Buccal cell FISH and blood PCR-Y detect high rates of X chromosomal mosaicism and Y chromosomal derivatives in patients with Turner syndrome

Turner syndrome (TS) is the result of (partial) X chromosome monosomy. In general, the diagnosis is based on karyotyping of 30 blood lymphocytes. This technique, however, does not rule out tissue mosaicism or low grade mosaicism in the blood. Because of the associated risk of gonadoblastoma, mosaicism is especially important in case this involves a Y chromosome. We investigated different approaches to improve the detection of mosaicisms in 162 adult women with TS (mean age 29.9 ± 10.3). Standard karyotyping identified 75 patients (46.3%) with a non-mosaic monosomy 45,X. Of these 75 patients, 63 underwent additional investigations including FISH on buccal cells with X- and Y-specific probes and PCR-Y on blood. FISH analysis of buccal cells revealed a mosaicism in 19 of the 63 patients (30.2%). In five patients the additional cell lines contained a (derivative) Y chromosome. With sensitive real-time PCR we confirmed the presence of this Y chromosome in blood in three of the five cases. Although Y chromosome material was established in ovarian tissue in two patients, no gonadoblastoma was found. Our results confirm the notion that TS patients with 45,X on conventional karyotyping often have tissue specific mosaicisms, some of which include a Y chromosome. Although further investigations are needed to estimate the risk of gonadoblastoma in patients with Y chromosome material in buccal cells, we conclude that FISH or real-time PCR on buccal cells should be considered in TS patients with 45,X on standard karyotyping.     

18例闭经患者的分子-细胞遗传学研究

目的探讨荧光原位杂交（fluorescencein situhybridization,FISH）和高分辨比较基因组杂交（highresolution-comparative genomic hybridization,HR-CGH）技术在闭经研究中的应用价值。方法17例原发闭经和1例继发闭经患者经常规妇科检查、B超及内分泌功能检查后,应用染色体核型分析,部分染色体异常患者采用FISH和HR-CGH技术相结合的分子-细胞遗传学检查诊断结果,并对其临床症状及发病机制进行了探讨。结果17例原发闭经患者中,7例为46,XX的正常女性核型;10例携带有异常染色体核型,所占比例为58.8%,其中3例为46,XY的女性患者,2例为45,X及45,X/46,XX的Turner＇s患者;其余5例均为携带有X染色体结构异常,包括X染色体部分单体、X等臂染色体和X/Y嵌合体等异常核型患者;1例继发性闭经患者为X染色体与常染色体易位的异常核型。结论应用FISH和HR-CGH技术与高分辨染色体显带技术,精确诊断患者的染色体核型,可为临床的诊断和治疗提供医学遗传学依据。     

High frequency of tissue-specific mosaicism in Turner syndrome patients

Interphase fluorescent studies of X chromosome aneuploidy in cultured and uncultured blood lymphocytes and oral mucosa epithelial cells using X centromere-specific DNA probe in addition to standard karyotype analysis were performed in 50 females with a clinical suspicion of Turner syndrome. All the patients were previously screened for the presence of 'hidden' Y chromosome mosaicism, using the primers DYZ3 and DYZ. The use of fluorescence in situ hybridization (FISH) analysis of interphase nuclei of tissues from different germ layers (lymphocytes from mesoderm and buccal epithelial cells from ectoderm) improves the accuracy of detection of low-level mosaicism. FISH studies on interphase nuclei revealed that 29% of patients with a pure form of monosomy X detected by metaphase analysis are, in fact, mosaics. The level of cells with the normal chromosomal constitution in lymphocytes of these cases as a rule was low, ranging from 3 to 18%, with an average of 7%. Two false-positive cases and one false-negative case of X monosomy mosaicism determined by standard cytogenetic approach were detected using FISH analysis. The majority of patients (92%) with mosaic form of Turner syndrome have considerable tissue-specific differences in levels of X aneuploidy. Our data indicate that in cases when mosaic aneuploidy with low-level frequency is questionable (approximately 10% and lower), the results of standard metaphase analysis should be supplemented with additional FISH studies of interphase nuclei. Tissue-specific differences in contents of different cell lines in the same patients point to the necessity of studying more than one tissue from each patient.     

FISH analysis helps identify low-level mosaicism in Ullrich-Turner syndrome patients.

