International Journal of Neonatal Screening

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12 pages, 2620 KiB

Open AccessArticle

A Biochemical Platform to Define the Relative Specific Activity of IDUA Variants Identified by Newborn Screening

by Seok-Ho Yu, Laura Pollard, Tim Wood, Heather Flanagan-Steet and Richard Steet

Int. J. Neonatal Screen. 2020, 6(4), 88; https://doi.org/10.3390/ijns6040088 - 12 Nov 2020

Cited by 2 | Viewed by 3118

Abstract

The lysosomal storage disorder, mucopolysaccharidosis I (MPSI), results from mutations in IDUA, the gene that encodes the glycosaminoglycan-degrading enzyme α-L-iduronidase. Newborn screening efforts for MPSI have greatly increased the number of novel IDUA variants identified, but with insufficient experimental evidence regarding their [...] Read more.

The lysosomal storage disorder, mucopolysaccharidosis I (MPSI), results from mutations in IDUA, the gene that encodes the glycosaminoglycan-degrading enzyme α-L-iduronidase. Newborn screening efforts for MPSI have greatly increased the number of novel IDUA variants identified, but with insufficient experimental evidence regarding their pathogenicity, many of these variants remain classified as variants of uncertain significance (VUS). Defining pathogenicity for novel IDUA variants is critical for decisions regarding medical management and early intervention. Here, we describe a biochemical platform for the characterization of IDUA variants that relies on viral delivery of IDUA DNA into IDUA-deficient HAP1 cells and isolation of single cell expression clones. The relative specific activity of wild-type and variant α-iduronidase was determined using a combination of Western blot analysis and α-iduronidase activity assays. The specific activity of each variant enzyme was consistent across different single cell clones despite variable IDUA expression and could be accurately determined down to 0.05–0.01% of WT α-iduronidase activity. With this strategy we compared the specific activities of known pseudodeficiency variants (p.His82Gln, p.Ala79Thr, p.Val322Glu, p.Asp223Asn) or pathogenic variants (p.Ser633Leu, p.His240Arg) with variants of uncertain significance (p.Ser586Phe, p.Ile272Leu). The p.Ser633Leu and p.His240Arg variants both show very low activities consistent with their association with Scheie syndrome. In our experiments, however, p.His240Arg exhibited a specific activity five times higher than p.Ser633Leu in contrast to other reports showing equivalent activity. Cell clones expressing the p.Ser586Phe and p.Ile272Leu variants had specific activities in the range of other pseudodeficiency variants tested. Our findings show that pseudodeficiency and pathogenic variants can be distinguished from each other with regard to specific activity, and confirms that all the pseudodeficiency variants variably reduce α-iduronidase activity. We envision this platform will be a valuable resource for the rigorous assessment of the novel IDUA variants emerging from the expansion of newborn screening efforts. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

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14 pages, 481 KiB

Open AccessArticle

Report of Five Years of Experience in Neonatal Screening for Mucopolysaccharidosis Type I and Review of the Literature

by Vincenza Gragnaniello, Daniela Gueraldi, Laura Rubert, Francesca Manzoni, Chiara Cazzorla, Antonella Giuliani, Giulia Polo, Leonardo Salviati and Alberto Burlina

Int. J. Neonatal Screen. 2020, 6(4), 85; https://doi.org/10.3390/ijns6040085 - 2 Nov 2020

Cited by 13 | Viewed by 4037

Abstract

Mucopolysaccharidosis type I (MPS I) is a progressive lysosomal storage disease, with neurological and visceral involvement, in which early diagnosis through newborn screening (NBS) and early treatment can improve outcomes. We present our first 5 years of experience with laboratory and clinical management [...] Read more.

