Deficiency of arylsulfatase C in cultured skin fibroblasts of X-linked ichthyosis

Inherited ichthyoses/generalized Mendelian disorders of cornification

Inherited ichthyoses, defined as the generalized form of Mendelian disorders of cornification, are characterized by visible scaling and/or hyperkeratosis of most or all of the skin. This etiologically and phenotypically heterogenous group of conditions is caused by mutations in various different genes important for keratinocyte differentiation and epidermal barrier function. Diagnosing a specific entity is a particular challenge for the nonspecialist presented with the common clinical scaling. For the clinician, this review outlines an algorithmic approach for utilizing diagnostic clues to narrow down the differential diagnosis and to guide further testing and treatment options.

Cholesterol sulfate is not degraded but does not accumulate in Epstein-Barr virus-transformed lymphoid cells from patients with X-linked ichthyosis

The metabolism of cholesterol sulfate (CS) was investigated in immortalized, Epstein-Barr virus-transformed lymphoid cell lines derived from normal individuals and patients affected with recessive X-linked ichthyosis (XLI). Normal lymphoid cells expressed arylsulfatase C and steroid sulfatase (including cholesterol sulfatase) activities, and these two sulfohydrolases showed the same enzyme properties as in other human cells, e.g., leukocytes or skin fibroblasts. XLI-derived lymphoid cell lines exhibited extremely deficient activity of both arylsulfatase C and steroid sulfatase. While normal and XLI intact, living lymphoid cells could take up exogenous radiolabelled CS through a non-receptor-mediated process. XLI cells were completely unable to degrade CS to cholesterol. However, despite their defect in CS degradation, steroid sulfatase-deficient cells did not accumulate CS because of outflux of this sterol. The potential implications of these findings to the pathogenesis of increased CS content in plasma and epidermis of XLI patients are discussed. This study also demonstrates that immortalized lymphoid cell lines may represent a useful experimental model system for the study of XLI.

Clinical pathologic correlation of superficial corneal opacities in X-linked ichthyosis

X-linked ichthyosis is a relatively common oculodermal disorder. Characteristic corneal opacities are small punctate or filiform lesions and are located in the deep corneal stroma. In an unusual case, a 73-year-old man with X-linked ichthyosis and steroid sulfatase deficiency had superficial corneal opacities. The corneal opacities were granular in nature, involving the subepithelial and anterior stromal layers. The opacities resulted in irregular overlying corneal epithelium and were white-gray in color in direct illumination. Histopathologic and electron microscopic studies demonstrated abnormalities of the corneal epithelial basement membrane. The epithelial basement membrane was thickened with irregular extensions into Bowman's layers. Abnormal depositions of basement membrane protein were seen in the anterior stroma. These abnormalities may have resulted from increased production of basement membrane proteins by the corneal epithelium, resulting from hyperactive turnover of the basal layer.

Detection of carriers for X-linked ichthyosis by Southern blot analysis and identification of one family with a de novo mutation

Scaling in patients with recessive X-linked ichthyosis is caused by lack of activity of the enzyme steroid sulfatase. In approximately 90% of kindreds, this lack is the result of a DNA deletion large enough to eliminate the coding region completely. We have used Southern blot hybridization of DNA isolated from peripheral blood leukocytes to measure gene dosage of the steroid sulfatase gene. This readily detects a half-normal dosage in women who are carriers and therefore can be used to diagnose the carrier status of female relatives of 90% of patients with the disease. We have found one family in whom the deletion arose on an allele inherited from the proband's clinically normal maternal grandfather.

A new syndrome of anosmia, ichthyosis, hypogonadism, and various neurological manifestations with deficiency of steroid sulfatase and arylsulfatase C

We describe a family consisting of 3 affected men with congenital ichthyosis, anosmia, hypogonadism, nystagmus with decreased visual acuity, strabismus, hypopigmentation of the iris, and mirror movements of the hands and feet. Two of them had limitation of ocular movement and unilateral renal agenesis or hypoplasia. The condition appears to be inherited as an X-linked recessive trait. Clinical, pathological, and biochemical evaluations were compatible with a diagnosis of X-linked ichthyosis. Steroid sulfatase and arylsulfatase C activities in leukocytes and fibroblasts were markedly diminished in the affected patients. Their hypogonadism was due to decreased luteinizing hormone-releasing hormone secretion (hypogonadotropic). Hyposecretion of antidiuretic hormone was also recognized. Chromosome analysis of leukocytes and skin fibroblasts revealed a normal 46,XY male karyotype in all of the patients.

