Partial duplication of Xp: a case report and review of previously reported cases

Autism in two females with duplications involving Xp11.22-p11.23

We present two phenotypically similar females with Xp duplication who have autism and epilepsy. Case 1 is a 14-year-old Honduran female with autism and medically refractory complex partial, secondarily generalized epilepsy. Case 2 is a 3-year-old Austrian female with autism and medically refractory complex partial epilepsy. Both patients also share features of severe intellectual disability (case 1 has a developmental quotient of 23, case 2 has a developmental quotient of 42) and dysmorphic facial features. Autism was confirmed by thorough clinical evaluations and testing. Case 1 has a karyotype of 46,X,dup(X)(p11.2-p22.33) and a highly skewed X-inactivation pattern (94:6). Brain magnetic resonance imaging (MRI) and electroencephalogram (EEG) were abnormal. Case 2 has a 5-megabase duplication of Xp11.22-p11.23 on chromosome microarray analysis. The patient has a random X-inactivation pattern (77:23). Brain MRI was normal, but EEG was abnormal. Both patients have duplications involving the Xp11.22-p11.23 region, indicating that this is an area of interest for future translational autism research.

Functional disomy of Xp: Prenatal findings and postnatal outcome

We report on trisomy of the short arm of the X chromosome (Xp11.2 --> pter) due to a de novo unbalanced X;13 translocation diagnosed prenatally in a female fetus. Amniocentesis was performed at 20-weeks' gestation following ultrasound finding of a Dandy-Walker malformation. The trisomy of Xp11.2 --> pter was confirmed with fluorescence in situ hybridization (FISH), using an X chromosome painting probe and telomeric FISH probes specific for the short arm of chromosome X. The karyotype was defined as 46,XX,der(13)t(X;13)(p11.2;p11.2). Molecular analysis suggested that the extra Xp material was of paternal origin. FISH analysis with an XIST probe showed that the derivative chromosome 13 did not include the XIST locus at the X-inactivation center (XIC). A complex phenotype was seen at birth including macrosomia, facial dysmorphism with preauricular tag, congenital heart defects, and structural brain malformations. Because the derivative chromosome was not subject to X inactivation, functional disomy of Xp11.2 --> pter most likely accounts for the abnormal phenotype in this patient.

The male pseudohermaphrodite XX polled goat is Zfy and Sry negative

The Polled mutation of the goat is inherited as an autosomal dominant trait. Homozygotes with a 60,XX karyotype develop into intersexes. We looked for the presence of Y-chromosomal sequences (Zfy and Sry) in a male pseudohermaphrodite polled goat by Southern blotting and PCR analysis. Molecular analysis revealed that this XX goat had no Sry sequence. It showed identical hybridization patterns, using the human SRY and ZFY probes at low stringency, with the normal XX female goat, whereas an XY male revealed prominent Sry and Zfy signals. Identical results were obtained from PCR analysis with the caprine Sry primers. The possible role of an autosomal recessive gene in the induction of testes and maleness is discussed.

Tall stature, gonadal dysgenesis, and stigmata of Turner's syndrome caused by a structurally altered X chromosome

Genetic analysis in a tall 14-year-old girl with gonadal dysgenesis and some stigmata of Turner's syndrome revealed a duplication of the short arm in a monocentric X chromosome with partial loss of Xq. We suggest that triple gene dosage of SHOX and estrogen deficiency caused the unique overgrowth.

Molecular cytogenetic analysis of a duplication Xp in a female with an abnormal phenotype and random X inactivation

We describe a female infant with severe abnormal phenotype with a de novo partial duplication of the short arm of the X chromosome. Chromosome painting confirmed the origin of this X duplication. Molecular cytogenetic analysis with fluorescence in situ hybridization (FISH) was performed with YAC probes, further delineating the breakpoints. The karyotype was 46, X dup(X)(p11-p21.2). Cytogenetic replication studies showed that the normal and duplicated X chromosomes were randomly inactivated in lymphocytes. In most females with structurally abnormal X chromosomes, the abnormal chromosome is inactivated and they are phenotypically apparently normal relatives of phenotypically abnormal males having dupX. Therefore, in this case, there is functional disomy of Xp11-p21.2 in the cells with an active dup(X), most likely resulting in abnormal clinical findings in the patient.

Schizophrenia susceptibility gene locus at Xp22.3

Multiple genetic loci have been implicated in the search for schizophrenia susceptibility genes, none having been proven as causal. Genetic heterogeneity is probable in the polygenic etiology of schizophrenia. We report on two unrelated Caucasian women with paranoid schizophrenia (meeting Diagnostic and Statistical Manual of Mental Disorders (DSM IV) criteria) who have an Xp22.3 overlapping deletion characterized by fluorescence in situ hybridization (FISH). Patient 1 was previously reported by us (Wyandt HE, Bugeau-Michaud L, Skare JC, Milunsky A. Partial duplication of Xp: a case report and review of previously reported cases. Amer J Med Genet 1991: 40: 280-283) to have a de novo partial duplication of Xp. At that time, she was a 24-year-old woman with short stature, irregular menses, other abnormalities suggestive of Turner syndrome, and paranoid schizophrenia. Recently, FISH analysis demonstrated that she has an inverted duplication (X)(p22.1p11.2) and a microscopic deletion (X)(p22.2p22.3) between DXS1233 and DXS7108 spanning approximately 16-18 cM. Patient 2 is a 14-year-old girl with short stature, learning disabilities, and paranoid schizophrenia. High-resolution chromosome analysis revealed a de novo deletion involving Xp22. FISH analysis showed that the deletion (X)(p22.2p22.3) spanned 10-12 cM between AFMB290XG5 and DXS1060. Given that deletions of Xp22 are not common events, the occurrence of two unrelated schizophrenia patients with an overlapping deletion of this region would be extraordinarily rare. Hence, the deletion within Xp22.3 almost certainly contains a gene involved in the pathogenesis of paranoid schizophrenia.

