A woman with an apparent non-mosaic 45,X delivered a 46,X,der(X) liveborn female

A liveborn female with a phenotype suggestive of Down syndrome is reported. Cytogenetic lymphocyte analysis showed a 46,X der(X) karyo-type. Fluorescence in situ hybridization (FISH) with a biotinylated probe specific for chromosome 21 showed no signal on the der(X). This marker was homogeneously painted using a specific probe for X chromosome. In addition, FISH analysis detected telomeres on the rearranged X. Therefore, the proband's karyotype was revaluated as 46,X,del(X) (pter p22.2::p11.3 qter). Cytogenetic analysis of 150 lymphocytes in the mother disclosed a homogeneous 45,X karyotype. FISH analysis of interphase nuclei using the X chromosome painting probe showed two domains of different sizes in 0.8% of cells. This led us to study further metaphases in the mother. In one out of 450 metaphases scored, after FISH with the X chromosome painting probe, the del(X) was observed, confirming that the rearranged X chromosome found in the newborn had segregated from a 45,X/46,X,del(X) mother.     

The frequency of micronuclei with X chromosome increases with age in human females

The rate of micronuclei counted on lymphocyte cultures from five healthy female donors, 27–80 years old, increased with age. Using pXBR1 probe, specific for the alphoid DNA of the X chromosome, the presence of this chromosome was investigated by FISH (fluoroscence in sity hybridization) in both micronucleic and metaphases. Both X aneuploidy and frequency of X chromosome per micronuclei increased with age. However, this overinvolvement of X chromosome was not sufficient to explain the overall increase of micronuclei with age, suggesting that autosomes are also involved. Thus, the higher increase of X than autosome aneyploidy in lymphocytes may result from both an excess of X choromosome losses and a better survival of cells with a monoosomy X.     

Attenuated phenotype in a child with trisomy for 1q due to unbalanced X;1 translocation [46,X,der(X),t(X;1)(q28;q32.1)

We report a case of an X;1 translocation in a 9-month-old female infant with mild dysmorphic features and developmental delay. High-resolution chromosome analysis revealed a de novo, unbalanced translocation between chromosomes X and 1 [46,X,der(X),t(X;1)(q28;q32.1)]. Breakpoints on the derivative X and the size of the translocated segment have been defined by fluorescence in situ hybridization (FISH) with Xq and 1q specific probes. The rearrangement in this patient results in monosomy for Xq28-qter and trisomy for 1q32.1-qter. Replication studies demonstrated late replication of the derivative X in 80% of the observed cells, with the exception of 20% of the cells where X inactivation failed to spread into the translocated 1q segment. Patients with pure trisomy for the distal segment of 1q present a considerably more severe phenotype compared to that seen in our patient, including facial dysmorphisms, urogenital and cardiac anomalies. We suggest that the absence of many of the characteristic features for trisomy 1q in our patient, may reflect a mosaic pattern of inactivation of the translocated autosomal segment on the derivative X chromosome.     

The genomic breakpoint in a patient with Philadelphia-positive acute leukemia is 5' of the breakpoint cluster region

We report a case of acute leukemia in which studies at presentation showed both myeloid and lymphoid cell surface markers. At relapse membrane markers studies were consistent with a leukemia of B-lymphoid lineage. However, immunoglobulin (Ig) and T cell receptor (TCR) beta chain genes were both found in a rearranged configuration. The majority of metaphases from the leukemic cells at presentation showed the Philadelphia chromosome, t(9;22)(q34;q11), whereas a minority were normal. At relapse both Ph-positive and -negative metaphases were still present in the bone marrow but some of the Ph-negative metaphases had acquired an additional chromosome #19 [47,XY, + 19]. Southern analysis of DNA from leukemic bone marrow cells at diagnosis showed no rearrangement of breakpoint cluster region (bcr). There was no bcr-abl chimeric mRNA typical of Ph-positive chronic myeloid leukemia (CML). However, the cells expressed an abl-related protein of Mr 190 kd with enhanced tyrosine kinase activity. Leukemic cell metaphases were studied by the technique of in situ hybridization with probes for C-lambda, sis, abl, and 5' bcr. The c-abl probe mapped to chromosome 22q11 in Ph-positive metaphases. The 5' bcr probe mapped to 9q+ in the Ph-positive metaphases and the C-lambda gene mapped to the Ph chromosome. Thus, the genomic breakpoint in this patient must lie upstream of the BCR defined by study of Ph-positive CML and downstream of the C-lambda gene locus. We speculate that the Ph-negative cells in this patient may represent a leukemic proliferation susceptible to acquisition of specific chromosomal changes.     

