Studies on cross-reacting material to steroid sulphatase in fibroblasts from patients affected by different types of steroid sulphatase deficiency

Biochemical and immunological characterization of X-linked ichthyosis

An immunoquantification protocol based on an enzyme-linked immunosorbent assay was developed to measure the abundance of the microsomal enzyme steroid sulphatase (STS). The two-step sandwich immunoassay is sufficiently sensitive to detect 100-200 pg purified steroid sulphatase in a 50-microliters sample. The steroid sulphatase content in fibroblast, leukocyte and placental extracts correlates with the steroid sulphatase activity in these extracts. No steroid sulphatase protein was found in approximately 350 micrograms plasma proteins from a normal person. In three of four X-linked ichthyosis patients a complete gene deletion was found by Southern hybridization with the full-length STS cDNA as probe. Neither steroid sulphatase protein nor enzymatic activity was found in fibroblast extracts of these three patients. In a fibroblast extract of another X-linked ichthyosis patient, which had a normal Southern blotting pattern, no immunoreactive protein was detected. Residual activity of steroid sulphatase was also not found after prolonged incubation of this fibroblast extract with the natural substrate oestrone sulphate.

Male infant with ichthyosis, Kallmann syndrome, chondrodysplasia punctata, and an Xp chromosome deletion

We report on a male infant with X-linked ichthyosis, X-linked Kallmann syndrome, and X-linked recessive chondrodysplasia punctata (CPXR). Chromosome analysis showed a terminal deletion with a breakpoint at Xp22.31, inherited maternally. This patient confirms the localization of XLI, XLK, and CPXR to this region of the X chromosome and represents an example of a "contiguous gene syndrome." A comparison of the manifestations of patients with CPXR, warfarin embryopathy, and vitamin K epoxide reductase deficiency shows a remarkable similarity. However, vitamin K epoxide reductase deficiency does not appear to be the cause of CPXR. We propose that CPXR may be due to a defect in a vitamin K-dependent bone protein such as vitamin K-dependent bone carboxylase, osteocalcin, or matrix Gla protein.

Molecular heterogeneity of steroid sulfatase deficiency: a multicenter study on 57 unrelated patients, at DNA and protein levels

Steroid sulfatase (STS) deficiency is the biochemical defect of X-linked ichthyosis (XLI), one of the most common X-linked disorders. We studied 57 European unrelated patients affected by STS deficiency. Twenty-eight patients were from Italy, 24 from the United Kingdom, 4 from The Netherlands, and 1 from Denmark. In two families XLI was associated with Kallmann syndrome (hypogonadotropic hypogonadism and anosmia). STS enzymatic activity was profoundly deficient in all cases. Direct DNA analysis, using cDNA and genomic probes from the STS gene and linked regions, demonstrated heterogeneity of the molecular defect. Forty-eight patients (84%) showed a deletion of the STS gene. In 44 cases the deletion also involved the STS flanking locus DXS237. In 1 patient a partial deletion of the STS gene was detected and in 9 patients no evidence of deletion was found. Locus DXS31 (probe M1A), previously mapped to Xp22.3-pter, was not deleted either in 24 patients with X-linked ichthyosis or in two families with X-linked ichthyosis associated with Kallmann syndrome. Consequently, the following loci order could be suggested: telomere--DXS31--(DXS237, STS)--Kallmann--centromere. Immunoblotting experiments, performed using anti-STS polyclonal antibodies, revealed the absence of cross-reacting material to STS in all cases tested, including 4 patients without evidence of deletions.

Deletions of the steroid sulphatase gene in "classical" X-linked ichthyosis and in X-linked ichthyosis associated with Kallmann syndrome

We have studied 16 men, from 10 unrelated Italian families, affected by steroid suphatase (STS) deficiency, which is the basic defect of X-linked ichthyosis (XLI). The patients' clinical diagnoses were of either isolated ichthyosis or ichthyosis associated with Kallmann syndrome (KS) (hypogonadotropic hypogonadism and anosmia). DNA from patients and their relatives was analysed by Southern blotting followed by hydridization with an STS cDNA probe. None of the patients affected by either XLI or XLI/KS showed any hybridization signal, thus revealing a deletion in the STS gene. We suggest that a gene deletion may be the most common molecular defect involved in XLI and that the syndrome XLI/KS may be due to a deletion of both the STS and the KS loci.