Molecular cytogenetic identification of four X chromosome duplications

Four cases with previously unidentified X-chromosome abnormalities were studied by standard cytogenetic techniques and FISH in order to demonstrate the origin of the extra segment on the abnormal X chromosomes. All cases were identified as X-chromosome duplications by using a chromosome-specific painting probe. Application of appropriate locus-specific DNA probes as an adjunct to GTG- and RBG-banding proved useful in defining the breakpoints and the extent of the duplications. Although the duplicated X chromosome in female cases was selectively inactivated, as demonstrated by its late-replicating pattern, abnormal clinical findings were manifested in 3 female patients.

Sex reversal in a child with duplication of sex reversing locus on the short arm of the X chromosome (Xp)

We report a child with a female phenotype possessing a karyotype of 46,XY,13p+. The child had female external genitalia, and manifested severe mental retardation, pulmonary atresia and multiple congenital abnormalities. Laparoscopy revealed the presence of streak gonads and Müllerian structures. Histological examination of the gonads showed ovarian-like stroma with immature seminiferous tubules. Chromosome and gene analyses demonstrated Xp11.23 (or 11.3)-pter duplication and an intact sex determinating factor of Y (SRY). The findings of this case suggest that duplication of Xp causes sex reversal in the presence of SRY.

Partial disomy of Xp and the presence of SRY in a phenotypic female

We present a study of a mentally retarded and mildly dysmorphic female in whom initial cytogenetic studies identified the karyotype 46,X, + mar. Further characterisation of the structurally abnormal chromosome by fluorescence in situ hybridisation (FISH) showed that it is composed of both X and Y chromosome material with a centromere originating from the Y chromosome. The presence of the DMD gene and the absence of the XIST gene was shown by FISH using locus specific probes. The Y segment included the SRY and ZFY genes. Based on these findings, the karyotype was defined as 46, X,der(Y)t(X;Y) (p21.1;q11). This case illustrates male to female sex reversal owing to a partial duplication of the short arm of the X chromosome in the presence of SRY.

Duplication Xp22.2 and pseudoisodicentric Yq detected by FISH and PCR in a sterile male

A chromosome mosaicism with two cell lines was diagnosed in a sterile man. One cell line had a 45, -Y, dup (X) (p22.2) karyotype and accounted for 83% of lymphocytes analyzed. Fluorescence in situ hybridization (FISH) analysis with specific X and Y probes excluded a translocation between the short arms of the X and Y chromosomes and showed that Xp duplication involved a region containing the DXS85 locus, distal to the ZFX and DSS sites. The other cell line consisted of a diploid karyotype with a rearranged Y chromosome, which was shown to be a pseudoisodicentric Yq by FISH. Moreover, FISH with a specific probe for the AZF locus and polymerase chain reaction using Yq SY108 and SY121 primers showed no signals for this region, possibly accounting for the azoospermia in this patient.

Partial X chromosome trisomy with functional disomy of Xp due to failure of X inactivation

A 5-month-old girl with mild phenotypic abnormalities, developmental delay, and seizures was found to have the de novo karyotype 46,XX,-13,+der(13)t(X;13)(p21.2;p11.1). The partial trisomy of Xp21.2-->pter was confirmed with fluorescence in situ hybridization, using an X chromosome painting probe and several cosmid and YAC probes for Xp sequences. Replication banding showed that one of the structurally normal X chromosomes was late-replicating, but that the Xp segment of the der(13) was early-replicating in all cells examined. Since segments of the X chromosome separated from the X inactivation center in Xq13.2 cannot undergo X inactivation, the result is functional disomy of distal Xp. As the loss of short arm material from chromosome 13 is not considered to be clinically significant, the genomic imbalance of Xp expressed in this patient most likely accounts for her abnormal phenotype.

Molecular cytogenetic analysis of a duplication Xp in a male: further delineation of a possible sex influencing region on the X chromosome

We describe a male infant with severe mental retardation and autism with a duplication of the short arm of the X chromosome. Chromosome painting confirmed the origin of this X duplication. Molecular cytogenetic analysis with fluorescence in situ hybridization (FISH) identified one copy of the zinc finger protein on the X chromosome (ZFX) and two copies of the steroid sulfatase gene (STS), further delineating the breakpoints. Based on cytogenetic and molecular comparisons of cases from the literature of sex-reversal in dup(X),Y patients and our patient, we suggest that a possible secondary sex-influencing gene involved in the regulation of sex determination or testis morphogenesis is present at the distal Xp21.1 to p21.2 region.