Screen-positive rate in cell-free DNA screening for microdeletion 22q11.2.

OBJECTIVE: To examine the impact of the fetal fraction (FF) on the screen-positive rate in screening for microdeletion 22q11.2. METHODS: This study is based on samples that were analyzed using the Harmony® Prenatal Test (Roche Inc). The study cohort comprised samples from women with singleton pregnancies who were at least 16 years old and at least at 11 weeks' gestation. Logistic regression analysis was used to determine significant covariates that carry an impact on the screen-positive rate. RESULTS: The study population consisted of 52,019 pregnancies, including 309 pregnancies with a high-risk result for microdeletion 22q11.2. Thus, the overall screen-positive rate was 0.59%. In the low-risk group, the FF was 10.1%, and in the high-risk group, it was 7.3%. Regression analysis indicated a strong correlation between the FF and the screen-positive rate. In the cases with an FF of <11.0%, the screen-positive rate was 0.92%, while it was 0.13% in the group with a higher FF. CONCLUSION: The screen-positive rate depends on the FF. In order to keep the rate low, we recommend restricting the analysis to samples with a FF of 11% and more.

The best smellers make the best choosers: mate choice is affected by female chemosensory receptor gene diversity in a mammal.

The products of the genes of the major histocompatibility complex (MHC) are known to be drivers of pathogen resistance and sexual selection enhancing offspring genetic diversity. The MHC further influences individual odour types and social communication. However, little is known about the receptors and their volatile ligands that are involved in this type of chemical communication. Here, we have investigated chemosensory receptor genes that ultimately enable females to assess male genes through odour cues. As a model, we used an invasive population of North American raccoons ( Procyon lotor) in Germany. We investigated the effect of two groups of chemosensory receptor genes-trace amine-associated receptors (TAARs) and olfactory receptors (ORs)-on MHC-dependent mate choice. Females with more alleles of the TAAR or OR loci were more likely to choose a male with a diverse MHC. We additionally found that MHC class I genes have a stronger effect on mate choice than the recently reported effect for MHC class II genes, probably because of their immunological relevance for viral resistance. Our study is among the first to show a genetic link between behaviour and chemosensory receptor genes. These results contribute to understanding the link between genetics, olfaction and associated life-history decisions.

Learning where to feed: the use of social information in flower-visiting Pallas' long-tongued bats (Glossophaga soricina).

Social learning is a widespread phenomenon among vertebrates that influences various patterns of behaviour and is often reported with respect to foraging behaviour. The use of social information by foraging bats was documented in insectivorous, carnivorous and frugivorous species, but there are little data whether flower-visiting nectarivorous bats (Phyllostomidae: Glossophaginae) can acquire information about food from other individuals. In this study, we conducted an experiment with a demonstrator-observer paradigm to investigate whether flower-visiting Pallas' long-tongued bats (Glossophaga soricina) are able to socially learn novel flower positions via observation of, or interaction with, knowledgeable conspecifics. The results demonstrate that flower-visiting G. soricina are able to use social information for the location of novel flower positions and can thereby reduce energy-costly search efforts. This social transmission is explainable as a result of local enhancement; learning bats might rely on both visual and echo-acoustical perception and are likely to eavesdrop on auditory cues that are emitted by feeding conspecifics. We additionally tested the spatial memory capacity of former demonstrator bats when retrieving a learned flower position, and the results indicate that flower-visiting bats remember a learned flower position after several weeks.

Concomitant aberrant overexpression of RUNX1 and NCAM in regenerating bone marrow of myeloid leukemia of Down's syndrome.

BACKGROUND AND OBJECTIVES: Myeloid leukemia of Down's syndrome (ML-DS) has characteristic biological features (e.g. expression of the truncated GATA1s), which are different from those of non-DS childhood acute myeloid leukemias (AML). The objective of this study was to investigate factors predisposing to the development of ML-DS. DESIGN AND METHODS: We analyzed 134 bone marrow specimens from 64 children with ML-DS and non-DS AML during chemotherapy and 7 specimens from DS children with- out leukemia,who did not receive any chemotherapy,The specimens were analyzed by multiparameter flow cytometry and quantitative reverse transcriptase polymerase chain reaction for transcription factors involved in hematopoiesis. RESULTS: Samples taken from children with ML-DS in complete remission during chemotherapy aberrantly expressed CD56 (NCAM) at the surface of monocytic and granulocytic cells. Compared to non-DS AML cases,children with ML-DS had a statistically significant higher proportion of CD56+ cells in the CD33+ fraction: 71%+/-6% vs. 4%+/-1% (p<0.00001). A significant decrease of the amount of CD33+/CD56+ cells was observed during and after maintenance therapy. An increased number of CD33+/CD56+ cells was also present (>85%) in children with DS who did not receive chemotherapy, but showed a left-shift (due to infection), compared with DS children without left-shift (<10% CD33+/CD56+ cells). Within the CD33+/CD56+ fraction, RUNX1 was overexpressed more than 5-fold (p<0.02) compared to CD33+/CD56- cells, whereas there were no differences regarding GATA1, SPI1, ERG or ETS-2 levels. INTERPRETATION AND CONCLUSIONS: The combined overexpression of RUNX1 and NCAM during stress hematopoiesis in children with DS might be a key factor in the development of overt leukemia and/or in the growth advantage of the malignant GATA1s clone in ML- DS.