Molecular analysis of the CYP1B1 gene: identification of novel truncating mutations in patients with primary congenital glaucoma.

BACKGROUND: Mutations and polymorphisms have been identified in the CYP1B1 gene; while mutations that affect the conserved core structures of cytochrome P4501B1 result in primary congenital glaucoma (PCG), mutations in other regions hold the potential to define differences in estrogen metabolism. In the present study, we analyzed the CYP1B1 gene in Mexican patients with PCG and described four novel mutations. MATERIALS AND METHODS: The sample included 12 nonrelated cases with PCG. Analysis of coding regions of the CYP1B1 gene was performed through PCR and DNA sequencing analysis from genomic DNA. RESULTS AND DISCUSSION: Molecular analysis of the CYP1B1 gene showed the following molecular defects: (1) a novel single-base pair deletion within codon 370 (1454delC) that produces a substitution of leucine instead of proline and a premature stop codon 57 amino acids after the last original amino acid; this family also harbored a novel polymorphic variant of the cytochrome P4501B1 with six single-nucleotide polymorphisms (142C-->G; 355G-->T; 729G-->C; 4326C-->G; 4360C-->G and 4379C-->T); (2) a novel single-base pair deletion within codon 277 (1176delT) that results in a premature stop codon; (3) a novel single-base pair deletion within codon 179 (880delG) that produces a substitution of arginine instead of alanine and a premature stop codon 17 amino acids downstream from the last original amino acid, and (4) a duplication (or insertion) of ten base pairs within codon 404 (1556dupATGCCACCAC) that results in a premature stop codon 26 amino acids after the last original amino acid. We also observed in 2 nonrelated patients a deletion of 13 bp (1410_1422delGAGTGCAGGCAGA) previously reported for other populations. CONCLUSION: We reported four novel mutations and a novel polymorphic variant in the CYP1B1 gene in PCG in the Mexican population; it has important implications in diagnosis and genetic counseling.

Unusual clinical presentation in two cases of multiple sulfatase deficiency.

Multiple sulfatase deficiency (MSD) is an inborn error of metabolism that combines the clinical features of late infantile metachromatic leukodystrophy and mucopolysaccharidosis. The characteristic biochemical abnormality is a reduction in the activities of several sulfatases, with consequent tissue accumulation of sulfatides, sulfated glycosaminoglycans, sphingolipids, and steroid sulfates. In this study we present two unusual cases of MSD with variable enzymatic deficiency of arylsulfatases A, B, and C. Both patients had ichthyosis, broad thumbs and index fingers, an unusually slow progression of the neurologic symptoms, and lacked the hepatosplenomegaly that is typical of MSD. Olivopontocerebellar atrophy was present and one patient had a large retrocerebellar cyst. Mucopolysaccharides were not detected in the urine from either subject. Leukocyte arylsulfatase A activity in patient 1 was 0.46 nmol/mg protein/hr and in patient 2 was 0.0 nmol/mg protein/hr (normal 0.7-5.0 nmol/mg protein/hr). Leukocyte arylsulfatase B activity in patient 1 was 24 nmol/mg protein/hr and in patient 2 was 22 nmol/mg protein/hr (normal 115-226 nmol/mg protein/hr). Leukocyte arylsulfatase C in patient 1 was 0.30 pmol/mg protein/hr and in patient 2 was 0.28 pmol/mg protein/hr (normal 0.84 pmol/mg protein/hr). In conclusion, these two patients with MSD had mild clinical presentations not previously reported and variable enzymatic deficiency of arylsulfatases A, B, and C.

Carrier identification by FISH analysis in isolated cases of X-linked ichthyosis.

X-linked ichthyosis (XLI) is an inborn error of metabolism due to steroid sulfatase (STS) deficiency. STS assay and FISH are useful in diagnosing carrier status of XLI. Biochemical analysis appears to indicate that most sporadic cases are inherited. Since this method does not seem to be completely reliable in recognizing XLI-carriers, the aim of the present study was to corroborate by FISH whether or not most sporadic cases of XLI had de novo mutations. XLI patients were classified through STS assay and PCR amplification of 5'-3' ends of the STS gene. XLI patients had undetectable levels of STS activity and complete deletion of the STS gene. Patients' mothers were studied through STS assay and FISH. Nine out of 12 mothers presented an STS activity compatible with XLI-carrier state. These mothers also had only one copy of the STS gene, indicating that they carry the primary gene defect. One mother had normal STS activity but only one copy of the STS gene. This data corroborated that most sporadic cases do not represent de novo mutations, and that FISH must be included in the analysis of mothers of sporadic cases when they present with normal STS activity, in order to correctly diagnose the XLI carrier state.

