Uniparental disomy in fetuses diagnosed with balanced Robertsonian translocations: risk estimate.

Forty-two fetuses with non-homologous Robertsonian translocations were analyzed for uniparental disomy (UPD). One fetus with a de novo translocation t(13q;14q) had maternal isodisomy of chromosome 14. In a summary of the published data (including the present study), 315 cases were analyzed for UPD after prenatal diagnosis of balanced Robertsonian translocations, of these two fetuses had UPD, giving a risk estimate of 0.65% (CI 0.2-2.3). This risk justifies the recommendation of UPD analysis in fetuses diagnosed prenatally with Robertsonian translocations, with the emphasis on the chromosomes known to contain imprinted genes, such as 14 and 15. We also discuss the possibility of UPD in offspring of Robertsonian translocation carriers with normal karyotype. Based on the risk for UPD in fetuses with Robertsonian translocation we suggest to test these fetuses for UPD and to do so on amniocytes rather than chorionic villi when the risk for unbalanced karyotype is approximately 1%, comparable to the risk for UPD.

Silverstein S ，Lerer I ，Sagi M ，Frumkin A ，Ben-Neriah Z ，Abeliovich D ... -  《PRENATAL DIAGNOSIS》

Prenatal search for UPD 14 and UPD 15 in 83 cases of familial and de novo heterologous Robertsonian translocations.

The presence in the conceptus of a Robertsonian translocation predisposes to UPD formation, mainly by post-zygotic events of chromosome abnormality rescue. This is due to the increased risk of generating aneuploid zygotes because the rearranged chromosome and the respective homologues are prone to non-disjunction errors. Given this, carriers and karyotypically normal individuals conceived from a parent with a Robertsonian translocation are at risk for UPD. Abnormal phenotypes due to an imprinting effect have been found to be associated with UPD 14 and 15. The aim of the study was to refine, at the time of prenatal diagnosis, the risk for UPD 14 and 15 in a population with Robertsonian translocations involving these chromosomes. Sixty-five cases of familial and de novo heterologous Robertsonian translocations involving chromosomes 14 and 15 and 18 fetuses with a normal karyotype, but conceived by a Robertsonian translocation carrier were prenatally studied to investigate the presence of UPD for chromosomes 14 and 15. Of the 65 Robertsonian translocation carriers, one fetus with a de novo der(14;21) showed maternal UPD 14. None of the 18 fetuses with a normal karyotype had UPD. Our data, combined with other previous prenatal investigations provide a general risk estimate for UPD 14 and 15 of 0.6%. Nevertheless, combining our data and those previously reported, all three fetuses with UPD had a de novo Robertsonian translocation, thus suggesting a risk of UPD formation of about 3% for this specific group of translocation carriers.

Ruggeri A ，Dulcetti F ，Miozzo M ，Grati FR ，Grimi B ，Bellato S ，Natacci F ，Maggi F ，Simoni G ... -  《PRENATAL DIAGNOSIS》

Nonhomologous Robertsonian translocations (NHRTs) and uniparental disomy (UPD) risk: an Italian multicentric prenatal survey.

The risk of uniparental disomy (UPD) occurrence associated with the prenatal finding of balanced nonhomologous Robertsonian translocations (NHRTs) has been estimated only on limited empirical data. The aim of the study was to verify the estimate of the general risk, to get narrower confidence intervals by cumulating the data and to obtain risk estimates for specific translocation types. We tested for UPD 160 prenatal specimens referred to the participant centers after the cytogenetic finding of NHRT. One case of upd(14)mat was found, associated with a 45,XX,der(14;22)mat fetal karyotype. The general empirical risk of UPD occurrence in NHRT carrier fetuses, corrected for the actual number of chromosomes analyzed, was 0.76% (95% CI 0.02-4.25%). Cumulative data with previous studies gives a general risk of UPD associated with NHRT of 0.80% (95% CI 0.17-2.34%). The UPD risk for the specific NHRT der(13;14) did not significantly differ from that of the other NHRTs taken together. The present survey confirms the previously estimated risk of occurrence of UPD in offspring of NHRT carriers as a low, but not negligible risk, worth being investigated in prenatal diagnosis.

Sensi A ，Cavani S ，Villa N ，Pomponi MG ，Fogli A ，Gualandi F ，Grasso M ，Sala E ，Pietrobono R ，Baldinotti F ，Savin E ，Ferlini A ，Cecconi M ，Rossi S ，Gallone S ，Bellini C ，Neri G ，Martinoli E ，Simi P ，Dalprà L ，Genuardi M ，Dagna-Bricarelli F ，Calzolari E ... -  《PRENATAL DIAGNOSIS》

Unbalanced and balanced acrocentric rearrangements involving chromosomes other than chromosome 21 at amniocentesis.

Chen CP ，Chern SR ，Wu PC ，Tsai FJ ，Lee CC ，Town DD ，Chen WL ，Chen LF ，Lee MS ，Pan CW ，Wang W ... -  《-》

Risk of mosaicism and uniparental disomy associated with the prenatal diagnosis of a non-homologous Robertsonian translocation carrier.

To estimate the fetal risk of uniparental disomy (UPD) associated with the presence of a Robertsonian translocation (RT) in a parent or in the fetus, to determine whether it is clinically indicated to test these pregnancies for UPD. Retrospective analysis of our Centre's experience in testing prenatal specimens for UPD in cases of known familial RTs or fortuitous RT finding. In addition, all reports dealing with prenatal UPD testing in similar populations obtained from PUBMED and the 1995-2001 American Society of Human Genetics Meeting's abstracts were assessed. No case of UPD 14 or 15 was found among the 51 tests performed at our Centre. Meta-analysis identified one case of UPD13 out of 687 UPD studies, conducted in 400 prenatal diagnoses. The 95% confidence interval of the risk of UPD in the population studied (1 in 738) is 0.02-0.76%. In one report, trisomy mosaicism for one of the chromosomes involved in the translocation was found in 3 cases out of 169 (95% confidence interval: 0.1-3 %). Fetuses carrying a Robertsonian translocation have a risk of UPD of 0.02-0.76% (95% CI). In this population, trisomy mosaicism is more frequent than UPD. This finding justifies the study of additional colonies in all cases of prenatally diagnosed RT.

Bruyère H ，Wilson RD ，Langlois S 《FETAL DIAGNOSIS AND THERAPY》