Gene targeting in the mouse nervous system

pre-printOur understanding of the development, connectivity and function of the nervous system has been facilitated by gene targeting technology. Here we summarize the historic background and the current state of this experimental approach with specific regard to neuroscience research. I. The Pioneering Experiments. Random mutagenesis is a very powerful method for elucidating gene function in simpler model organisms. Given the size of the genome and slow reproductive cycles, however, a more direct approach is required for mammalian models. This need was met in the early 1980's by establishing gene targeting in embryonic stem cells, later nicknamed mouse knockout. This technology was born at the confluence of two lines of experimentation: Firstly, the capacity of most mammalian somatic cells to carry out homologous recombination between endogenous loci and exogenous DNA was discovered. Secondly, pluripotent embryonic stem cell lines have been established that maintained the ability to intermingle with the early mouse embryo and contribute to the germline, thereby conferring heritability, even after extensive culturing in vitro

Nature-Inspired Algorithms in Real-World Optimization Problems

Eight popular nature inspired algorithms are compared with the blind random search and three advanced adaptive variants of differential evolution (DE) on real-world problems benchmark collected for CEC 2011 algorithms competition. The results show the good performance of the adaptive DE variants and their superiority over the other algorithms in the test problems. Some of the nature-inspired algorithms perform even worse that the blind random search in some problems. This is a strong argument for recommendation for application, where well-verified algorithm successful in competitions should be preferred instead of developing some new algorithms

Exploring the dynamics of adult Axin2 cell lineage integration into dentate gyrus granule neurons

The Wnt pathway plays critical roles in neurogenesis. The expression of Axin2 is induced by Wnt/β-catenin signaling, making this gene a reliable indicator of canonical Wnt activity. We employed pulse-chase genetic lineage tracing with the Axin2-CreERT2 allele to follow the fate of Axin2+ lineage in the adult hippocampal formation. We found Axin2 expressed in astrocytes, neurons and endothelial cells, as well as in the choroid plexus epithelia. Simultaneously with the induction of Axin2 fate mapping by tamoxifen, we marked the dividing cells with 5-ethynyl-2′-deoxyuridine (EdU). Tamoxifen induction led to a significant increase in labeled dentate gyrus granule cells three months later. However, none of these neurons showed any EdU signal. Conversely, six months after the pulse-chase labeling with tamoxifen/EdU, we identified granule neurons that were positive for both EdU and tdTomato lineage tracer in each animal. Our data indicates that Axin2 is expressed at multiple stages of adult granule neuron differentiation. Furthermore, these findings suggest that the integration process of adult-born neurons from specific cell lineages may require more time than previously thought

Preclinical models of middle cerebral artery occlusion: new imaging approaches to a classic technique

Stroke remains a major burden on patients, families, and healthcare professionals, despite major advances in prevention, acute treatment, and rehabilitation. Preclinical basic research can help to better define mechanisms contributing to stroke pathology, and identify therapeutic interventions that can decrease ischemic injury and improve outcomes. Animal models play an essential role in this process, and mouse models are particularly well-suited due to their genetic accessibility and relatively low cost. Here, we review the focal cerebral ischemia models with an emphasis on the middle cerebral artery occlusion technique, a “gold standard” in surgical ischemic stroke models. Also, we highlight several histologic, genetic, and in vivo imaging approaches, including mouse stroke MRI techniques, that have the potential to enhance the rigor of preclinical stroke evaluation. Together, these efforts will pave the way for clinical interventions that can mitigate the negative impact of this devastating disease

Preclinical Models of Middle Cerebral Artery Occlusion: New Imaging Approaches to a Classic Technique

Stroke remains a major burden on patients, families, and healthcare professionals, despite major advances in prevention, acute treatment, and rehabilitation. Preclinical basic research can help to better define mechanisms contributing to stroke pathology, and identify therapeutic interventions that can decrease ischemic injury and improve outcomes. Animal models play an essential role in this process, and mouse models are particularly well-suited due to their genetic accessibility and relatively low cost. Here, we review the focal cerebral ischemia models with an emphasis on the middle cerebral artery occlusion technique, a gold standard in surgical ischemic stroke models. Also, we highlight several histologic, genetic, and in vivo imaging approaches, including mouse stroke MRI techniques, that have the potential to enhance the rigor of preclinical stroke evaluation. Together, these efforts will pave the way for clinical interventions that can mitigate the negative impact of this devastating disease

Reversal of Hox1 gene subfunctionalization in the mouse

In vertebrates, paralogous Hox genes play diverse biological roles. We examined the interchangeability of Hoxa1 and Hoxb1 in mouse development by swapping their protein-coding regions. Remarkably, the mice expressing the Hox-B1 protein from the Hoxa1 locus, and vice versa, are essentially normal. We noted, nonetheless, a specific facial nerve hypomorphism in hemizygous Hoxb1 A1/2 mice and decreased viability in homozygous Hoxa1 B1/B1 embryos. Further, we established a mouse line in which we have inserted the 107 bp Hoxb1 autoregulatory enhancer into the Hoxa1 promoter. Strikingly, the newly generated autoregulatory Hoxa1 gene can deliver the functionality of both paralogs in these mice, providing normal viability as well as proper facial nerve formation even in the Hoxb1 mutant background. This study affirms that subfunctionalization of the transcriptional regulatory elements has a principal role in the diversification of paralogous Hox genes. Moreover, we show that the ancestral vertebrate Hox1 gene can still be experimentally reconstructed

In Vivo Imaging of Microglial Calcium Signaling in Brain Inflammation and Injury

Microglia, the innate immune sentinels of the central nervous system, are the most dynamic cells in the brain parenchyma. They are the first responders to insult and mediate neuroinflammation. Following cellular damage, microglia extend their processes towards the lesion, modify their morphology, release cytokines and other mediators, and eventually migrate towards the damaged area and remove cellular debris by phagocytosis. Intracellular Ca2+ signaling plays important roles in many of these functions. However, Ca2+ in microglia has not been systematically studied in vivo. Here we review recent findings using genetically encoded Ca2+ indicators and two-photon imaging, which have enabled new insights into Ca2+ dynamics and signaling pathways in large populations of microglia in vivo. These new approaches will help to evaluate pre-clinical interventions and immunomodulation for pathological brain conditions such as stroke and neurodegenerative diseases

Broadcasting in All-output-port Meshes of Trees with Distance-insensitive Routing.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Optimal broadcasting and gossiping in one-port meshes of trees with distance-insensitive routing.

Available from STL, Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi