in-vivo-imaging-optic-nerve-fiber-integrity-contrast-enhanced-mri

<em>In vivo</em> Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice

The rodent visual system encompasses retinal ganglion cells and their axons that form the optic nerve to enter thalamic and midbrain centers, and ...

Jena University Hospital

Somatic genetic alterations in cancers have been linked with response to targeted therapeutics by creation of specific dependency on activated oncogenic signaling pathways. However, no tools currently exist to systematically connect such genetic lesions to therapeutic vulnerability. We have therefore developed a genomics approach to identify lesions associated with therapeutically relevant oncogene dependency. Using integrated genomic profiling, we have demonstrated that the genomes of a large panel of human non-small cell lung cancer (NSCLC) cell lines are highly representative of those of primary NSCLC tumors. Using cell-based compound screening coupled with diverse computational approaches to integrate orthogonal genomic and biochemical data sets, we identified molecular and genomic predictors of therapeutic response to clinically relevant compounds. Using this approach, we showed that v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations confer enhanced Hsp90 dependency and validated this finding in mice with KRAS-driven lung adenocarcinoma, as these mice exhibited dramatic tumor regression when treated with an Hsp90 inhibitor. In addition, we found that cells with copy number enhancement of v-abl Abelson murine leukemia viral oncogene homolog 2 (ABL2) and ephrin receptor kinase and v-src sarcoma (Schmidt-Ruppin A-2) viral oncogene homolog (avian) (SRC) kinase family genes were exquisitely sensitive to treatment with the SRC/ABL inhibitor dasatinib, both in vitro and when it xenografted into mice. Thus, genomically annotated cell-line collections may help translate cancer genomics information into clinical practice by defining critical pathway dependencies amenable to therapeutic inhibition.

Predicting drug susceptibility of non-small cell lung cancers based on genetic lesions.

In cancer, genetically activated proto-oncogenes often induce "upstream" dependency on the activity of the mutant oncoprotein. Therapeutic inhibition of these activated oncoproteins can induce massive apoptosis of tumor cells, leading to sometimes dramatic tumor regressions in patients. The PI3K and MAPK signaling pathways are central regulators of oncogenic transformation and tumor maintenance. We hypothesized that upstream dependency engages either one of these pathways preferentially to induce "downstream" dependency. Therefore, we analyzed whether downstream pathway dependency segregates by genetic aberrations upstream in lung cancer cell lines. Here, we show by systematically linking drug response to genomic aberrations in non-small-cell lung cancer, as well as in cell lines of other tumor types and in a series of in vivo cancer models, that tumors with genetically activated receptor tyrosine kinases depend on PI3K signaling, whereas tumors with mutations in the RAS/RAF axis depend on MAPK signaling. However, efficacy of downstream pathway inhibition was limited by release of negative feedback loops on the reciprocal pathway. By contrast, combined blockade of both pathways was able to overcome the reciprocal pathway activation induced by inhibitor-mediated release of negative feedback loops and resulted in a significant increase in apoptosis and tumor shrinkage. Thus, by using a systematic chemo-genomics approach, we identify genetic lesions connected to PI3K and MAPK pathway activation and provide a rationale for combined inhibition of both pathways. Our findings may have implications for patient stratification in clinical trials.

Identifying genotype-dependent efficacy of single and combined PI3K- and MAPK-pathway inhibition in cancer.

Ectopic expression of defined sets of genetic factors can reprogram somatic cells to create induced pluripotent stem (iPS) cells. The capacity to direct human iPS cells to specific differentiated lineages and to their progenitor populations can be used for disease modeling, drug discovery, and eventually autologous cell replacement therapies. During mouse cardiogenesis, the major lineages of the mature heart, cardiomyocytes, smooth muscle cells, and endothelial cells arise from a common, multipotent cardiovascular progenitor expressing the transcription factors Isl1 and Nkx2.5. Here we show, using genetic fate-mapping, that Isl1(+) multipotent cardiovascular progenitors can be generated from mouse iPS cells and spontaneously differentiate in all 3 cardiovascular lineages in vivo without teratoma. Moreover, we report the identification of human iPS-derived ISL1(+) progenitors with similar developmental potential. These results support the possibility to use patient-specific iPS-generated cardiovascular progenitors as a model to elucidate the pathogenesis of congenital and acquired forms of heart diseases.-Moretti, A., Bellin, M., Jung, C. B., Thies, T.-M., Takashima, Y., Bernshausen, A., Schiemann, M., Fischer, S., Moosmang, S., Smith, A. G., Lam, J. T., Laugwitz, K.-L. Mouse and human induced pluripotent stem cells as a source for multipotent Isl1(+) cardiovascular progenitors.

