Browsing by Subject "Galactosylceramidase"
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Item Open Access Lymphocyte Galactocerebrosidase Activity by LC-MS/MS for Post-Newborn Screening Evaluation of Krabbe Disease.(Clinical chemistry, 2017-08) Liao, Hsuan-Chieh; Spacil, Zdenek; Ghomashchi, Farideh; Escolar, Maria L; Kurtzberg, Joanne; Orsini, Joseph J; Turecek, Frantisek; Scott, C Ronald; Gelb, Michael HBackground
Deficiency of the lysosomal enzyme galactosylcerebrosidase (GALC) causes Krabbe disease. Newborn screening for Krabbe disease is ongoing, but improved methods for follow-up analysis of screen-positive babies are needed to better advise families and to optimize treatment. We report a new assay for the enzymatic activity of GALC in lymphocytes.Methods
T lymphocytes were isolated from venous blood by magnetic bead technology. The assay used a close structural analog of the natural substrate and LC-MS/MS to quantify the amount of product with the aid of a chemically identical internal standard.Results
The analytical range of the assay (ratio of assay response for the QC high standard to that from all non-enzymatic-dependent processes) was 20-fold greater than that for the conventional radiometric GALC assay. The LC-MS/MS could distinguish cells that were null in GALC from those that contained traces of active enzyme (down to 0.3% of normal). There was a good correlation between the level of residual GALC activity in lymphocytes and the severity of Krabbe disease.Conclusions
The new assay can measure small amounts of residual GALC activity in leukocytes with high accuracy compared to previous assays and can contribute, along with genotyping, biomarker analysis, and neurological imaging, a better plan for post-newborn screening follow-up for Krabbe disease.Item Open Access Newborn screening for Krabbe disease in New York State: the first eight years' experience.(Genetics in medicine : official journal of the American College of Medical Genetics, 2016-03) Orsini, Joseph J; Kay, Denise M; Saavedra-Matiz, Carlos A; Wenger, David A; Duffner, Patricia K; Erbe, Richard W; Biski, Chad; Martin, Monica; Krein, Lea M; Nichols, Matthew; Kurtzberg, Joanne; Escolar, Maria L; Adams, Darius J; Arnold, Georgianne L; Iglesias, Alejandro; Galvin-Parton, Patricia; Kronn, David F; Kwon, Jennifer M; Levy, Paul A; Pellegrino, Joan E; Shur, Natasha; Wasserstein, Melissa P; Caggana, Michele; New York State Krabbe Disease ConsortiumPurpose
Krabbe disease (KD) results from galactocerebrosidase (GALC) deficiency. Infantile KD symptoms include irritability, progressive stiffness, developmental delay, and death. The only potential treatment is hematopoietic stem cell transplantation. New York State (NYS) implemented newborn screening for KD in 2006.Methods
Dried blood spots from newborns were assayed for GALC enzyme activity using mass spectrometry, followed by molecular analysis for those with low activity (≤12% of the daily mean). Infants with low enzyme activity and one or more mutations were referred for follow-up diagnostic testing and neurological examination.Results
Of >1.9 million screened, 620 infants were subjected to molecular analysis and 348 were referred for diagnostic testing. Five had enzyme activities and mutations consistent with infantile KD and manifested clinical/neurodiagnostic abnormalities. Four underwent transplantation, two are surviving with moderate to severe handicaps, and two died from transplant-related complications. The significance of many sequence variants identified is unknown. Forty-six asymptomatic infants were found to be at moderate to high risk for disease.Conclusions
The positive predictive value of KD screening in NYS is 1.4% (5/346) considering confirmed infantile cases. The incidence of infantile KD in NYS is approximately 1 in 394,000, but it may be higher for later-onset forms.Item Open Access The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease.(Genetics in medicine : official journal of the American College of Medical Genetics, 2020-06) Guenzel, Adam J; Turgeon, Coleman T; Nickander, Kim K; White, Amy L; Peck, Dawn S; Pino, Gisele B; Studinski, April L; Prasad, Vinod K; Kurtzberg, Joanne; Escolar, Maria L; Lasio, Maria Laura Duque; Pellegrino, Joan E; Sakonju, Ai; Hickey, Rachel E; Shallow, Natalie M; Ream, Margie A; Orsini, Joseph J; Gelb, Michael H; Raymond, Kimiyo; Gavrilov, Dimitar K; Oglesbee, Devin; Rinaldo, Piero; Tortorelli, Silvia; Matern, DietrichPurpose
Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring. We report a highly sensitive PSY assay that allows identification of KD patients with minimal PSY elevations.Methods
PSY was extracted from dried blood spots or erythrocytes with methanol containing d5-PSY as internal standard, and measured by liquid chromatography-tandem mass spectrometry.Results
Analysis of PSY in samples from controls (N = 209), GALC pseudodeficiency carriers (N = 55), GALC pathogenic variant carriers (N = 27), patients with infantile KD (N = 26), and patients with late-onset KD (N = 11) allowed for the development of an effective laboratory screening and diagnostic algorithm. Additional longitudinal measurements were used to track therapeutic efficacy of hematopoietic stem cell transplantion (HSCT).Conclusion
This study supports PSY quantitation as a critical component of NBS for KD. It helps to differentiate infantile from later onset KD variants, as well as from GALC variant and pseudodeficiency carriers. Additionally, this study provides further data that PSY measurement can be useful to monitor KD progression before and after treatment.