No mutations in the coding region of the Rett syndrome gene MECP2 in 59 autistic patients.

Autistic disorder is a pervasive developmental disorder considered to have a multigenic origin. Mental retardation is present in 75% of autistic patients. Autistic features are found in Rett syndrome, a neurological disorder affecting girls and associated with severe mental retardation. Recently, the gene responsible for the Rett syndrome, methyl CpG-binding protein (MECP2) gene, was identified on the X chromosome by a candidate gene strategy. Mutations in this gene were also observed in some mentally retarded males. In this study we tested MECP2 as a candidate gene in autistic disorder by a DGGE analysis of its coding region and intron-exon boundaries. Among 59 autistic patients, 42 males and 17 females, mentally retarded or not, no mutations or polymorphisms were present in the MECP2 gene. Taking into account the size of our sample, we conclude that MECP2 coding sequence mutations are not an important factor (less than 5% of cases) in the aetiology of autistic disorder.     

X chromosome inactivation pattern in female carriers of X linked hypophosphataemic rickets.

X linked hypophosphataemia (XLH) results from an abnormality of renal tubular phosphate reabsorption. The disorder is inherited as an X linked dominant trait and the gene has been mapped to Xp22.1-p22.2. A candidate gene (PEX) has recently been isolated. The most striking clinical features are growth retardation and skeletal abnormalities. As expected for X linked dominant disorders, females are less affected. However, such a gene dosage effect does not exist for renal phosphate reabsorption. Preferential X chromosome inactivation has been proposed as a possible explanation for this lack of gene dosage. We have examined the X inactivation pattern in peripheral blood cells from 12 females belonging to seven families with XLH using PCR analysis at the androgen receptor locus. The X inactivation pattern in these patients did not differ significantly from the pattern in 30 healthy females. The X inactivation pattern in peripheral blood cells does not necessarily reflect the X inactivation pattern in renal cells. However, the finding of a normal distribution of X inactivation in peripheral blood cells indicates that the similarity in the renal handling of phosphate in male and female patients is not related to a ubiquitous preferential X inactivation.     

Microarray comparative genomic hybridization analysis of 59 patients with schizophrenia

Schizophrenia is a common psychiatric disorder with a strong genetic contribution. Disease-associated chromosomal abnormalities in this condition may provide important clues, such as DISC1. In this study, 59 schizophrenia patients were analyzed by microarray comparative genomic hybridization (CGH) using custom bacterial artificial chromosome (BAC) microarray (4,219 BACs with 0.7-Mb resolution). Chromosomal abnormalities were found in six patients (10%): 46,XY,der(13)t(12;13)(p12.1; p11).ish del(5)(p11p12); 46,XY, ish del(17)(p12p12); 46,XX.ish dup(11)(p13p13); and 46,X,idic(Y)(q11.2); and in two cases, mos 45,X/46XX. Autosomal abnormalities in three cases are likely to be pathogenic, and sex chromosome abnormalities in three follow previous findings. It is noteworthy that 10% of patients with schizophrenia have (sub)microscopic chromosomal abnormalities, indicating that genome-wide copy number survey should be considered in genetic studies of schizophrenia.     

MECP2 mutations account for most cases of typical forms of Rett syndrome

Rett syndrome (RTT) is a severe progressive neurological disorder that affects almost exclusively females, with an estimated prevalence of approximately one in 10 000-15 000 female births. Most cases are sporadic, but several reports about familial recurrence support X-linked dominant inheritance with male lethality. The gene responsible for this disorder, MECP2, was recently identified by candidate gene strategy. Mutations were detected in <25% of RTT cases in this first report. To characterize the spectrum of mutations in the MECP2 gene in RTT patients, we selected 46 typical RTT patients and performed mutation screening by denaturing gradient gel electrophoresis combined with direct sequencing. We identified 30 mutations, accounting for 65% of RTT patients. They include 12 novel mutations (11 located in exon 3 and one in exon 2). Mutations, such as R270X and frameshift deletions in a (CCACC) (n) rich region, have been found with multiple recurrences. Most of the mutations were de novo, except in one family where the non-affected transmitter mother exhibited a bias of X inactivation. Although this study showed that MECP2 mutations account for most cases of typical forms of RTT (65%) and mutations in non-coding regions cannot be excluded for the remaining cases, an alternative hypothesis that takes into account the homogeneous phenotype and exclusive involvement of females, could be the implication in RTT of a putative second X-linked gene.     

