of dehydrocholesterols on cholesterol 7α-hydroxylase and 27-hydroxylase activities in rat liver. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33396-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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47
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Anstey AV, Taylor CR. Photosensitivity in the Smith-Lemli-Opitz syndrome: the US experience of a new congenital photosensitivity syndrome. J Am Acad Dermatol 1999; 41:121-3. [PMID: 10411425 DOI: 10.1016/s0190-9622(99)70420-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Photosensitivity has been briefly mentioned in several publications on the Smith-Lemli-Opitz (SLO) syndrome, an autosomal recessive mental retardation syndrome. We conducted a questionnaire-based survey to determine the incidence and main features of photosensitivity in SLO. We confirmed a high incidence, and initial evidence suggests that SLO may be the first example of an inherited photosensitivity disorder in which sensitivity to UVA is common.
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Affiliation(s)
- A V Anstey
- Department of Dermatology, University Hospital of Wales, Heath Park, Cardiff, United Kingdom
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48
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Bae SH, Lee JN, Fitzky BU, Seong J, Paik YK. Cholesterol biosynthesis from lanosterol. Molecular cloning, tissue distribution, expression, chromosomal localization, and regulation of rat 7-dehydrocholesterol reductase, a Smith-Lemli-Opitz syndrome-related protein. J Biol Chem 1999; 274:14624-31. [PMID: 10329655 DOI: 10.1074/jbc.274.21.14624] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cDNA encoding the 471-amino acid rat 7-dehydrocholesterol reductase (DHCR), an enzyme that has been implicated in both cholesterol biosynthesis and developmental abnormalities (e.g. Smith-Lemli-Opitz syndrome) in mammals, has been cloned and sequenced, and the primary structure of the enzyme has been deduced. The DHCR gene was mapped to chromosome 8q2.1 by fluorescence in situ hybridization. Rat DHCR, calculated molecular mass of 54.15-kDa polypeptide, shares a close amino acid identity with mouse and human DHCRs (96 and 87%, respectively) as compared with its other related proteins (e.g. fungal sterol Delta14-reductase) and exhibits high hydrophobicity (>68%) with 9 transmembrane domains. Five putative sterol-sensing domains were predicted to be localized in transmembrane domains 4-8, which are highly homologous to those found in 3-hydroxymethylglutaryl-CoA reductase, sterol regulatory element-binding protein cleavage-activating protein, and patched protein. The polypeptide encoded by DHCR cDNA was expressed in yeast as a 55.45-kDa myc-tagged fusion protein, which was recognized with anti-myc monoclonal antibody 9E10 and shown to possess full DHCR activity with respect to dependence on NADPH and sensitivity to DHCR inhibitors. Northern blot analysis indicates that the highest expression of DHCR mRNA was detected in liver, followed by kidney and brain. In rat brains, the highest level of mRNA encoding DHCR was detected in the midbrain, followed by the spinal cord and medulla. Feeding rats 5% cholestyramine plus 0.1% lovastatin in chow resulted in both approximately a 3-fold induction of DHCR mRNA and a 5-fold increase of the enzymic activity in the liver. When rats were fed 0.1% (w/w) AY-9944 (in chow) for 14-days, a complete inhibition of DHCR activity and a significant reduction in serum total cholesterol level were observed. However, the level of hepatic DHCR mRNA fell only slightly, suggesting that AY-9944 may act more rapidly at the protein level than at the level of transcription of the DHCR gene under these conditions.
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Affiliation(s)
- S H Bae
- Department of Biochemistry and Bioproducts Research Center, Yonsei University, Seoul, Korea
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49
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Gaoua W, Chevy F, Roux C, Wolf C. Oxidized derivatives of 7-dehydrocholesterol induce growth retardation in cultured rat embryos: a model for antenatal growth retardation in the Smith-Lemli-Opitz syndrome. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)32450-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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50
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Abstract
Smith-Lemli-Opitz syndrome (SLO) is a recognized clinical entity with distinctive anomalies. Recently it has been shown that a specific defect in cholesterol metabolism, 7-dehydroxycholesterol reductase deficiency, causes the multiple abnormalities seen in SLO. There have been two reports of first-trimester nuchal translucency associated with SLO. We report two cases of SLO in the third trimester, one with persisting nuchal oedema and the other presenting with hydrops. These findings may explain a proportion of the perinatal loss associated with this syndrome.
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Affiliation(s)
- R Maymon
- Fetal Medicine Unit, Obstetric Hospital, London, UK
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