Mutation analysis of a Japanese patient with fucosidosis

Fucosidosis-Clinical Manifestation, Long-Term Outcomes, and Genetic Profile-Review and Case Series

Fucosidosis is a neurodegenerative disorder which progresses inexorably. Clinical features include coarse facial features, growth retardation, recurrent upper respiratory infections, dysostosis multiplex, and angiokeratoma corporis diffusum. Fucosidosis is caused by mutations in the FUCA1 gene resulting in α-L-fucosidase deficiency. Only 36 pathogenic variants in the FUCA1 gene are related to fucosidosis. Most of them are missense/nonsense substitutions; six missense and 11 nonsense mutations. Among deletions there were eight small and five gross changes. So far, only three splice site variants have been described—one small deletion, one complete deletion and one stop-loss mutation. The disease has a significant clinical variability, the cause of which is not well understood. The genotype–phenotype correlation has not been well defined. This review describes the genetic profile and clinical manifestations of fucosidosis in pediatric and adult cases.

Development of a UHPLC-MS method for inhibitor screening against α-L-1,3-fucosidase

α-L-Fucosidase (AFU) is a promising therapeutic target for the treatment of inflammation, cancer, cystic fibrosis, and fucosidosis. Some of the existing analytical methods for the assessment of AFU activity are lacking in sensitivity and selectivity, since most of them are based on spectrofluorimetric methods. More recently, mass spectrometry (MS) has evolved as a key technology for enzyme assays and inhibitor screening as it enables accurate monitoring of the conversion of substrate to product in enzymatic reactions. In this study, UHPLC-MS has been utilized to develop a simple, sensitive, and accurate assay for enzyme kinetics and inhibition studies of AFU3, a member of the AFU family. A reported method for analyzing saccharide involving a porous graphitic carbon column, combined with reduction by NaBH₄/CH₃OH, was used to improve sensitivity. The conversion of saccharide into alditol could reach nearly 100% in the NaBH₄ reduction reaction. In addition, the bioanalytical quantitative screening method was validated according to US-FDA guidance, including selectivity, linearity, precision, accuracy, stability, and matrix effect. The developed method displayed a good accuracy, high sensitivity (LOD = 0.05 mg L^-1), and good reproducibility (RSD < 15%). The assay accurately measured an IC₅₀ value of 0.40 μM for the known AFU inhibitor, deoxyfuconojirimycin, which was consistent with results reported in the literature. Further validation of the assay was achieved through the determination of a high Z'-factor value of 0.89. The assay was applied to screen a marine-derived chemical library against AFU3, which revealed two marine-oriented pyrimidine alkaloids as potential AFU3 inhibitors. Graphical abstract.

A novel homozygous frameshift mutation in the FUCA1 gene causes both severe and mild fucosidosis

AIMS

Fucosidosis is a rare autosomal recessive lysosomal storage disorder caused by α-L-fucosidase deficiency as a result of FUCA1 gene mutations. Here, we studied clinical features and the molecular basis of fucosidosis in a family from Iran, including two probands and nine family members.

METHODS

DNA sample of two probands were screened for gene defects using a next generation sequencing technique. The sequencing processes were performed on an Illumina Hiseq 4000 platform. Sequence reads were analysed using BWA-GATK.

RESULTS

Next generation sequencing revealed a frameshift mutation caused by 2 bp deletion (c.837_838 delTG; p.Cys279) in the FUCA1 gene. The identified mutation was tested in all participants. Homozygous patients had almost all the complications associated with fucosidosis, while heterozygous carriers were unaffected.

CONCLUSIONS

The variant c.837_838 delTG; p.Cys279 has not been reported previously and is predicted to be pathogenic due to a premature stop codon.

Mutation identification and characterization of a Taiwanese patient with fucosidosis

Fucosidosis is a rare lysosomal storage disease caused by a defect of the alpha-L: -fucosidase (FUCA1) gene. Worldwide 26 mutations underlying the disease have been reported. By direct DNA sequencing of exons and flanking introns, homozygous Y126X mutation and Q281R polymorphism were found in a Taiwanese patient with fucosidosis. Upon expressing in COS-7 cells, 97.4% of alpha-L: -fucosidase activity compared with that of the wild-type construct was observed in the cDNA containing Q281R polymorphism. Western blot analysis revealed a 58-kDa precursor and 56-kDa mature forms for cells transfected with wild-type and Q281R enzymes. Using the fluorogenic substrate, the Michaelis constants and maximal velocities of both enzymes were very similar. While no appreciable enzyme activity (0.0%) was observed with Y126X mutation, no apparent decrease in FUCA1 mRNA level was seen with Y126X mutation. The expressed truncated Y126X protein was unstable and largely degraded. The delineation of the molecular defect could serve to complement future prenatal diagnosis for this family when necessary.

A case of chronic infantile type of fucosidosis: clinical and magnetic resonance image findings

Fucosidosis is a rare autosomal recessive disorder resulting from a deficiency of alpha-L-fucosidase. In this report, we describe clinical and magnetic resonance image (MRI) findings of a chronic infantile type patient heterozygous for a nonsense mutation and a large deletion. The disease onset occurred at 2-3 years of age. She was bound to a wheelchair at 6 years of age, and developed dystonia at the age of 13 years. Brain MRI at 13 years of age showed marked cerebral and cerebellar atrophy, high intensities in the white matter of the frontal and occipital lobes, and low intensities of the bilateral thalamus, striatum, substantia nigra, red nucleus and mamillary bodies on T2-weighted images. The low intensities of basal ganglia on T2-weighted images seems characteristic of lesions in fucosidosis.