Risk Factors,Treatment, and Immune Dysregulation in Autoimmune Cytopenia after Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients

Autoimmune or alloimmune cytopenia (AIC) is a known rare complication of hematopoietic stem cell transplantation (SCT). AIC after SCT is considered difficult to treat and is associated with high morbidity and mortality. In this retrospective study in pediatric patients we evaluated incidence, outcome, potential risk factors, and current treatment strategies. A nested matched case-control study was performed to search for biomarkers associated with AIC. Of 531 consecutive SCTs at our center between 2000 and 2016, 26 were complicated by the development of AIC (cumulative incidence, 5.0%) after a median of 5 months post-SCT. Autoimmune hemolytic anemia was the most common AIC with 12 patients (46%). We identified nonmalignant disease, alemtuzumab serotherapy pre-SCT, and cytomegalovirus (CMV) reactivation as independently associated risk factors. The cytokine profile of patients at the time of AIC diagnosis appeared to skew toward a more pronounced Th 2 response compared with control subjects at the corresponding time point post-SCT. Corticosteroids and intravenous immunoglobulin as first-line treatment or a wait-and-see approach led to resolution of AIC in 35% of cases. Addition of step-up therapies rituximab (n?=?15), bortezomib (n?=?7), or sirolimus (n?=?3) was associated with AIC resolution in 40%, 57%, and 100% of cases, respectively. In summary, we identified CMV reactivation post-SCT as a new clinical risk factor for the development of AIC in children. The cytokine profile during AIC appears to favor a Th 2 response. Rituximab, bortezomib, and sirolimus are promising step-up treatment modalities.     

A Rett syndrome patient with a ring X chromosome: further evidence for skewing of X inactivation and heterogeneity in the aetiology of the disease

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder, characterised by regression of development in young females. Recently, mutations in the MECP2 gene were found to be present in 80% of sporadic cases, but in much lower frequency (< 30%) among familial cases. Several reports claim that the pattern of X chromosome inactivation (XCI) relates to the penetrance of RTT; in some cases skewed XCI is seen in Rett patients, and in others it is observed among normal carriers. We present here a case of RTT with a 46,X,r(X) in which complete skewed inactivation of the ring was demonstrated. Further, no mutations were found in the MECP2 gene present on the intact X. Our data, in conjunction with two previously published cases of X chromosome abnormalities in RTT, indicate that X chromosome rearrangements are sporadically associated with RTT in conjunction with extreme skewing of X inactivation. Based on our case and reported data, we discuss the evidence for a second X-linked locus for RTT associated with lower penetrance, and a different pattern of XCI, than for MECP2. This would result in a larger proportion of phenotypically normal carrier women transmitting the mutation for this putative second locus, and account for the minority of sporadic and majority of familial cases that are negative for MECP2 mutations.     

Breakpoint determination of X;autosome balanced translocations in four patients with premature ovarian failure

Premature ovarian failure (POF) is a disorder characterized by amenorrhea and elevated serum gonadotropins before 40 years of age. As X chromosomal abnormalities are often recognized in POF patients, defects of X-linked gene may contribute to POF. Four cases of POF with t(X;autosome) were genetically analyzed. All the translocation breakpoints were determined at the nucleotide level. Interestingly, COL4A6 at Xq22.3 encoding collagen type IV alpha 6 was disrupted by the translocation in one case, but in the remaining three cases, breakpoints did not involve any X-linked genes. According to the breakpoint sequences, two translocations had microhomology of a few nucleotides and the other two showed insertion of 3-8 nucleotides with unknown origin, suggesting that non-homologous end-joining is related to the formation of all the translocations.     

