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Keratosis follicularis spinulosa decalvans (KFSD) or Siemens-1 syndrome is a rare X-linked disease of unknown etiology affecting the skin and the eye. Although most affected families are compatible with X-linked inheritance, KFSD appears to be clinically and genetically heterogeneous. So far, the gene has been mapped to Xp22.13p22.2 in two extended KFSD families. Analysis of additional recombination events in the first Dutch pedigree located the gene to an interval covering approximately 1 Mb between markers DXS7163 and DXS7593/DXS7105, whereas haplotype reconstruction in the second German family positioned the gene outside the previously identified region, proximal to marker DXS274. We report here the molecular characterization of an Xp21.1p22.12 duplication present in a patient affected with dosage-sensitive sex reversal (DSS) and KFSD. The duplicated region includes both the DAX1 gene (previously demonstrated to be responsible for DSS) and the KFSD interval, in which the gene encoding spermidine/spermine N(1)-acetyltransferase ( SSAT) is located. This enzyme catalyzes the N(1)-acetylation of spermidine and spermine and, by the successive activity of polyamine oxidase, the spermine can be converted to spermidine and the spermidine to putrescine. Overexpression of the SSAT enzyme in a mouse model results in putrescine accumulation and a phenotype with skin and hair abnormalities reminiscent of human KFSD. Analysis of polyamine metabolism in the cells of the patient indicated that the levels of metabolites such as putrescine, spermidine and spermine were consistent with the overexpression of the SSAT gene as in the murine model. Thus, we propose that overexpression of SSAT and the consequent putrescine accumulation are involved in the KFSD phenotype, at least in our propositus.

Sanfilippo syndrome type B (mucopolysaccharidosis IIIB) is a rare autosomal recessive disorder characterized by the inability to degrade heparan sulfate because of a deficiency of the lysosomal enzyme alpha-N-acetylglucosaminidase (NAGLU). We performed mutation screening in a group of 20 patients, identyifing 28 mutations, 14 of which were novel (L35F, 204delC, 221insGCGCG, G82D, W156C, 507delC, IVS3+1G-->A, E336X, V501G, R520W, S534Y, W649C, 1953insGCCA, 2185delAGA). Four of these mutations were found in homozygosity and only one was seen in two different patients, showing the remarkable molecular heterogeneity of the disease. Mutation IVS3+1G-->A produces aberrant RNA splicing: it represents a base substitution from G to A of the invariant GT dinucleotides at the splicing donor site of intron 3 resulting in the skipping of exon 3 and both exons 2 and 3. Transient transfection of COS cells, by DNA mutagenized with NAGLU mutations, produced enzymatic molecules without activity, demonstrating the deleterious nature of the defects. Metabolic labeling of transfected mutants suggested a normal synthesis of the involved polypeptide for missense alterations, whereas increased protein or mRNA instability was shown for nonsense and most of the frameshift mutations.

A 9-bp deletion (2320del9) was detected in the arylsulfatase A genes of a patient with late infantile metachromatic leukodystrophy and of a patient with nonprogressive neurological symptoms and very low arylsulfatase A activity. Both patients are heterozygous for the deletion, which involves codons 406-408 and causes loss of a Ser-Asp-Thr tract in the predicted protein. In both patients the 9-bp deletion lies in a pseudodeficiency allele. The patient with metachromatic leukodystrophy carries the common 459 + 1G > A mutation in the other allele. The other patient is homozygous for the pseudodeficiency allele, and consequently is a compound heterozygote for a metachromatic leukodystrophy allele and a pseudodeficiency allele. We hypothesize that the compound heterozygosity predisposes to the development of nonprogressive neurological symptoms in the presence of additional, still unknown, genetic or nongenetic factors.

A metachromatic leukodystrophy (MLD) patient affected with the late infantile form was found to be homozygous for an AT-deletion (2324delAT) in the arylsulfatase A gene. The mutation causes a frameshift at the beginning of exon 8 leading to an early termination codon. The parents and unaffected brother of the patient were heterozygous for the microdeletion. The mutation was not detected in another 31 MLD Italian patients. No aberrant transcript caused by the mutation was revealed by the reverse transcription-polymerase chain reaction method.

