Auts2 enhances neurogenesis and promotes expansion of the cerebral cortex.

Introduction: The AUTS2 gene is associated with various neurodevelopmental and psychiatric disorders and has been suggested to play a role in acquiring human-specific traits. Functional analyses of Auts2 knockout mice have focused on postmitotic neurons, and the reported phenotypes do not faithfully recapitulate the whole spectrum of AUTS2-related human diseases.

Objective: The objective of the study is to assess the role of AUTS2 in the biology of neural progenitor cells, cortical neurogenesis and expansion; and understand how its deregulation leads to neurological disorders.

DIAPH3 predicts survival of patients with -methylated glioblastoma.

Background: Glioblastoma is one of the most aggressive primary brain tumors, with a poor outcome despite multimodal treatment. Methylation of the promoter, which predicts the response to temozolomide, is a well-established prognostic marker for glioblastoma. However, a difference in survival can still be detected within the methylated group, with some patients exhibiting a shorter survival than others, emphasizing the need for additional predictive factors.

KIF2A deficiency causes early-onset neurodegeneration.

KIF2A is an atypical kinesin that has the capacity to depolymerize microtubules. Patients carrying mutations in KIF2A suffer from progressive microcephaly and mental disabilities. While the role of this protein is well documented in neuronal migration, the relationship between its dysfunction and the pathobiology of brain disorders is unclear.

WNT signaling at the intersection between neurogenesis and brain tumorigenesis.

Neurogenesis and tumorigenesis share signaling molecules/pathways involved in cell proliferation, differentiation, migration, and death. Self-renewal of neural stem cells is a tightly regulated process that secures the accuracy of cell division and eliminates cells that undergo mitotic errors. Abnormalities in the molecular mechanisms controlling this process can trigger aneuploidy and genome instability, leading to neoplastic transformation.

The Celsr3-Kif2a axis directs neuronal migration in the postnatal brain.

The tangential migration of immature neurons in the postnatal brain involves consecutive migration cycles and depends on constant remodeling of the cell cytoskeleton, particularly in the leading process (LP). Despite the identification of several proteins with permissive and empowering functions, the mechanisms that specify the direction of migration remain largely unknown. Here, we report that planar cell polarity protein Celsr3 orients neuroblasts migration from the subventricular zone (SVZ) to olfactory bulb (OB).

DIAPH3 deficiency links microtubules to mitotic errors, defective neurogenesis, and brain dysfunction.

Diaphanous (DIAPH) three (DIAPH3) is a member of the formin proteins that have the capacity to nucleate and elongate actin filaments and, therefore, to remodel the cytoskeleton. DIAPH3 is essential for cytokinesis as its dysfunction impairs the contractile ring and produces multinucleated cells. Here, we report that DIAPH3 localizes at the centrosome during mitosis and regulates the assembly and bipolarity of the mitotic spindle.

Genetic mutations associated with lung cancer metastasis to the brain.

Approximately 90% of all cancer deaths arise from the metastatic spread of primary tumours. Of all the processes involved in carcinogenesis, local invasion and the formation of metastases are clinically the most relevant, but they are the least well understood at the molecular level. As a barrier to metastasis, cells normally undergo an apoptotic process known as 'anoikis', in circulation.

Spatial distribution and molecular dynamics of dystrophin glycoprotein components at the neuromuscular junction .

A bimolecular fluorescence complementation (BiFC) approach was used to study the molecular interactions between different components of the postsynaptic protein complex at the neuromuscular junction of living mice. We show that rapsyn forms complex with both α-dystrobrevin and α-syntrophin at the crests of junctional folds. The linkage of rapsyn to α-syntrophin and/or α-dystrobrevin is mediated by utrophin, a protein localized at acetylcholine receptor (AChR)-rich domains.

AChRs Are Essential for the Targeting of Rapsyn to the Postsynaptic Membrane of NMJs in Living Mice.

Unlabelled: Rapsyn, a 43 kDa scaffold protein, is required for the clustering of acetylcholine receptors (AChRs) at synaptic sites between mammalian motor neurons and muscle cells. However, the mechanism by which rapsyn is inserted and retained at postsynaptic sites at the neuromuscular junction (NMJ) in vivo remains largely unknown. We found that neither the N-terminal myristoylation nor the cysteine-rich RING H2 domain of rapsyn is required for its stable association with the postsynaptic membrane of NMJs.

Failure of lysosome clustering and positioning in the juxtanuclear region in cells deficient in rapsyn.