1.4 Mb candidate gene region for X linked dyskeratosis congenita defined by combined haplotype and X chromosome inactivation analysis.

Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the early onset of reticulate skin pigmentation, nail dystrophy, and mucosal leucoplakia. In over 80% of cases bone marrow failure develops and this is the main cause of early mortality. The DC1 gene responsible for the X linked form (MIM 305000) of dyskeratosis congenita has been mapped to Xq28. In order to narrow the candidate gene region, genetic linkage analysis was performed in eight X linked pedigrees using a set of markers spanning Xq28. A maximum lod score of 5.31 with no recombinations was achieved with marker DXS1073. Two recombination events were identified; one of these uses X chromosome inactivation pattern analysis to determine carrier status and haplotype analysis to fine map the recombination breakpoint. The fine mapping of these recombination events has enabled the candidate gene region for X linked dyskeratosis congenita to be defined as the 1.4 Mb interval between Xq3274 and DXS1108.     

Deletion of VCX-A due to NAHR plays a major role in the occurrence of mental retardation in patients with X-linked ichthyosis

X-linked ichthyosis (XLI) is often associated with a recurrent microdeletion at Xp22.31 due to non-allelic homologous recombination between the CRI-S232 low-copy repeat regions flanking the STS gene. The clinical features of these patients may include mental retardation (MR) and the VCX-A gene has been proposed as the candidate MR gene. Analysis of DNA from four XLI patients with MR by array-comparative genomic hybridization (array-CGH) on a 150 kb resolution X chromosome-specific array revealed a 1.5 Mb interstitial microdeletion with breakpoints in the CRI-S232 repeat sequences, each of which harbors a VCX gene. We demonstrate that the recombination sites in all four cases are situated in the 1 kb repeat unit 2 region present at the 3' ends of the VCX-A and VCX-B genes thereby deleting VCX-A and VCX-B1 but not VCX-B and VCX-C. Array-CGH with DNA of an XLI patient with MR and an inherited t(X;Y)(p22.31;q11.2) showed an Xpter deletion of 8.0 Mb resulting in the deletion of all four VCX genes and duplication of both VCY homologs. These data confirm the role of VCX-A in the occurrence of MR in XLI patients. Moreover, we propose a VCX/Y teamwork-dependent mechanism for the incidence of mental impairment in XLI patients.     

A novel phenotype characterized by digital abnormalities,intellectual disability,and short stature in a Mexican family maps to Xp11.4–p11.21

The family observed in this study included affected males and asymptomatic females. The patients shared specific digital abnormalities including postaxial polydactyly, cutaneous syndactyly, and brachydactyly. In addition, the patients exhibited mild‐to‐moderate intellectual disability and short stature coupled with microbrachycephaly, scoliosis, and cerebellar and renal hypoplasia. No chromosomal alterations or copy number variations were found in the index case. The genetic linkage analysis, which focused on the X chromosome, and the haplotype analysis detected a ～15.74 Mb candidate region located at Xp11.4–p11.21 with a LOD score of 4.8. Additionally, half of the mothers showed skewed X‐inactivation, while the other mothers exhibited random inactivation patterns. The candidate region includes 28 protein‐encoding genes that have not yet been implicated in human disorders. We speculate that the observed phenotype is compatible with a monogenic disorder in which the mutant gene plays a significant role during embryonic development. Based on the patients' clinical features, image studies, pedigree, chromosome location, and X‐inactivation studies in the mothers, we propose that this family has a novel, specific syndrome with an X‐linked recessive mode of inheritance. © 2013 Wiley Periodicals, Inc.     

