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Mole SE, Schulz A, Badoe E, Berkovic SF, de Los Reyes EC, Dulz S, Gissen P, Guelbert N, Lourenco CM, Mason HL, Mink JW, Murphy N, Nickel M, Olaya JE, Scarpa M, Scheffer IE, Simonati A, Specchio N, Von Löbbecke I, Wang RY, Williams RE. Guidelines on the diagnosis, clinical assessments, treatment and management for CLN2 disease patients. Orphanet J Rare Dis 2021; 16:185. [PMID: 33882967 PMCID: PMC8059011 DOI: 10.1186/s13023-021-01813-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 04/06/2021] [Indexed: 11/28/2022] Open
Abstract
Background CLN2 disease (Neuronal Ceroid Lipofuscinosis Type 2) is an ultra-rare, neurodegenerative lysosomal storage disease, caused by an enzyme deficiency of tripeptidyl peptidase 1 (TPP1). Lack of disease awareness and the non-specificity of presenting symptoms often leads to delayed diagnosis. These guidelines provide robust evidence-based, expert-agreed recommendations on the risks/benefits of disease-modifying treatments and the medical interventions used to manage this condition. Methods An expert mapping tool process was developed ranking multidisciplinary professionals, with knowledge of CLN2 disease, diagnostic or management experience of CLN2 disease, or family support professionals. Individuals were sequentially approached to identify two chairs, ensuring that the process was transparent and unbiased. A systematic literature review of published evidence using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance was independently and simultaneously conducted to develop key statements based upon the strength of the publications. Clinical care statements formed the basis of an international modified Delphi consensus determination process using the virtual meeting (Within3) online platform which requested experts to agree or disagree with any changes. Statements reaching the consensus mark became the guiding statements within this manuscript, which were subsequently assessed against the Appraisal of Guidelines for Research and Evaluation (AGREEII) criteria. Results Twenty-one international experts from 7 different specialities, including a patient advocate, were identified. Fifty-three guideline statements were developed covering 13 domains: General Description and Statements, Diagnostics, Clinical Recommendations and Management, Assessments, Interventions and Treatment, Additional Care Considerations, Social Care Considerations, Pain Management, Epilepsy / Seizures, Nutritional Care Interventions, Respiratory Health, Sleep and Rest, and End of Life Care. Consensus was reached after a single round of voting, with one exception which was revised, and agreed by 100% of the SC and achieved 80% consensus in the second voting round. The overall AGREE II assessment score obtained for the development of the guidelines was 5.7 (where 1 represents the lowest quality, and 7 represents the highest quality). Conclusion This program provides robust evidence- and consensus-driven guidelines that can be used by all healthcare professionals involved in the management of patients with CLN2 disease and other neurodegenerative disorders. This addresses the clinical need to complement other information available. Supplementary Information The online version contains supplementary material available at 10.1186/s13023-021-01813-5.
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Affiliation(s)
| | - Angela Schulz
- Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Eben Badoe
- Korle Bu Teaching Hospital, University of Ghana Medical School, Accra, Ghana
| | - Samuel F Berkovic
- Austin Health Victoria, University of Melbourne, Heidelberg, VIC, Australia
| | | | - Simon Dulz
- Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Paul Gissen
- University College London, London, UK.,NIHR Great Ormond Street Hospital Biomedical Research Centre, London, UK
| | | | - Charles M Lourenco
- Universidade de São Paulo Faculdade de Medicina de Ribeirão Preto, Riberirao Preto, Brazil
| | | | - Jonathan W Mink
- Golisano Childrens' Hospital, University of Rochester Medical Center, Rochester, NY, USA
| | - Noreen Murphy
- Batten Disease Support and Research Association (BDSRA), Columbus, OH, USA
| | - Miriam Nickel
- Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Joffre E Olaya
- Children's Hospital of Orange County, Orange County, CA, USA
| | - Maurizio Scarpa
- Regional Coordinating Center for Rare Diseases, University Hospital Udine, Udine, Italy
| | - Ingrid E Scheffer
- Austin Health Victoria, University of Melbourne, Heidelberg, VIC, Australia.,Royal Children's Hospital, Florey and Murdoch Children's Research Institutes, Melbourne, Australia
| | - Alessandro Simonati
- Department of Surgery, Dentistry, Paediatrics and Gynaecology, University of Verona School of Medicine, Verona, Italy
| | | | | | - Raymond Y Wang
- Children's Hospital of Orange County, Orange County, CA, USA
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Gardner E, Bailey M, Schulz A, Aristorena M, Miller N, Mole SE. Mutation update: Review of TPP1 gene variants associated with neuronal ceroid lipofuscinosis CLN2 disease. Hum Mutat 2019; 40:1924-1938. [PMID: 31283065 PMCID: PMC6851559 DOI: 10.1002/humu.23860] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 06/25/2019] [Accepted: 06/28/2019] [Indexed: 01/03/2023]
Abstract