Recessive X-linked ichthyosis: lack of immunologically detectable steroid sulfatase enzyme protein

Patients with recessive X-linked ichthyosis (RXLI), one hereditary form of scaly skin, lack activity of the enzyme steroid sulfatase in all tissues studied. To investigate the molecular defect underlying the lack of enzyme activity, we prepared antisera against normal enzyme by injecting normal placental microsomal suspensions or partially purified steroid sulfatase into rabbits. Antibody activity was assessed by immunoprecipitation of detergent solubilized steroid sulfatase. In addition, we prepared rabbit antisera against RXLI placental microsomal suspensions. To detect immunologically cross-reactive material in patients' placentas, extracts were studied by immunoblot techniques and by competition with normal enzyme for antibody binding. Patients' extracts did not contain immunoreactive material co-migrating on electrophoresis with purified enzyme nor did they inhibit immunoprecipitation of normal enzyme. Sera from rabbits immunized with RXLI placental microsomes contain no antibodies to normal steroid sulfatase, as judged by their failure to immunoprecipitate normal enzyme or to react with normal steroid sulfatase on immunoblot. Thus the mutation in RXLI appears to reduce steroid sulfatase enzyme protein as well as enzyme activity.

Hormonal induction of steroid sulphatase in the mouse

By comparing steroid sulphatase levels per se, and also ratios to alpha-galactosidase, in 6 sets of mice - normal females, entire and castrated males both with and without exogenous testosterone administration - we obtained support for the contention that induction of this enzyme is in part controlled by male hormones.

Estrone- and dehydroepiandrosterone-sulfatase activities in human female epidermis

Estrone (E1)-sulfatase and dehydroepiandrosterone (DHEA)-sulfatase activities were studied in human female epidermis. Skin specimens were obtained by abdominal or plantar biopsies. The apparent Michaelis-Menten constants for E1 and DHEA sulfatases were 35.2 microM and 8.7 microM, respectively. A substrate inhibition was only observed for DHEA sulfatase. Both sulfatases had an elevated temperature optimum (65 degrees C). The effect of inorganic salts was also tested. In normal epidermis, E1-sulfatase activity was constantly higher than DHEA-sulfatase activity, but no correlation between these activities was observed. On the other hand, E1- and DHEA-sulfatase activities were lower in plantar than in abdominal epidermis. In plantar epidermis of palmoplantar keratoderma, large variations in E1-sulfatase activity, but no significant variation in DHEA-sulfatase activity, were observed. In human epidermis, the findings were consistent with the existence of two different sulfatases: E1 sulfatase and DHEA sulfatase. It would also appear that sulfatase activities are not linked to the abnormal shedding of plantar stratum corneum in palmoplantar keratoderma.

A comparative study on steroid sulfatase and arylsulfatase C in fibroblast clones from 45,X/47,XXX and 69,XXY

Steroid sulfatase (STS) and arylsulfatase C ( ARSC ) were studied in fibroblast clones from a 45,X/47,XXX mosaic and from a 69,XXY triploidy with one or two active X chromosomes. The comparison of the 47,XXX with 45,X clones showed an incomplete gene dosage effect (1.8 for STS and 2.0 for ARSC ). This was not the case for the triploid clones with different X-inactivation patterns. These results confirm previous reports on the non-inactivation of the STS gene, and establish X linkage and non-inactivation for the ARSC gene as well.

Cholesterol sulphate in the microsomal sulphatase deficient placenta

Placental sulphatase deficiency (PSD) and recessive X-linked ichthyosis (RXLI) are known as a nosological entity, due to deficiency of the enzyme, steroid sulphatase. Prior studies have demonstrated high urinary excretion and some accumulation of sulphated steroids prenatally, and of accumulation of cholesterol sulphate postnatally. This study was undertaken to investigate the level of cholesterol sulphate in the sulphatase deficient placenta. Whereas cholesterol sulphate levels are elevated in blood, erythrocyte membrane and stratum corneum of patients with RXLI, cholesterol sulphate content of four investigated sulphatase deficient placentas was normal in comparison to six normal male controls and four male controls with low oestrogen excretion in the third trimester of pregnancy but with normal placental sulphatase activity. The explanation for normal cholesterol sulphate content of sulphatase deficient placentas is unknown but may be due to placental transport, rapid metabolism to other sulphated steroids or age-related differences in residual enzyme activities.