Candidate genes in polycystic ovary syndrome

The candidate gene approach has already paid some dividends in trying to understand the complex genetics of polycystic ovary syndrome (PCOS). In terms of steroidogenic abnormalities, CYP11a-encoding P450 side chain cleavage-appears to be a major susceptibility locus. In relation to the well-described metabolic disturbances in PCOS, the insulin gene variable number tandem repeat (VNTR) appears to be a promising candidate, at least in populations studied in the UK. Finally, genes implicated in ovarian follicular development may have a role in the aetiology of PCOS, as demonstrated by recent identification of the follistatin gene as a potential disease locus. It seems unlikely that PCOS can be explained on the basis of a single gene disorder although, in a given family, one gene may have a predominant effect. An oligogenic model seems the most appropriate basis on which to understand the genetic origins of this very common disorder. The candidate gene approach has been useful to date, but it may prove important in the near future to perform an anonymous genome-wide scan to identify hitherto unheralded susceptibility loci.     

Case with autistic syndrome and chromosome 22q13.3 deletion detected by FISH

Autism is a rare neurodevelopmental disorder with a strong genetic component. Co-occurrence of autism and chromosomal abnormalities is useful to localize candidate regions that may include gene(s) implicated in autism determinism. Several candidate chromosomal regions are known, but association of chromosome 22 abnormalities with autism is unusual. We report a child with autistic syndrome and a de novo 22q13.3 cryptic deletion detected by FISH. Previously described cases with 22q13.3 deletions shared characteristic developmental and speech delay, but autism was not specifically reported. This case emphasizes a new candidate region that may bear a gene involved in autism etiopathogenesis. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:839-844, 2000.     

The FG syndrome: report of a large Italian series

Initially described as a rare MCA/MR syndrome occurring only in boys, due to a recessive mutation on the X chromosome [Opitz and Kaveggia, 1974], the FG syndrome (FGS) now emerges as a more common disorder also occurring in girls. Based on over 50 reported cases, FGS is associated with developmental delay (especially speech), hypotonia, postnatal onset relative macrocephaly, prominent forehead, frontal hair upsweep, telecanthus, or ocular hypertelorism, thin vermilion border of the upper lip, relatively short fingers with broad thumbs and halluces, persistent fetal fingertip pads, anal anomalies, and/or constipation. Major malformations are rare, and include pyloric stenosis, anal agenesis, cryptorchidism, hypospadias, and congenital heart defects. Abnormal EEGs and seizures have been reported in almost 70% of patients. Brain MRI shows corpus callosum abnormalities associated with dilatation of lateral ventricles and, less frequently, periventricular nodular heterotopias, mild cerebellar defects, and reduced periventricular white matter. Chiari 1 malformation seems to be frequent. The behavior phenotype appears to be characterized by ADHD, and relatively less developed language, fine motor and executive function skills; whereas visual-spatial abilities seem to be a relative strength. Five candidate loci are already known but no gene identified. We describe 25 patients referred to the Stella Maris Institute for evaluation of DD/MR, and diagnosed as FGS. They were between 2 and 15 1/2 years at the first observation. High resolution banding, FRAXA/FRAXE DNA analysis, and subtelomere FISH analysis were performed in all of them, and all had normal results. Thirteen patients were followed-up from 6 months to 9 years. Our report focuses on physical, neurological, developmental findings, and natural history of FGS. Experience with our series of patients suggests that the syndrome may be common, and should be routinely considered in the evaluation of children and adolescents with DD/MR.     