Mouse and human induced pluripotent stem cells as a source for multipotent Isl1+ cardiovascular progenitors.

Despite the successful introduction of potent anti-cancer therapeutics, most of these drugs lead to only modest tumor-shrinkage or transient responses, followed by re-growth of tumors. Combining different compounds has resulted in enhanced tumor control and prolonged survival. However, methods querying the efficacy of such combinations have been hampered by limited scalability, analytical resolution, statistical feasibility, or a combination thereof. We have developed a theoretical framework modeling cellular viability as a stochastic lifetime process to determine synergistic compound combinations from high-throughput cellular screens. We apply our method to data derived from chemical perturbations of 65 cancer cell lines with two inhibitors. Our analysis revealed synergy for the combination of both compounds in subsets of cell lines. By contrast, in cell lines in which inhibition of one of both targets was sufficient to induce cell death, no synergy was detected, compatible with the topology of the oncogenically activated signaling network. In summary, we provide a tool for the measurement of synergy strength for combination perturbation experiments that might help define pathway topologies and direct clinical trials.

Analysis of compound synergy in high-throughput cellular screens by population-based lifetime modeling.

Activity-dependent means of altering calcium (Ca(2)(+)) influx are assumed to be of great physiological consequence, although definitive tests of this assumption have only begun to emerge. Facilitation and inactivation offer two opposing, activity-dependent means of altering Ca(2+) influx via cardiac Ca(v)1.2 calcium channels. Voltage- and frequency-dependent facilitation of Ca(v)1.2 has been reported to depend on Calmodulin (CaM) and/or the activity of Calmodulin kinase II (CaMKII). Several sites within the cardiac L-type calcium channel complex have been proposed as the targets of CaMKII. Here, we generated mice with knockin mutations of alpha(1)1.2 S1512 and S1570 phosphorylation sites [sine facilitation (SF) mice]. Homocygote SF mice were viable and reproduced in a Mendelian ratio. Voltage-dependent facilitation in ventricular cardiomyocytes carrying the SF mutation was decreased from 1.58- to 1.18-fold. The CaMKII inhibitor KN-93 reduced facilitation to 1.28 in control cardiomyocytes. SF mutation negatively shifted the voltage-dependent inactivation and slowed recovery from inactivation, thereby making fewer channels available for activation. Telemetric ECG recordings at different heart rates showed that QT time decreased significantly more in SF than in control mice at higher rates. Our results strongly support the notion that CaMKII-dependent phosphorylation of Cav1.2 at S1512 and S1570 mediates Ca(2+) current facilitation in the murine heart.

Facilitation of murine cardiac L-type Ca(v)1.2 channel is modulated by calmodulin kinase II-dependent phosphorylation of S1512 and S1570.

Three-dimensional structures of NagZ of Bacillus subtilis, the first structures of a two-domain β-N-acetylglucosaminidase of family 3 of glycosidases, were determined with and without the transition state mimicking inhibitor PUGNAc bound to the active site, at 1.84- and 1.40-Å resolution, respectively. The structures together with kinetic analyses of mutants revealed an Asp-His dyad involved in catalysis: His(234) of BsNagZ acts as general acid/base catalyst and is hydrogen bonded by Asp(232) for proper function. Replacement of both His(234) and Asp(232) with glycine reduced the rate of hydrolysis of the fluorogenic substrate 4'-methylumbelliferyl N-acetyl-β-D-glucosaminide 1900- and 4500-fold, respectively, and rendered activity pH-independent in the alkaline range consistent with a role of these residues in acid/base catalysis. N-Acetylglucosaminyl enzyme intermediate accumulated in the H234G mutant and β-azide product was formed in the presence of sodium azide in both mutants. The Asp-His dyad is conserved within β-N-acetylglucosaminidases but otherwise absent in β-glycosidases of family 3, which instead carry a "classical" glutamate acid/base catalyst. The acid/base glutamate of Hordeum vulgare exoglucanase (Exo1) superimposes with His(234) of the dyad of BsNagZ and, in contrast to the latter, protrudes from a second domain of the enzyme into the active site. This is the first report of an Asp-His catalytic dyad involved in hydrolysis of glycosides resembling in function the Asp-His-Ser triad of serine proteases. Our findings will facilitate the development of mechanism-based inhibitors that selectively target family 3 β-N-acetylglucosaminidases, which are involved in bacterial cell wall turnover, spore germination, and induction of β-lactamase.

