De novo X;Y translocation associated with imperforate anus and retinal pigmentary abnormalities

Long-term follow-up of females with unbalanced X;Y translocations-reproductive and nonreproductive consequences

Background

Females with Xp;Yq translocations manifest short stature and normal fertility, but rarely have follow-up. The study purpose was to define the phenotype of a family with t(X;Y)(p22.3;q11.2), determine long-term reproductive function, and compare to all reported female cases.

Methods

Comprehensive clinical and molecular analyses were performed on the female proband, who had regular menses, normal endocrine function, and three pregnancies spanning seven years--a normal liveborn male and two with unbalanced translocations (liveborn female and stillborn male).

Results

The translocation truncated KAL1 and deleted 44 genes on der(X). Our report constitutes the longest follow-up of an X;Y translocation female. She had no evidence of Kallmann syndrome, gonadoblastoma, or cardiovascular disease. Detailed analysis of 50 published female cases indicated a uniform lack of follow-up and significant morbidity—intellectual disability (10%), facial dysmorphism (28%), eye abnormalities (14%), and skeletal defects (28%).

Conclusions

Our findings indicate normal ovarian function to date in a woman with an t(X;Y)(p22.3;q11.2). However, additional published studies in the literature suggest careful follow-up is necessary and contradict the generalization that females with Xp;Yq translocations are usually normal except for short stature.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-015-0112-0) contains supplementary material, which is available to authorized users.

FISH deletion mapping defines a single location for the Y chromosome stature gene, GCY

At least 1 in 1000 males lacks part of the long arm of the Y chromosome. This chromosomal aberration is often associated with short stature and infertility. Deletion mapping and genotype-phenotype analysis have previously defined two non-overlapping critical regions for growth controlling gene(s), GCY(s), on the euchromatic portion of the Y chromosome long arm. These initial mapping assignments were based on the analysis of patients carrying a pure 46,XYq- karyotype as defined by classical cytogenetic karyotyping. Four genes have been assigned to the distal one of the two critical regions. To determine whether one or both of these two critical regions harbours GCY and whether one of the four genes assigned to the distal region is involved in determination of stature, nine adult patients with Yq chromosomal abnormalities were studied in detail. By PCR and FISH analysis, we showed that all patients with a previously defined pure 46,XYq- karyotype are actually mosaics with cells containing an idic(Y) or ring(Y) chromosome in association with 45,X0 cells. This leads us to conclude that (1) FISH is an absolute prerequisite for the correct identification of Y chromosomal rearrangements and (2) only patients with interstitial Y deletions are reliable predictors for the physical location of stature gene(s) on Yq. Our molecular analyses of chromosomes from patients with interstitial Yq deletions finally establishes the proximal interval between markers DYZ3 and DYS11 as the only GCY critical interval. No functional gene has so far been identified in this region adjacent to the centromere.

Characterization and physical mapping in human and mouse of a novel RING finger gene in Xp22

Microphthalmia with linear skin defects (MLS) is an X-linked dominant male-lethal syndrome caused by different deletions of chromosome Xp22. Through the screening of cDNA libraries with the cross-species conserved marker 61B3-R (DXS1141), we identified a new gene at the telomeric breakpoint of the MLS critical region, which encodes a transcript containing a RING finger domain. This novel gene was independently cloned by another group and found to be mutated in Opitz syndrome. In this study we characterized the expression pattern of this gene, identified various splice variants, delineated its exon-intron boundaries, and determined that it is not mutated in either Aicardi or Goltz syndrome, two X-linked dominant conditions with phenotypes that overlap with that of MLS syndrome. This novel RING finger gene is expressed throughout mouse embryonic development, with the highest levels of expression in E7-E11. FISH and hybridization to mouse YACs confirmed human and mouse synteny in the order of this gene and other genes in the MLS critical region; however, this gene spans the boundary of the pseudoautosomal region in mouse but not in humans.

Opitz G/BBB syndrome, a defect of midline development, is due to mutations in a new RING finger gene on Xp22

Opitz syndrome (OS) is an inherited disorder characterized by midline defects including hypertelorism, hypospadias, lip-palate-laryngotracheal clefts and imperforate anus. We have identified a new gene on Xp22, MID1 (Midline 1), which is disrupted in an OS patient carrying an X-chromosome inversion and is also mutated in several OS families. MID1 encodes a member of the B-box family of proteins, which contain protein-protein interaction domains, including a RING finger, and are implicated in fundamental processes such as body axis patterning and control of cell proliferation. The association of MID1 with OS suggests an important role for this gene in midline development.

Molecular studies of an X;Y translocation chromosome in a woman with deletion of the pseudoautosomal region but normal height

A translocation chromosome in a woman with the karyotype 46,X,der(X)t(X;Y)(p22.3; q11.2) was investigated by FISH and STS analysis with molecular probes derived from the sex chromosomes. Due to the partial deletion of the short arm pseudoautosomal region (PAR1) from DXYS14 to DXYS147 in the translocation chromosome, the proband is hemizygous for the gene responsible for growth control (SS) located in this region, yet does not show growth retardation. Molecular analysis of the Yq arm of the translocation chromosome revealed the presence of markers DYS273 to DYS246 harboring the hypothesized growth control gene critical region (GCY) on Yq, thereby placing the deletion breakpoint between markers DYS11 and DYS273. These results suggest that the Y-specific growth gene GCY on Yq compensates for the missing growth gene SS on Xp22.3.

