Functional assessment of IDUA variants of uncertain significance identified by newborn screening.

With the expansion of newborn screening efforts for MPS disorders, the number of identified variants of uncertain significance in IDUA continues to increase. To better define functional consequences of identified IDUA variants, we developed a HEK293-based expression platform that can be used to determine the relative specific activity of variant α-iduronidases by combining a fluorescence-based activity assay and semi-quantitative western blotting. We employed the current platform to characterize over thirty different IDUA variants, including known benign and pathogenic variants, as well as multiple variants of uncertain significance identified through newborn screening.

High precision newborn screening for mucopolysaccharidosis type I by enzymatic activity followed by endogenous, non-reducing end glycosaminoglycan analysis.

Measurement of enzymatic activity in newborn dried blood spots (DBS) is the preferred first-tier method in newborn screening (NBS) for mucopolysaccharidosis (MPS) disorders. However, false positives are observed due mainly to the presence of pseudodeficiencies. Our previous publications on glycosaminoglycan (GAG) biomarker levels in dried blood spots (DBS) for mucopolysaccharidoses demonstrated that second-tier GAG biomarker analysis can dramatically reduce the false positive rate in NBS.

Analysis of Free Oligosaccharides in Urine by High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

Oligosaccharidoses are a group of lysosomal storage disorders characterized by abnormal storage and excretion of incompletely processed glycan structures. As with other inherited metabolic disorders, early diagnosis and initiation of treatment are essential for optimizing outcomes. Biochemical investigation of suspected oligosaccharidoses has traditionally included thin layer chromatography to detect the presence of disease-specific free oligosaccharides in urine; however, this qualitative method has long been known to have limited sensitivity and specificity.

Generation and characterization of two iPSC lines derived from subjects with Free Sialic Acid Storage Disorder (FSASD).

Free sialic acid storage disorder (FSASD) is a rare, autosomal recessive, neurodegenerative disorder caused by biallelic mutations in SLC17A5, encoding the lysosomal transmembrane sialic acid exporter, SLC17A5. Defects in SLC17A5 lead to lysosomal accumulation of free sialic acid and other acid hexoses. The clinical spectrum of FSASD ranges from mild (Salla disease) to severe infantile forms.

Myosin-I synergizes with Arp2/3 complex to enhance the pushing forces of branched actin networks.

Class I myosins (myosin-Is) colocalize with Arp2/3 complex-nucleated actin networks at sites of membrane protrusion and invagination, but the mechanisms by which myosin-I motor activity coordinates with branched actin assembly to generate force are unknown. We mimicked the interplay of these proteins using the "comet tail" bead motility assay, where branched actin networks are nucleated by the Arp2/3 complex on the surface of beads coated with myosin-I and nucleation-promoting factor. We observed that myosin-I increased bead movement efficiency by thinning actin networks without affecting growth rates.