Molecular Analysis of X-Linked Ichthyosis in Japan

Abstract

Background: X-linked ichthyosis (XLI) is an inherited skin disorder caused by a deficiency of steroid sulfatase (STS). The gene and protein of STS were examined in 19 Japanese patients with XLI. Results: In Western blotting analysis, no cross-reacting peptide was detected in the patients’ placenta, although a single band (63 kD) corresponding to STS in a normal subject was observed. Southern blotting was performed using EcoRI digests of cellular DNA from 13 XLI patients and full-length human STS cDNA as a probe. Normal males had bands of 20, 15, 10, 9.0, 6.1, 4.2, 2.6, and 1.5 kb. Twelve of the 19 patients had only 20- and 1.5-kb bands. Only one patient had the same band pattern as that of normal males. The STS gene was analyzed by PCR in 6 of the 19 patients. PCR amplification products were sequenced to analyze the STS gene. Two cases with one-base change in the STS gene and variation in amino acids H444R and E560P were found. Mutant STS cDNA was transfected into COS-1 cells and the STS enzyme activity was assayed. The enzyme activities were less than the minimum detection value of the detection system. Conclusions: These results suggest that XLI is mainly caused by an extensive deletion of the STS gene and that the PCR method is useful for detection of STS point mutations.

Filaggrin Mutations Are Genetic Modifying Factors Exacerbating X-Linked Ichthyosis

“…The steroid sulfatase gene, STS, located on the X chromosome, causing XLI, was the first keratinizing disorder gene to be identified (Ballabio et al, 1987;Bonifas et al, 1987;Gillard et al, 1987). A genomic deletion involving the entire gene, which is readily detectable by fluorescent in situ hybridization, appears to be the most common cause of XLI in the human population (Bonifas et al, 1987); however, less frequent point mutations in STS have also been described (Basler et al, 1992;Alperin and Shapiro, 1997;Morita et al, 1997;Sugawara et al, 2000Sugawara et al, , 2001Valdes-Flores et al, 2000Ghosh, 2004;Gonzalez-Huerta et al, 2006). Very recently, loss-of-function mutations in the gene encoding filaggrin (FLG) have been shown to underlie IV, which is inherited as a semidominant Mendelian trait where heterozygotes may have a mild sub-clinical presentation compared with homozygotes who present with marked scaling (Sandilands et al, 2006;Smith et al, 2006;Gruber et al, 2007).…”

Both N-terminal and C-terminal regions of steroid sulfatase are important for enzyme activity

“…Human STS cDNA (2·0 kb) encoding a full-length STS protein expression vector (pSTS) was prepared by inserting an EcoRI fragment from human STS cDNA into pSV⋅SPORT-1 (Sugawara et al 2001). We previously reported a case of XLI with a one-base change in the STS gene and variation in amino acid Q560P, a mutant lacking STS enzyme activity (Sugawara et al 2000).…”

“…We previously reported a case of XLI with a one-base change in the STS gene and variation in amino acid Q560P, a mutant lacking STS enzyme activity (Sugawara et al 2000). Q560P mutation was produced with a Transformer Site Directed Mutagenesis kit (Clontech) to yield the plasmid Q560P, as described previously (Sugawara et al 2001). STS has N-terminal signal peptides of 23 amino acids, which start with a methionine and an N-glycosylation site at asparagine residue 47 in the N-terminal region.…”

“…COS-1 cells were grown in 35 mm plastic dishes and cultured in Dulbecco's Modified Eagles' Medium (DMEM) supplemented with 10% (v/v) fetal calf serum (FCS) and 50 µg/ml gentamycin. COS-1 cells were transfected with wild-type STS cDNA and truncated mutant STS cDNA expression vectors, using FuGENE 6 (Roche), as described previously (Sugawara et al 2001). Some cultures were cotransfected with wild-type STS cDNA and truncated mutant STS.…”

Point mutation in the STS gene in a severely affected patient with X-linked recessive ichthyosis

“…In some cases, abnormal pairing of the low copy number repeats G1.3 and CRI-S232, on either side of the STS gene, seems to be responsible for these interstitial deletions (3). Only a few patients have been reported with partial deletions (4-8) or point mutations in the STS gene (9)(10)(11)(12)(13)(14)(15)(16). In the present study we analysed a severely affected XLRI patient with a missense mutation in exon 8 that seems to be a critical region in the presence of point mutations in XLRI.…”