We have studied, by the polymerase chain reaction, the beta-galactosidase cDNA from several Italian patients with infantile GM1-gangliosidosis. One homozygote for a previously undiscovered G > A mutation at position 1479, causing an arginine to histidine change, was detected. The same mutation, in heterozygosis, was identified in 6 unrelated patients, but not in 100 normal chromosomes.

Gastrinomas are pancreatic endocrine neoplasms that arise either sporadically or are inherited as part of the multiple endocrine neoplasia type I syndrome (MENI). Loss of heterozygosity (LOH) in the region flanking the MENI gene at chromosome 11q13 has been documented in a few sporadic and familial pancreatic endocrine tumors, but not previously in sporadic gastrinomas. It has therefore been suggested that gastrinomas develop by a mechanism different from other tumors associated with the MENI syndrome. We report LOH on chromosome 11 in 5 of 11 sporadic gastrinomas. Four of these tumors have LOH for markers flanking the MENI region. Molecular evaluation of segments of chromosomes 3, 13, and 17 known to contain cloned or putative tumor suppressor genes fail to show LOH except at one locus in one tumor. These data suggest that a tumor suppressor DNA segment exists at 11q13 that may be involved in the development of sporadic gastrinomas.

After testing a population sample of 185 hospitalized Italian children for the plasma alpha-L-fucosidase deficiency and establishing an approximate threshold value between heterozygotes and wild-type homozygotes, we analyzed by two statistical methods the distribution of the two genotypes. The results obtained by probit analysis agree with threshold and average values expected on the basis of the Hardy-Weinberg equilibrium. In addition, the level of alpha-fucosidase in leukocytes of 12 individuals with deficiency of alpha-fucosidase in plasma was found to be significantly lower than that of 61 controls (P less than 0.005). These results indicate that the mutation(s) causing a deficiency of alpha-fucosidase in plasma is (are) also expressed in leukocytes.

Genomic DNA and mRNA from six unrelated Italian patients affected with fucosidosis were analyzed using two probes (AF3 and AF11B) of partial length cDNA coding for the lysosomal enzyme alpha-L-fucosidase. DNA from patient 2, digested with EcoRI, showed a variant pattern of hybridization caused by the loss of an EcoRI site. The same patient showed a markedly decreased amount of mRNA on Northern blot hybridization. Among the remaining patients, who showed no variation at the DNA level, two apparently lacked mRNA for alpha-L-fucosidase whereas the other three showed a transcript similar in size and amount to that observed in controls. These data confirm the genetic heterogeneity of the molecular defects causing fucosidosis in Italy.

A significant proportion of patients affected with fucosidosis have Italian ancestors. We assayed for alpha-fucosidase activity purified mononuclear cells and/or leukocytes obtained from 64 members of two large pedigrees from Calabria, in which seven children had been diagnosed as affected with fucosidosis. Of these 64 individuals, 22 were diagnosed as carriers, while the values for the remainder were within normal limits, indicating a clear bimodal distribution among individuals at risk. These data confirm that carrier detection for fucosidosis requires the measurement of alpha-L-fucosidase activity in purified mononuclear cells from peripheral blood. In addition, this program has made prenatal identification of an affected fetus possible.

The variant alpha-L-fucosidase genotype, phenotypically observed as a low plasma level of alpha-L-fucosidase in healthy individuals, can modify the plasma expression of the primary genetic defect in mucolipidosis III. Three patients with clinical, radiological, and biochemical features of mucolipidosis III, had a normal plasma level of alpha-L-fucosidase activity. The thermostability curves for the plasma alpha-L-fucosidase from these patients and the plasma alpha-L-fucosidase of the parents of one of them, are discussed to support the suggestion that they are homozygous for the autosomal recessive variant alpha-L-fucosidase trait. From a practical point of view, these observations warn against the use of the plasma alpha-L-fucosidase assay as a screening test for mucolipidoses.