X long arm deletion with oligomenorrhoea.

A 35-year-old female patient with oligomenorrhoea had a deletion of the long arm of the X chromosome. The breakpoint at band q23 caused infertility in spite of excessive pituitary stimulation. The aberrant X chromosome was inactivated in all cells analysed.     

Severe phenotype resulting from an active ring X chromosome in a female with a complex karyotype: characterisation and replication study.

We report on the characterisation of a complex chromosome rearrangement, 46,X,del(Xq)/47,X,del(Xq),+r(X), in a female newborn with multiple malformations. Cytogenetic and molecular methods showed that the del(Xq) contains the XIST locus and is non-randomly inactivated in all metaphases. The tiny r(X) chromosome gave a positive FISH signal with UBE1, ZXDA, and MSN cosmid probes, but not with a XIST cosmid probe. Moreover, it has an active status, as shown by a very short (three hour) terminal BrdU pulse followed by fluorescent anti-BrdU antibody staining. The normal X is of paternal origin and both rearranged chromosomes originate from the same maternal chromosome. We suggest that both abnormal chromosomes result from the three point breakage of a maternal isodicentric idic(X)(q21.1). Finally, the phenotype of our patient is compared to other published cases and, despite the absence of any 45,X clone, it appears very similar to those with a 45,X/46,X,r(X) karyotype where the tiny r(X) is active.     

Familial X-linked mental retardation with an X chromosome abnormality.

An X-linked pattern of transmission observed in four families with familial mental retardation in several generations was associated with a probable secondary constriction at the distal end of the q arms of the X chromosome. Twenty retarded males and no retarded females were observed. All available live retarded males and most of their normal mothers were found to have the abnormal X chromosome. The marker chromosome was shown to be the X chromosome in each case by Giemsa banding. In affected male and female carriers the marker chromosome varied in appearance and was not present in all metaphases. The significance of this study in relation to previously reported pedigrees showing non-specific X-linked mental retardation is discussed.     

X染色体倾斜失活人胚胎干细胞的拷贝数变异

背景：倾斜性与随机X染色体失活的人胚胎干细胞拷贝数变异是否存在差异不清楚。 目的：在全基因组水平分析倾斜性X染色体失活的人胚胎干细胞的拷贝数变异情况,分析其涵盖基因及其对细胞功能产生的影响。 方法：3株倾斜性X染色体失活细胞为研究组,两株随机X染色体失活细胞为对照组。运用美国Affymetrix公司Cytogenetics Whole-Genome 2.7M 芯片对其进行全基因组拷贝数变异分析,数据经ChAS软件、OMIM等工具分析,在3株倾斜性X染色体失活细胞中寻找相同拷贝数变异区域及其涵盖基因。 结果与结论：①研究组中大于50 kb的拷贝数变异数均超过130个,高于对照组的平均36个,两组中拷贝数变异改变均以重复为主(> 70%)。②研究组中共发现9个共同拷贝数变异区域,分布于1q22、1p34.1、6q16.3、7q31.32、11q13.1、16q12.2、19p13.12、Xp22.33及Xq26.2,均为3个拷贝的重复,总共涵盖19个基因。对照组中这些区域及基因均为正常2个拷贝。③拷贝数变异涵盖基因多与DNA及核苷酸结合等功能相关,Xq26.2区域的GPC3基因突变与倾斜性X染色体失活可能有关联。结果表明倾斜性X染色体失活细胞相对随机失活细胞具有更多的微小基因组改变,拷贝数变异涵盖的重要基因可能对人胚胎干细胞功能产生不利影响。     