Neuronal ceroid lipofuscinosis type 2 (CLN2 disease) is an autosomal recessive condition caused by variants in the TPP1 gene, leading to deficient activity of the lysosomal enzyme tripeptidyl peptidase I (TPP1). We update on the spectrum of TPP1 variants associated with CLN2 disease, comprising 131 unique variants from 389 individuals (717 alleles) collected from the literature review, public databases, and laboratory communications. Previously unrecorded individuals were added to the UCL TPP1‐specific database. Two known pathogenic variants, c.509–1 G>C and c.622 C>T (p.(Arg208*)), collectively occur in 60% of affected individuals in the sample, and account for 50% of disease‐associated alleles. At least 86 variants (66%) are private to single families. Homozygosity occurs in 45% of individuals where both alleles are known (87% of reported individuals). Atypical CLN2 disease, TPP1 enzyme deficiency with disease onset and/or progression distinct from classic late‐infantile CLN2, represents 13% of individuals recorded with associated phenotype. NCBI ClinVar currently holds records for 37% of variants collected here. Effective CLN2 disease management requires early diagnosis; however, irreversible neurodegeneration occurs before a diagnosis is typically reached at age 5. Timely classification and public reporting of TPP1 variants is essential as molecular testing increases in use as a first‐line diagnostic test for pediatric‐onset neurological disease.
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Affiliation(s)
- Emily Gardner
- UCL MRC Laboratory for Molecular Cell Biology and UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Mitch Bailey
- Global Scientific Affairs, BioMarin Pharmaceutical Inc, Novato, California
| | - Angela Schulz
- Department of Paediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Mikel Aristorena
- UCL MRC Laboratory for Molecular Cell Biology and UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Nicole Miller
- Global Scientific Affairs, BioMarin Pharmaceutical Inc, Novato, California
| | - Sara E Mole
- UCL MRC Laboratory for Molecular Cell Biology and UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
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Sheth J, Mistri M, Bhavsar R, Pancholi D, Kamate M, Gupta N, Kabra M, Mehta S, Nampoothiri S, Thakker A, Jain V, Shah R, Sheth F. Batten disease: biochemical and molecular characterization revealing novel PPT1 and TPP1 gene mutations in Indian patients. BMC Neurol 2018; 18:203. [PMID: 30541466 PMCID: PMC6292089 DOI: 10.1186/s12883-018-1206-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/27/2018] [Indexed: 12/12/2022] Open
Abstract
Background Neuronal ceroid lipofuscinoses type I and type II (NCL1 and NCL2) also known as Batten disease are the commonly observed neurodegenerative lysosomal storage disorder caused by mutations in the PPT1 and TPP1 genes respectively. Till date, nearly 76 mutations in PPT1 and approximately 140 mutations, including large deletion/duplications, in TPP1 genes have been reported in the literature. The present study includes 34 unrelated Indian patients (12 females and 22 males) having epilepsy, visual impairment, cerebral atrophy, and cerebellar atrophy. Methods The biochemical investigation involved measuring the palmitoyl protein thioesterase 1 and tripeptidy peptidase l enzyme activity from the leukocytes. Based on the biochemical analysis all patients were screened for variations in either PPT1 gene or TPP1 gene using bidirectional Sanger sequencing. In cases where Sanger sequencing results was uninformative Multiplex Ligation-dependent Probe Amplification technique was employed. The online tools performed the protein homology modeling and orthologous conservation of the novel variants. Results Out of 34 patients analyzed, the biochemical assay confirmed 12 patients with NCL1 and 22 patients with NCL2. Molecular analysis of PPT1 gene in NCL1 patients revealed three known mutations (p.Val181Met, p.Asn110Ser, and p.Trp186Ter) and four novel variants (p.Glu178Asnfs*13, p.Pro238Leu, p.Cys45Arg, and p.Val236Gly). In the case of NCL2 patients, the TPP1 gene analysis identified seven known mutations and eight novel variants. Overall these 15 variants comprised seven missense variants (p.Met345Leu, p.Arg339Trp, p.Arg339Gln, p.Arg206Cys, p.Asn286Ser, p.Arg152Ser, p.Tyr459Ser), four frameshift variants (p.Ser62Argfs*19, p.Ser153Profs*19, p.Phe230Serfs*28, p.Ile484Aspfs*7), three nonsense variants (p.Phe516*, p.Arg208*, p.Tyr157*) and one intronic variant (g.2023_2024insT). No large deletion/duplication was identified in three NCL1 patients where Sanger sequencing study was normal. Conclusion The given study reports 34 patients with Batten disease. In addition, the study contributes four novel variants to the spectrum of PPT1 gene mutations and eight novel variants to the TPP1 gene mutation data. The novel pathogenic variant p.Pro238Leu occurred most commonly in the NCL1 cohort while the occurrence of a known pathogenic mutation p.Arg206Cys dominated in the NCL2 cohort. This study provides an insight into the molecular pathology of NCL1 and NCL2 disease for Indian origin patients. Electronic supplementary material The online version of this article (10.1186/s12883-018-1206-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jayesh Sheth
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, Gujarat, 380015, India.
