Multimeric complexes of the PML-retinoic acid receptor alpha fusion protein in acute promyelocytic leukemia cells and interference with retinoid and peroxisome-proliferator signaling pathways.

The t(15;17) chromosomal translocation, specific for acute promyelocytic leukemia (APL), fuses the PML gene to the retinoic acid receptor alpha (RAR alpha) gene, resulting in expression of a PML-RAR alpha hybrid protein. In this report, we analyzed the nature of PML-RAR alpha-containing complexes in nuclear protein extracts of t(15;17)-positive cells. We show that endogenous PML-RAR alpha can bind to DNA as a homodimer, in contrast to RAR alpha that requires the retinoid X receptor (RXR) dimerization partner. In addition, these cells contain oligomeric complexes of PML-RAR alpha and endogenous RXR. Treatment with retinoic acid results in a decrease of PML-RAR alpha protein levels and, as a consequence, of DNA binding by the different complexes. Using responsive elements from various hormone signaling pathways, we show that PML-RAR alpha homodimers have altered DNA-binding characteristics when compared to RAR alpha-RXR alpha heterodimers. In transfected Drosophila SL-3 cells that are devoid of endogenous retinoid receptors PML-RAR alpha inhibits transactivation by RAR alpha-RXR alpha heterodimers in a dominant fashion. In addition, we show that both normal retinoid receptors and the PML-RAR alpha hybrid bind and activate the peroxisome proliferator-activated receptor responsive element from the Acyl-CoA oxidase gene, indicating that retinoids and peroxisome proliferator receptors may share common target genes. These properties of PML-RAR alpha may contribute to the transformed phenotype of APL cells.

Rare chromosome abnormalities, prevalence and prenatal diagnosis rates from population-based congenital anomaly registers in Europe.

The aim of this study is to quantify the prevalence and types of rare chromosome abnormalities (RCAs) in Europe for 2000-2006 inclusive, and to describe prenatal diagnosis rates and pregnancy outcome. Data held by the European Surveillance of Congenital Anomalies database were analysed on all the cases from 16 population-based registries in 11 European countries diagnosed prenatally or before 1 year of age, and delivered between 2000 and 2006. Cases were all unbalanced chromosome abnormalities and included live births, fetal deaths from 20 weeks gestation and terminations of pregnancy for fetal anomaly. There were 10,323 cases with a chromosome abnormality, giving a total birth prevalence rate of 43.8/10,000 births. Of these, 7335 cases had trisomy 21,18 or 13, giving individual prevalence rates of 23.0, 5.9 and 2.3/10,000 births, respectively (53, 13 and 5% of all reported chromosome errors, respectively). In all, 473 cases (5%) had a sex chromosome trisomy, and 778 (8%) had 45,X, giving prevalence rates of 2.0 and 3.3/10,000 births, respectively. There were 1,737 RCA cases (17%), giving a prevalence of 7.4/10,000 births. These included triploidy, other trisomies, marker chromosomes, unbalanced translocations, deletions and duplications. There was a wide variation between the registers in both the overall prenatal diagnosis rate of RCA, an average of 65% (range 5-92%) and the prevalence of RCA (range 2.4-12.9/10,000 births). In all, 49% were liveborn. The data provide the prevalence of families currently requiring specialised genetic counselling services in the perinatal period for these conditions and, for some, long-term care.

Recurrent deletions and reciprocal duplications of 10q11.21q11.23 including CHAT and SLC18A3 are likely mediated by complex low-copy repeats.

We report 24 unrelated individuals with deletions and 17 additional cases with duplications at 10q11.21q21.1 identified by chromosomal microarray analysis. The rearrangements range in size from 0.3 to 12 Mb. Nineteen of the deletions and eight duplications are flanked by large, directly oriented segmental duplications of >98% sequence identity, suggesting that nonallelic homologous recombination (NAHR) caused these genomic rearrangements. Nine individuals with deletions and five with duplications have additional copy number changes. Detailed clinical evaluation of 20 patients with deletions revealed variable clinical features, with developmental delay (DD) and/or intellectual disability (ID) as the only features common to a majority of individuals. We suggest that some of the other features present in more than one patient with deletion, including hypotonia, sleep apnea, chronic constipation, gastroesophageal and vesicoureteral refluxes, epilepsy, ataxia, dysphagia, nystagmus, and ptosis may result from deletion of the CHAT gene, encoding choline acetyltransferase, and the SLC18A3 gene, mapping in the first intron of CHAT and encoding vesicular acetylcholine transporter. The phenotypic diversity and presence of the deletion in apparently normal carrier parents suggest that subjects carrying 10q11.21q11.23 deletions may exhibit variable phenotypic expressivity and incomplete penetrance influenced by additional genetic and nongenetic modifiers.

Global methylation state at base-pair resolution of the Caulobacter genome throughout the cell cycle.

The Caulobacter DNA methyltransferase CcrM is one of five master cell-cycle regulators. CcrM is transiently present near the end of DNA replication when it rapidly methylates the adenine in hemimethylated GANTC sequences. The timing of transcription of two master regulator genes and two cell division genes is controlled by the methylation state of GANTC sites in their promoters. To explore the global extent of this regulatory mechanism, we determined the methylation state of the entire chromosome at every base pair at five time points in the cell cycle using single-molecule, real-time sequencing. The methylation state of 4,515 GANTC sites, preferentially positioned in intergenic regions, changed progressively from full to hemimethylation as the replication forks advanced. However, 27 GANTC sites remained unmethylated throughout the cell cycle, suggesting that these protected sites could participate in epigenetic regulatory functions. An analysis of the time of activation of every cell-cycle regulatory transcription start site, coupled to both the position of a GANTC site in their promoter regions and the time in the cell cycle when the GANTC site transitions from full to hemimethylation, allowed the identification of 59 genes as candidates for epigenetic regulation. In addition, we identified two previously unidentified N(6)-methyladenine motifs and showed that they maintained a constant methylation state throughout the cell cycle. The cognate methyltransferase was identified for one of these motifs as well as for one of two 5-methylcytosine motifs.

Changes in cannabis and tobacco use trajectories from age 17 to age 23

Much like the first volume published in 2011, the second volume of this anthology series gathers a selection of analyses which are empirically based on the data of the Swiss panel study TREE (Transitions from Education to Employment). The contributions of this volume carry on the investigation of the critical transitions during youth and young adulthood, drawing on sociological, economic, psychological and pedagogical research questions and thus highlighting the analytic and pluri-disciplinary research potential of the TREE data. One of the topical foci is the long-term influence of social origin on education and labour market pathways, particularly with regard to access to higher education.