Phenotype/karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

Over 600 cases with a Y aneuploidy (other than non-mosaic 47,XYY) were reviewed for phenotype/karyotype correlations. Except for 93 prenatally diagnosed cases of mosaicism 45,X/46,XY (79 cases), 45,X/47,XYY (8 cases), and 45,X/46,XY/47,XYY (6 cases), all other cases were ascertained postnatally. Special emphasis was placed on structural abnormalities. This review includes 11 cases of 46,XYp-; 90 cases of 46,XYq- (52 cases non-mosaic; 38 cases 45,X mosaic); 34 cases of 46,X,r(Y) (9 cases non-mosaic and 25 cases 45,X mosaic); 8 cases of 46,X,i(Yp) (4 non-mosaic and 4 mosaic with 45,X); 12 cases of 46,X,i(Yq) (7 non-mosaic and 5 mosaic); 44 cases of 46,X,idic(Yq); 80 cases of 46,X, idic(Yp) (74 cases had breakpoints at Yq11 and 6 cases had breakpoints at Yq12); 130 cases of Y/autosome translocations (50 cases with a Y/A reciprocal translocation, 20 cases of Y/A translocation in 45,X males, 60 cases of Y/DP or Y/Gp translocations); 52 cases of Y/X translocations [47 cases with der(X); 4 cases with der(Y), and 1 case with 45,X with a der(X)], 7 cases of Y/Y translocations; 151 postnatally diagnosed cases of 45,X/46,XY; 14 postnatally diagnosed cases of 45,X/47,XYY; 18 cases of 45,X/46,XY/47,XYY; and 93 aforementioned prenatally diagnosed cases with a 45,X cell line. It is clear that in the absence of a 45,X cell line, the presence of an entire Yp or a region of it including SRY would lead to a male phenotype in an individual with a Y aneuploidy, whereas the lack of Yp invariably leads to a female phenotype with typical or atypical Ullrich-Turner syndrome (UTS). Once there is a 45,X cell line, regardless of whether there is Yp, Yq, or both Yp and Yq, or even a free Y chromosome in other cell line, there is an increased chance for that individual to be a phenotypic female with UTS manifestations or to have ambiguous external genitalia. This review once again shows a major difference in reported phenotypes between postnatally and prenatally diagnosed cases of 45,X/46,XY, 45,X/47,XYY, and 45,X/46,XY/47,XYY mosaicism. It appears that ascertainment bias can explain the fact that all known patients with postnatal diagnosis are phenotypically abnormal, while over 90% of prenatally diagnosed cases are reported to have a normal male phenotype. Further elucidation of major Y genes and their clinical significance can be expected in the rapidly expanding gene mapping projects. More, consequently better, phenotype/karyotype correlations can be anticipated at both the cytogenetic and the molecular level.

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.

Combined Goltz and Aicardi syndromes in a terminal Xp deletion: are they a contiguous gene syndrome?

We report on 2 girls with a terminal deletion of the short arm of chromosome X. They had microphthalmia, cloudy corneae, mild linear skin lesions, and agenesis of corpus callosum. A comparison of clinical and cytogenetic findings in similar cases suggested that the critical genes for the Goltz and Aicardi syndromes might be contiguous in the region Xp22.31.

Molecular analysis of aberrations of Xp and Yq

Three cases of Y chromosomal aberrations were studied using a panel of Y-specific DNA sequences from both Yp and euchromatic Yq. One case was a phenotypic male fetus with a Y-derived marker chromosome. The short arm of this chromosome was intact, but most of its long arm was missing. The second case had a 46,XYq- karyotype with portions of euchromatic Yq, including the spermatogenesis region, missing. The third case was a phenotypic female with a 46,XXp+ karyotype. The extra material on the Xp+ chromosome was derived from the heterochromatic, and part of the euchromatic, portion of Yq. Application of X-specific DNA sequences demonstrated that the distal portion of the short arm of the translocation X chromosome was deleted (Xpter-p22.3). The three examples demonstrate the importance of diagnostic DNA analysis in cases of marker chromosomes, and X and Y chromosomal aberrations. In addition, the findings in the patients facilitate further deletion mapping of euchromatic Yq.

X/Y translocations resulting from recombination between homologous sequences on Xp and Yq

Several regions of sequence homology between the human X and Y chromosomes have been identified. These segments are thought to represent areas of these chromosomes that have engaged in meiotic recombination in relatively recent evolutionary times. Normally, the X and Y chromosomes pair during meiosis and exchange DNA only within the pseudoautosomal region at the distal short arms of both chromosomes. However, it has been suggested that aberrant recombination involving other segments of high homology could be responsible for the production of X/Y translocations. We have studied four X/Y translocation patients using molecular probes detecting homologous sequences on X and Y chromosomes. In one translocation the breakpoints have been isolated and sequenced. The mapping data are consistent with the hypothesis that X/Y translocations arise by homologous recombination. The sequencing data from one translocation demonstrate this directly.

Two 46,XX,t(X;Y) females with linear skin defects and congenital microphthalmia: a new syndrome at Xp22.3

We describe two females with de novo X;Y translocations, who presented at birth with irregular linear areas of erythematous skin hypoplasia involving the head and neck, along with eye findings that included microphthalmia, corneal opacities, and orbital cysts. The features in these children are similar to but distinct from those seen in females with Goltz syndrome and incontinentia pigmenti. Cytogenetic analysis has shown the X chromosome breakpoint in both females to be at Xp22.3. We suggest that this syndrome is the result of a deletion or disruption of DNA sequences in the region of Xp22.3.