Supernumerary marker chromosomes (SMCs) in Turner syndrome are mostly derived from the Y chromosome

Identification of Y-Chromosome Sequences in Turner Syndrome

OBJECTIVES

To investigate the presence of Y-chromosome sequences and determine their frequency in patients with Turner syndrome.

METHODS

The study included 23 patients with Turner syndrome from Brazil, who gave written informed consent for participating in the study. Cytogenetic analyses were performed in peripheral blood lymphocytes, with 100 metaphases per patient. Genomic DNA was also extracted from peripheral blood lymphocytes, and gene sequences DYZ1, DYZ3, ZFY and SRY were amplified by Polymerase Chain Reaction.

RESULTS

The cytogenetic analysis showed a 45,X karyotype in 9 patients (39.2 %) and a mosaic pattern in 14 (60.8 %). In 8.7 % (2 out of 23) of the patients, Y-chromosome sequences were found. This prevalence is very similar to those reported previously. The initial karyotype analysis of these patients did not reveal Y-chromosome material, but they were found positive for Y-specific sequences in the lymphocyte DNA analysis.

CONCLUSION

The PCR technique showed that 2 (8.7 %) of the patients with Turner syndrome had Y-chromosome sequences, both presenting marker chromosomes on cytogenetic analysis.

Clinical implications of the detection of Y-chromosome mosaicism in Turner's syndrome: report of 3 cases

OBJECTIVE

To determine the clinical implications of the presence of a Y chromosome in Turner's syndrome patients with karyotype abnormalities.

DESIGN

To investigate the presence of Y-chromosome sequences in different tissue samples.

SETTING

Endocrinology outpatient clinic of a federal university in Brazil.

PATIENT(S)

Five Turner's syndrome patients with karyotype abnormalities such as marker chromosomes, additional material, or ring chromosomes.

INTERVENTION(S)

Peripheral blood, oral epithelial cells, and hair root samples were collected.

MAIN OUTCOME MEASURE(S)

The SRY gene and the DYZ3 repeat region were amplified by polymerase chain reaction followed by gel electrophoresis mobility of amplified genomic DNA, and ultraviolet visualization. Prophylactic gonadectomy was offered to the Y-positive patients.

RESULT(S)

The analysis of the different tissues revealed that three of the five patients studied presented Y-chromosome mosaicism. These three patients underwent prophylactic gonadectomy, and in one of them, the histopathologic study of the gonads disclosed hilus cell hyperplasia and stromal luteoma with contralateral nodular hyperthecosis.

CONCLUSION(S)

A systematic search for Y-chromosome mosaicism in Turner's syndrome patients is justified by the risk of developing gonadal tumors or androgen-producing lesions.

Gonadoblastoma in Turner syndrome and Y-chromosome-derived material

The identification of Y-chromosome material is important in females with Ullrich-Turner syndrome (UTS) due to the risk of developing gonadoblastoma or other gonadal tumors. There is controversy regarding the frequency of the Y-chromosome-derived material and the occurrence of gonadoblastoma in these patients. The aim of our study was to evaluate a large number of patients with UTS, followed before and during the pubertal age for the prevalence of Y-chromosome derived material, the occurrence of gonadoblastoma, and the incidence of possible neoplastic degeneration. An unselected series of 171 patients with UTS (1-34 years old), diagnosed cytogenetically, was studied for Y-chromosome markers (SRY and Y-centromeric DYZ3 repeats). The follow-up was of 2-22 years; 101 of these patients were followed during pubertal age. Y-chromosome material was found in 14 patients (8%): 12 of these were gonadectomized (2.8-25.9 years). A gonadoblastoma was detected in four patients under 16 years of age: in two, Y-material was detected only at molecular analysis (at conventional cytogenetic analysis, one was included in the 45,X group and one in the X + mar group) and one had also an immature teratoma and an endodermal sinus carcinoma. The prevalence of gonadoblastoma in our series of gonadectomized UTS patients with Y-positive material was of 33.3% (4/12). Our data suggest that the age of appearance and the possibility of malignant degeneration of gonadoblastoma can occur early in life. These patients, in particular those with 45,X or a marker chromosome may benefit from molecular screening to detect the presence of Y-chromosome material; PCR is a rapid and inexpensive technique. At the moment, laparoscopy and preventive gonadectomy performed as soon as possible remain the procedures of choice for patients with UTS, when Y-chromosome has been identified, as we are still unable to predict a future malignant evolution of gonadoblastoma.