Deletion of exons 1-5 of the STS gene causing X-linked ichthyosis.

X-linked ichthyosis is an inherited disorder due to steroid sulfatase deficiency. It is clinically characterized by dark, adhesive, and regular scales of the skin. Most X-linked ichthyosis patients present large deletions of the STS gene and flanking markers; a minority show a point mutation or partial deletion of the STS gene. In this study we analyzed the STS gene in a family with simultaneous occurrence of X-linked ichthyosis and ichthyosis vulgaris. X-linked ichthyosis diagnosis was confirmed through steroid sulfatase assay in leukocytes using 7-[3H]-dehydroepiandrosterone sulfate as a substrate. Exons 1, 2, 5, and 6-10, and the 5' flanking markers DXS1130, DXS1139, and DXS996 of the STS gene were analyzed by polymerase chain reaction. X-linked ichthyosis patients of the family (n = 4 males) had undetectable levels of STS activity (0.00 pmol per mg protein per h). The DNA analysis showed that only exons 6-10 and the 5' flanking markers of the STS gene were present. We report the first partial deletion of the STS gene spanning exons 1-5 in X-linked ichthyosis patients.

Deletion pattern of the STS gene in X-linked ichthyosis in a Mexican population.

BACKGROUND: X-linked ichthyosis (XLI) is an inherited disorder due to steroid sulfatase deficiency (STS). Most XLI patients (>90%) have complete deletion of the STS gene and flanking sequences. The presence of low copy number repeats (G1.3 and CRI-S232) on either side of the STS gene seems to play a role in the high frequency of these interstitial deletions. In the present study, we analyzed 80 Mexican patients with XLI and complete deletion of the STS gene. MATERIALS AND METHODS: STS activity was measured in the leukocytes using 7-[(3)H]-dehydroepiandrosterone sulfate as a substrate. Amplification of the regions telomeric-DXS89, DXS996, DXS1139, DXS1130, 5' STS, 3' STS, DXS1131, DXS1133, DXS237, DXS1132, DXF22S1, DXS278, DXS1134-centromeric was performed through PCR. RESULTS: No STS activity was detected in the XLI patients (0.00 pmoles/mg protein/h). We observed 3 different patterns of deletion. The first two groups included 25 and 32 patients, respectively, in which homologous sequences were involved. These subjects showed the 5' STS deletion at the sequence DXS1139, corresponding to the probe CRI-S232A2. The group of 32 patients presented the 3' STS rupture site at the sequence DXF22S1 (probe G1.3) and the remaining 25 patients had the 3' STS breakpoint at the sequence DXS278 (probe CRI-S232B2). The third group included 23 patients with the breakpoints at several regions on either side of the STS gene. No implication of the homologous sequences were observed in this group. CONCLUSION: These data indicate that more complex mechanisms, apart from homologous recombination, are occurring in the genesis of the breakpoints of the STS gene of XLI Mexican patients.

Mutation report: a novel partial deletion of exons 2-10 of the STS gene in recessive X-linked ichthyosis.

X-linked ichthyosis is an inherited disease due to steroid sulfatase deficiency. Onset is at birth or early after birth with dark, regular, and adherent scales of skin. Approximately 85%-90% of X-linked ichthyosis patients have large deletions of the STS gene and flanking sequences. Three patients have been identified with partial deletions of the gene. Two deletions have been found at the 3' extreme and the other one implicating exons 2-5. This study describes a novel partial deletion of the STS gene in an X-linked ichthyosis patient. The subject was classified through steroid sulfatase assay in leukocytes using 7-[3H]-dehydroepiandrosterone sulfate as a substrate. Exons 1, 2, 5, and 7-10, and 3' flanking sequences DXS1131, DXS1133, DXS237, DXS1132, DXF22S1, and DXS278 of the STS gene were analyzed through polymerase chain reaction. The DNA analysis showed that exon 1 and 3' flanking sequences from DXS237 to DXS278 were present. In this study we report the fourth partial deletion of the STS gene and the first spanning exons 2-10 in X-linked ichthyosis patients.

Most "sporadic" cases of X-linked ichthyosis are not de novo mutations.

X-linked ichthyosis is an inherited disease with dark, regular and adherent scales as clinical characteristics. It is caused by a deficiency of the steroid sulphatase enzyme. Steroid sulphatase assay is a relative easy tool that enables correct diagnosis of X-linked ichthyosis patients and carriers. A large number of X-linked ichthyosis patients correspond to non-familial cases that seem to represent de novo mutations. In this study, we examined the X-linked ichthyosis carrier state of the mothers of 42 non-familial cases to determine whether their children corresponded to de novo mutations. To classify patients and carriers, a steroid sulphatase assay was performed in leukocytes using 7-[3H]-dehydroepiandrosterone sulphate as substrate. In 36 mothers (85%) we found steroid sulphatase activity compatible with the carrier state of X-linked ichthyosis. This data suggest that most of the mothers of these patients present the primary gene defect, excluding de novo mutations in the patients.

