Abnormal expression of alpha-L-fucosidase in lymphoid cell lines of fucosidosis patients

Pedigree analysis of alpha-L-fucosidase gene mutations in a fucosidosis family

Fucosidosis is an autosomal recessive lysosomal storage disease resulting from absence of alpha-L-fucosidase activity. Lymphoid cell lines from two siblings with fucosidosis and a healthy individual (control) had alpha-L-fucosidase mRNA of normal size (2.3 kb) but the level of alpha-L-fucosidase mRNA in the patients' cells was reduced. cDNA was prepared and amplified from alpha-L-fucosidase mRNA of lymphoid cells of the patients, their carrier parents, and the control. Direct DNA sequencing demonstrated three mutations in the fucosidosis family. One mutation, C1282-->T, changed the codon (CAA) for Gln-422 to a stop codon (UAA). This mutation was heterozygous (C and T) in the patients and their father and independently confirms an earlier report (J. Mol. Neurosci. (1989) 1, 177). Another mutation, C247-->T, changed the codon (CAG) for Gln-77 to a stop codon (UAG) and was heterozygous (C and T) in the patients and their mother. The third mutation, A860-->G, changed the codon CAG for Gln-281 to the codon (CGG) for Arg and was heterozygous (A and G) in the patients but homozygous in their father. alpha-L-Fucosidase activity in cells of the father was 37% of controls indicating that homozygosity of the A860-->G mutation did not cause an absence of alpha-L-fucosidase activity and fucosidosis. This mutation probably results in a normal polymorphic variant of alpha-L-fucosidase. It is proposed that the combination of the C247-->T mutation on the maternal allele of the alpha-L-fucosidase gene and the C1282-->T mutation on the paternal allele caused fucosidosis in the patients.

Prophylaxis in ovarian cancer

The only prophylaxis for ovarian cancer is oophorectomy, except in the very rare case when an ovarian cancer appears to arise from the mesothelial tissue of the abdominal cavity. It has been shown that women who have taken the oral contraceptive pill for 4 or 5 years decreases the incidence of ovarian cancer by approximately 40%. It is estimated that the oral contraceptive pill can prevent approximately 1500 ovarian cancers each year. The postmenopausal palpable ovary syndrome is simply the palpation of what is interpreted as a normal-sized ovary in the premenopausal woman represents an ovarian tumor in the postmenopausal woman. It addresses the size and consistency and has nothing to do with the small cysts reported by the sonographer. A patient who has two first-degree blood relatives or a mother, sister, or daughter who has developed ovarian cancer premenopausally is at high risk to develop ovarian cancer. Because ovarian cancer is the leading cause of death from gynecologic cancer, it is important to explore all options for prophylaxis in the prevention of ovarian cancer.

A mutation generating a stop codon in the alpha-L-fucosidase gene of a fucosidosis patient

Fucosidosis is an autosomal recessive, lysosomal storage disease featured by deficient activity of alpha-L-fucosidase. Lymphoid cell lines from a fucosidosis patient (JT) and a healthy individual (control) contained alpha-L-fucosidase mRNA of the same size, 2.3 Kb, as determined by Northern blot analysis. cDNA was prepared from alpha-L-fucosidase mRNA of JT and control cells and each cDNA was amplified by the polymerase chain reaction. Direct DNA sequencing of the amplified products revealed a single mutation in JT, a G1141-->T transition. This changed the codon (GAA) for Glu-375 to a stop codon (UAA). Amplification and sequencing of the area containing the G1141-->T transition in genomic DNA of JT and control cells demonstrated that the mutation was homozygous in JT. Analysis of cDNA and genomic DNA derived from lymphoid cells of mother JT revealed her to be heterozygous (G and T) at position 1141. The G1141-->T mutation is probably responsible for disease in JT.

The early and late processing of lysosomal enzymes: proteolysis and compartmentation

Lysosomal enzymes are subjected to a number of modifications including carbohydrate restructuring and proteolytic maturation. Some of these reactions support lysosomal targeting, others are necessary for activation or keeping the enzyme inactive before being segregated, while still others may be adventitious. The non-segregated fraction of the enzyme is secreted and can be isolated from the medium. It is considered that the secreted lysosomal enzymes fulfill certain physiological and pathophysiological roles. By comparing the secreted and the intracellular enzymes it is possible to distinguish between the reactions that occur before and after the segregation. In this review the reactions that may influence the segregation are referred to as the early processing and those characteristic for the enzymes isolated from lysosomal compartments as the late processing. The early processing is characterized mainly by modifications of carbohydrate side chains. In the late processing, proteolytic fragmentation represents the most conspicuous changes. The review focuses on the compartmentation of the reactions and the proteolytic fragmentation of lysosomal enzyme precursors. While a plethora of proteolytic reactions are involved, our knowledge of the proteinases responsible for the particular maturation reactions remains very limited. The review points also to work with cells from patients affected with lysosomal storage disorders, which contributed to our understanding of the lysosomal apparatus.

