Novel ring chromosome composed of X‐ and Y‐derived material in a girl with manifestations of Ullrich‐Turner syndrome

We present a female infant who has a novel genetic variant of Ullrich‐Turner syndrome. Chromosome analysis on amniotic fluid cells obtained because of ultrasound observation of nuchal thickening showed 45,X in all cells. The infant was born with a low posterior hairline and moderate edema over hands and feet. Postnatal chromosome analysis demonstrated two cell lines—47% of the metaphases were 45,X, but 53% had a ring chromosome in addition to the normal X. FISH studies using alpha satellite probes, an X‐whole‐chromosome‐paint (WCP) probe, and a Y‐cocktail probe determined that the ring was composed of both X and Y sequences. FISH studies also determined that the KAL locus was present on the ring, but that XIST was absent. PCR‐based analysis of lymphocyte DNA documented that the ring contained sequences from both the short and the long arm of the Y chromosome. X‐chromosome analysis using a panel of highly polymorphic markers indicated that the ring contained material derived only from Xp22.1 to Xp21.3. No Xq material was identified on the ring, and androgen receptor‐based X‐inactivation studies suggested that the intact X chromosome was not subject to random X inactivation. Am. J. Med. Genet. 93:343–348, 2000. © 2000 Wiley‐Liss, Inc.     

Identification of WASP mutations in 14 Spanish families with Wiskott‐Aldrich syndrome

The Wiskott‐Aldrich syndrome (WAS) is an X‐linked immunodeficiency caused by mutations in the WASP gene. The disease is known to be associated with extensive clinical variability, and mutation studies indicate that genotypes are also highly variant among WAS patients. In this study, we performed mutation analysis of the WASP gene in 14 unrelated Spanish families by single strand conformation analysis (SSCA) and sequencing, resulting in the identification of a novel mutation and nine known mutations. No mutation was identified in one family. The ten different mutations include point mutations resulting in amino acid substitutions, stop codons, and small deletions and insertions causing frameshifts. Missense mutations were preferentially located in the amino‐terminal part of the protein, exons 2 and 4, whereas stop and frameshift mutations were located in the carboxyl‐terminal region, exons 10 and 11. However, in two families, two missense mutations in exon 11 were identified. Our study demonstrates that WASP genotypes have some concordance with the patients' phenotypes, although mutation 1019delC, identified in a family with several affected members, resulted in high intrafamilial clinical variability. © 2001 Wiley‐Liss, Inc.     

Identification of five novel WASP mutations in Chinese families with Wiskott-Aldrich syndrome

The Wiskott-Aldrich Syndrome (WAS) is an X-linked recessive immunodeficiency caused by mutation in the gene encoding WAS protein (WASP). The disease is characterized by eczema, thrombocytopenia and severe immunodeificency and is associated with extensive clinical heterogeneity. Mutation studies indicated that the mutated genotypes are also highly variable. In this study, we performed PCR-direct sequencing analysis of the WAS gene in six unrelated Chinese families. Five novel mutations identified, included two nonsense mutations (506C-->T, 1388-->T), a small insertion (685-686insCGCA) and two single-base deletions (384delT, 984delC). All of the mutations are predicted to lead to premature translational termination of WASP.     

The RBMX gene as a candidate for the Shashi X‐linked intellectual disability syndrome

A novel X‐linked intellectual disability (XLID) syndrome with moderate intellectual disability and distinguishing craniofacial dysmorphisms had been previously mapped to the Xq26‐q27 interval. On whole exome sequencing in the large family originally reported with this disorder, we identified a 23 bp frameshift deletion in the RNA binding motif protein X‐linked (RBMX) gene at Xq26 in the affected males (n = 7), one carrier female, absent in unaffected males (n = 2) and in control databases (7800 exomes). The RBMX gene has not been previously causal of human disease. We examined the genic intolerance scores for the coding regions and the non‐coding regions of RBMX; the findings were indicative of RBMX being relatively intolerant to loss of function variants, a distinctive pattern seen in a subset of XLID genes. Prior expression and animal modeling studies indicate that loss of function of RBMX results in abnormal brain development. Our finding putatively adds a novel gene to the loci associated with XLID and may enable the identification of other individuals affected with this distinctive syndrome.     