PURPOSE: To search for X or Y chromosome mosaicism in 45,X individuals using fluorescent in situ hybridization (FISH). METHODS: From our series of 53 Ullrich-Turner syndrome patients, we used interphase FISH to evaluate the 19 who had an apparently nonmosaic 45,X karyotype with G-banding. RESULTS: Of those 19 patients, mosaicism was detected in seven (37%), five patients had an XX line, one had a monocentric isochromosome X, and one had a dicentric isochromosome X. No Y chromosome mosaic was identified. CONCLUSION: FISH analysis is a sensitive and cost-effective adjunct to karyotype analysis to identify sex chromosome mosaicism in UTS.     

Detection of monosomy 7 by fluorescenceIn situ hybridization in acute nonlymphocytic leukemia and myelodysplastic syndrome

Summary Fluorescencein situ hybridization (FISH) with a chromosome 7 specific alpha satellite DNA probe was used to detect monosomy 7 in interphase and metaphase cells obtained from patients with myelodysplastic syndrome (MDS) and acute nonlymphocytic leukemia (ANLL). Chromosome analysis revealed monosomy 7, either alone or as part of a complex chromosome abnormality, in all cell samples. FISH analyses of 12 marrow samples and a blood sample using a chromosome 7 specific alpha satellite DNA probe revealed a single fluorescence spot in 80.5–97.5% of interphase cells indicating monosomy 7. In contrast, 83.5–92.0% of the same cells had two copies of chromosome 17 as two fluorescent spots were detected using a chromosome 17 specific alpha satellite DNA probe used as a positive control. The proportion of interphase cells with monosomy 7 did not correlated with the percentage of metaphase cells with monosomy 7 detected by conventional karyotyping or with the percentage of blast cells in the bone marrow.     

Chromosome studies and fertility treatment in women with ovarian failure

In vitro fertilization and embryo transfer or gamete (or zygote) intra-Fallopian transfer after ovum donation were performed in 16 patients with primary or secondary amenorrhea, associated with chromosome abnormalities. The patients showed the wide range of (mostly X) chromosome abnormalities characteristic for women with primary or premature ovarian failure. Four of these patients became pregnant and three of them have delivered healthy infants with a normal karyotype. This pregnancy rate is far superior to the accepted fertility figure in these patients. When these results were compared with the fertility treatment results of three other groups of women with absent ovarian function (1. ovarian dysgenesis; 2. surgical castration; 3. premature menopause) but with a normal 46,XX karyotype, no difference in treatment efficiency could be detected. These results offer a promising approach for the treatment of infertility in agonadal patients with chromosome aberrations.     

Detection of low level sex chromosome mosaicism in Ullrich-Turner syndrome patients

Ullrich-Turner syndrome (UTS) is most commonly due to a 45,X chromosome defect, but is also seen in patients with a variety of X-chromosome abnormalities or 45,X/46,XY mosaicism. The phenotype of UTS patients is highly variable, and depends largely on the karyotype. Patients are at an increased risk of gonadoblastoma when a Y-derived chromosome or chromosome fragment is present. Since constitutional mosaicism is present in approximately 50% of UTS patients, the identification of minor cell populations is clinically important and a challenge to laboratories. We identified 50 females with a 45,X karyotype as the sole abnormality or as part of a more complex karyotype. Twenty two (44%) had a 45,X karyotype; mosaicism for a second normal or structurally abnormal X was observed in 24 (48%) samples, and mosaicism for Y chromosomal material in 4 (8%) cases. To further investigate the possibility of mosaicism in the 22 patients with an apparently non-mosaic 45,X karyotype, we performed FISH using centromere probes for the X and Y chromosomes. A minor XX cell line was identified in 3 patients, and the 45,X result was confirmed in 19 samples. No samples with XY mosaicism were identified. We describe our validation process for a FISH assay to be used in clinical practice to identify XX or XY mosaicism. FISH as an adjunct to karyotype analysis provides a sensitive and cost-effective technique to identify sex chromosome mosaicism in UTS patients.     