| | - Mehul Mistri
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, Gujarat, 380015, India
| | - Riddhi Bhavsar
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, Gujarat, 380015, India
| | - Dhairya Pancholi
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, Gujarat, 380015, India
| | - Mahesh Kamate
- Department of Pediatric Neurology, KLES Prabhakar Kore Hospital, Belgaum, Karnataka, 590010, India
| | - Neerja Gupta
- Division of Genetics (Pediatrics), All India Institute of Medical Sciences, New Delhi, 110029, India
| | - Madhulika Kabra
- Division of Genetics (Pediatrics), All India Institute of Medical Sciences, New Delhi, 110029, India
| | - Sanjiv Mehta
- Usha-Deep Children Neurology and Epilepsy clinic, Ahmedabad, 380014, India
| | - Sheela Nampoothiri
- Department of Pediatric Genetics, Amrita Institute of Medical Science and Research Centre, Kochi, Kerala, 682041, India
| | - Arpita Thakker
- Department of Neurology, Lokmanya Tilak Medical College, Sion Hospital, Mumbai, Maharashtra, 400022, India
| | - Vivek Jain
- Department of Neurology, Santokba Durlabhji Hospital, Jaipur, 302015, Rajasthan, India
| | - Raju Shah
- Ankur Neonatal Nursery, Ahmedabad, 380009, Gujarat, India
| | - Frenny Sheth
- FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, Gujarat, 380015, India
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Getty AL, Rothberg PG, Pearce DA. Diagnosis of neuronal ceroid lipofuscinosis: mutation detection strategies. ACTA ACUST UNITED AC 2013; 1:351-62. [PMID: 23489355 DOI: 10.1517/17530059.1.3.351] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The neuronal ceroid lipofuscinoses (NCL) are a group of rare genetically inherited neurodegenerative disorders in children. These diseases are classified by age of onset (congenital, infantile, late-infantile, juvenile and adult-onset) and by the gene bearing mutations (CLN10/CTSD, CLN1/PPT1, CLN2/TPP1, CLN3, CLN5, CLN6, CLN7/MFSD8 and CLN8). Enzyme activity assays are helpful in identifying several of these disorders; however confirmation of the mutation in the gene causing these diseases is vital for definitive diagnosis. There exists considerable heterogeneity in the NCLs as a whole and within each type of NCL both in phenotype (disease manifestation and progression) and genotype (type of mutation), which complicates NCL diagnosis. In order to streamline the diagnostic process, the age of symptom onset, geography and/or ethnicity, and enzyme activity may be considered together. However, these ultimately serve to guide targeting the correct route to genetic confirmation of an NCL through mutational analysis. Herein, an effective protocol to diagnose NCLs using these criteria is presented.
