Structural Characterization of Variant Forms of Arylsulfatase A that Associate with Alcoholism

Several electrophoretic forms of human platelet arylsulfatase A (ASA), including variant type III_a and normal type IV_a, have been identified by nondenaturing polyacrylamide gel electrophoresis. An alcoholic population that we have analyzed is enriched in variant type III_a compared with nonalcoholic psychiatric and normal controls. Individuals with the III_a enzyme possess greatly reduced levels of ASA activity. To understand further the structural basis for the differences and their potential biological consequences, the nature of the ASA variant expressed by fibroblasts from different individuals was explored. The electrophoretic patterns of fibroblast ASA from the III_a and IV_a individuals differ in degree of phosphorylation. Furthermore, fibroblast ASA from III_a individuals lacks an N -linked glycan found in ASA from IV_a individuals. In addition, differences in peptide and/or posttranslational modification unrelated to the N -linked carbohydrate or phosphorylation exist between the fibroblast ASA from III_a and IV_a individuals. The finding that both fibroblasts and platelets exhibit related electrophoretic isoform patterns characteristic of the donor's ASA type allows for the use of fibroblasts to study the impact of ethanol on the metabolism of cells possessing different ASA types.     

MRI and CT in Krabbe's disease: case report

A case of infantile Krabbe's disease was first recognised as areas of relatively increased density on CT in the thalamus lateral geniculate body and dentate nucleus. These sites were subsequently shown on MRI to have a paramagnetic effect, being characterised by short T2 and T1. Subsequent examinations showed development of atrophy and high signal in white matter.     

Two Autopsied Cases of Familial Sudanophilic Leukodystrophy

Abstract: Two autopsied female sibling cases of sudanophilic leukodystrophy are reported. Case A and case B were the second and third of seven siblings, and a sister and a brother died from severe progressive neurological disease with similar symptoms. Consanguineous marriages were noted in the family of both cases through the past three generations. Case A gradually developed intellectual deterioration and tetraplegia at the age of 29, progressed to akinetic mutism within one year and thereafter survived for 14 years. Neuropathologically, a severe atrophy and degeneration were noted in the white matter of the whole cerebrum, sparing the subcortical U-fibers. Myelin and axons were severely damaged with peripheral astrocytic gliosis. Case B developed similar clinical symptoms at the age of 20 and survived for 7 years in the state of akinetic mutism. Similar postmortem findings as those of case A were found in the white matter of the cerebrum with formation of sudanophilic breakdown products and with thick fibrillary gliosis. The pyramidal tract was completely degenerated. There was no accumulation of abnormal lipid in the brains of both cases.     

Diagnosis of arylsulfatase A deficiency in intact cultured cells using a fluorescent derivative of cerebroside sulfate

A fluorescent derivative of cerebroside sulfate (12-(1-pyrene)dodecanoyl-sphingosylgalactosyl-0-3-sulfate (P12-sulfatide) has been synthesized as a potential substrate for the determination of cerebroside sulfatidase (or arylsulfatase A) activity. It was administered into cultured human skin fibroblasts and thereby utilized for the diagnosis of arylsulfatase A deficiency. Cultured skin fibroblasts from normal individuals and healthy persons suffering from a pseudoarylsulfatase A deficiency (PD) degraded the P12-sulfatide, while in cells derived from a metachromatic leukodystrophy (MLD) patient it remained essentially intact. This contrasts with in vitro determinations of enzymatic activity, where the MLD or PD-derived arylsulfatase A exhibit similar deficiency, in spite of a profoundly different clinical course. Administration of the fluorescent sulfatide into the intact cells permitted a sensitive and rapid diagnosis of MLD and its distinction from the PD-phenomenon. This might be of particular importance for cases in which a rapid diagnosis is required and for prenatal diagnosis of fetuses from families afflicted with both MLD and pseudo-deficiency mutant genes.     

Estimating the relative frequency of leukodystrophies and recommendations for carrier screening in the era of next‐generation sequencing

Leukodystrophies are a heterogeneous group of heritable disorders characterized by abnormal brain white matter signal on magnetic resonance imaging (MRI) and primary involvement of the cellular components of myelin. Previous estimates suggest the incidence of leukodystrophies as a whole to be 1 in 7,000 individuals, however the frequency of specific diagnoses relative to others has not been described. Next generation sequencing approaches offer the opportunity to redefine our understanding of the relative frequency of different leukodystrophies. We assessed the relative frequency of all 30 leukodystrophies (associated with 55 genes) in more than 49,000 exomes. We identified a relatively high frequency of disorders previously thought of as very rare, including Aicardi Goutières Syndrome, TUBB4A‐related leukodystrophy, Peroxisomal biogenesis disorders, POLR3‐related Leukodystrophy, Vanishing White Matter, and Pelizaeus‐Merzbacher Disease. Despite the relative frequency of these conditions, carrier‐screening laboratories regularly test only 20 of the 55 leukodystrophy‐related genes, and do not test at all, or test only one or a few, genes for some of the higher frequency disorders. Relative frequency of leukodystrophies previously considered very rare suggests these disorders may benefit from expanded carrier screening.     

