Combined deficiency of beta-galactosidase and neuraminidase: three affected siblings in a French family

Cathepsin A deficiency in galactosialidosis: studies of patients and carriers in 16 families

Deficiency of lysosomal protective protein/cathepsin A in humans is the primary cause of galactosialidosis, a lysosomal storage disease characterized by combined deficiency of beta-galactosidase and neuraminidase. We have investigated 20 galactosialidosis patients and nine of their obligate heterozygous parents. A group of 12 patients with the early infantile type of the disease exhibited practically complete absence of cathepsin A activity, whereas eight patients with either the late infantile or the juvenile/adult type had 2-5% residual activity. Highest levels (5%) were present in two patients with milder clinical manifestations and later onset of the disease. In most fibroblast strains, beta-galactosidase activity was 10-15% of normal levels, whereas neuraminidase was reduced to less than 4%. Interestingly, a substantial residual activity (10%) of the latter enzyme was detected in the patient with the mildest phenotype and the highest cathepsin A activity. Heterozygous values for cathepsin A were reduced on average to half of normal levels. However, in two cell strains, the activity was far below control range, and in these cases, neuraminidase activity was severely depressed. Finally, we showed that cathepsin A had considerable activity in chorionic villi and amniocytes, but was deficient in amniocytes from a pregnancy with an affected fetus, indicating the relevance of cathepsin A assay for prenatal diagnosis of galactosialidosis.

Heterogeneity of carboxypeptidase activity in infantile-onset galactosialidosis

The clinical presentation and laboratory findings in seven patients with neonatal/infantile-onset galactosialidosis are presented. We detected no carboxypeptidase activity in two of these patients, while an enzyme with different apparent Km, or both Km and Vm, were found in five others. We could not establish a correlation between the biochemical characteristics of carboxypeptidase and the age of onset, progression, or other clinical features of galactosialidosis.

Biochemical study of sialidosis type I in a Russian family

A 7-year-old boy from a Russian family with decreased vision and a cherry-red spot but without any somatic and mental abnormalities is described in this paper. The decreased neuraminidase activity in the child's leukocytes and cultured skin fibroblasts and his 10-fold increase in urinary sialyloligosaccharides allowed us to conclude that he was affected by type I sialidosis. Some other results of the biochemical study of this child and his parents are presented. It is the first case of sialidosis in the Russian population.

Sialidosis and galactosialidosis: chromosomal assignment of two genes associated with neuraminidase-deficiency disorders

The inherited human disorders sialidosis and galactosialidosis are the result of deficiencies of glycoprotein-specific alpha-neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18; sialidase) activity. Two genes were determined to be necessary for expression of neuraminidase by using human-mouse somatic cell hybrids segregating human chromosomes. A panel of mouse RAG-human hybrid cells demonstrated a single-gene requirement for human neuraminidase and allowed assignment of this gene to the (pter----q23) region of chromosome 10. A second panel of mouse thymidine kinase (TK)-deficient LM/TK- -human hybrid cells demonstrated that human neuraminidase activity required both chromosomes 10 and 20 to be present. Analysis of human neuraminidase expression in interspecific hybrid cells or polykaryocytes formed from fusion of mouse RAG (hypoxanthine/guanine phosphoribosyltransferase deficient) or LM/TK- cell lines with human sialidosis or galactosialidosis fibroblasts indicated that the RAG cell line complemented the galactosialidosis defect, but the LM/TK- cell line did not. This eliminates the requirement for this gene in RAG-human hybrid cells and explains the different chromosome requirements of these two hybrid panels. Fusion of LM/TK- cell hybrids lacking chromosome 10 or 20 (phenotype 10+,20- and 10-,20+) and neuraminidase-deficient fibroblasts confirmed by complementation analysis that the sialidosis disorder results from a mutation on chromosome 10, presumably encoding the neuraminidase structural gene. Galactosialidosis is caused by a mutation in a second gene required for neuraminidase expression located on chromosome 20.

Combined sialidase (neuraminidase) and beta-galactosidase deficiency. Clinical, morphological and enzymological observations in a patient

A patient with combined deficiency of sialidase and beta-galactosidase is described. This now 39-year-old man, who is of Japanese origin, showed gradually progressive clinical features from the age of six years. Many of these features are commonly found in sialidosis type 2 or in GM1-gangliosidosis. Both sialidase and beta-galactosidase activities were deficient in leucocytes and cultured fibroblasts. Leucocytes of his mother showed activities of both enzymes in the lower limit of the control range. Morphologically, the pattern of storage products in a skin biopsy resembled in many respects that seen in GM1-gangliosidosis. Moreover, storage products which could be typical of sialidosis were also observed. Since the patient showed angiokeratomata, the morphological findings were compared with those specific to Fabry's disease, but no similarities were found. An enzymological diagnosis of the disease is most reliable on cultured fibroblasts, discriminating it from sialidosis type 2 and GM1-gangliosidosis. In view of recent findings, leucocytes seem to be less suitable for the establishment of the diagnosis galactosialidosis.

beta-Galactosidase-neuraminidase deficiency (galactosialidosis): clinical, pathological, and enzymatic studies in a postmortem case

Three male siblings in a Japanese family were affected with beta-galactosidase-neuraminidase deficiency (galactosialidosis). One patient died at 45 years of age, and postmortem liver and brain tissues were studied enzymatically. The residual activity of neuraminidase was relatively high in these tissues. Neuraminidase activity did not change in the tissues after repeated freezing and thawing of the homogenates, whereas this enzyme in control tissues lost 30 to 60% of its activity. There was a profound deficiency of beta-galactosidase in the tissues of the patient. Michaelis constant, pH profiles, and cryostability were identical for the patient and control patients. Cathepsin B was moderately increased in activity in the patient's tissues.

Neuropathological findings of an autopsy case of adult beta-galactosidase and neuraminidase deficiency

An autopsy case of a Japanese male with familial beta-galactosidase and neuraminidase deficiency is reported. The clinical picture was characterized by adult onset, a gargoyle-like face, cerebellar ataxia, myoclonus, convulsions, retinal degeneration and cortical blindness. Histopathologically, most neurons seemed to have become degenerated in the whole cerebral cortex. Moreover, the calcarine cortex appeared spongy with depopulation of nerve cells. Stuffed neurons or neuronal storage changes were found throughout the brain, especially in the motor nuclei of the spinal cord and brain stem. The inclusions in the stuffed neurons revealed various profiles on the electron microscope. They were composed of membranous lamellar and/or multilamellar structures, often accompanying vacuoles and reminiscent of lipofuscin-like profiles.