An active ring X and haploinsufficiency of SHOX contribute to short stature,congenital anomalies,and developmental delay in a female

We report on a female infant with short stature and mesomelic limb shortening, multiple congenital abnormalities, developmental delay, and Rieger anomaly. Cytogenetic analysis revealed a complex rearrangement of the sex chromosomes in this patient. In addition to a normal X chromosome, a derivative Y [der(Y)] chromosome composed of X and Y material and a ring X [r(X)] were present. Consistent with the fact that this infant had normal female genitalia, the SRY gene was not detected in the Y chromosome portion of the der(Y). By fluorescence in situ hybridization (FISH), XIST was present on the normal X and the r(X), but not on the der(Y). The normal X was late replicating (inactive) and the r(X) early replicating (active) in all lymphocyte metaphases examined. As the X chromosome material on the der(Y) cannot be inactivated, the unusual skew of activation toward the r(X) presumably resulted in the least amount of functional disomy of X‐linked genes in the cells of this patient. Deletion of one copy of the SHOX gene was detected in this patient. Haploinsufficiency of this gene is known to be correlated with short stature and mesomelic limb shortening. © 2002 Wiley‐Liss, Inc.     

Unusual clinical course and acquisition of del(11)(q23) in second lymphatic blastic phase of a Ph-positive chronic myeloid leukemia.

We describe unusual clinical and cytogenetic findings of a 29-year-old female with a Philadelphia chromosome (Ph)-positive chronic myeloid leukemia (CML), who showed a mosaic of apparently normal cells and cells bearing the classical t(9;22)(q34;q11) during the first lymphatic blastic phase (BP). The second lymphatic BP developed 10 years later. In addition to the t(9;22), which was detected in all metaphases, a del(11)(q23) was identified as a subclonal change in 4 of 25 metaphases. Fluorescence in situ hybridization (FISH) analysis using a chromosome 11-specific library probe and a probe covering the breakpoint cluster region of the MLL gene revealed hybridization signals of both probes on the normal and the deleted chromosome 11, indicating that the breakpoint on chromosome 11 occurred telomerically to the breakpoint cluster region of the MLL gene. Chemotherapeutic treatment resulted in reconstitution of the chronic phase with persistence of the Ph translocation as the sole chromosomal abnormality.     

Distinct chromosome abnormalities in ataxia telangiectasia with chronic T-cell lymphocytic leukemia

We report chromosomal studies of a 27-year-old male patient with ataxia telangiectasia who developed a chronic T-cell lymphocytic leukemia. The leukemic cells grew spontaneously although a better yield of metaphases could be obtained after PHA stimulation. Chromosome analysis revealed a hypodiploid leukemic clone (44 chromosomes) and a single remaining normal metaphase. An isochromosome 8q was detected in a subclone at an early analysis, which was lost during clonal evolution. At the time of the last analysis, 6 months before the patient died, the diploid metaphases disappeared completely. The karyotype of the final chromosome study showed a monoclonal condition with the following abnormalities: 44,X,-Y,4q-,6p-,14q-,19p+,20q+,-20,22q-. Loss of the Y chromosome was limited to the leukemic cells. Comparing our data with the chromosome abnormalities reported in the literature, breakpoints at band 14q11-12 (location of the gene for the alpha chain of the T-cell receptor), loss of a normal chromosome #20, as well as structural abnormalities of the remaining chromosome 20p seem to be nonrandom in T-CLL arising in patients with ataxia telangiectasia. A Philadelphia-like marker that seems to be a peculiar feature of the case described here, however, resembles a small marker chromosome qualified as unidentifiable in a similar case of T-CLL reported in the literature.     

Balanced X;15 translocation 46,X,t(X;15)(q21;q23) associated with primary amenorrhea

Cytogenetic studies on a woman with primary amenorrhea showed an X;15 translocation, karyotype 46,X,t(X;15)(q21;q23). Fifteen percent of the buccal cells showed a normal-sized sex chromatin body. The normal X chromosome was uniformly inactivated. Many balanced X;15 translocations have been reported; however, breakpoints in our patient differ from those reported previously. This case also supports earlier evidence that ovarian development fails when the breakpoint of the X chromosome is in the region X q13-q25 or q13-q27.     