Molecular cytogenetic studies of Xq critical regions in premature ovarian failure patients

BACKGROUND: Premature ovarian failure (POF) is defined as amenorrhoea for more than 6 months, occurring before the age of 40, with an FSH serum level higher than 40 mIU/ml. Cytogenetically visible rearrangements of the X chromosome are associated with POF. Our hypothesis was that cryptic Xq chromosomal rearrangements could be an important etiological contributor of POF. METHODS: Ninety POF women were recruited and compared to 20 control women. Peripheral blood samples were collected and metaphase chromosomes were prepared using standard cytogenetic methods. To detect Xq chromosomal micro-rearrangements, fluorescence in situ hybridization (FISH) analysis was performed using a selection of 30 bacterial artificial chromosome (BAC) and P1 artificial chromosome clones, spanning Xq13-q27. We further localized the translocation breakpoints by FISH with additional BAC clones. RESULTS: Chromosomal abnormalities were identified in 8.8% of our 90 patients [one triple X, three large Xq deletions 46,X,del(X)(q22.3), 46,X,del(X)(q21.2) and 46,X,del(X)(q21.32), two balanced X;autosome translocations 46,X,t(X;1) (q21.1;q32) and 46,X,t(X;9)(q21.31;q21.2) and two Robertsonian translocations 45,XX,der(15;22)(q10;q10) and 45,XX,der(14;21)(q10;q10)]. The two Xq translocation breakpoints were among a cluster of repetitive elements without any known genes. FISH analysis did not reveal any Xq chromosomal micro-rearrangement. CONCLUSIONS: Karyotyping is definitely helpful in the evaluation of POF patients. No submicroscopic chromosomal rearrangements affecting Xq region were identified. Further analysis using DNA microarrays should help delineate Xq regions involved in POF.     

RAPID DETECTION OF KARYOTYPE CHANGES IN INTERPHASE BONE MARROW CELLS BY OLIGONUCLEOTIDE PRIMED IN SITU HYBRIDIZATION (PRINS)

Fluorescence in situ hybridization (FISH) using DNA probes of several hundred or thousand base pairs in length enables the visualization of chromosomal aberrations in interphase nuclei. A new method for in situ labelling of chromosomes is the oligonucleotide primed in situ labelling (PRINS) technique. So far, this has mainly been used to demonstrate subtle changes in metaphase spreads. The aim of the present study was to investigate the suitability of PRINS for detecting chromosome gains or losses in interphase nuclei. This technique was compared with FISH analysis by examining the bone marrow cells of ten patients in whom the karyotypes were known from conventional chromosome banding. Corresponding results by both PRINS and FISH were obtained for chromosomes 1, 3, 7, 8, and Y in five patients with normal chromosome patterns, as well as in five patients with clonal karyotype changes, e.g., monosomy 7, trisomy 8, or loss of the Y chromosome. Being faster and approximately ten times less expensive, PRINS can replace FISH for detecting numerical karyotype changes. © 1997 by John Wiley & Sons, Ltd.     

一例外周血染色体核型为单纯型18三体但智力正常女性的遗传学研究

目的分析1例外周血染色体核型为单纯型18三体但智力正常女性的遗传学机制。方法用G显带染色体核型分析、荧光原位杂交(fluorescence in situ hybridization,FISH)和单核苷酸多态性微阵列芯片(single nucleotide polymorphism microarray,SNP-array)技术对患者的外周血和颊粘膜细胞进行检测。结果患者的外周血染色体核型、SNP-array以及FISH检测结果均提示为47,XX,+18;颊粘膜间期细胞FISH检测结果提示为45,X合并低比例的18三体和18单体。结论胚层染色体嵌合的个体临床表现复杂,遗传学异常所造成的影响取决于相关胚层分化所形成的器官及功能。     

A man who inherited his SRY gene and Leri‐Weill dyschondrosteosis from his mother and neurofibromatosis type 1 from his father

