24557128
Activation of Ets-2 by oxidative stress induces Bcl-xL expression and accounts for glial survival in amyotrophic lateral sclerosis.
Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease characterized by selective degeneration of motor neurons and glial activation. Cell-specific transcriptional regulation induced by oxidative stress may contribute to the survival and activation of astrocytes in the face of motor neuron death. In the present study, we demonstrate an age-dependent increase in Bcl-xL and Ets-2 immunoreactivity that correlates with an increase of glial fibrillary acidic protein (GFAP)-positive cells in the ventral horn of the spinal cord in both ALS transgenic mice [mutant SOD1 (G93A)] and affected humans. Chromatin immunoprecipitation (ChIP) analysis verified that Ets-2 preferentially occupies the Ets-2 binding element in the promoter of Bcl-xL in primary astrocytes under oxidative stress conditions as well as in G93A spinal cords. Ets-2 small-interfering RNA down-regulated the transcriptional activity of Bcl-xL. In primary glial cultures, Bcl-xL overexpression and mutant SOD1 (G93A) both conferred resistance to oxidative stress-induced cell death. Our findings suggest that Ets-2 transcription factor activation of Bcl-xL gene may protect glia from constitutive oxidative stress that is thought to be a key mechanism contributing to the pathogenesis of ALS. This survival pathway may contribute to the glial survival and activation seen in the spinal cord of ALS patients.
23992310
Differential regulation of neuronal and inducible nitric oxide synthase (NOS) in the spinal cord of mutant SOD1 (G93A) ALS mice.
Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder characterized by degeneration of motor neurons throughout the central nervous system. Mutations of the free radical scavenging enzyme superoxide dismutase-1 (SOD1) are a cause of familial ALS but it is not known how mutations lead to cell death. Free radicals such as nitric oxide (NO) are thought to play a key pathogenic role. NO is synthesized by NO synthases (NOSs) from arginine, which is a rate-limiting factor for NO production. We found that neuronal NOS (nNOS)-positive motor neurons were depleted while inducible NOS (iNOS)-positive activated glial cells were increased in transgenic mtSOD1 (G93A) ALS mice. iNOS expression was up regulated consistent with the increases of motor neuron loss and glial activation and citrulline and NO levels while nNOS expression was decreased in G93A ALS mice. Administration of l-arginine to G93A mice reduced the severity of motor neuron depletion and glial activation. In treated animals, nNOS expression was preserved while citrulline and NO were reduced, possibly due to reduced activation of glia expressing iNOS. Our findings show that high concentrations of NO correlate with iNOS expression rather than nNOS expression in G93A ALS mice. This suggests that therapy focused on iNOS inhibition might be a fruitful direction for future ALS therapeutic trials.
4611561
Protein structure prediction based on fragment assembly and parameter optimization.
We propose a novel method for ab-initio prediction of protein tertiary structures based on the fragment assembly and global optimization. Fifteen residue long fragment libraries are constructed using the secondary structure prediction method PREDICT, and fragments in these libraries are assembled to generate full-length chains of a query protein. Tertiary structures of 50 to 100 conformations are obtained by minimizing an energy function for proteins, using the conformational space annealing method that enables one to sample diverse low-lying local minima of the energy. Then in order to enhance the performance of the prediction method, we optimize the linear parameters of the energy function, so that the native-like conformations become energetically more favorable than the non-native ones for proteins with known structures. We test the feasibility of the parameter optimization procedure by applying it to the training set consisting of three proteins: the 10-55 residue fragment of staphylococcal protein A (PDB ID 1bdd), a designed protein betanova, and 1fsd.
16618892
Akt mediates self-renewal division of mouse spermatogonial stem cells
Spermatogonial stem cells have unique properties to self-renew and support spermatogenesis throughout their lifespan. Although glial cell line-derived neurotrophic factor (GDNF) has recently been identified as a self-renewal factor for spermatogonial stem cells, the molecular mechanism of spermatogonial stem cell self-renewal remains unclear. In the present study, we assessed the role of the phosphoinositide-3 kinase (PI3K)-Akt pathway using a germline stem (GS) cell culture system that allows in vitro expansion of spermatogonial stem cells. Akt was rapidly phosphorylated when GDNF was added to the GS cell culture, and the addition of a chemical inhibitor of PI3K prevented GS cell self-renewal. Furthermore, conditional activation of the myristoylated form of Akt-Mer (myr-Akt-Mer) by 4-hydroxy-tamoxifen induced logarithmic proliferation of GS cells in the absence of GDNF for at least 5 months. The myr-Akt-Mer GS cells expressed spermatogonial markers and retained androgenetic imprinting patterns. In addition, they supported spermatogenesis and generated offspring following spermatogonial transplantation into the testes of infertile recipient mice, indicating that they are functionally normal. These results demonstrate that activation of the PI3K-Akt pathway plays a central role in the self-renewal division of spermatogonial stem cells.
17985839
Estimation of anatomical locations using standard frame of reference in chest CT scans
We propose a method to establish the standard chest frame of reference (CFOR) using the rib cage in a lung CT scan. Such a reference frame is essential for referring to a certain location within a chest region and may facilitate the registration across multiple scans of a given subject as well as the comparative studies within a cohort of subjects. The robustness of the established CFOR was evaluated by estimating the anatomical locations within chest in the follow-up scan given the location in the first scan. Specifically, tracheal bifurcation point of airway tree and the center of pulmonary nodule were used as the anatomical points of interest. The CFOR was also used for exploring the spatial distribution of the anatomical location for a large number of individuals. The results show that on average the point of interest can be estimated accurately within 10.3 mm for the bifurcation point and within 12.5 mm for the pulmonary nodule’s center point. Further analyzing the spatial distribution of the CFOR coordinates across 86 subjects shows that we can localize the bifurcation point to the small subregion within the CFOR.
4366904
Principles of locomotion for simple-shaped cells
MOVING cells display a variety of shapes and modes of locomotion1, but it is not clear how motility at the molecular level relates to the locomotion of a whole cell, a problem compounded in studies of cells with complex shapes2–5. A striking feature of fish epidermal keratocyte locomotion is its apparent simplicity6. Here we present a kinematic description of locomotion which is consistent with the semicircular shape and persistent 'gliding'; motion of fish epidermal keratocytes. We propose that extension of the front and retraction of the rear of these cells occurs perpendicularly to the cell edge, and that a graded distribution of extension and retraction rates along the cell margin maintains cell shape and size during locomotion. Evidence for this description is provided by the predicted circumferential motion of lamellar features and the curvature of 'photo-marked' lines within specific molecular components of moving keratocytes. Our description relates the dynamics of molecular assemblies to the movement of a whole cell.
35129948
Receptor-activity modifying protein 1 expression is increased in the striatum following repeated L-DOPA administration in a 6-hydroxydopamine lesioned rat model of Parkinson's disease.
Abnormalities in signaling by G-protein coupled receptors (GPCRs) within the striatum are involved in the pathophysiology of Parkinson's disease (PD) and L-DOPA induced dyskinesia (LID). Receptor activity modifying proteins (RAMPs) are single transmembrane accessory proteins crucial for both trafficking and defining the phenotype of GPCRs. In the CNS, RAMP1 mRNA is predominantly expressed in striatum, cortex, and olfactory tubercles. In the present study, expression of RAMP1 mRNA is increased in the striatum (68-77%), following repeated L-DOPA administration, in the 6-hydroxydopamine-lesioned rat. These data are the first to describe regulation of RAMP1 expression in the CNS and suggest that changes in RAMP1 activity are involved in the pathophysiology of LID.