X;14 translocation:an exception to the critical region hypothesis on the human X-chromosome

We report on a family in which an X;14 translocation has been identified. A phenotypically normal female, carrier of an apparently balanced X-autosome translocation t(X;14)(q22;q24.3) in all her cells and a small interstitial deletion of band 15q112 in some of her cells had 2 offspring. She represents a fifth case of balanced X-autosome translocation with the break point inside the postulated critical region of Xq(q13 q26) associated with fertility. The break point in this case is located in Xq22, the same band as in four previously published exceptional cases. In most of her cells, the normal X was inactivated. Her daughter, the proposita, has an unbalanced karyotype 46,X,der(X), t(X;14)(q22;q24.3)mat, del(15)(q11.1q11.3)mat. She is mildly retarded and has some Prader-Willi syndrome manifestations. She has two normal 14 chromosomes, der(X), and deletion 15q11.2. Her clinical abnormalities probably could be attributed to the deletions 15q and Xq rather than 14q duplication. In most of cells, der(X) was inactivated. We assume that spreading of inactivation was extended to the 14q segment on the derivative X. Late replication and gene dose studies support this view. Another daughter, who inherited the balanced X;14 translocation and not deletion 15 chromosome, is phenotypically normal.     

Molecular characterization of a deleted X chromosome (Xq13.3-Xq21.31) exhibiting random X inactivation

As a result of selection following random X chromosome inactivation in human females, X chromosomes with visible deletions are usually inactive in every somatic cell. We have studied a female with mental retardation and dysmorphic features whose karyotype includes an X chromosome with a visible interstitial deletion in the proximal long arm. Based on cytogenetic analysis, the proximal breakpoint appeared to be in band Xq13.1, and the distal one in band q21.3. However, molecular analyses show that less of the q13 band is missing than cytogenetic studies indicated, as the deletion includes only loci from the region Xq13.3 to Xq21.31. Unexpectedly, studies of chromosome replication show that the pattern of X inactivation is random. Whereas the deleted X chromosome is late replicating in some cells from all tissues studied, it is early replicating in the majority of blood lymphocytes and skin fibroblasts, and is the active X chromosome in many of the hybrids derived from skin fibroblasts. As this chromosome is able to inactivate, it must include those DNA sequences from the X-inactivation center (XIC) that are essential forcis X inactivation. Molecular studies show that the XIC region, at Xq13.2, is present, so it is unlikely that the lack of consistent inactivation of this chromosome is attributable to close proximity of the breakpoint to the XIC. Supporting this conclusion is the similarity of the breakpoints to those of the other chromosomes we studied, whose deletions clearly do not interfere with the ability to inactivate. Our results show that deletions distal to DXS441 in Xq13.2 do not interfere withcis X inactivation. We attribute the random pattern of X inactivation reported here to the fact that in the tissues studied, cells with this interstitial deletion are not at a selective disadvantage.     

An active ring X and haploinsufficiency of SHOX contribute to short stature,congenital anomalies,and developmental delay in a female

We report on a female infant with short stature and mesomelic limb shortening, multiple congenital abnormalities, developmental delay, and Rieger anomaly. Cytogenetic analysis revealed a complex rearrangement of the sex chromosomes in this patient. In addition to a normal X chromosome, a derivative Y [der(Y)] chromosome composed of X and Y material and a ring X [r(X)] were present. Consistent with the fact that this infant had normal female genitalia, the SRY gene was not detected in the Y chromosome portion of the der(Y). By fluorescence in situ hybridization (FISH), XIST was present on the normal X and the r(X), but not on the der(Y). The normal X was late replicating (inactive) and the r(X) early replicating (active) in all lymphocyte metaphases examined. As the X chromosome material on the der(Y) cannot be inactivated, the unusual skew of activation toward the r(X) presumably resulted in the least amount of functional disomy of X-linked genes in the cells of this patient. Deletion of one copy of the SHOX gene was detected in this patient. Haploinsufficiency of this gene is known to be correlated with short stature and mesomelic limb shortening.     

