Multiple sulfatase deficiency (MSD) is an inherited lysosomal storage disease characterized by the deficiency of at least seven sulfatases. The basic defect in MSD is thought to be in a post-translational modification common to all sulfatases. In accordance with this concept, RNAs of normal size and amount were detected in MSD fibroblasts for three sulfatases tested. cDNAs encoding arylsulfatase A, arylsulfatase B, or steroid sulfatase were introduced into MSD fibroblasts and fibroblasts with a single sulfatase deficiency by retroviral gene transfer. Infected fibroblasts overexpressed the respective sulfatase polypeptides. While in single-sulfatasedeficiency fibroblasts a concomitant increase of sulfatase activities was observed, MSD fibroblasts expred sulfatase polypeptides with a severely diminished catalytic activity.From these results we conclude that the mutation in MSD severely decreases the capacity of a co-or post-translational process that renders sulfatases enzymatically active or prevents their premature inactivation.

By in situ hybridization, Y-specific DNA sequences were localized on Xp22.3-Xpter of one of the two X chromosomes in all of eleven XX males studied. In nine of the cases the presence of the Y-specific DNA did not affect random X inactivation in fibroblasts. Fibroblasts of the other two cases showed a preferential inactivation of the Y DNA-carrying X chromosome. In only one of these two exceptions blood lymphocytes could also be studied, and here, random inactivation of the Y DNA-carrying X chromosome occurred. Furthermore, the gene dosage of steroid sulfatase (STS) was examined by Southern blot analysis. In ten of the cases including the one showing random X-inactivation in lymphocytes but not in fibroblasts, a double dosage of the STS gene is present. The remaining case with non-random inactivation shows a single STS gene dosage. This case was reported previously to have STS enzyme activity in the male range. It is assumed that, as a consequence DNA sequences may result in the preferential inactivation of the Y DNA-carrying X chromosome.

The Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI; MPS VI) is a lysosomal storage disease caused by deficiency of the enzyme arylsulphatase B (ASB). A human ASB cDNA has been subcloned into the retroviral vector pXT1 containing the bacterial neomycin-resistance gene and an internal thymidine kinase promoter for transcription of the inserted gene. Replication defective retrovirus was generated by transfecting the construct into the amphotropic packaging cell line PA317. Human MPS VI fibroblasts infected with recombinant retrovirus integrated the provirus into their genome and expressed retrovirus-encoded ASB mRNAs. In infected fibroblasts the level of ASB was up to 36-fold higher than in normal fibroblasts. Biosynthesis and processing of ASB in infected MPS VI fibroblasts was accomplished as in normal fibroblasts, and mature, enzymically active, ASB accumulated in dense lysosomes, indicating that the ASB deficiency in MPS VI fibroblasts was corrected by the retroviral gene transfer.

Homologous recombination between microinjected SV40 DNA fragments and endogenous SV40 DNA in COS7 cells was analysed by immunofluorescence staining and DNA blotting. Time course experiments revealed that recombination between the transferred (trans) DNA and the chromosomal DNA occurred about 8 hours after microinjection with high efficiency in a gene dose independent fashion. Deletions of up to 1018 basepairs (bp) within the early or the late SV40 region were efficiently repaired after the transfer of linear but not of circular DNA molecules. A 22 bp homology between the trans DNA and the endogenous DNA was sufficient to initiate recombination but 14 nonhomologous bp at one open end of the SV40 DNA fragments hindered gap repair.

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