Linkage analysis in Spanish families with nonspecific X‐linked mental retardation: Significant linkage at Xq13–q21

Mental retardation (MR) is a genetically heterogeneous, clinically variable condition. Many cases of MR are linked to the X chromosome. The aim of this study was to identify candidate loci for nonspecific MR in Spanish samples. We selected seven families with nonspecific MR and a pattern of inheritance compatible with an X‐linked disorder and a group of 26 sib pairs of mentally retarded individuals. We performed linkage analysis with a panel of 15 markers evenly distributed along the X chromosome. The study showed linkage to marker DXS8076, located in Xq21.1, by the lod score method (z = 2.11 at θ = 0.155) and the nonparametric extended relative pair analysis method (χ² = 5.32; P < 0.03). Genetic heterogeneity was found, with an estimated 75% of the families linked at recombination fraction θ = 0.10 to the DXS8076 locus (χ² = 9.51; P < 0.009). Xq13–q21 is one of the critical regions for X‐linked MR previously reported, and our study supports the idea that this region may contain a locus for MR in Spanish patients. © 2001 Wiley‐Liss, Inc.     

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. © 2001 Wiley‐Liss, Inc.     

Osteopathia striata cranial sclerosis: Non‐random X‐inactivation suggestive of X‐linked dominant inheritance

Osteopathia striata with cranial sclerosis (OS‐CS) is a rare syndrome comprising macrocephaly, minor anomalies, conductive hearing loss, and mild mental retardation. The diagnosis is based on radiological findings, including cranial sclerosis and longitudinal striations of metaphyses of long bones. Here we report on 10 new cases of OS‐CS, including two sporadic cases and three families, with an excess of affected females (9F/1M). Phenotypic variability was observed in our patients as well as several unusual findings. Hirschsprung disease, Pierre Robin sequence, coronal craniostenosis, and laryngotracheomalacia were associated with a poor prognosis. The X‐inactivation pattern of peripheral blood lymphocytes in a mildly affected mother and her severely affected boy demonstrated a non‐random X‐inactivation in the mother. This finding, in combination with a sex ratio in favor of females and an increased morbidity and mortality in males, is highly suggestive of X‐linked dominant inheritance. © 2001 Wiley‐Liss, Inc.     

Association between a polymorphism in the pseudoautosomal X‐linked gene SYBL1 and bipolar affective disorder

In the past decade, several chromosomal regions have been analyzed for linkage with bipolar affective disorder (BPAD). There have been conflicting results regarding the involvement of X‐chromosomal regions in harboring susceptibility genes for BPAD. Recently, a new candidate gene (SYBL1) for BPAD has been described on Xq28. SYBL1, which maps to the Xq pseudoautosomal region (PAR), encodes a member of the synaptobrevin family of proteins involved in synaptic vesicle docking, exocytosis, and membrane transport. A subsequent case‐control association study, including 110 US‐American patients with BPAD and 119 unrelated controls, investigated a potential etiological role of a novel polymorphism (G→C transversion) in a regulatory region of the SYBL1 gene. In this analysis, the C allele showed a statistical trend to be more frequent in males with BPAD than in respective controls (P = 0.06). This finding prompted us to verify whether a similar effect was also present in a larger German sample of 164 unrelated patients with BPAD (148 patients with BP I disorder, 16 patients with BP II disorder) and 267 controls. We observed a significantly increased frequency of genotypes homozygous for the C allele in females with BPAD in comparison with controls (P = 0.017). Thus, our data strengthen the role of the SYBL1 gene as a candidate gene for BPAD. © 2001 Wiley‐Liss, Inc.     