Turner''s syndrome with a duplication-deficiency X chromosome derived from a maternal pericentric inversion X chromosome

A 31-year-old woman of short stature with severe oligomenorrhea was found to carry a duplication-deficiency X chromosome, 46,X,rec(X)dup q,inv(X)(p22q11), inherited from her mother who carried a pericentric inversion X chromosome, 46,X,inv(X)(p22q11). By a combination of autoradiography and BUdR incorporation, the duplication-deficiency X chromosome was always found to be the inactive and late replicating one. In the cultured fibroblasts with the recombinant X chromosome, some of the cells were seen to have bipartite X chromatin bodies. In the mother with inv(X), the normal and the inverted X chromosome were inactivated at random.     

X;14 translocation: An exception to the critical region hypothesis on the human X-chromosome

We report on a family in which an X;14 translocation has been identified. A phenotypically normal female, carrier of an apparently balanced X-autosome translocation t(X;14) (q22;q24.3) in all her cells and a small interstitial deletion of band 15q 112 in some of her cells had 2 offspring. She represents a fifth case of balanced X-autosome translocation with the break point inside the postulated critical region of Xq(q13 q26) associated with fertility. The break point in this case is located in Xq22, the same band as in four previously published exceptional cases. In most of her cells, the normal X was inactivated. Her daughter, the proposita, has an unbalanced karyotype 46,X,der(X), t(X;14)(q22;q24.3)mat, del(15)(q11.1q11.3)mat. She is mildly retarded and has some Prader-Willi syndrome manifestations. She has two normal 14 chromosomes, der(X), and deletion 15q11.2. Her clinical abnormalities probably could be attributed to the deletions 15q and Xq rather than 14q duplication. In most of cells, der(X) was inactivated. We assume that spreading of inactivation was extended to the 14q segment on the derivative X. Late replication and gene dose studies support this view. Another daughter, who inherited the balanced X;14 translocation and not deletion 15 chromosome, is phenotypically normal.     

The fragile X chromosome: Current methods

At the International Congress of Human Genetics (Jerusalem, September, 1981) a Workshop was held on the fragile X chromosome; it was entitled “The Fragile X Chromosome: Current Methods.” It was to focus on laboratory methods required to detect or to enhance the detection of the fragile X. The fragile site on the X chromosome is one of 13 proven fragile sites known in humans. (A diagram of these sites is provided.) The fragile site on the X is sensitive to the concentration of folic acid in the medium in which cells are cultured. Cytologically, gaps and breaks are increased at the X fragile site, which is located at band Xq27–28. To enhance expression in lymphocytes, prolongation of culture time to 96 hours, elevation of the pH, diminution of the colcemid effect, and air drying of slides are helpful. The need for methionine in low-folate media can be overridden by the addition of fluorodeoxyuridine (FUdR). Detection of the fragile X in males requires meticulous attention to methods of lymphocyte culture and metaphase preparation and then the examination of a sufficient number of mitoses, eg, 50–100 metaphases per individual. Detection of the fragile X in female carriers is often more difficult. Uniform detection of all obligate female carriers has not been achieved. Difficulty may correlate with increasing age or intelligence of females. Key methodologic advances with the fragile X include the addition of methotrexate, trifluorothymidine or, especially of FUdR to the culture medium. FUdR, for example, is helpful in demonstrating the fragile X in lymphoblastoid cell lines and fibroblasts. Both of these cell types now represent an opportunity to study the biochemistry of the fragile X. The success of the FUdR technique with skin fibroblasts heralds the feasibility of demonstrating the fragile X chromosome in cultured amniocytes. Since the Workshop, it has been reported that with FUdR the fragile X could in fact be detected in 46,XY amniotic fluid cells.     

Structural aberration of the X chromosome in a patient with gonadal dysgenesis: an approach to karyotype-phenotype correlation.

An 18-year-old female with some stigmata of pure dysgenesis had a chromosome constitution of 46,X,dir dup(X) (pter leads to q27: :q21 leads to qter). The abnormal chromosome was always late replicating. The clinical and cytogenetic picture is compared with that of patients with X;X translocation and some problems of karyotype-phenotype correlation are discussed.