Lurdes Lopes

Prevalence of lysosomal storage diseases in Portugal

Lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders individually considered as rare, and few data on its prevalence has been reported in the literature. The overall birth prevalence of the 29 different LSDs studied in the Portuguese population was calculated to be 25/100 000 live births, twice the prevalence previously described in Australia and in The Netherlands. The comparison of the prevalence profile of the LSDs presenting a prevalence higher than 0.5/100 000 in the Portuguese, Dutch and Australian populations showed, in the Portuguese, the existence of a higher prevalence of GM2 gangliosidoses (B variant), mucolipidoses (II and III), Niemman-Pick type C and metachromatic leukodystrophy (MLD), and a lower prevalence of Pompe and Fabry. The highest prevalence value for a single LSD is the one of GM2 gangliosidoses (B variant), corresponding to 3/100 000, a value which is significantly higher than the prevalence of the most frequent LSD in Dutch, Pompe disease (2/100 000) and Australians, Gauchers disease (GD) (1.8/100 000). It is worth noting that the highest prevalence of GM2 gangliosidoses found in the Portuguese is mainly due to the existence of a unique subtype, the rare juvenile B1 variant.

Clinicopathological and molecular characterization of neuronal ceroid lipofuscinosis in the Portuguese population

Abstract. A series of 53 Portuguese patients (derived from 43 families) born in the period 1963–1999 have been diagnosed with neuronal ceroid lipofuscinosis (NCL) based on clinicopathological findings. Plotting the cumulative number of new cases per year against the year of birth resulted in a slightly S-shaped curve, with a nearly straight central segment over a period of 14 years (1977–1990) indicating a continuous registration of new cases born during the corresponding time period. In this period the prevalence of overall NCL in the Portuguese population was calculated to be 1.55 per 100.000 live births.Twenty-six patients from 20 unrelated families were further evaluated by combining clinicopathological with biochemical and genetic data. No intra-familial heterogeneity was observed. Four sub-types of childhood NCL were identified: infantile NCL (INCL) with granular osmiophilic inclusions (GROD) and PPT1 deficiency (1/26), classical LINCL with curvilinear (CV) inclusions and tripeptidyl peptidase (TPP1) deficiency (3/26), variant late infantile NCL (LINCL) with fingerprint/curvilinear (FP/CV) inclusions and normal TPP1 enzyme activity (11/26) and juvenile NCL (JNCL) with a mix of FP/CV (11/26). Eight of 11 JNCL patients were homozygous for the 1.02-kb deletion in the CLN3 gene, and 3 were heterozygous with an unidentified mutation in the second allele. The 1.02-kb deletion in the CLN3 gene accounted for 86.3 % (19/22) of CLN3-causing alleles and 36.5 % (19/52) of childhood NCL defects. The causal mutations for CLN1 and CLN2 were V181M (2/2) and R208X (4/6), respectively. CLN1, CLN2 and CLN3 affected 3.8 %, 11.5 % and 42.3 % of NCL Portuguese patients, respectively. In 42.3 % of patients affected by the vLINCL form, CLN3, CLN5 and CLN8 gene defects were excluded by direct sequencing of cDNA. Genetic variants such as CLN6 might therefore cause a significant portion of childhood NCL in the Portuguese population.The relative frequency of classical childhood forms of NCL in the Portuguese population is reported and contributes to the knowledge of genetic epidemiology of these world-widely distributed disorders.

Retrovirus-Mediated Transfer and Expression of β-Hexosaminidase α-Chain cDNA in Human Fibroblasts from GM2-Gangliosidosis B1 Variant

Mutations in the α-chain of lysosomal hexosaminidase (EC 3.2.1.52) underlie two distinct biochemical phenotypes known as variant B and variant B1 of GM2 gangliosidosis. This paper shows that the transduction of human B1-type fibroblasts (producing catalytically inactive α-chains) with a retroviral vector encoding the human hexosaminidase α-chain leads to a complete correction of HexA (αβ dimer) activity with both synthetic and natural substrates. The α-subunit overexpression leads to a partial HexB (ββ dimer) depletion corresponding to about 10% of control HexB activity. The newly synthesized enzyme is correctly processed and targeted to the lysosomes in transduced cells. The high levels of recombinant enzyme correctly produced the metabolic defect, enabling the cells efficiently to degrade the accumulated storage product present in lysosomes. The transduced fibroblasts are also able to secrete HexA efficiently into the culture medium. Moreover, transfer of the human transgene product to B1-type deficient...