Identification of differentially expressed genes in blood cells of narcolepsy patients

STUDY OBJECTIVE: A close association between the human leukocyte antigen (HLA)-DRB1*1501/DQB1*0602 and abnormalities in some inflammatory cytokines have been demonstrated in narcolepsy. Specific alterations in the immune system have been suggested to occur in this disorder. We attempted to identify alterations in gene expression underlying the abnormalities in the blood cells of narcoleptic patients. DESIGNS: Total RNA from 12 narcolepsy-cataplexy patients and from 12 age- and sex-matched healthy controls were pooled. The pooled samples were initially screened for candidate genes for narcolepsy by differential display analysis using annealing control primers (ACP). The second screening of the samples was carried out by semiquantitative PCR using gene-specific primers. Finally, the expression levels of the candidate genes were further confirmed by quantitative real-time PCR using a new set of samples (20 narcolepsy-cataplexy patients and 20 healthy controls). RESULTS: The second screening revealed differential expression of 4 candidate genes. Among them, MX2 was confirmed as a significantly down-regulated gene in the white blood cells of narcoleptic patients by quantitative real-time PCR. CONCLUSION: We found the MX2 gene to be significantly less expressed in comparison with normal subjects in the white blood cells of narcoleptic patients. This gene is relevant to the immune system. Although differential display analysis using ACP technology has a limitation in that it does not help in determining the functional mechanism underlying sleep/wakefulness dysregulation, it is useful for identifying novel genetic factors related to narcolepsy, such as HLA molecules. Further studies are required to explore the functional relationship between the MX2 gene and narcolepsy pathophysiology.     

Cryptic Xp duplication including the SHOX gene in a woman with 46,X, del(X)(q21.31) and premature ovarian failure

BACKGROUND: Premature ovarian failure (POF) is defined as amenorrhoea for >6 months, occurring before the age of 40, with an FSH serum level in the menopausal range. Although Xq deletions have been known for a long time to be associated with POF, the mechanisms involved in X deletions in order to explain ovarian failure remain unknown. In order to look for potentially cryptic chromosomal imbalance, we used high-resolution genomic analysis to characterize X chromosome deletions associated with POF. METHODS: Three patients with POF presenting terminal Xq deletions detected by conventional cytogenetics were included in the study. Genome wide microarray comparative genomic hybridization (CGH) at a resolution of 1 Mb and fluorescence in situ hybridization (FISH) was performed. RESULTS: Microarray CGH and FISH studies characterized the three deletions as del(X)(q21.2), del(X)(q21.31) and del(X)(q22.33). Microarray CGH showed that the del(X)(q21.31) was also associated with a Xpter duplication including the SHOX gene. In these patients with POF, deletions or duplications of autosomes have been excluded. CONCLUSION: This study is the first one using microarray in patients with POF. It demonstrates that putative X chromosome deletions can be associated with other chromosomal imbalances such as duplications, and therefore illustrates the use of microarray CGH to screen chromosomal abnormalities in patients with POF.     

Prenatal diagnosis of de novo X;autosome translocations

The identification of a de novo apparently balanced structural chromosome rearrangement at prenatal diagnosis can be problematic and raises unique genetic counseling issues. Two breakpoint rearrangements such as reciprocal translocations or inversions have a 6.7% empiric risk of phenotypic abnormality. Abnormal phenotypes are thought to result from gene disruption, position effect, or deletion at one of the breakpoints. Prenatal diagnosis of de novo X;autosome translocations is rare, and presents additional unique risks due to the effects of X-inactivation and the possibility of disruption of the single active copy of an X-linked gene. We report the identification of a de novo apparently balanced t(X;6)(q26;q23) ascertained after amniocentesis for advanced maternal age. The parents were counseled regarding the risk of a de novo apparently balanced translocation, including the potential risk of an X-linked Mendelian disorder resulting from disruption of a gene at the Xq26 breakpoint. While the normal X chromosome was late replicating in all metaphases, no conclusions from this data could be drawn as the X-inactivation ratio in amniocytes might not be representative of other tissues. The possibility of future premature ovarian failure was also noted due to the position of the breakpoint at Xq26, although no specific risk could be ascribed. The parents elected to continue the pregnancy, and at 17 months of age, the proband was phenotypically and developmentally normal. Long-term follow-up will be required to assess development delay and any fertility issues. Based on review of the few cases reported to date and excluding any risk for later reproductive abnormalities, we estimated the risk of phenotypic abnormality or developmental delay in a prenatally ascertained de novo X;autosome carrier to be as high as 50%. This case illustrates the complexities in counseling for prenatally ascertained de novo X;autosome translocations and the need for additional cases to be reported.     

