Two cases of steroid sulfatase deficiency with complex phenotype due to contiguous gene deletions

X linked recessive ichthyosis: Current concepts

In the present review, we describe the most important aspects of the X-linked ichthyosis (XLI) and make a compilation of the some historic details of the disease. The aim of the present study is an update of the XLI. Historical, clinical, epidemiological, and molecular aspects are described through the text. Recessive XLI is a relatively common genodermatosis affecting different ethnic groups. With a high spectrum of the clinical manifestations due to environmental factors, the disease has a genetic heterogeneity that goes from a point mutation to a large deletion involving several genes to produce a contiguous gene syndrome. Most XLI patients harbor complete STS gene deletion and flanked sequences; seven intragenic deletions and 14 point mutations with a complete loss of the steroid sulfatase activity have been reported worldwide. In this study, we review current knowledge about the disease.

Mutation screening in the Greek population and evaluation of NLGN3 and NLGN4X genes causal factors for autism

Molecular and neurobiological evidence for the involvement of neuroligins (particularly NLGN3 and NLGN4X genes) in autistic disorder is accumulating. However, previous mutation screening studies on these two genes have yielded controversial results. The present study explores, for the first time, the contribution of NLGN3 and NLGN4X genetic variants in Greek patients with autistic disorder. We analyzed the full exonic sequence of NLGN3 and NLGN4X genes in 40 patients strictly fulfilling the Diagnostic and Statistical Manual of Mental Disorders, 4th ed. criteria for autistic disorder. We identified nine nucleotide changes in NLGN4X--one probable causative mutation (p.K378R) previously reported by our research group, one novel variant (c.-206G>C), one nonvalidated single nucleotide polymorphism (SNP, rs111953947), and six known human SNPs reported in the SNP database--and one known human SNP in NLGN3 also reported in the SNP database. The variants identified are expected to be benign. However, they should be investigated in the context of variants in interacting cellular pathways to assess their contribution to the etiology of autism.

Chondrodysplasia punctata: a clinical diagnostic and radiological review

Chondrodysplasia punctata (CDP) is associated with a number of disorders, including inborn errors of metabolism, involving peroxisomal and cholesterol pathways, embryopathy and chromosomal abnormalities. Several classification systems of the different types of CDP have been suggested earlier. More recently, the biochemical and molecular basis of a number of CDP syndromes has recently been elucidated and a new aetiological classification has emerged. Here we provide an updated version with an overview of the different types of CDP, a discussion of the aetiology and a description of the clinical and radiographic findings. An investigative guideline to help determine the exact diagnosis in new cases is also presented.

Normal intelligence and social interactions in a male patient despite the deletion of NLGN4X and the VCX genes

Xp22.3 deletion in males can be associated with short stature (SHOX), chondrodysplasia punctata (ARSE), mental retardation (MRX49 locus), ichthyosis (STS), Kallmann syndrome (KAL1) and ocular albinism (OA1), according to the size of the deletion. Studies of terminal and interstitial deletions in male patients with a partial nullisomy of the X chromosome have led to the identification of the VCX-3A gene at the MRX49 locus on Xp22.3. The NLGN4X gene has then been identified less than 350 kb away from VCX-3A. Nonsense mutations in NLGN4X have been associated with autism and/or moderate mental retardation in males. We report a 17-year old male patient presenting with severe ichthyosis and Kallmann syndrome related to a 3.7 Mb interstitial Xp22.3 deletion, encompassing STS and KAL1 genes, respectively. However, despite the deletion of NLGN4X and all VCX genes, including VCX-3A, our patient did not manifest any learning disabilities or behavioural problems. Therefore, our case argues against a major role of NLGN4X and the VCX genes alone in cognitive development and/or communication processes.

