A 5' splice site mutation in fucosidosis

Long-term outcomes in two adult siblings with Fucosidosis - Diagnostic odyssey and clinical manifestations

Fucosidosis (OMIN# 230000) is a rare lysosomal storage disorder (LSDs) caused by mutations in the FUCA1 gene, leading to alpha-L-fucosidase deficiency; it is inherited as an autosomal recessive trait. Fucosidosis represents a disease spectrum with a wide variety of clinical features, but most affected patients have slow neurologic deterioration. Many patients die young and the long-term clinical outcomes in adult patients are poorly documented. Here, we report the long-term follow up of two Caucasian siblings, a 31-year-old man and 25-year-old woman. We describe the clinical, biochemical, radiological and genetic findings in two siblings affected by Fucosidosis and the differences between them after 19-years follow up. The dermatological features of the younger sibling have been reported previously by Bharati et al. (2007). Both patients have typical features of Fucosidosis, such as learning difficulties, ataxia, and angiokeratomas with differing severity. Case 1 presents severe ataxia with greater limitation of mobility, multiple dysostoses, angiokeratomas on his limbs, retinal vein enlargement and increased tortuosity in the eye and gastrointestinal symptoms. Biochemical analysis demonstrated a deficiency of alpha-fucosidase in leucocytes. Case 2 has a greater number of angiokeratomas and has suffered three psychotic episodes. The diagnosis of Fucosidosis was confirmed in cultured skin fibroblast at the age of 12 years. Molecular analysis of the FUCA1 gene showed a heterozygous mutation c.998G > A p.(Gly333Asp), with a pathogenic exon 4 deletion in the other allele in both patients. Conclusion. Fucosidosis presents a wide clinical heterogeneity and intrafamilial variability of symptoms. Psychosis and gastrointestinal symptoms have not been reported previously in Fucosidosis.

Fucosidosis in Tunisian patients: mutational analysis and homology-based modeling of FUCA1 enzyme

BACKGROUND

Fucosidosis is an autosomal recessive lysosomal storage disease caused by defective alpha-L-fucosidase (FUCA1) activity, leading to the accumulation of fucose-containing glycolipids and glycoproteins in various tissues. Clinical features include angiokeratoma, progressive psychomotor retardation, neurologic signs, coarse facial features, and dysostosis multiplex.

METHODS

All exons and flanking intron regions of FUCA1 were screened by direct sequencing to identify mutations and polymorphisms in three unrelated families with fucosidosis. Bioinformatics tools were then used to predict the impacts of novel alterations on the structure and function of proteins. Furthermore, the identified mutations were localized onto a 3D structure model using the DeepView Swiss-PdbViewer 4.1 software, which established a function-structure relationship of the FUCA1 proteins.

RESULTS

Four novel mutations were identified in this study. Two patients (P1 and P2) in Families 1 and 2 who had the severe phenotype were homoallelic for the two identified frameshift mutations p.K57Sfs*75 and p.F77Sfs*55, respectively. The affected patient (P3) from Family 3, who had the milder phenotype, was heterozygous for the novel missense mutation p.G332E and the novel splice site mutation c.662+5g>c. We verified that this sequence variation did not correspond to a polymorphism by testing 50 unrelated individuals. Additionally, 16 FUCA1 polymorphisms were identified. The structure prediction analysis showed that the missense mutation p.G332E would probably lead to a significant conformational change, thereby preventing the expression of the FUCA1 protein indeed; the 3D structural model of the FUCA1 protein reveals that the glycine at position 332 is located near a catalytic nucleophilic residue. This makes it likely that the enzymatic function of the protein with p.G332E is severely impaired.

CONCLUSION

These are the first FUCA1 mutations identified in Tunisia that cause the fucosidosis disease. Bioinformatics analysis allowed us to establish an approximate structure-function relationship for the FUCA1 protein, thereby providing better genotype/phenotype correlation knowledge.

The Identification of a Novel Fucosidosis-Associated FUCA1 Mutation: A Case of a 5-Year-Old Polish Girl with Two Additional Rare Chromosomal Aberrations and Affected DNA Methylation Patterns

Fucosidosis is a rare neurodegenerative autosomal recessive disorder, which manifests as progressive neurological and psychomotor deterioration, growth retardation, skin and skeletal abnormalities, intellectual disability and coarsening of facial features. It is caused by biallelic mutations in FUCA1 encoding the α-L-fucosidase enzyme, which in turn is responsible for degradation of fucose-containing glycoproteins and glycolipids. FUCA1 mutations lead to severe reduction or even loss of α-L-fucosidase enzyme activity. This results in incomplete breakdown of fucose-containing compounds leading to their deposition in different tissues and, consequently, disease progression. To date, 36 pathogenic variants in FUCA1 associated with fucosidosis have been documented. Among these are three splice site variants. Here, we report a novel fucosidosis-related 9-base-pair deletion (NG_013346.1:g.10233_10241delACAGGTAAG) affecting the exon 3/intron 3 junction within a FUCA1 sequence. This novel pathogenic variant was identified in a five-year-old Polish girl with a well-defined pattern of fucosidosis symptoms. Since it is postulated that other genetic, nongenetic or environmental factors can also contribute to fucosidosis pathogenesis, we performed further analysis and found two rare de novo chromosomal aberrations in the girl’s genome involving a 15q11.1-11.2 microdeletion and an Xq22.2 gain. These abnormalities were associated with genome-wide changes in DNA methylation status in the epigenome of blood cells.