We report on a man with neurofibromatosis type 1 (NF1) and Leri‐Weill dyschondrosteosis (LWD). His father had NF1. His mother had LWD plus additional findings of Turner syndrome (TS): high arched palate, bicuspid aortic valve, aortic stenosis, and premature ovarian failure. The proband's karyotype was 46,X,dic(X;Y)(p22.3;p11.32). Despite having almost the same genetic constitution as 47,XXY Klinefelter syndrome, he was normally virilized, although slight elevation of serum gonadotropins indicated gonadal dysfunction. His mother's karyotype was mosaic 45,X[17 cells]/46,X,dic(X;Y)(p22.3;p11.32)[3 cells].ish dic(X;Y)(DXZ1 + ,DYZ1 + ). The dic(X;Y) chromosome was also positive for Y markers PABY, SRY, and DYZ5, but negative for SHOX. The dic(X;Y) chromosome was also positive for X markers DXZ1 and a sequence < 300 kb from PABX, suggesting that the deletion encompassed only pseudoautosomal sequences. Replication studies indicated that the normal X and the dic(X;Y) were randomly inactivated in the proband's lymphocytes. LWD in the proband and his mother was explained by SHOX haploinsufficiency. The mother's female phenotype was most likely due to 45,X mosaicism. This family segregating Mendelian and chromosomal disorders illustrates extreme sex chromosome variation compatible with normal male and female sexual differentiation. The case also highlights the importance of karyotyping for differentiating LWD and TS, especially in patients with findings such as premature ovarian failure or aortic abnormalities not associated with isolated SHOX haploinsufficiency. © 2001 Wiley‐Liss, Inc.     

Ring chromosome 20 syndrome without deletions of the subtelomeric and CHRNA4--KCNQ2 genes loci

Ring chromosome 20 [r(20)] syndrome is a rare disease characterized by refractory epilepsy, moderate mental retardation and particular electroencephalographic disorder with non-convulsive status epilepticus. Here, we report a new case of r(20) syndrome in a 12 year old female who presented minimal dysmorphism, generalised tonic–clonic and absence seizures refractory to medical therapy and behavioural troubles.

Among 20 cytogenetically analysed cells, 14 (70%) exhibited a 46,XX,r(20)(p13q13.3) karyotype and 6 (30%) showed a normal 46,XX caryotype. Interphasic FISH using centromeric probe of chromosome 20 detects the presence of a chromosome 20 monosomy in 7% and a duplicated ring chromosome 20 in 8% of studied cells. Metaphase FISH using chromosome 20 telomeric probes and specific probes of CHRNA4 and KCNQ2 genes detects the absence of any deletion in the ring chromosome 20.

Clinical symptoms of r(20) syndrome are attributed to telomeric partial monosomy generated by ring chromosome and causing an haploinsufficiency of two epilepsy genes CHRNA4 and KCNQ2. However, our patient presents the typical epilepsy disorder but no detectable deletion in the ring chromosome 20. We speculate that clinical features of ring chromosome 20 syndrome are caused by low mosaicism of chromosome 20 monosomy caused by the loss of the ring chromosome 20.     

Familial Turner syndrome with an X;Y translocation mosaicism: Implications for genetic counseling

Spontaneous fertility is rare among patients with Turner syndrome and is most likely in women with mosaicism for a normal 46,XX cell line. We report an unusual case of familial Turner syndrome with mosaicism for a novel X;Y translocation involving Xp and Yp. The chromosomal analysis was carried out through cytogenetics and molecular karyotyping using a SNP array platform. The mother, a Turner syndrome woman, diagnosed in midchildhood because of short stature, was found to have a 45,X/46,X,der(X)t(X;Y)(p11.4;p11.2) karyotype, with a predominant 45,X cell line. Her parents decided against prophylactic gonadectomy, generally recommended at an early age when Y chromosome has been identified, because at age 13, she had spontaneous puberty and menarche. She reached a final height of 154 cm after treatment with growth hormone. At age 24, she became spontaneously pregnant. She had a mild aortic coarctation and close follow-up cardiac evaluation, including cardiac magnetic resonance imaging, had been performed during her pregnancy, which progressed uneventfully, except for intra-uterine growth retardation. Prenatal diagnosis revealed a female karyotype, with transmission of the maternal translocation with an unexpected different mosaic:47,X,der(X)t(X;Y)x2/46,X,der(X)t(X;Y) karyotype. This complex and unusual karyotype, including a mosaic partial trisomy X and a non-mosaic Xpter-Xp11.4 monosomy, results in transmission of Turner syndrome from mother to daughter. At birth, the girl had normal physical examination except for growth retardation. This family illustrates the complexity and difficulties, in term of patient counseling and management in Turner syndrome, in determining ovarian status, fertility planning, risks associated with pregnancies, particularly when mosaicism for Y material chromosome is identified.     