X-linked recessive chondrodysplasia punctata: spectrum of arylsulfatase E gene mutations and expanded clinical variability

X-linked chondrodysplasia punctata (CDPX1), due to mutations of the arylsulfatase E (ARSE) gene, is a congenital disorder characterized by abnormalities in cartilage and bone development. We performed mutational analysis of the ARSE gene in a series of 16 male patients, and we found mutations in 12 subjects. Clinical variability was observed among the patients, including severe presentations with early lethality in one of them, and symptoms such as cataract and respiratory distress. This indicates that the clinical spectrum of CDPX1, commonly considered a relatively mild form of chondrodysplasia punctata, is wider than previously reported. Different types of mutations were found among the patients examined. Three missense mutations (I80N, T481M, P578S) were expressed in Cos7 cells to study the effects on arylsulfatase E catalytic activity. These mutations caused impaired enzymatic activity suggesting that they are responsible for the disease. Two nonsense mutations, W581X in four patients and R540X in one, were found. One patient showed an insertion (T616ins). In three patients we found deletions of the ARSE gene: in one the deletion involved only the 3' end of the gene, while in two the ARSE gene was completely deleted.

Brachytelephalangic dwarfism due to the loss of ARSE and SHOX genes resulting from an X;Y translocation

Here we report an 8-year-old male patient who had mesomelic shortening of forearms and legs, brachytelephalangia and ichthyotic skin lesions. Chromosomal analysis showed an X;Y translocation involving the short arm of the X chromosome (Xp). Fluorescence in situ hybridization (FISH) and molecular studies localized the breakpoints on Xp22.3 in the immediate vicinity of the KAL gene demonstrating deletions of steroid sulfatase (STS), arylsulfatase E (ARSE), and short stature homeo box (SHOX) genes. It was suspected that the patient was suffering from chondrodysplasia punctata because of a loss of the arylsulfatase E (ARSE) gene. However, no stippled epiphyses were to be seen in the neonatal radiograph. Interestingly, this patient is the first case with a proven loss of the ARSE gene without chondrodysplasia punctata, assuming that chondrodysplasia punctata is not an obligatory sign of ARSE gene loss. Brachytelephalangia was the only result of ARSE gene deletion in this case. The patient's mother also had dwarfism and showed Madelung deformity of the forearms. She was detected as a carrier of the same aberrant X chromosome. The male patient did not show Madelung deformity, demonstrating that Lerri-Weill syndrome phenotype may be still incomplete in children with SHOX gene deletion. The wide clinical spectrum in the male and the Leri-Weill phenotype in his mother are the results of both a deletion involving several sulfatase genes in Xp22.3 and the SHOX gene located in the pseudoautosomal region. Nevertheless, there is no explanation for the absence of chondrodysplasia punctata despite the total loss of the ARSE gene. Further studies are necessary to investigate genotype/phenotype correlation in cases with translocations or microdeletions on Xp22.3, including the ARSE and the SHOX gene loci.

A member of a gene family on Xp22.3, VCX-A, is deleted in patients with X-linked nonspecific mental retardation

X-linked nonspecific mental retardation (MRX) has a frequency of 0.15% in the male population and is caused by defects in several different genes on the human X chromosome. Genotype-phenotype correlations in male patients with a partial nullisomy of the X chromosome have suggested that at least one locus involved in MRX is on Xp22.3. Previous deletion mapping has shown that this gene resides between markers DXS1060 and DXS1139, a region encompassing approximately 1.5 Mb of DNA. Analyzing the DNA of 15 males with Xp deletions, we were able to narrow this MRX critical interval to approximately 15 kb of DNA. Only one gene, VCX-A (variably charged, X chromosome mRNA on CRI-S232A), was shown to reside in this interval. Because of a variable number of tandem 30-bp repeats in the VCX-A gene, the size of the predicted protein is 186-226 amino acids. VCX-A belongs to a gene family containing at least four nearly identical paralogues on Xp22.3 (VCX-A, -B, -B1, and -C) and two on Yq11.2 (VCY-D, VCY-E), suggesting that the X and Y copies were created by duplication events. We have found that VCX-A is retained in all patients with normal intelligence and is deleted in all patients with mental retardation. There is no correlation between the presence or absence of VCX-B1, -B, and VCX-C and mental status in our patients. These results suggest that VCX-A is sufficient to maintain normal mental development.

Léri-Weill syndrome as part of a contiguous gene syndrome at Xp22.3

We report on a mother and her 5-year old son, both with a terminal deletion of the short arm of the X chromosome. By molecular genetic analysis the breakpoint was located distal to steroid sulfatase gene. The boy manifested, due to nullisomy of this region, short stature (SHOX), chondrodysplasia punctata (ARSE), and mental retardation (putative mental retardation gene MRX 49). Short stature is present in mother and son, but both also had bilateral Madelung deformity, a key finding in the Léri-Weill syndrome. We discuss the phenotype in relationship to hitherto published cases with chromosomal aberrations and contiguous gene syndromes of Xp22.3.