Fluorometric determination of DNA in epidermis and cultured fibroblasts, using 4'-6-diamidino-2-phenylindole (DAPI)

4'-6-diamidino-phenylindole (DAPI) which is used for the detection of mycoplasmic infections of cell cultures or cytofluorometric investigations proved to be a sensitive agent for the fluorometric assay of alkali extracted DNA in cultured cells and human epidermis. Various experiments to optimize assay conditions led to the following procedure: 1 part of freeze dried tissue (1 mg/ml) and 1 part of 0.2 mol/l NaOH(w/v) were heated at 95 degrees for 40 min. After cooling for 1 h to room temperature, 0.1 ml alkaline extract was mixed with 2.9 ml DAPI-solution (0.2 microgram/ml in McIlvaine buffer containing 1 mmol/l MgCl2). After 10 min in the dark the emitted fluorescence was estimated at 453 nm with an excitation at 360 nm. This assay procedure allowed a detection limit of 25 ng DNA.

The ichthyoses--pathogenesis and prenatal diagnosis: a review of recent advances

Disturbances in the process of normal cornification leading to pathologic scaling provide the pathophysiologic basis for the ichthyoses. These disturbances may result from either abnormalities in protein metabolism (keratinization) (i.e., the "bricks") or in lipid metabolism (i.e., the "mortar") (Fig. 1). The evidence linking the various ichthyoses to defects in protein or lipid metabolism have been reviewed. It is likely that future advances will lead not only to a more complete understanding of the pathogenesis of these disorders, but also will shed significant light on the normal stratum corneum functions of barrier formation and desquamation, as well as lead the way to more rational and effective therapies. In recent years, prenatal diagnosis has been successfully performed in several of the ichthyoses. It is likely that improvements in our ability to prenatally diagnose those disorders will advance hand-in-hand with further progress in unraveling their underlying causes.

A new method for the determination of steroid sulphatase activity in leukocytes in X-linked recessive ichthyosis

The diagnosis of X-linked ichthyosis can now be reliably established by using a non-radioactive method to detect steroid sulphatase deficiency in leukocytes. This new method yields the same results with leukocytes as with cultured fibroblasts. The second type of microsomal arylsulphatase previously described in cultured fibroblasts is also present in leukocytes.

Review: genetics of steroid sulphatase deficiency and X-linked ichthyosis

Steroid sulphatase deficiency which started out as a curious placental microsomal enzyme deficiency associated with low maternal urinary oestrogen excretion and difficulties in delivery, first described only twelve years ago, has now become a generalized enzyme deficiency associated also with a common skin disease. It turns out not only to be inherited in an X-linked recessive manner, but to be part of a gene cluster which includes the Xg blood group gene and which has been precisely assigned to the distal tip of the short arm of the X-chromosome. This cluster is unique for genes on the X-chromosome in escaping X-inactivation. It remains to be unequivocally demonstrated whether steroid sulphatase is identical to arylsulphatase C or whether these are two enzymes sharing a common polypeptide chain determined by a single gene. However, Rose (1982) presents evidence that one steroid sulphatase is probably identical with arylsulphatase C. It also remains to be conclusively demonstrated whether the gene for the enzyme deficiency is also that for ichthyosis or whether they are two very closely linked genes. If the former is true the role of steroid sulphatase in the abnormal keratinization of ichthyosis is still to be elucidated. Above all the special nature of the DNA in this unique region awaits description.

Cellular localization of neuraminidases in cultured human fibroblasts

The cellular localization of glycoprotein and ganglioside sialidases in normal and I-cell-disease cultured fibroblasts has been investigated. Cellular organelles have been separated on a colloidal silica gradient. The subcellular distribution of these enzymes indicated that the glycoprotein sialidase is mainly a lysosomal hydrolase, whereas the ganglioside sialidase is primarily located in the plasma membranes. The latter isoenzymes is tightly bound to these membranes and thus could not be extracted by homogenization in the presence of Triton X-100. The interpretation of this finding and its relation to the pathochemistry of sialidase-deficient disorders is discussed.

Biochemical investigation to the reliability of the histochemical demonstration of microsomal arylsulphatase activity in cryostat sections

Polyacrylamide gel-electrophoresis was performed with an extract from cultivated skin fibroblasts. Arylsulphatase activity is measured and visualised using the biochemical substrate dehydroepiandrosterone sulphate and the histochemical substrate 6-bromo-2-naphthyl sulphate respectively. The histochemical substrate was hydrolysed at Rf = 0.49 and 0.58 while the biochemical substrate was hydrolysed only at 0.49. We conclude that two different microsomal arylsulphatases exist: a sulphatase able to hydrolyse steroid sulphatases (Rf = 0.49) and one unable to hydrolyse steroid sulphatases (RF = 0.58). In consequence if is recommended to carry out an electrophoresis experiment after the histochemical investigation, in order to discriminate between these two types of sulphatase.