Genetic disorders in premature ovarian failure

This review presents the genetic disorders associated with premature ovarian failure (POF), obtained by Medline, the Cochrane Library and hand searches of pertinent references of English literature on POF and genetic determinants cited between the year 1966 and February 2002. X monosomy or X deletions and translocations are known to be responsible for POF. Turner's syndrome, as a phenotype associated with complete or partial monosomy X, is linked to ovarian failure. Among heterozygous carriers of the fragile X mutation, POF was noted as an unexpected phenotype in the early 1990s. Autosomal disorders such as mutations of the phosphomannomutase 2 (PMM2) gene, the galactose-1-phosphate uridyltransferase (GALT) gene, the FSH receptor (FSHR) gene, chromosome 3q containing the Blepharophimosis gene and the autoimmune regulator (AIRE) gene, responsible for polyendocrinopathy-candidiasis-ectodermal dystrophy, have been identified in patients with POF. In conclusion, the relationship between genetic disorders and POF is clearly demonstrated in this review. Therefore, in the case of families affected by POF a thorough screening, including cytogenetic analysis, should be performed.     

Detection and incidence of cryptic Y chromosome sequences in Turner syndrome patients

The presence of Y chromosome sequences in Turner syndrome (TS) patients may predispose them to gonadoblastoma formation with an estimated risk of 15–25%. The aim of this study was to determine the presence and the incidence of cryptic Y chromosome material in the genome of TS patients. The methodology involved a combination of polymerase chain reaction (PCR) and nested PCR followed by Southern blot analysis of three genes—the sex determining region Y (SRY), testis specific protein Y encoded (TSPY) and RNA binding motif protein (RBM) (previously designated as YRRM) and nine additional STSs spanning all seven intervals of the Y chromosome. The methodology has a high sensitivity as it detects one 46, XY cell among 10⁵ 46, XX cells. Reliability was ensured by taking several precautions to avoid false positive results. We report the results of screening 50 TS patients and the identification of cryptic Y chromosome material in 12 (24%) of them. Karyotypes were divided in four groups: 5 (23.8%) patients out of the 21 TS patients which have the 45, X karyotype (group A) also have cryptic Y sequences; none (0%) of the 7 patients who have karyotypes with anomalies on one of the X chromosomes have Y mosaicism (group B); 1 (6.3%) of the 16 patients with a mosaic karyotype have Y material (group C); and 6 (100%) out of 6 patients with a supernumerary marker chromosome (SMC) have Y chromosome sequences (group D). Nine of the 12 patients positive for cryptic Y material were recalled for a repeat study. Following new DNA extraction, molecular analysis was repeated and, in conjunction with fluorescent in situ hybridization (FISH) analysis using the Y centromeric specific probe Yc-2, confirmed the initial positive DNA findings. This study used a reliable and sensitive methodology to identify the presence of Y chromosome material in TS patients thus providing not only a better estimate of a patient's risk in developing either gonadoblastoma or another form of gonadal tumor but also the overall incidence of cryptic Y mosaicism.     

Mosaic r(13) resulting in large deletion of chromosome 13q in a newborn female with multiple congenital anomalies

A newborn female presented with multiple congenital anomalies including facial dysmorphism, agenesis of the corpus callosum, type I laryngeal cleft, tracheal stenosis, bilaterally small kidneys, segmental vertebral anomalies, extranumerary rib, bilateral hip dislocation, digital anomalies, and growth retardation. Newborn aneuploidy detection (NAD) based on interphase fluorescence in situ hybridization (FISH) indicated monosomy 13 in 47 of 200 (23.5%) peripheral blood cells (normal cutoff 8.5% at 95% CI). The follow-up banded metaphase-based analysis of 20 cells revealed a karyotype of 46,XX. The analysis of 30 additional cells revealed one cell to have monosomy 13 and a small ring chromosome. In the abnormal cell line, the ring was positive for whole chromosome paint (wcp) 13 and negative for Rb1 (13q14.3). The ring was detected in 4% of 80 additional metaphases studied by FISH. Therefore, the ring was present in 4% (5/130) of metaphases from peripheral blood. Analysis of buccal cells by FISH indicated the ring was present in 36% of cells. A higher degree of mosaicism (60%) was detected in fibroblast cultures from a skin biopsy. The low-level mosaicism of ring 13 in metaphase cells from peripheral blood would have been missed if the standard 20 GTL-banded metaphases had been analyzed. In this case, a preliminary interphase FISH study had indicated monosomy 13 resulting from a large 13q deletion that included the Rb1 locus. This finding initiated the analysis of additional metaphases by GTL-banding and the analysis of metaphases and interphases by FISH. The clinical presentation of our patient was consistent with reported cases of 13q deletions. In addition, our patient had airway anomalies, including a type I laryngeal cleft and tracheal stenosis, which are previously unreported.     