Mucopolysaccharidosis type I (MPS I) is a progressive lysosomal storage disease, with neurological and visceral involvement, in which early diagnosis through newborn screening (NBS) and early treatment can improve outcomes. We present our first 5 years of experience with laboratory and clinical management of NBS for MPS I. Since 2015, we have screened 160,011 newborns by measuring α-L-iduronidase (IDUA) activity and, since 2019, glycosaminoglycans (GAGs) in dried blood spot (DBS) as a second-tier test. Positive screening patients were referred to our clinic for confirmatory clinical and molecular testing. We found two patients affected by MPS I (incidence of 1:80,005). Before the introduction of second-tier testing, we found a high rate of false-positives due to pseudodeficiency. With GAG analysis in DBS as a second-tier test, no false-positive newborns were referred to our clinic. The confirmed patients were early treated with enzyme replacement therapy and bone-marrow transplantation. For both, the clinical outcome of the disease is in the normal range. Our experience confirms that NBS for MPS I is feasible and effective, along with the need to include GAG assay as a second-tier test. Follow-up of the two positive cases identified confirms the importance of early diagnosis through NBS and early treatment to improve the outcome of these patients. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

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13 pages, 1233 KiB

Open AccessArticle

Validation and Implementation of a Highly Sensitive and Efficient Newborn Screening Assay for Mucopolysaccharidosis Type II

by Heather Bilyeu, Jon Washburn, Lacey Vermette and Tracy Klug

Int. J. Neonatal Screen. 2020, 6(4), 79; https://doi.org/10.3390/ijns6040079 - 14 Oct 2020

Cited by 13 | Viewed by 3928

Abstract

Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome, is a lysosomal storage disorder (LSD) caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS). MPS II satisfies all criteria defined by the Advisory Committee on Heritable Disorders in Newborns and Children [...] Read more.

Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome, is a lysosomal storage disorder (LSD) caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS). MPS II satisfies all criteria defined by the Advisory Committee on Heritable Disorders in Newborns and Children (ACHDNC) for inclusion in the Recommended Uniform Screening Panel (RUSP) for newborn screening, apart from the fact that only minimal prospective population screening data are available. This report details the analytical validation, clinical validation, and implementation of a fluorometric assay for measurement of IDS activity in newborn dried blood spot (DBS) specimens at the Missouri State Public Health Laboratory (MSPHL). The assay is performed in a microwell plate format requiring approximately 15 min of hands-on time per plate and an incubation time of two hours. The analytical validation of this assay included linearity, analytical sensitivity, precision, and carry-over testing. Clinical validation was completed using more than 5000 deidentified presumptive normal newborn DBS specimens as well as seven specimens from patients known to be affected with MPS II. Following validation, MSPHL began prospective screening using the IDS assay on 1 November 2018. In the first 18 months of screening (to 30 June 2020), 146,954 specimens were prospectively screened using the method. Two newborns were identified with severe Hunter syndrome and the assay had a presumptive positive rate of 0.022%. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

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6 pages, 202 KiB

Open AccessArticle

Newborn Screening for Mucopolysaccharidosis Type II in Illinois: An Update

by Barbara K. Burton, Rachel Hickey and Lauren Hitchins

Int. J. Neonatal Screen. 2020, 6(3), 73; https://doi.org/10.3390/ijns6030073 - 3 Sep 2020

Cited by 19 | Viewed by 3089

Abstract

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare, progressive multisystemic lysosomal storage disorder with significant morbidity and premature mortality. Infants with MPS II develop signs and symptoms of the disorder in the early years of life, yet diagnostic delays are very [...] Read more.

