K. von Figura

Genetic heterogeneity and clinical variability in the Sanfilippo syndrome (types A, B, and C)

A study of 73 patients with the Sanfilippo syndrome (36 patients with Sanfilippo A disease, 23 with Sanfilippo B disease and 14 with Sanfilippo C disease) revealed both intertype and intratype variability. The course of the disease was relatively mild in Sanfilippo B disease and dementia was less severe. Type A showed earlier onset with more severe clinical manifestations and an earlier age at death. Sanfilippo C disease was slightly less severe than Sanfilippo A disease. The intratype variability may be explained in part by differences in genetic and environmental background. In Sanfilippo B disease, genetic heterogeneity is suggested by the observation of a more severe and a mild variant, and this variation may be due to the involvement of different allelic mutations. The intra‐familial variability of the different types was small, but in three families with Sanfilippo B disease intrafamilial variability was evident.

Carbohydrate-free carboxypeptidase Y is transferred into the lysosome-like yeast vacuole

Abstract Carboxypeptidase Y, localized in the lysosome-like yeast vacuole, has been metabolically labeled with [2- 3 H]mannose. After immunoprecipitation the carbohydrate moieties were released by treatment with endo-β-N-acetyl-glucosaminidase H and separated by paper electrophoresis. Evidence for the presence of phospho-monoester and -diester groups in the molecule has been obtained. In the latter phosphate links C-1 of mannose or of mannosyl 1,3-mannose to C-6 of a mannose residue within a larger oligomannose moiety. In the presence of tunicamycin yeast cells synthesize a carbohydrate-free carboxypeptidase Y, which could be traced after metabolic labeling with [ 14 C]-phenylalanine. The carbohydrate-free enzyme was segregated into the vacuoles to the same extent as the intact glycoprotein.

Sanfilippo type D disease: Clinical findings in two patients with a new variant of mucopolysaccharidosis III

A fourth genetic subtype of the Sanfilippo syndrome due to a deficiency of N-acetylglucosamine-6-sulfate sulfatase which is required for heparan sulfate degradation has recently been described. The clinical findings of two patients with a deficiency of this enzyme are reported here. Differential diagnosis from the other types of the Sanfilippo syndrome cannot be made by clinical criteria, but rests on specific enzyme assays. Since patients of either sex are known and consanguinity was present in one case, autosomal recessive inheritance is most probable.

Morquio syndrome: Clinical findings in 11 patients with MPS IVA and 2 patients with MPS IVB

SummaryGenetic heterogeneity of the Morquio syndrome has been known since deficiency of β-galactosidase was detected in some patients in addition to the deficiency of N-acetylgalactosamine-6-sulphate sulphatase in the classical form of Morquio syndrome. The clinical findings of 11 patients with MPS IVA, the classical form, and 2 patients with MPS IV B, a variant form, are described. All of the patients with MPS IV A showed extraskeletal manifestations of their disease. The patients with MPS IV B seem to be less severely affected.

Uptake of hyaluronate by cultured cells.

[14C]hyaluronate is internalized by adsorptive pinocytosis by cultured rat hepatocytes and human synovial cells, but not by human skin fibroblasts and smooth muscle cells. Hyaluronate oligosaccharides compete for the uptake of hyaluronate by hepatocytes without being internalized themselves at the doses used. It is suggested that for adsorptive pinocytosis a hyaluronate molecule has to bind to at least two receptors on the cell membrane.

Sanfilippo B disease: Serum assays for detection of homozygous and heterozygous individuals in three families

Three assays for the determination of N-acetyl-α-D-glucosaminidase activity in the serum are described. In three families with patients suffering from Sanfilippo B disease, the affected individuals had a residual enzyme activity in the range of 2 to 16 per cent that of normal control subjects. Their obligate heterozygous parents had an activity diminished to 26 to 35 per cent. Nine other members of these families had enzyme activities lowered to the same extent and were therefore considered to be heterozygous carriers of the Sanfilippo B gene.

Synthesis of lysosomal α-mannosidase in normal and mannosidosis fibroblasts

Summary The biosynthesis and secretion of lysosomal α-mannosidase was studied in metabolically labelled fibroblasts from controls and two patients with manosidosis. Normal fibroblasts secrete α-mannosidase as a 110kDa polypeptide. Intracellularly α-mannosidase is represented by several polypeptides with apparent M r s ranging from 40 to 67kDa. In two mannosidosis cell lines none of intra- and extracellular polypeptides of α-mannosidase were detectable. The mannosidosis fibroblasts secreted acid α-mannosidase activity at one third of the normal rate. In contrast to normal cells the secretion was not enhanced by NH 4 Cl and the secreted activity was not immunoprecipitable, indicating that the acid α-mannosidase activity secreted by mannosidosis fibroblasts is not related to the lysosomal α-mannosidase.

Late onset form of mucopolysaccharidosis type I: Clinical aspect and biochemical characterization of residual α-l-iduronidase activity

Clinical and roentgenographic features of two patients with the late onset form of mucopolysaccharidosis type I are presented. The residual α-L-iduronidase in cultured fibroblasts had an abnormalKm which differed from that found in the early onset (Hurler) form.

Acid Hydrolase Production, Release and Uptake by Cultured Fibroblasts

Cultivated skin fibroblasts have become a major tool for the biochemical investigation of lysosomal storage diseases, since fibroblasts grown from the skin of patients affected with one of these genetic disorders express the basic defect in cell culture (Hers and van Hoof, 1973). The elucidation of the various enzyme defects during the last decade has facilitated the genotype specific classification and diagnosis of these diseases, and has provided the basis for prenatal diagnosis and genetic counselling. Moreover, promising in vitro models for specific enzyme replacement therapy have been developed using cultivated skin fibroblasts as a test system. These investigations have extended our basic knowledge of the physiological function of lysosomal hydrolases in the degradation of macromolecules such as mucopolysaccharides and sphingolipids.