Identification of high frequency of Y chromosome deletions in patients with sex chromosome mosaicism and correlation with the clinical phenotype and Y-chromosome instability

A mosaic karyotype consisting of a 45,X cell line and a second cell line containing a normal or an abnormal Y chromosome is relatively common and is associated with a wide spectrum of clinical phenotypes. The aim of this study was to investigate patients with such a mosaic karyotype for Y chromosome material loss and then study the possible association of the absence of these regions with the phenotype, diagnosis, and Y-chromosome instability. We studied 17 clinically well-characterized mosaic patients whose karyotype consisted of a 45,X cell line and a second cell line containing a normal or an abnormal Y chromosome. The presence of the Y chromosome centromere was verified by fluorescence in situ hybridization (FISH) and was then characterized by 44 Y-chromosome specific-sequence tagged site (STS) markers. This study identifies a high frequency of Yq chromosome deletions (47%). The deletions extend from interval 5 to 7 sharing a common deleted interval (6F), which overlaps with the azoospermia factor region (AZF) region. This study finds no association between Y-chromosome loci hosting genes other than SRY, and the phenotypic sex, the diagnosis, and the phenotype of the patients. Furthermore, this study shows a possible association of these deletions with Y-chromosome instability.

Health supervision for children with Turner syndrome

This report is designed to assist the pediatrician in caring for the child in whom the diagnosis of Turner syndrome has been confirmed by karyotyping. The report is meant to serve as a supplement to the American Academy of Pediatrics' "Recommendations for Preventive Pediatric Care" and emphasizes the importance of continuity of care and the need to avoid its fragmentation by ensuring a medical home for every girl with Turner syndrome. The pediatrician's first contact with a child with Turner syndrome may occur during infancy or childhood. This report also discusses interactions with expectant parents who have been given the prenatal diagnosis of Turner syndrome and have been referred for advice.

Molecular breakpoint analysis and relevance of variable mosaicism in a woman with short stature, primary amenorrhea, unilateral gonadoblastoma, and a 46,X,del(Y)(q11)/45,X karyotype

We report on a 30-year-old woman with short stature, completely female external genitalia, primary amenorrhea, bilateral streak gonads, unilateral gonadoblastoma, and a 46,X,del(Y)(q11)/45,X karyotype. Variable levels of mosaicism were found in blood and cultivated fibroblasts from both the skin and ovaries, with the percentage of the 45,X lineage never exceeding 33%. Fluorescence in situ hybridization (FISH) was performed with alpha satellite centromere region probes of the X and Y chromosomes (DXZ1 and DXZ3) as well as with the unique-sequence, locus-specific, sex-determining region of the Y chromosome gene (SRY) and the DXZ1 probes. Each signal was noted for DXZ1 on the X chromosome and for the Y probes on the marker chromosome. Molecular investigations with a panel of PCR markers spread over the whole Y chromosome indicated a deletion breakpoint between sY 78 (interval 4) and sY 151 (interval 5F). No mutation of the high mobility group-box (HMG-box) of the SRY gene could be found following sequence analysis. The phenotype/genotype correlation demonstrates the broad phenotypic range of low-level 45,X mosaicism with the resultant short stature and external female phenotype, despite the presence of SRY in a high proportion of cells in various tissues.

Detection of Y-specific sequences in 122 patients with Turner syndrome: nested PCR is not a reliable method

The incidence of Y chromosome sequences in patients with Turner syndrome has been evaluated in several studies, and its frequency varied from 0% to 61%, depending on the molecular methodology used. The aim of our study was to screen for Y chromosome sequences in 122 patients with Turner syndrome without cytogenetic evidence of this chromosome. DNA of 100 normal women was also screened and it was used as a negative control. To identify cryptic Y mosaicism, eight regions of Y chromosome were amplified by PCR. In order to increase the sensitivity of Y sequence detection, a nested PCR of the SRY and TSPY genes was also performed. All patients had several stigmata of Turner syndrome and none of them presented with signs of virilization. The most frequent karyotype was 45,X (54.1%), followed by mosaicism involving structural aberration of the X chromosome. There were 12 patients who carried a marker or ring chromosome. First-round PCR identified Y chromosome sequences in only four patients (3%), and all of them had a chromosome mosaicism with at least one cell lineage with a marker chromosome. After nested PCR, 25% of the patients and 14% of the normal women were positive for the presence of Y sequences. Contamination with extraneous genomic DNA was ruled out by microsatellite studies, but we cannot eliminate the possibility of contamination with PCR products, despite careful handling. We conclude that nested PCR overestimated the frequency of Y sequences in patients with Turner syndrome and should be avoided to prevent false positive results, which lead to unnecessary surgical treatment of these patients.