X-linked recessive chondrodysplasia punctata due to a new point mutation of the ARSE gene

Chondrodysplasia punctata (CP) is a heterogeneous group of bone dysplasias that are characterized by abnormal calcium deposition in areas of enchondral bone formation. The existence of an X-linked recessive form of chondrodysplasia punctata (CDPX) has been recognized in patients who are nullisomic for the Xp22.3 region, presenting with complex phenotypes. The gene of CDPX has been identified recently, and five point mutations of the gene, named ARSE, have been described. Here, we report on the clinical and molecular characterization of a patient with CDPX. The patient presented at birth with cranial and facial anomalies and short stature; an x-ray skeletal survey showed punctate calcifications and striking hand and foot abnormalities. Single strand conformation polymorphism (SSCP) and sequence analysis of the patient's DNA allowed the identification of a new mutation of the ARSE gene; this mutation causes an amino acid substitution from cysteine to tyrosine at position 492 of the ARSE predicted protein product. The clinical description of patients with CDPX due to known mutation of the ARSE is of interest for the precise delineation of the clinical spectrum of the disease.

Allergic disease as an association of steroid sulphatase deficiency

Ten of 31 patients with steroid sulphatase (STS) deficiency were found to have an allergic disease (bronchial asthma, allergic rhinitis, or atopic dermatitis). STS deficiency may predispose patients to allergic disease.

Cloning of the gene for ocular albinism type 1 from the distal short arm of the X chromosome

Ocular albinism type 1 (OA1) is an X-linked disorder characterized by severe impairment of visual acuity, retinal hypopigmentation and the presence of macromelanosomes. We isolated a novel transcript from the OA1 critical region in Xp22.3-22.2 which is expressed at high levels in RNA samples from retina, including the retinal pigment epithelium, and from melanoma. This gene encodes a protein of 424 amino acids displaying several putative transmembrane domains and sharing no similarities with previously identified molecules. Five intragenic deletions and a 2 bp insertion resulting in a premature stop codon were identified from DNA analysis of patients with OA1, indicating that we have identified the OA1 gene.

A high resolution deletion map of human chromosome Xp22

We have developed a 32-interval deletion panel for human chromosome Xp22 spanning about 30 megabases of genomic DNA. DNA samples from 50 patients with chromosomal rearrangements involving Xp22 were tested with 60 markers using a polymerase chain reaction strategy. The ensuing deletion map allowed us to confirm and refine the order of previously isolated and newly developed markers. Our mapping panel will provide the framework for mapping new sequences, for orienting chromosome walks in the region and for projects aimed at isolating genes responsible for diseases mapping to Xp22.

Enzymatic diagnosis of steroid sulfatase deficiency by high performance liquid chromatography

We established a reversed phase high performance liquid chromatographic (HPLC) method of assaying lymphocyte steroid sulfatase activity using estrone sulfate as the substrate. Application of this method for diagnosis of 8 patients allowed us to clearly distinguish the patients from the normal controls. This method is simpler and less expensive than the method previously reported, since neither radioisotope labeled substrates nor radioisotope facilities are required. We consider it to be easily used and widely available in most clinical laboratories.

Chromosomal localisation of a pseudoautosomal growth gene(s)

Although recent molecular studies in patients with sex chromosome aberrations are consistent with a growth gene(s) being present in the pseudoautosomal region (PAR), the precise location has not been determined. In this report, we describe a Japanese boy and his mother with an interstitial deletion in Xp22.3 and review the correlation between genotype and stature in six cases of partial monosomy of the PAR. The results indicate that the region from DXYS20 to DXYS15 is the critical region for the putative growth gene(s).

The gene for X-linked Kallmann syndrome: a human neuronal migration defect

A new gene from the distal short arm of the human X chromosome has recently been cloned and characterized. Mutations in this gene lead to the neuronal migration defect observed in Kallmann syndrome. Although there is no direct proof for the involvement of this gene in neuronal migration, significant similarities between its predicted protein product and neural adhesion molecules have been found. X-linked Kallmann syndrome represents the first example in vertebrates of a neuronal migration defect for which the gene has been isolated.