Prevalence of recurrent pathogenic microdeletions and microduplications in over 9500 pregnancies.

OBJECTIVES: The implementation of chromosomal microarray analysis (CMA) in prenatal testing for all patients has not achieved a consensus. Technical alternatives such as Prenatal BACs-on-Beads(TM) (PNBoBs(TM) ) have thus been applied. The aim of this study was to provide the frequencies of the submicroscopic defects detectable by PNBoBs(TM) under different prenatal indications. METHODS: A total of 9648 prenatal samples were prospectively analyzed by karyotyping plus PNBoBs(TM) and classified by prenatal indication. The frequencies of the genomic defects and their 95%CIs were calculated for each indication. RESULTS: The overall incidence of cryptic imbalances was 0.7%. The majority involved the DiGeorge syndrome critical region (DGS). The additional diagnostic yield of PNBoBs(TM) in the population with a low a priori risk was 1/298. The prevalences of DGS microdeletion and microduplication in the low-risk population were 1/992 and 1/850, respectively. CONCLUSIONS: The constant a priori risk for common pathogenic cryptic imbalances detected by this technology is estimated to be ~0.3%. A prevalence higher than that previously estimated was found for the 22q11.2 microdeletion. Their frequencies were independent of maternal age. These data have implications for cell-free DNA screening tests design and justify prenatal screening for 22q11 deletion, as early recognition of DGS improves its prognosis.

Prenatal diagnosis of 24 cases of microduplication 22q11.2: an investigation of phenotype-genotype correlations.

OBJECTIVE: Microduplication 22q11.2 is primarily characterized by a highly variable clinical phenotype, which ranges from apparently normal or slightly dysmorphic features (in the presence or absence of learning disorders) to severe malformations with profound mental retardation. Hence, genetic counseling is particularly challenging when microduplication 22q11.2 is identified in a prenatal diagnosis. Here, we report on 24 prenatal cases of microduplication 22q11.2. METHODS: Seventeen of the cases were also reanalyzed by microarray analysis, in order to determine copy number variations (CNVs, which are thought to influence expressivity). We also searched for possible correlations between fetal phenotypes, indications for invasive prenatal diagnosis, inheritance, and pregnancy outcomes. RESULTS: Of the 24 cases, 15 were inherited, six occurred de novo, and three were of unknown origin. Termination of pregnancy occurred in seven cases and was mainly decided on the basis of ultrasound findings. Moreover, additional CNVs were found in some patients and we try to make a genotype-phenotype correlation. CONCLUSION: We discuss the complexity of genetic counseling for microduplication 22q11.2 and comment on possible explanations for the clinical heterogeneity of this syndrome. In particular, we assessed the co-existence of additional CNVs and their contribution to phenotypic variations in chromosome 22q11.2 microduplication syndrome.

Prenatal diagnosis of 17p13.1p13.3 duplication.

We present here the first prenatal diagnosis of 17p13.1p13.3 duplication. 17p13.3 duplication has recently been defined as a new distinctive syndrome with several diagnosed patients. In the current case prenatal chromosome analysis (G-banding) performed on cultured amniocytes revealed additional material in chromosome 19p. This was further defined as a chromosome 17p13.1p13.3 duplication by FISH and genomic microarray analysis (GMA). In addition Prenatal BACs-on-Beads (PN_BoBs) assay was performed, which detected the duplication clearly. This enables rapid prenatal diagnosis of the duplication for this family in the future.

A microduplication on chromosome 17p13.1p13.3 including the PAFAH1B1 (LIS1) gene.

Recently, three children with a microduplication in 17p13 including the PAFAH1B1 gene that encodes LIS1 were reported. LIS1 overexpression has earlier been shown to affect brain development by causing migrational defects and reductions in brain volume [Bi et al., 2009]. Here, we report an additional patient with a microduplication on chromosome 17p13.1p13.3 including the PAFAH1B1 gene, that was inserted into the long arm of chromosome 4. The patient had psychomotor and growth retardation, dysmorphic features, small ventricular septal defect (VSD), and immunoglobulin abnormality. Only subtle abnormalities in brain MRI scan were seen. Interestingly, the facial features of our patient closely resemble those previously reported in 17p trisomy patients.

Distinct differentiation characteristics of individual human embryonic stem cell lines.

BACKGROUND: Individual differences between human embryonic stem cell (hESC) lines are poorly understood. Here, we describe the derivation of five hESC lines (called FES 21, 22, 29, 30 and 61) from frozen-thawed human embryos and compare their individual differentiation characteristic. RESULTS: The cell lines were cultured either on human or mouse feeder cells. The cells grew significantly faster and could be passaged enzymatically only on mouse feeders. However, this was found to lead to chromosomal instability after prolonged culture. All hESC lines expressed the established markers of pluripotent cells as well as several primordial germ cell (PGC) marker genes in a uniform manner. However, the cell lines showed distinct features in their spontaneous differentiation patterns. The embryoid body (EB) formation frequency of FES 30 cell line was significantly lower than that of other lines and cells within the EBs differentiated less readily. Likewise, teratomas derived from FES 30 cells were constantly cystic and showed only minor solid tissue formation with a monotonous differentiation pattern as compared with the other lines. CONCLUSION: hESC lines may differ substantially in their differentiation properties although they appear similar in the undifferentiated state.

Elevated incidence of chromosomally chaotic embryos among frozen-thawed preimplantation embryos.

OBJECTIVE: The aim of the study was to evaluate the effect of cryopreservation on the formation of chromosomal abnormalities in human preimplantation embryos. STUDY DESIGN: The chromosomal constitutions of cleavage stage embryos (n = 61) were assessed using fluorescent in situ hybridisation (FISH) technique, applying probes for chromosomes 13, 16, 18, 21, X and Y. Study group embryos frozen at zygote or two-cell stage (n = 29) were cultured in vitro post-thawing until they reached four- to six-cell stage, after which their chromosomal constitutions were assessed. Control group embryos frozen at four- to six-cell stage (n = 32) were analysed immediately after thawing in order to exclude any post-thaw effect. The proportions of genetically normal and abnormal embryos were compared between study and control group. RESULTS: The proportions of normal, aneuploid and mosaic embryos were similar in both groups. However, significantly (P < 0.05) higher proportion of chaotic embryos in study (24.1%) compared to control group (6.3%) was observed. CONCLUSION: The elevated level of chromosomally chaotic embryos among embryos that had undergone cellular division after thawing as compared to embryos analysed immediately after thawing indicates a potential negative impact of cryopreservation on the formation of chromosomal abnormalities in preimplantation embryos.