A non-sex chromosome marker in a patient with an atypical Ullrich-Turner phenotype and mosaicism of 46,X,mar/46,XX

The absence of a sex chromosome in conjunction with the presence of a marker chromosome generally implicates a sex chromosome origin for such marker chromosomes. These types of findings are frequently associated with Ullrich-Turner syndrome. We report a patient that presented with an atypical Ullrich-Turner phenotype and a cytogenetic mosaicism of 46,X,mar/46,XX. The marker chromosome was derived from chromosome 20, not from the X or Y chromosome. The patient's clinical features are described and discussed relative to the cytogenetic findings. This case further demonstrates the necessity of marker chromosome identification for accurate phenotype-karyotype correlation.

ZNF232: structure and expression analysis of a novel human C(2)H(2) zinc finger gene, member of the SCAN/LeR domain subfamily

We have identified a novel zinc finger gene, ZNF232, mapped to human chromosome 17p12. The coding region of the gene is organized in three exons corresponding to a 417 amino acid long polypeptide containing a SCAN/LeR domain and five C(2)H(2)-type zinc fingers. ZNF232 is possibly a nuclear protein, as suggested by expression analysis of GFP/ZNF232 chimeric constructs. ZNF232 transcripts were detected in a wide collection of adult human tissues. The gene is possibly subjected to tissue-specific post-transcriptional regulation by means of alternative splicing.

Molecular genetics of Turner syndrome: correlation with clinical phenotype and response to growth hormone therapy

To correlate the origin of the retained X in Turner syndrome with phenotype, pre-treatment height and response to recombinant human growth hormone (rhGH) therapy, systematic clinical assessment and molecular studies were carried out in 33 Greek children with Turner syndrome and their parents including 18 children with 45,X and 15 with X-mosaicism. Microsatellite markers on X chromosomes (DXS101 and DXS337) revealed that the intact X was paternal (Xp) in 15/30 and maternal (Xm) in 15/30 children, while 3/33 families were non-informative. No significant relationship was found between parental origin of the retained X and birth weight/length/gestational age, blepharoptosis, pterygium colli, webbed neck, low hairline, abnormal ears, lymphoedema, short 4th metacarpal, shield chest, widely spaced nipples, cubitus valgus, pigmented naevi, streak gonads, and cardiovascular/renal anomalies. With regard to the children's pre-treatment height, there was a significant correlation with maternal height and target height in both Xm and Xp groups. No differences were found between Xm and Xp groups and the improvement of growth velocity (GV) during the first and second year of rhGH administration, while for both groups GV significantly improved with rhGH by the end of the first and the second year. To our knowledge, this is the first attempt to correlate the parental origin of Turner syndrome with the response to rhGH therapy.

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 10(5) 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.

Frequency of Y chromosomal material in Mexican patients with Ullrich-Turner syndrome

Cytogenetic studies have shown that 40-60% of patients with Ullrich-Turner syndrome (UTS) are 45,X, whereas the rest have structural aberrations of the X chromosome or mosaicism with a second cell line containing a structurally normal or abnormal X or Y chromosome. However, molecular analysis has demonstrated a higher proportion of mosaicism, and studies in different populations have shown an extremely variable frequency of Y mosaicism of 0-61%. We used Southern blot analysis and polymerase chain reaction (PCR) to detect the presence of Ycen, ZFY, SRY, and Yqh in 50 Mexican patients with UTS and different karyotypes to determine the origin of marker chromosomes and the presence of Y sequences. Our results indicated the origin of the marker chromosome in 1 patient and detected the presence of Y sequences in 4 45,X patients. Taken together, we found a 12% incidence of Y sequences in individuals with UTS. The amount of Y-derived material was variable, making the correlation between phenotype and molecular data difficult. Only 1 patient had a gonadoblastoma. We discuss the presence of Y chromosomes or Y sequences in patients with UTS and compare our frequency with that previously reported.