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.

Application of magnetic chromatography to the isolation of lysosomes from fibroblasts of patients with lysosomal storage disorders

A method for the purification of lysosomes from fibroblasts has been developed which uses endocytosis of superparamagnetic colloidal iron dextran particles followed by separation of the iron-containing lysosomes in a magnetic field. This permitted isolation of lysosomes from fibroblasts from patients with infantile sialic acid storage disorder and other lysosomal storage diseases in which a shift in lysosomal density induced by the storage material prevents purification by centrifugation in a Percoll gradient. The magnetic lysosomes isolated from these cells are very similar to those from normal cells as judged by lysosomal marker enzyme activity and 2D-PAGE analysis of the enriched proteins.

Fucosidosis: genetic and biochemical analysis of eight cases

The molecular basis of the deficiency of alpha-L-fucosidase has been investigated in eight patients who had been diagnosed clinically and enzymatically as suffering from the autosomal recessive lysosomal storage disease fucosidosis. None of the patients had a deletion or gross alteration of the alpha-L-fucosidase gene (FUCA1). Single strand conformation polymorphism (SSCP) analysis followed by direct sequencing of amplified exons and flanking regions identified putative disease causing mutations in six of the patients, who had severe forms of the disease and very low residual alpha-L-fucosidase activity and protein. They were a 10 bp deletion in exon 1 (E113fs), a 1 bp deletion at position -2 of intron 2 (S216fs), a g-->a transition at IVS5+1, point mutations W183X and N329Y in exons 3 and 6, respectively, and a compound allele consisting of a point mutation in the signal peptide in exon 1, P5R, and a 1 bp insertion in exon 6 (Y330fs). One patient in whom an SSCP change was not detected had residual alpha-L-fucosidase activity and cross reacting protein in the heterozygous range and normal metabolism of metabolites containing fucose in his fibroblasts, consistent with the low activity polymorphism. The eighth patient, who had a partial deficiency of alpha-L-fucosidase in her fibroblasts and leucocytes at a young age but normal alpha-L-fucosidase activity and protein at a later age, was homozygous for the common Q281R polymorphism in exon 5. She had no other sequence changes and Kivlin (Peters plus) syndrome has subsequently been diagnosed. The basis of her transient deficiency of alpha-L-fucosidase is not known. The detection of five novel mutations in six severely affected patients confirms the genetic heterogeneity in fucosidosis.

The molecular defect underlying canine fucosidosis

Fucosidosis is a lysosomal storage disease which affects humans and English springer spaniel dogs. The disease is recessively inherited in both species and results from a deficiency of the enzyme alpha-L-fucosidase. We have recently cloned and sequenced the canine fucosidase gene (EMBL sequence admission number X92448 (cDNA) and X92671-X92678 (individual exonic data)). The gene spans 12 kb and consists of eight exons. SSCP based mutation analysis of affected animals was carried out on the coding region of this gene both with exonic primers, and intronic primer pairs for each exon. A 14 base pair deletion of the cDNA was identified at the 3' end of exon 1 in fucosidosis affected animals. Surprisingly, PCR based genomic cloning of DNA from these animals showed an identical deletion in this DNA, ending at the start of intron 1. This change causes a frameshift and, in consequence, 25 novel codons are transcribed in exon 2 before the first of two adjacent premature stop codons is encountered.

Isolation of the canine alpha-L-fucosidase cDNA and definition of the fucosidosis mutation in English Springer Spaniels

Fucosidosis is a lysosomal storage disorder caused by deficiency of alpha-L-fucosidase. A biochemically and clinically well characterized canine model of fucosidosis exists in a colony of English Springer Spaniels. To facilitate its use as a model for gene therapy and enzyme replacement therapy in lysosomal storage disorders displaying neurological symptoms, isolation of the canine alpha-L-fucosidase cDNA was undertaken. Both the nucleotide sequence and the predicted amino acid sequence of canine fucosidase show high levels of identity with the human and rat sequences. Fucosidosis dogs were found to have a greatly reduced level of alpha-L-fucosidase mRNA when compared with normal dogs by Northern blot analysis. Direct PCR sequencing of products generated from cDNA demonstrated a 14-bp deletion in mRNA from affected dogs. This deletion creates a frameshift mutation and introduces a premature translation termination codon at amino acid position 152 and was shown to correspond to a deletion of the last 14 base pairs of exon 1 of the canine alpha-L-fucosidase gene. Rapid PCR-based screening for the mutation has now been performed on genomic DNA from dogs within the colony, enabling detection of both carriers and homozygotes.

Mutations in fucosidosis gene: a review

Fucosidosis is an autosomal recessive disorder caused by a deficiency of alpha-L-fucosidase. Up to now 79 cases have been described and several others identified but not yet published. The higher incidence of the disease is in Italy, where nearly 20 patients have been identified. Fourteen disease-causing mutations have been detected and four of them, Q422X, G60D, E375X, P141fs are present in more than 70% of the forty patients studied. In Italian patients, only seven mutations have been described and P141fs and G60D mutations are present in more than 50% of the cases. The P141fs mutation is absent in other ethnic groups. It has been impossible to establish genotype-phenotype correlation so far and the clinical variability of the disease cannot be explained only by genetic heterogeneity.

Molecular basis of the common electrophoretic polymorphism (Fu1/Fu2) in human alpha-L-fucosidase

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