Maternal germinal mosaicism of X‐linked agammaglobulinemia

X‐linked agammaglobulinemia (XLA) is an immunodeficiency caused by abnormalities in tyrosine kinase (BTK), and is characterized by a deficiency of peripheral blood B cells. We studied cytoplasmic expression of BTK protein and analyzed the BTK gene (BTK) in peripheral blood mononuclear cells from two siblings with XLA and additional family members. Cytoplasmic expression of BTK protein in monocytes was not detected in either patient with XLA. A single base deletion (C563) in BTK‐exon 6, which encodes the TH domain, was identified in both XLA patients. However, normal cytoplasmic expression of BTK protein in monocytes was detected in their mother without any BTK mutation. These results strongly suggest germinal mosaicism in the mother. © 2001 Wiley‐Liss. Inc.     

Uruguay facio‐cardio‐musculo‐skeletal syndrome: A novel X‐linked recessive disorder

We report on three male patients from a single family with a brachyturricephaly, “pugilistic” facial appearance, a muffled voice, cardiomyopathy, muscular hypertrophy, broad hands, wide feet with progressive pes cavus deformities, dislocation of toes, variable congenital hip dislocation, and scoliosis. Three other males in the family, now deceased from cardiac disease, appear to have had the same disorder. The mother of the propositus has milder signs of the syndrome. All affected males are related through the maternal line. These cases represent an apparently previously undescribed X‐linked recessive syndrome. Am. J. Med. Genet. 95:247–265, 2000.     

Phenotypic variation in Melnick‐Needles syndrome is not reflected in X inactivation patterns from blood or buccal smear

Melnick‐Needles syndrome is a rare putative X‐linked dominant bone dysplasia. The patients have short stature, characteristic facial features, and a normal intelligence. The skeletal dysplasia includes S‐shaped curvature of tubular bones and sclerosis of the base of the skull. The phenotype of affected individuals varies, even within families. This could be related to X chromosome inactivation. We report here on a very mildly affected mother and her two severely affected daughters with characteristic features of Melnick‐Needles syndrome. In addition, the two daughters had very similar pigmented nevi on their back. X chromosome inactivation analysis of blood DNA revealed a skewed X inactivation pattern in all three affected females, with the normal X chromosome as the predominating active X chromosome. The X inactivation pattern was similar in buccal smear and blood DNA in the mother and one of the daughters, whereas the other daughter had a skewed pattern in blood only. X chromosome inactivation in blood and buccal smear DNA therefore does not explain the phenotypic variation in this family. The skewed X chromosome inactivation is in agreement with X‐linked inheritance of Melnick‐Needles syndrome and suggests a critical role of the Melnick‐Needles gene in hematopoietic cell proliferation. Clinical evidence indicates that Melnick‐Needles syndrome is allelic to the otopalatodigital syndromes, which have been assigned to Xq26‐28. Haplotype analysis of the X chromosomes in this family was in agreement with the localization of the gene for Melnick‐Needles syndrome to Xq25‐qtel. © 2002 Wiley‐Liss, Inc.     

Clinical and genetic analysis of patients with X‐linked hyper‐IgM syndrome

Congenital adrenal hyperplasia (CAH) due to 21‐hydroxylase deficiency (21‐OHD) is a common autosomal recessive disorder caused by mutations in the CYP21A2 gene. The carrier frequency of CYP21A2 mutations has been estimated to be 1:25 to 1:10 on the basis of newborn screening. The main objective of this study was to determine the carrier frequency in the Cypriot population of mutations in the CYP21A2 gene. Three hundred unrelated subjects (150 males and 150 females) from the general population of Cyprus were screened for mutations in the CYP21A2 gene and its promoter. The CYP21A2 genotype analysis identified six different mutants and revealed a carrier frequency of 9.83% with the mild p.Val281Leu being the most frequent (4.3%), followed by p.Qln318stop (2.5%), p.Pro453Ser (1.33%), p.Val304Met (0.83%), p.Pro482Ser (0.67%) and p.Met283Val (0.17%). The notable high CYP21A2 carrier frequency of the Cypriot population is one of the highest reported so far by genotype analysis. Knowledge of the mutational spectrum of CYP21A2 will enable to optimize mutation detection strategy for genetic diagnosis of 21‐OHD not only in Cyprus, but also the greater Mediterranean region.