A forward genetic screen with a thalamocortical axon reporter mouse yields novel neurodevelopment mutants and a distinct emx2 mutant phenotype

<p>Abstract</p> <p>Background</p> <p>The dorsal thalamus acts as a gateway and modulator for information going to and from the cerebral cortex. This activity requires the formation of reciprocal topographic axon connections between thalamus and cortex. The axons grow along a complex multistep pathway, making sharp turns, crossing expression boundaries, and encountering intermediate targets. However, the cellular and molecular components mediating these steps remain poorly understood.</p> <p>Results</p> <p>To further elucidate the development of the thalamocortical system, we first created a thalamocortical axon reporter line to use as a genetic tool for sensitive analysis of mutant mouse phenotypes. The TCA-<it>tau-lacZ </it>reporter mouse shows specific, robust, and reproducible labeling of thalamocortical axons (TCAs), but not the overlapping corticothalamic axons, during development. Moreover, it readily reveals TCA pathfinding abnormalities in known cortical mutants such as <it>reeler</it>. Next, we performed an unbiased screen for genes involved in thalamocortical development using random mutagenesis with the TCA reporter. Six independent mutant lines show aberrant TCA phenotypes at different steps of the pathway. These include ventral misrouting, overfasciculation, stalling at the corticostriatal boundary, and invasion of ectopic cortical cell clusters. An outcross breeding strategy coupled with a genomic panel of single nucleotide polymorphisms facilitated genetic mapping with small numbers of mutant mice. We mapped a ventral misrouting mutant to the <it>Emx2 </it>gene, and discovered that some TCAs extend to the olfactory bulbs in this mutant. Mapping data suggest that other lines carry mutations in genes not previously known for roles in thalamocortical development.</p> <p>Conclusions</p> <p>These data demonstrate the feasibility of a forward genetic approach to understanding mammalian brain morphogenesis and wiring. A robust axonal reporter enabled sensitive analysis of a specific axon tract inside the mouse brain, identifying mutant phenotypes at multiple steps of the pathway, and revealing a new aspect of the <it>Emx2 </it>mutant. The phenotypes highlight vulnerable choice points and latent tendencies of TCAs, and will lead to a refined understanding of the elements and interactions required to form the thalamocortical system.</p> <p>See Commentary: <url>http://www.biomedcentral.com/1741-7007/9/1</url></p

Comparison of an ordinal endpoint to time-to-event, longitudinal, and binary endpoints for use in evaluating treatments for severe influenza requiring hospitalization

Background/aims: The Food and Drug Administration recommends research into developing well-defined and reliable endpoints to evaluate treatments for severe influenza requiring hospitalization. A novel 6-category ordinal endpoint of patient health status after 7 days that ranges from death to hospital discharge with resumption of normal activities is being used in a randomized placebo-controlled trial of intravenous immunoglobulin (IVIG) for severe influenza (FLU-IVIG). We compare the power of the ordinal endpoint under a proportional odds model to other types of endpoints as a function of various trial parameters. // Methods: We used closed-form analysis and empirical simulation to compare the power of the ordinal endpoint to time-to-event, longitudinal, and binary endpoints. In the simulation setting, we varied the treatment effect and the distribution of the placebo group across the follow-up period with consideration of adjustment for baseline health status. // Results: In the analytic setting, ordinal endpoints of high granularity provided greater power than time-to-event endpoints when most patients in the placebo group had either naturally progressed to the category of hospital discharge by day 7 or were far from hospital discharge on day 7. In the simulation setting, adjustment for baseline health status universally raised power for the proportional odds model. Across different placebo group distributions of the ordinal endpoint regardless of adjustment for baseline health status, only time-to-event endpoints yielded higher power than the ordinal endpoint for certain treatment effects. // Conclusions: In this case study, the FLU-IVIG ordinal endpoint provided greater power than time-to-event, binary, and longitudinal endpoints for most scenarios of the treatment effect and placebo group distribution, including the target population studied for FLU-IVIG. The ordinal endpoint was only surpassed by the time-to-event endpoint when many patients in the placebo group were on the cusp of hospital discharge on day 7 and the follow-up period for the time-to-event endpoint was extended to allow for additional events. Our general approach for evaluating the power of several potential endpoints for an influenza trial can be used for designing other influenza trials with different target populations and for other trials in other disease areas

Utility of high-sensitivity cardiac troponin T in patients receiving anthracycline chemotherapy

Anne H Blaes,1&nbsp;Aamer Rehman,2 David M Vock,3,4 Xianghua Luo,3,4 Mark Menge,5 Douglas Yee,3 Emil Missov,6 Daniel Duprez6 1Division of Hematology/Oncology/Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, 2Division of Cardiology, University of Louisville, Louisville, KY, 3Masonic Cancer Center, 4Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, 5Park Nicollet Frauenshuh Cancer Center, St Louis Park, 6Division of Cardiology, Department of Medicine, University of Minnesota, Minneapolis, MN, USA Background: Anthracycline chemotherapy remains an integral part of the care for curative intent chemotherapy in breast cancer and non-Hodgkin lymphoma patients. Better tools need to be identified to predict cardiac complications of anthracycline chemotherapy. Materials and methods: We investigated the utility of high-sensitivity cardiac troponin T (hscTnT), N-terminal pro-B-type natriuretic peptide, cardiac troponin T and I, and creatine kinase (CK)-MB in cancer patients receiving anthracycline-based chemotherapy, in order to determine whether baseline levels or changes in these biomarkers may help predict the onset of congestive heart failure. Results: Eighteen consecutive patients with a pathologic diagnosis of breast cancer or non-Hodgkin lymphoma were enrolled. The median dose of doxorubicin exposure was 240 mg/m2 (range 240&ndash;400 mg/m2). After treatment with doxorubicin, the hscTnT increased to 19.1 pg/mL (P&lt;0.001). CKMB and N-terminal pro-B-type natriuretic peptide levels increased to 1.1 ng/mL and 88.3 pg/mL, respectively (P=0.02). When subjects who had a decline in left ventricular ejection fraction (LVEF) by equilibrium radionuclide ventriculography were compared to those who did not have a change in LVEF, there was a suggestion that those subjects with an elevated baseline hscTnT were more likely to have a decline in LVEF (2.7 pg/mL and 0.1 pg/mL, respectively; P=0.07). Spearman correlation demonstrated that patients with higher baseline hscTnT and CKMB tended to have a greater decline in LVEF (Spearman correlation -0.54, 95% confidence interval -0.80 to -0.08 [P=0.02], and -0.49, 95% confidence interval -0.77 to -0.01 [P=0.04], respectively). Conclusion: Elevations in baseline hscTnT levels are suggestive of an oncology subgroup at high risk of developing cardiac complications from their chemotherapy. Early detection by oncologists with the use of baseline biomarkers may be clinically important in designing interventions to prevent serious anthracycline-based chemotherapy complications. Keywords: troponin T, doxorubicin, cardiomyopathy, chemotherap