Placental mosaicism for Trisomy 13: a challenge in providing the cell-free fetal DNA testing.

PURPOSE: We investigated the disagreement between the positive cell-free fetal DNA test for trisomy 13 and the standard cytogenetic diagnosis of one case. METHODS: Cell-free fetal DNA testing was performed by massively parallel sequencing. We used conventional cytogenetic analysis to confirm the commercial cell-free fetal DNA testing. Additionally, postnatal fluorescent in situ hybridization (FISH) testing was performed on placental tissues. RESULTS: The cell-free fetal DNA testing result was positive for trisomy 13. G-banded analysis of amniotic fluid was normal, 46, XY. FISH testing of tissues from four quadrants of the placenta demonstrated mosaicism for trisomy 13. CONCLUSIONS: A positive cell-free fetal DNA testing result may not be representative of the fetal karyotype because of placental mosaicism. Cytogenetic analysis should be performed when abnormal cell-free fetal DNA test results are obtained.

45,X mosaicism in northeast China: a clinical report and review of the literature.

PURPOSE: To explore the prevalence and clinical features, especially the reproductive function, of 45,X mosaicism patients in northeast China. METHODS: GTG-banding was performed on a series of 2,250 patients from our genetic counseling clinic. Each of these patients underwent a physical examination and was interviewed about their medical history and reproductive problems. Literature on 45,X mosaicism was accessed using PubMed and reviewed. RESULTS: The prevalence of 45,X mosaicism in northeast China is 0.36 % (8/2250), and the mosaic karyotype of our study accounted for 61.54 % (8/13) of Turner syndrome cases. This is comparable with studies from Asia, Europe, South America and other regions. The affected patients showed genital abnormalities, abnormal pregnancy or infertility. CONCLUSION: 45,X mosaicism is commonly seen in the genetic counseling clinic. Extensive cytogenetic assessment may improve the detection rate in patients with congenital dysplasia, or history of abnormal pregnancy or infertility. Karyotyping plays a key role in prognosis and assisted reproduction or early surgical treatment.

Prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome (sSMC) inherited from her mosaic sSMC(15) mother and a literature review.

OBJECTIVE: We characterized a maternally inherited small supernumerary marker chromosome (sSMC) derived from chromosome 15 according to prenatal detection and made a review on the prenatal sSMC(15) cases with mosaic maternal inheritance. CASE REPORT: A 29-year-old woman underwent amniocentesis at 19 weeks of gestation due to the high risk of Down syndrome in maternal serum screening. No abnormalities were observed in prenatal ultrasound findings. G-banding analysis revealed a karyotype of 47,XX,+mar. Subsequently, we recalled the couple back for chromosomal analysis. The father's karyotype was normal while the mother's karyotype was 47,XX,+mar[15]/46,XX[35]. Molecular genetic analysis was utilized to identify the marker chromosome. The chromosomal microarray analysis (CMA) results of the mother showed there existed microduplications in the locus of 14q32.33, 15q21.1, 19p12 and Xq26.2, respectively. Then Fluorescence in situ hybridization (FISH) using specific probes for chromosomes 13/21, 14/22, and 15 was applied on the mother and the fetus. And the marker chromosomes for the mother and the fetus were all finally identified as inv dup(15) (D15Z1++, SNRPN-, PML-), which illustrated that the fetus inherited the sSMC(15) from her mother. Finally, a healthy female infant was delivered with no phenotypic abnormalities at 39 weeks. CONCLUSION: The combined utilization of the molecular genetic technologies, such as FISH and CMA, plays a critical role in the identification of the origins and genetic constitutions of sSMC, which would make a significant contribution to genetic counseling and prenatal diagnosis.

AZFa Microdeletions: Occurrence in Chinese Infertile Men and Novel Deletions Revealed by Semiconductor Sequencing.

OBJECTIVE: To evaluate the frequency of azoospermia factor (AZFa) microdeletions among infertile men and establish a new high-throughput sequencing method to detect novel deletion types. MATERIALS AND METHODS: A total of 3731 infertile men were included. Karyotype analysis was performed using G-band staining of peripheral blood lymphocytes. Polymerase chain reaction (PCR) amplification using specific sequence-tagged sites (STS) was performed to screen for AZF region microdeletions of the Y chromosome. A novel semiconductor sequencing method was established to detect high-resolution AZFa microdeletions. RESULTS: Of 3731 infertile men, 341 (9.14%) had microdeletions in AZFa, AZFb, or AZFc. Thirteen of these (3.81%) had a deletion in the AZFa region (mean age: 27.3 ± 4 years, range: 22-34), which included 12 subjects with a normal karyotype (46, XY) and 1 with Klinefelter syndrome (47, XXY). Four of 10 subjects with complete AZFa microdeletions (sY86 and sY84 loss) underwent semiconductor sequencing. They all had DNA sequence deletions from nt 14469266 to 15195932, whereas their fathers had no deletions. One subject with partial AZFa microdeletion (sY86 loss) and his father underwent semiconductor sequencing and STS-PCR analysis. The same deletion (sY86 loss with DNA sequence deletion from nt 14469266 to 14607672) was identified in both subjects. Forty sperm donators and 50 infertile men showed no AZFa microdeletions by either method. CONCLUSION: AZFa deletions are present at a low frequency in men with azoospermia or oligozoospermia. Novel sequencing methods can be used for these patients to reveal high-resolution AZFa microdeletions.