Analysis of sex chromosome aneuploidy in 41 patients with Turner syndrome: a study of 'hidden' mosaicism

We performed a genetic study of sex chromosome mosaicism in 41 Turner syndrome patients. The investigation was carried out in four phases: cytogenetics (G-banding), FISH, PCR for SRY in all 41 cases, and sequencing of the SRY gene in the 2 patients with the Y chromosome. The application of classical alpha-satellite probes (CEP-X and CEP-Y), painting probes (WCP-X and WCP-Y) and also XIST, DXZ4 and two subchromosomal painting libraries (SCPL 116 and SCPL102) covering the short and the long arm of the X chromosome, respectively, allowed us to find new mosaic cell lines (mosaicism) in 37 out of 41 patients; only 4 patients were defined as 45,X non-mosaic. The most frequent hidden mosaic was 45,X/46,XX in 32% of the cases; the presence of isochromosomes comprised 25% and markers 5%. The patients who had been previously diagnosed as mosaics displayed a higher complexity in their karyotypes due to the presence of new cell lines. The Y chromosome and the SRY gene were present in blood and ovarian tissue in 2 patients with karyotypes 45,X/46,XY and 45,X/46,X,idic(Ynf). In both patients, the sequencing of the SRY gene confirmed a nucleotide sequence identical to that of a control male. Our results support the hypothesis of 'the necessity of mosaicism for survival', and thus, a mitotic origin for this syndrome.     

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.     

Genetic significance of skewed X-chromosome inactivation in premature ovarian failure

To determine the relationship between premature ovarian failure (POF) and skewed X-chromosome inactivation (XCI), karyotype, and XCI status in 43 patients with POF (group I) and 43 age-matched control women with regular menstrual cycles (group II) were evaluated. Evaluation of XCI status was based on the CAG triplet repeat polymorphism assay in the androgen receptor gene after sodium bisulfite treatment of DNA samples, and XCI patterns were classified as random (XCI < 70% skewing) or skewed (> or =70%). Furthermore, skewed XCI was classified under three different thresholds (> or =70, > or =80, or > or =90%). Karyotyping by G-banding and fluorescence in situ hybridization (FISH) on peripheral blood lymphocytes showed that one patient in group I had a deletion of Xq22, and another was 47,XXX. The frequency of low-level 45,X/46,XX mosaicism was nearly equal in both groups. In women without any X-chromosomal aberrations, the incidence of skewed XCI in group I was significantly higher than in group II on all threshold levels. Furthermore, extremely skewed XCI (> or =90%) was observed only in group I. These results indicate that POF may be caused by some underlying genetic disorders, which may induce skewed XCI.     

Cytogenetic evaluation,fluorescence in situ hybridization,and molecular study of psu idic(X)(pter-->q22.3::q22.3-->pter) chromosome abberation in a girl with moderate growth retardation

Combined cytogenetic, fluorescence in situ hybridization (FISH), and molecular analysis are useful in the diagnosis of sex chromosome aberrations. These methods were used in karyotype analysis of a 4-year-old girl with mild dysmorphism and growth retardation. Standard cytogenetic and FISH analysis was done on slides obtained from peripheral blood lymphocyte culture, and the molecular study was performed by using DNA polymorphism analysis. Both parents had normal karyotypes. Chromosome analysis of the proband identified the karyotype with 46 chromosomes and a late replicating dicentric X. Interphase FISH with an alpha satellite X centromere probe revealed two mosaic cell lines. Three signals were observed at 84.5% and one signal at 15.5% of the interphase cells. Molecular analysis showed that the dicentric X chromosome was of paternal origin. Based on this study, we concluded that the karyotype of the patient was 45,X/46,X, psu idic(X)(q22.3), with the trisomy Xpter-->q22.3 and monosomy Xqter-->q22.3. Dicentric X was the result of an isolocal break in both chromatids of the paternal X chromosome and subsequent rejoining of the broken ends, followed by the inactivation of one centromere. This study illustrates the usefulness of combined cytogenetic and molecular investigations for the detection of mosaicism, understanding the mechanism of the formation and parental origin of chromosomal rearrangement, and establishing the diagnosis.