Excess of high activity monoamine oxidase A gene promoter alleles in female patients with panic disorder

A genetic contribution to the pathogenesis of panic disorder has been demonstrated by clinical genetic studies. Molecular genetic studies have focused on candidate genes suggested by the molecular mechanisms implied in the action of drugs utilized for therapy or in challenge tests. One class of drugs effective in the treatment of panic disorder is represented by monoamine oxidase A inhibitors. Therefore, the monoamine oxidase A gene on chromosome X is a prime candidate gene. In the present study we investigated a novel repeat polymorphism in the promoter of the monoamine oxidase A gene for association with panic disorder in two independent samples (German sample, n = 80; Italian sample, n = 129). Two alleles (3 and 4 repeats) were most common and constituted >97% of the observed alleles. Functional characterization in a luciferase assay demonstrated that the longer alleles (3a, 4 and 5) were more active than allele 3. Among females of both the German and the Italian samples of panic disorder patients (combined, n = 209) the longer alleles (3a, 4 and 5) were significantly more frequent than among females of the corresponding control samples (combined, n = 190, chi2 = 10.27, df = 1, P = 0.001). Together with the observation that inhibition of monoamine oxidase A is clinically effective in the treatment of panic disorder these findings suggest that increased monoamine oxidase A activity is a risk factor for panic disorder in female patients.     

Molecular analysis of a new translocation, t(X;14)(q28;q11), in premalignancy and in leukaemia associated with ataxia telangiectasia.

The disease ataxia telangiectasia (A-T) is a multifaceted disorder in which patients have an increased chance of developing a T-cell leukaemia, often with abnormalities of chromosome 14, but sometimes with rare translocations, like t(X;14)(q28;q11). We describe the cloning of the breakpoint of one such novel t(X;14) from an A-T patient. The translocation breaks within the T cell receptor alpha chain gene on chromosome 14 at band q11 and in a region of the X chromosome, within about 1 Mb of the telomere of the long arm. The patient subsequently developed T-cell prolymphocytic leukaemia (T-PLL), and molecular examination showed that the tumour cells carried the same t(X;14) breakpoint as that cloned from the premalignant cells. The same breakpoint could be detected in blood samples taken as much as 5 years prior to diagnosis of T-PLL. This suggests a role for the abnormality in the tumour development in this patient but implies that other mutational events were necessary for overt disease to become manifest.     

Comprehensive genetic analysis of OEIS complex reveals no evidence for a recurrent microdeletion or duplication

Omphalocele-exstrophy of the bladder-imperforate anus-spinal defects (OEIS) complex, or cloacal exstrophy (EC), is a rare constellation of malformations in humans involving the urogenital, gastrointestinal, and skeletal systems, and less commonly the central nervous system. Although OEIS complex is well-recognized in the clinical setting, there remains a significant lack of understanding of this condition at both the developmental and the genetic level. While most cases are sporadic, familial cases have been reported, suggesting that one or more specific genes may play a significant role in this condition. Several developmental mechanisms have been proposed to explain the etiology of OEIS complex, and it is generally considered to be a defect early in caudal mesoderm development and ventral body wall closure. The goal of this study was to identify genetic aberrations in 13 patients with OEIS/EC using a combination of candidate gene analysis and microarray studies. Analysis of 14 candidate genes in combination with either high resolution SNP or oligonucleotide microarray did not reveal any disease-causing mutations, although novel variants were identified in five patients. To our knowledge, this is the most comprehensive genetic analysis of patients with OEIS complex to date. We conclude that OEIS is a complex disorder from an etiological perspective, likely involving a combination of genetic and environmental predispositions. Based on our data, OEIS complex is unlikely to be caused by a recurrent chromosomal aberration.