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Affiliation(s)
- Amanda L Getty
- University of Rochester School of Medicine and Dentistry, Center for Neural Development and Disease, Aab Institute of Biomedical Sciences, Box 645, Rochester, New York 14642, USA +1 585 506 1972 ;
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Kousi M, Lehesjoki AE, Mole SE. Update of the mutation spectrum and clinical correlations of over 360 mutations in eight genes that underlie the neuronal ceroid lipofuscinoses. Hum Mutat 2011; 33:42-63. [DOI: 10.1002/humu.21624] [Citation(s) in RCA: 235] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2011] [Accepted: 08/29/2011] [Indexed: 12/17/2022]
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Tian Y, Sohar I, Taylor JW, Lobel P. Determination of the Substrate Specificity of Tripeptidyl-peptidase I Using Combinatorial Peptide Libraries and Development of Improved Fluorogenic Substrates. J Biol Chem 2006; 281:6559-72. [PMID: 16339154 DOI: 10.1074/jbc.m507336200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Classical late-infantile neuronal ceroid lipofuscinosis is a fatal neurodegenerative disease caused by mutations in CLN2, the gene encoding the lysosomal protease tripeptidyl-peptidase I (TPP I). The natural substrates for TPP I and the pathophysiological processes associated with lysosomal storage and disease progression are not well understood. Detailed characterization of TPP I substrate specificity should provide insights into these issues and also aid in the development of improved clinical and biochemical assays. To this end, we constructed fluorogenic and standard combinatorial peptide libraries and analyzed them using fluorescence and mass spectrometry-based activity assays. The fluorogenic group 7-amino-4-carbamoylmethylcoumarin was incorporated into a series of 7-amino-4-carbamoylmethylcoumarin tripeptide libraries using a design strategy that allowed systematic evaluation of the P1, P2, and P3 positions. TPP I digestion of these substrates liberates the fluorescence group and results in a large increase in fluorescence that can be used to calculate kinetic parameters and to derive the substrate specificity constant kcat/KM. In addition, we implemented a mass spectrometry-based assay to measure the hydrolysis of individual peptides in peptide pools and thus expand the scope of the analysis. Nonfluorogenic tetrapeptide and pentapeptide libraries were synthesized and analyzed to evaluate P1' and P2' residues. Together, this analysis allowed us to predict the relative specificity of TPP I toward a wide range of potential biological substrates. In addition, we evaluated a variety of new fluorogenic peptides with a P3 Arg residue, and we demonstrated their superiority compared with the widely used substrate Ala-Ala-Phe-AMC for selectively measuring TPP I activity in biological specimens.
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Affiliation(s)
- Yu Tian
- Center for Advanced Biotechnology and Medicine, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
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Burneo JG, Arnold T, Palmer CA, Kuzniecky RI, Oh SJ, Faught E. Adult-onset neuronal ceroid lipofuscinosis (Kufs disease) with autosomal dominant inheritance in Alabama. Epilepsia 2003; 44:841-6. [PMID: 12790899 DOI: 10.1046/j.1528-1157.2003.39802.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Jorge G Burneo
- Department of Neurology, University of Alabama at Birmingham, Birmingham, Alabama, USA
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Rust RS, Karluk D. Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 27-2002. A 5(1/2)-year-old boy with seizures and progressive deterioration of cognitive and motor function. N Engl J Med 2002; 347:672-80. [PMID: 12200556 DOI: 10.1056/nejmcpc020110] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Brooks SS. Genetic counseling in the neuronal ceroid lipofuscinoses. ADVANCES IN GENETICS 2001; 45:159-67. [PMID: 11332771 DOI: 10.1016/s0065-2660(01)45009-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- S S Brooks
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314, USA.
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Abstract
Eight different NCL forms have been recognized to be encoded by genes CLN1-8. CLN1,2,3,5,and 8 have been cloned, and at least 85 mutations have been detected. Molecular technology can now be applied to genetic testing for NCLs; testing is now available in clinic diagnostic and research laboratories for CLN genes that have been cloned. Molecular genetic testing makes it possible not only to confirm clinical and pathological diagnoses but also to offer pre-symptom diagnosis and carrier screening for NCL families. In addition, DNA-based mutation analysis may predict prenatal outcome more accurately for pregnant women in NCL families.
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Affiliation(s)
- N Zhong
- Molecular Neurogenetic Diagnostic Laboratory, New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314, USA.