Metachromatic leukodystrophy caused by a partial cerebroside sulfatase defect

A patient with neuropathy and myopathy since infancy but whose neuropathy had been stable for a number of years showed a profound deficiency of arylsulfatase A in leukocytes and urine. Urine contained material that stained metachromatically and cochromatographed with cerebroside sulfate. In contrast, cultured fibroblasts contained about 10-20% of normal arylsulfatase A with properties identical to properties of normal fibroblast enzyme, except that it showed no cerebroside sulfatase activity. Growing fibroblasts in the cerebroside sulfate loading test had an attenuated rate of sulfatide hydrolysis. A re-examination of the cerebroside sulfatase reaction revealed that while only limited hydrolysis occurred with low concentrations of taurodeoxycholate or cholate (type I activation), significant hydrolysis of the natural substrate did take place with high concentrations of cholate (type II activation). This suggests that there is a partial cerebroside sulfatase defect in this atypical form of metachromatic leukodystrophy.     

Late-onset globoid cell leukodystrophy

During the past 12 years, ten cases of globoidcell leukodystrophy (GLD) have been followed up: seven of these patients were affected by the late infantile form. The authors point out the clinical aspects and the course of these patients and stress the high frequency of this form of GLD in Sicily.     

Fetal Krabbe leukodystrophy

Summary Two new cases of Krabbe disease were diagnosed prenatally in a family with two previous affected children. The activity of galactosylceramide--galactosidase was virtually absent in cultured amniotic cells.The prenatal diagnosis was confirmed enzymatically in cultured fibroblasts, brain, and visceral organs.Light and electron microscopy studies in both fetuses, 20 and 23 weeks of gestational age respectively, revealed the presence of typical globoid cells in the white matter of the spinal cord. Specific inclusions were also found in the brain stem and in peripheral nerves of the second fetus.A comparison with other Krabbe disease fetuses described in the literature contributes to the consensus that abnormal morphological findings can be expected in particular in the most actively myelinating areas of the nervous system.Although most of the cells containing the specific melusions are probably non-glial in nature, some of them could represent myelination glia.This work was supported by the FGWO (grants nos. 3.0033.77 and 3.0012.77), by the FRSM (grant no. 3.4542.79), and by the Baron Charles Bracht Foundation     

Low arylsulphatase A activity and choreoathetotic syndrome in three siblings: differentiation of pseudodeficiency from metachromatic leukodystrophy

We report on a family with a sibship of three children for whom the diagnosis of an unusual form of metachromatic leukodystrophy (MLD) had been suggested earlier. The patients had choreiform movements and dystomic posturing accompanied by dysarthria since childhood. The availability of the polymerase chain reaction enabled us to show that the three siblings have a pseudodeficiency genotype (ASA_p/ASA_p). There was no abnormal sulphatiduria, and we propose that the neurological disease and low arylsulphatase A activity are unrelated to one another in this family. A diagnosis of MLD carries very serious implications, and we recommend that gene amplification by polymerase chain reaction and hybridization with allele-specific oligonucleotide probes should be used to corroborate the diagnosis, especially when there is no abnormal sulphatiduria and when metachromatic material cannot be demonstrated in a sural nerve biopsy.     

晚婴型脑白质营养不良诱发电位改变及诊断价值探讨

目的探讨晚婴型异染性脑白质营养不良(MLD)患儿脑诱发电位改变特点及应用价值.方法对6例MLD患儿进行了脑干听觉诱发电位(BAEP)和正中神经体感诱发电位(MNSEP)测试,并与头颅CT结果比较.结果6例MLD患儿BAEP和MNSEP结果均异常,BAEP异常主要包括Ⅰ波潜伏期延长、Ⅰ～Ⅲ和Ⅰ～Ⅴ峰间期延长;MNSEP异常主要有N9波低平、波潜伏期延长或波形消失,N9～N13和N13～N20峰间期延长,而N20波幅改变不明显.结果还表明,诱发电位的异常早于头颅CT结果.结论诱发电位较早地反映患儿神经传导功能障碍,可以作为无创性早期诊断手段.