Structural and kinetic analysis of Bacillus subtilis N-acetylglucosaminidase reveals a unique Asp-His dyad mechanism.

The heart muscle responds to physiological needs with a short-term modulation of cardiac contractility. This process is determined mainly by properties of the cardiac L-type Ca(2+) channel (Ca(v)1.2), including facilitation and Ca(2+)-dependent inactivation (CDI). Both facilitation and CDI involve the interaction of calmodulin with the IQ motif of the Ca(v)1.2 channel, especially with Ile-1624. To verify this hypothesis, we created a mouse line in which Ile-1624 was mutated to Glu (Ca(v)1.2(I1624E) mice). Homozygous Ca(v)1.2(I1624E) mice were not viable. Therefore, we inactivated the floxed Ca(v)1.2 gene of heterozygous Ca(v)1.2(I1624E) mice by the α-myosin heavy chain-MerCreMer system. The resulting I/E mice were studied at day 10 after treatment with tamoxifen. Electrophysiological recordings in ventricular cardiomyocytes revealed a reduced Ca(v)1.2 current (I(Ca)) density in I/E mice. Steady-state inactivation and recovery from inactivation were modified in I/E versus control mice. In addition, voltage-dependent facilitation was almost abolished in I/E mice. The time course of I(Ca) inactivation in I/E mice was not influenced by the use of Ba(2+) as a charge carrier. Using 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid as a chelating agent for intracellular Ca(2+), inactivation of I(Ca) was slowed down in control but not I/E mice. The results show that the I/E mutation abolishes Ca(2+)/calmodulin-dependent regulation of Ca(v)1.2. The Ca(v)1.2(I1624E) mutation transforms the channel to a phenotype mimicking CDI.

Facilitation and Ca2+-dependent inactivation are modified by mutation of the Ca(v)1.2 channel IQ motif.

Dysfunctional NF-κB and brain myelin formation.

Muscle tissue has a great intrinsic adaptability to changing functional demands. Triggering more gradual responses such as tissue growth, the immediate responses to altered loading conditions involve changes in the activity. Because the reduction in a limb's function is associated with marked deviations in the gait pattern, understanding the muscular responses in laming animals will provide further insight into their compensatory mechanisms as well as help to improve treatment options to prevent musculoskeletal sequelae in chronic patients. Therefore, this study evaluated the changes in muscle activity in adaptation to a moderate, short-term, weight-bearing hindlimb lameness in two leg and one back muscle using surface electromyography (SEMG). In eight sound adult dogs that trotted on an instrumented treadmill, bilateral, bipolar recordings of the m. triceps brachii, the m. vastus lateralis and the m. longissimus dorsi were obtained before and after lameness was induced. Consistent with the unchanged vertical forces as well as temporal parameters, neither the timing nor the level of activity changed significantly in the m. triceps brachii. In the ipsilateral m. vastus lateralis, peak activity and integrated SEMG area were decreased, while they were significantly increased in the contralateral hindlimb. In both sides, the duration of the muscle activity was significantly longer due to a delayed offset. These observations are in accordance with previously described kinetic and kinematic changes as well as changes in muscle mass. Adaptations in the activity of the m. longissimus dorsi concerned primarily the unilateral activity and are discussed regarding known alterations in trunk and limb motions.

Stefanie Fischer

Hans Berger Department of Neurology

Jena University Hospital

In vivo Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice

Stefanie Fischer

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Hans Berger Department of Neurology

Jena University Hospital

In vivo Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice

Hans Berger Department of Neurology