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Josephson SA, Schmidt RE, Millsap P, McManus DQ, Morris JC. Autosomal dominant Kufs' disease: a cause of early onset dementia. J Neurol Sci 2001; 188:51-60. [PMID: 11489285 DOI: 10.1016/s0022-510x(01)00546-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Kufs' disease is the rare, adult-onset form of the neuronal ceroid-lipofuscinoses (NCL). Two clinical Kufs' phenotypes have been described, one featuring generalized tonic-clonic seizures and the other characterized by dementia. Autosomal dominant inheritance of Kufs' disease has been reported for only two families. The genetic and molecular defects underlying Kufs' disease are unknown. We report a third family with apparent autosomal dominant Kufs' disease in a family of English ancestry. Ten individuals (five men, five women) have been affected over five generations. Age of onset typically is in the fourth decade of life and is heralded by seizures. Clinical and neuropsychological assessments in several affected individuals, however, confirm the presence of dementia and follow-up evaluations suggest that dementia is the primary disabling feature of the illness. Motor abnormalities also are frequent. Neuropathological examination (three cases) documents the presence of neuronal lipopigment accumulation consistent with NCL. The combination of dementia and seizures in this and two other reported families with autosomal dominant Kufs' disease suggest that this entity represents a distinctive clinicopathological entity. Dementia is prominent but is almost always associated with generalized seizures and motoric disturbances early in the disease course. Kufs' disease should be considered in the differential diagnosis of early onset, atypical dementia.
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Affiliation(s)
- S A Josephson
- Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO 63110, USA
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Kleijer WJ, van Diggelen OP, Keulemans JL, Losekoot M, Garritsen VH, Stroink H, Majoor-Krakauer D, Franken PF, Eurlings MC, Taschner PE, Los FJ, Galjaard RJ. First-trimester diagnosis of late-infantile neuronal ceroid lipofuscinosis (LINCL) by tripeptidyl peptidase I assay and CLN2 mutation analysis. Prenat Diagn 2001; 21:99-101. [PMID: 11241534 DOI: 10.1002/1097-0223(200102)21:2<99::aid-pd988>3.0.co;2-f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Late-infantile neuronal ceroid lipofuscinosis (LINCL) is a progressive neurodegenerative disorder caused by the deficiency of lysosomal tripeptidyl peptidase I (TPP-I) encoded by the CLN2 gene. We report the first case of early prenatal diagnosis of LINCL by combined enzyme and mutation analysis. TPP-I activity in chorionic villi (CV) was less than 2% of the mean normal control level and g.1946A > G and g.3670C > T mutations were demonstrated, as in the two previously affected children. After termination of pregnancy, TPP-I deficiency was confirmed in cultured CV cells and in the fetal skin fibroblasts. The expression of unequivocal TPP-I deficiency in CV demonstrates that enzyme assay is a reliable option for prenatal diagnosis of LINCL.
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Affiliation(s)
- W J Kleijer
- Department of Clinical Genetics, University Hospital Dijkzigt, Erasmus University, Rotterdam, The Netherlands.
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Junaid MA, Brooks SS, Pullarkat RK. Specific substrate for CLN2 protease/tripeptidyl-peptidase I assay. Eur J Paediatr Neurol 2001; 5 Suppl A:63-8. [PMID: 11589010 DOI: 10.1053/ejpn.2000.0437] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The classic late infantile neuronal ceroid lipofuscinosis (LINCL, CLN2) is a fatal neurodegenerative disorder that results from mutations in a gene encoding a lysosomal proteinase, known as CLN2 protease (CLN2p) or tripeptidyl peptidase I (TPP-I). Three different substrates, fluorescein isothiocyanate-labelled haemoglobin, A-F-F-7-amino-4-methylcoumarin (AAF-AMC) and G-F-F-L-7-amino-4-trifluoromethylcoumarin (GFFL-AFC) have been used for the CLN2p/TPP-I assay with varying degrees of residual activities in patients with LINCL. Further, conclusive identification of carriers are not possible with the first two substrates. An assay for the CLN2p/TPP-I based on the cleavage of amino terminal tripeptide from G-F-F-L-AFC was applied to prenatal and postnatal diagnosis of LINCL patients and heterozygote carriers. In leukocytes, the CLN2p/TPP-I activities in controls and heterozygote carriers were 1995 +/- 154 (n = 15) and 918 +/- 253 (n = 15) nmol/h/mg protein respectively. No CLN2p/TPP-I activity was detectable in all but two patients. These two patients had less than 2% residual activity, and had delayed clinical symptoms for LINCL. This shows that the G-F-F-L-AFC is a highly specific substrate for the CLN2p/TPP-I assay. The fact that with this substrate the enzyme cleaves a peptide bond between the two amino acids may be the reason for the high level of specificity.
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Affiliation(s)
- M A Junaid
- Department of Developmental Biochemistry, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314, USA.
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