Steroid sulfatase activity in leukocytes: a comparative study in 45,X; 46,Xi(Xq) and carriers of steroid sulfatase deficiency.

The enzyme steroid sulfatase (STS) hydrolyses 3-beta-hydroxysteroid sulfates. The female-male STS activity ratio is 1.04-1.7:1 in several cell lines in adults and reaches 2:1 in prepubertal subjects. In fibroblasts, STS values in X-chromosome abnormalities show a partial positive correlation according to the number of X-chromosomes. X-linked ichthyosis (XLI) carriers, with only one copy of the STS gene, present lower STS levels than normal controls. This study analyzes the STS activity in leukocytes of 46,Xi(Xq); 45,X; XLI carriers and normal controls using 7-[3H]-dehydroepiandrosterone sulfate as substrate. X-monosomy (1.07 +/- 0.18 pmol/mg protein/h), Xq isochromosome (1.02 +/- 0.12 pmol/mg protein/h) and normal females (1.03 +/- 0.11 pmol/mg protein/h) had similar STS values (p > 0.05). XLI-carriers and males showed the lowest STS levels (0.34 +/- 0.04 pmol/mg protein/h, p < 0.001 and 0.82 +/- 0.14 pmol/mg protein/h, p < 0.05, respectively). Female-male STS activity ratio in leukocytes was 1.3:1. These data indicate that a complex mechanism regulates the STS expression depending on each type of cell line.

X-linked ichthyosis in Mexico: high frequency of deletions in the steroid sulfatase encoding gene.

The present study analyzes the frequency of molecular deletions in the steroid sulfatase (STS) encoding gene in a sample of 50 Mexican subjects with biochemical diagnosis of X-linked ichthyosis (XLI). To establish the correct diagnosis, STS activity was determined in leukocytes using 7-(3)H-dehydroepiandrosterone sulfate as the substrate. No amplification of the 3' and 5' ends of the STS gene by PCR was detected in the DNA of 49 patients, whereas only one sample of 50 presented a normal amplification. This report shows a very high frequency of deletions in the human STS encoding gene in a representative sample of the Mexican population, and it defines the characteristics of XLI in patients whose STS gene has a complete deletion as a major molecular defect.

Accuracy of the clinical diagnosis of recessive X-linked ichthyosis vs ichthyosis vulgaris.

The present study analyzes the accuracy of the clinical diagnosis of X-linked ichthyosis (XLI) vs ichthyosis vulgaris (IV), in a sample of Mexican patients. The study was double blind, using steroid sulfatase (STS) activity as the golden standard. Twenty male patients were included; 16 corresponded to XLI and 4 to IV. The clinical diagnosis was correct in 9 of the 16 XLI cases (56%) and in 2 of the 4 IV cases (50%). Some clinical findings in XLI, such as cryptorchidism in patients and delayed labor in their mothers, were important features for diagnosis. Statistical analysis of the results showed: among physicians (n = 2) Kappa value 0.50, specific concordance 0.40, and absolute concordance 0.75; other values were sensibility 0.56, specificity 0.50, positive predictive value 0.82, negative predictive value 0.22, accuracy 0.55, prevalence 0.80. In conclusion, the differential diagnosis of XLI and IV is very difficult, and we consider that this is not explained either by personal skills or by other conditions. It could be attributed to the similarities in skin manifestations of these two diseases. The performance of the STS assay is imperative in order to correctly diagnose the disease and offer adequate genetic counseling.

[The human Y chromosome]. / El cromosoma Y humano.

Recent findings concerning the human Y chromosome are reviewed. Normally the presence of the Y chromosome is related to male differentiation; however until recently nothing was known about chromosome Y and the development of the testis at the molecular level. Initially the most plausible assumption in this field was the "H-Y hypothesis" which suggested that the presence of a male specific antigen called H-Y, controlled by a gene(s) on the Y chromosome, was responsible for the differentiation of the primitive gonad into a testis. An alternative was a series of DNA sequences termed Bkm which were thought to play an important role in sex determination. These two hypothesis were refuted. More recently, molecular studies in XX males have shown the presence of Y-DNA in their genome suggesting that a small fragment of the Y (probably a single gene) is responsible for testis development in the majority of these patients. This gene has been termed TDF or ZFY and encodes a protein that could act as a regulating factor of the male pathway. Also reviewed are the actions of various genes recently assigned to the Y chromosome.