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare, progressive multisystemic lysosomal storage disorder with significant morbidity and premature mortality. Infants with MPS II develop signs and symptoms of the disorder in the early years of life, yet diagnostic delays are very common. Enzyme replacement therapy is an effective treatment option. It has been shown to prolong survival and improve or stabilize many somatic manifestations of the disorder. Our initial experience with newborn screening in 162,000 infants was previously reported. Here, we update that experience with the findings in 339,269 infants. Measurement of iduronate-2-sulfatase (I2S) activity was performed on dried blood spot samples submitted for other newborn screening disorders. A positive screen was defined as I2S activity less than or equal to 10% of the daily median. In this series, 28 infants had a positive screening test result, and four other infants had a borderline result. Three positive diagnoses of MPS II were established, and 25 were diagnosed as having I2S pseudodeficiency. The natural history and the clinical features of MPS II make it an ideal target for newborn screening. Newborn screening was effective in identifying affected infants in our population with an acceptable rate of false positive results. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

13 pages, 3859 KiB

Open AccessArticle

Evaluation of Multiple Methods for Quantification of Glycosaminoglycan Biomarkers in Newborn Dried Blood Spots from Patients with Severe and Attenuated Mucopolysaccharidosis-I

by Zackary M. Herbst, Leslie Urdaneta, Terri Klein, Maria Fuller and Michael H. Gelb

Int. J. Neonatal Screen. 2020, 6(3), 69; https://doi.org/10.3390/ijns6030069 - 26 Aug 2020

Cited by 30 | Viewed by 4708

Abstract

All newborn screening (NBS) for mucopolysaccharidosis-I (MPS-I) is carried out by the measurement of α-iduronidase (IDUA) enzymatic activity in dried blood spots (DBS). The majority of low enzyme results are due to pseudodeficiencies, and studies from the Mayo Clinic have shown that the [...] Read more.

All newborn screening (NBS) for mucopolysaccharidosis-I (MPS-I) is carried out by the measurement of α-iduronidase (IDUA) enzymatic activity in dried blood spots (DBS). The majority of low enzyme results are due to pseudodeficiencies, and studies from the Mayo Clinic have shown that the false positive rate can be greatly reduced by including a second-tier analysis of glycosaminoglycans (GAGs) in DBS as part of NBS. In the present study, we obtained newborn DBS from 13 patients with severe MPS-I and 2 with attenuated phenotypes. These samples were submitted to four different GAG mass spectrometry analyses in a comparative study: (1) internal disaccharide; (2) endogenous disaccharide; (3) Sensi-Pro; (4) Sensi-Pro Lite (a variation of Sensi-Pro with a simplified workflow). Patients with attenuated MPS-I show less GAG elevation than those with severe disease, and all MPS-I patients were separated from the reference range using all four methods. The minimal differential factor (lowest GAG marker level in MPS-I samples divided by highest level in the reference range of 30 random newborns) was about two for internal disaccharide, Sensi-Pro, and Sensi-Pro Lite methods. The endogenous disaccharide was clearly the best method with a minimal differential of 16-fold. This study supports use of second-tier GAG analysis of newborn DBS, especially the endogenous disaccharide method, as part of NBS to reduce the false positive rate. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

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Review

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9 pages, 1563 KiB

Open AccessReview

Neonatal Screening for MPS Disorders in Latin America: A Survey of Pilot Initiatives

by Francyne Kubaski, Inês Sousa, Tatiana Amorim, Danilo Pereira, Joe Trometer, Alexandre Souza, Enzo Ranieri, Giulia Polo, Alberto Burlina, Ana Carolina Brusius-Facchin, Alice Brinckmann Oliveira Netto, Shunji Tomatsu and Roberto Giugliani

Int. J. Neonatal Screen. 2020, 6(4), 90; https://doi.org/10.3390/ijns6040090 - 13 Nov 2020

Cited by 7 | Viewed by 3110

Abstract

Newborn screening enables the diagnosis of treatable disorders at the early stages, and because of its countless benefits, conditions have been continuously added to screening panels, allowing early intervention, aiming for the prevention of irreversible manifestations and even premature death. Mucopolysaccharidoses (MPS) are [...] Read more.