Binding receptors for alpha-L-fucosidase in human B-lymphoid cell lines

An established mechanism for directing newly made acid hydrolases to lysosomes involves acquisition of mannose 6-phosphate residues by the carbohydrate portion of acid hydrolases followed by binding to specific membrane-bound transport receptors and delivery to lysosomes. Two distinct phosphomannosyl receptors (CI-MPR and CD-MPR) have been identified. Alternative mechanisms for trafficking acid hydrolases exist. This report examines means for the possible receptor-mediated intracellular transport of alpha-L- fucosidase in lymphoid cells. The binding of alpha-L-fucosidase to intact cells and to total cell membrane preparations, in conjunction with immunoassays of solubilized membrane preparations, revealed the presence of CI-MPR and CD-MPR on human lymphoid and fibroblast cell lines. The mean level of CD-MPR in nine lymphoid cell lines was 7.2-fold greater than CI-MPR. The mean level of CI-MPR in two fibroblast lines was 3.8-fold greater than CD-MPR. The mean content of CI-MPR was 19.5-fold greater in the fibroblasts than in the lymphoid cells. The CD-MPR content of fibroblasts and lymphoid cells was nearly equivalent. Among these cell lines were a fibroblast and a lymphoid line from the same individual. These results indicate that human B-lymphoid cells are deficient in CI-MPR and suggest that modulation of expression of CI-MPR and CD-MPR in lymphoid cells differs from that in fibroblasts, including cell lines with identical genomes. No specific receptor capable of binding alpha-L-fucosidase independent of mannose 6-phosphate was demonstrable, despite published results that support the existence of a mannose 6-phosphate independent trafficking mechanism in lymphoid cells for this enzyme.

Defective expression of alpha-L-fucosidase by lymphoid cells of a fucosidosis patient

Fucosidosis is an inherited lysosomal storage disease due to a deficiency of alpha-L-fucosidase activity. Exponentially growing lymphoid cell cultures from a fucosidosis patient (JH) had 16-fold lower extracellular alpha-L-fucosidase protein and 72-fold lower intracellular alpha-L-fucosidase protein with negligible catalytic activity as compared with the mean of 19 control cultures. The percentage of total alpha-L-fucosidase protein released extracellularly by JH cells was 71% as compared with 35% +/- 9% for control cells. During a 1.5 h pulse with 35S-methionine, alpha-L-fucosidase was synthesized by JH cells as an intracellular doublet with Mr of 58,000 and 56,000 and by control cells as an intracellular form with Mr = 58,000. During a subsequent 21 h chase with unlabeled methionine, JH alpha-L-fucosidase was entirely secreted. In contrast, only 25%-30% of control enzyme was secreted with the remainder retained intracellularly. Thus, JH lymphoid cells synthesized a reduced amount of alpha-L-fucosidase that was catalytically inefficient and was hypersecreted. Treatment of JH alpha-L-fucosidase with N-glycanase produced polypeptide chains with Mr of 52,000 and 54,000. Previously, treatment of control alpha-L-fucosidase with N-glycancase produced a single polypeptide chain with Mr of 52,000 (Biochem Genet 1988; 26: 401-20). The doublet polypeptide chains of alpha-L-fucosidase in JH cultures may represent expression of two distinct allelic forms of mutant alpha-L-fucosidase.

Fucosidosis revisited: a review of 77 patients

Fucosidosis is a rare, autosomal recessive, lysosomal storage disorder caused by a severe deficiency of alpha-L-fucosidase in all tissues. We have conducted a review of fucosidosis, compiling data from published reports and an international questionnaire survey. Seventy-seven patients affected with fucosidosis of which 19 had not been reported before have been identified. A major aim of the present study was to define the natural history of fucosidosis. The clinical picture of fucosidosis consists of progressive mental (95%) and motor (87%) deterioration, coarse facies (79%), growth retardation (78%), recurrent infections (78%), dysostosis multiplex (58%), angiokeratoma corporis diffusum (52%), visceromegaly (44%), and seizures (38%). Whereas the original fucosidosis patients described by Durand et al. (J. Pediatr 75:665-674, 1969) were decerebrate and died before age 5 years, most fucosidosis patients have a slower course of degeneration. Mortality before age 5 years was observed in only 7 patients (9%), whereas 36 patients (64%) reached the second decade. We did not find evidence for the existence of clinical heterogeneity with a rapidly progressive type I and a slowly progressive type II fucosidosis as suggested in the literature. Instead, there seems to exist a wide continuous clinical spectrum. At the biochemical level no heterogeneity in residual fucosidase enzyme activity or cross-reacting immunoreactive fucosidase protein was observed. At the DNA level at least 4 different mutations must be responsible for fucosidosis. These genotypic differences however do not explain the observed phenotypic differences.