Newborn screening enables the diagnosis of treatable disorders at the early stages, and because of its countless benefits, conditions have been continuously added to screening panels, allowing early intervention, aiming for the prevention of irreversible manifestations and even premature death. Mucopolysaccharidoses (MPS) are lysosomal storage disorders than can benefit from an early diagnosis, and thus are being recommended for newborn screening. They are multisystemic progressive disorders, with treatment options already available for several MPS types. MPS I was the first MPS disorder enrolled in the newborn screening (NBS) panel in the USA and a few other countries, and other MPS types are expected to be added. Very few studies about NBS for MPS in Latin America have been published so far. In this review, we report the results of pilot studies performed in Mexico and Brazil using different methodologies: tandem mass spectrometry, molecular analysis, digital microfluidics, and fluorimetry. These experiences are important to report and discuss, as we expect to have several MPS types added to NBS panels shortly. This addition will enable timely diagnosis of MPS, avoiding the long diagnostic odyssey that is part of the current natural history of this group of diseases, and leading to a better outcome for the affected patients. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

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11 pages, 222 KiB

Open AccessReview

Digital Microfluidics in Newborn Screening for Mucopolysaccharidoses: A Progress Report

by Jon Washburn and David S. Millington

Int. J. Neonatal Screen. 2020, 6(4), 78; https://doi.org/10.3390/ijns6040078 - 8 Oct 2020

Cited by 10 | Viewed by 3129

Abstract

Newborn screening (NBS) for mucopolysaccharidosis type I (MPS I, Hurler syndrome) is currently conducted in about two-fifths of the NBS programs in the United States and in a few other countries. Screening is performed by measurement of residual activity of the enzyme alpha [...] Read more.

Newborn screening (NBS) for mucopolysaccharidosis type I (MPS I, Hurler syndrome) is currently conducted in about two-fifths of the NBS programs in the United States and in a few other countries. Screening is performed by measurement of residual activity of the enzyme alpha-l-iduronidase in dried blood spots using either tandem mass spectrometry or digital microfluidic fluorometry (DMF). In this article, we focus on the development and practical experience of using DMF to screen for MPS I in the USA. By means of their responses to a questionnaire, we determined for each responding program that is screening for MPS I using DMF the screen positive rate, follow-up methods, and classification of confirmed cases as either severe or attenuated. Overall, the results show that at the time of reporting, over 1.3 million newborns in the US were screened for MPS I using DMF, 2094 (0.173%) of whom were screen positive. Of these, severe MPS I was confirmed in five cases, attenuated MPS I was confirmed in two cases, and undetermined phenotype was reported in one case. We conclude that DMF is an effective and economical method to screen for MPS I and recommend second-tier testing owing to high screen positive rates. Preliminary results of NBS for MPS II and MPS III using DMF are discussed. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

Other

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5 pages, 198 KiB

Open AccessCommentary

Newborn Screening for Mucopolysaccharidosis I: Moving Forward Learning from Experience

by Lorne A. Clarke, Patricia Dickson, N. Matthew Ellinwood and Terri L. Klein

Int. J. Neonatal Screen. 2020, 6(4), 91; https://doi.org/10.3390/ijns6040091 - 19 Nov 2020

Cited by 10 | Viewed by 2825

Abstract

There have been significant advances allowing for the integration of mucopolysaccharidosis I into newborn screening programs. Initial experiences using a single-tier approach for this disorder have highlighted shortcomings that require immediate remediation. The recent evaluation of a second-tier biomarker integrated into the MPS [...] Read more.

There have been significant advances allowing for the integration of mucopolysaccharidosis I into newborn screening programs. Initial experiences using a single-tier approach for this disorder have highlighted shortcomings that require immediate remediation. The recent evaluation of a second-tier biomarker integrated into the MPS I newborn screening protocol has been demonstrated to greatly improve the precision and predictive value of newborn screening for this disorder. This commentary urges newborn screening programs to learn from these experiences and improve newborn screening for mucopolysaccharidosis I and future mucopolysaccharidoses newborn screening programs by implementation of a second-tier biomarker analyte. Full article

(This article belongs to the Special Issue Neonatal Screening for Mucopolysaccharidoses)

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