Rapsyn, a scaffold protein, is required for the clustering of acetylcholine receptors (AChRs) at contacts between motor neurons and differentiating muscle cells. Rapsyn is also expressed in cells that do not express AChRs. However, its function in these cells remains unknown.

The knockdown of αkap alters the postsynaptic apparatus of neuromuscular junctions in living mice.

A muscle-specific nonkinase anchoring protein (αkap), encoded within the calcium/calmodulin kinase II (camk2) α gene, was recently found to control the stability of acetylcholine receptor (AChR) clusters on the surface of cultured myotubes. However, it remains unknown whether this protein has any effect on receptor stability and the maintenance of the structural integrity of neuromuscular synapses in vivo. By knocking down the endogenous expression of αkap in mouse sternomastoid muscles with shRNA, we found that the postsynaptic receptor density was dramatically reduced, the turnover rate of receptors at synaptic sites was significantly increased, and the insertion rates of both newly synthesized and recycled receptors into the postsynaptic membrane were depressed.

A role for the calmodulin kinase II-related anchoring protein (αkap) in maintaining the stability of nicotinic acetylcholine receptors.

αkap, a muscle specific anchoring protein encoded within the Camk2a gene, is thought to play a role in targeting multiple calcium/calmodulin kinase II isoforms to specific subcellular locations. Here we demonstrate a novel function of αkap in stabilizing nicotinic acetylcholine receptors (AChRs). Knockdown of αkap expression with shRNA significantly enhanced the degradation of AChR α-subunits (AChRα), leading to fewer and smaller AChR clusters on the surface of differentiated C2C12 myotubes.

Plasma membrane association of p63 Rho guanine nucleotide exchange factor (p63RhoGEF) is mediated by palmitoylation and is required for basal activity in cells.

Activation of G protein-coupled receptors at the cell surface leads to the activation or inhibition of intracellular effector enzymes, which include various Rho guanine nucleotide exchange factors (RhoGEFs). RhoGEFs activate small molecular weight GTPases at the plasma membrane (PM). Many of the known G protein-coupled receptor-regulated RhoGEFs are found in the cytoplasm of unstimulated cells, and PM recruitment is a critical aspect of their regulation.

Galpha q allosterically activates and relieves autoinhibition of p63RhoGEF.

Galpha(q) directly activates p63RhoGEF and closely related catalytic domains found in Trio and Kalirin, thereby linking G(q)-coupled receptors to the activation of RhoA. Although the crystal structure of G alpha(q) in complex with the catalytic domains of p63RhoGEF is available, the molecular mechanism of activation has not yet been defined. In this study, we show that membrane translocation does not appear to play a role in G alpha(q)-mediated activation of p63RhoGEF, as it does in some other RhoGEFs.

Structure and function of heterotrimeric G protein-regulated Rho guanine nucleotide exchange factors.

Activation of certain classes of G protein-coupled receptors (GPCRs) can lead to alterations in the actin cytoskeleton, gene transcription, cell transformation, and other processes that are known to be regulated by Rho family small-molecular-weight GTPases. Although these responses can occur indirectly via cross-talk from canonical heterotrimeric G protein cascades, it has recently been demonstrated that Dbl family Rho guanine nucleotide exchange factors (RhoGEFs) can serve as the direct downstream effectors of heterotrimeric G proteins. Heterotrimeric Galpha(12/13), Galpha(q), and Gbetagamma subunits are each now known to directly bind and regulate RhoGEFs.

A conserved hydrophobic surface of the LARG pleckstrin homology domain is critical for RhoA activation in cells.

Leukemia associated Rho guanine nucleotide exchange factor (LARG) activates RhoA in response to signals received by specific classes of cell surface receptors. The catalytic core of LARG is a Dbl homology (DH) domain whose activity is modulated by an adjacent pleckstrin homology (PH) domain. In this study, we used a transcriptional assay and confocal microscopy to examine the roles of several novel structural features of the LARG DH/PH domains, including a conserved and exposed hydrophobic patch on the PH domain that mediates protein-protein interactions in crystal structures of LARG and its close homolog PDZ-RhoGEF.

Structural and thermodynamic evidence for a stabilizing role of Nop5p in S-adenosyl-L-methionine binding to fibrillarin.

In Archaea, fibrillarin and Nop5p form the core complex of box C/D small ribonucleoprotein particles, which are responsible for site-specific 2'-hydroxyl methylation of ribosomal and transfer RNAs. Fibrillarin has a conserved methyltransferase fold and employs S-adenosyl-l-methionine (AdoMet) as the cofactor in methyl transfer reactions. Comparison between recently determined crystal structures of free fibrillarin and fibrillarin-Nop5p-AdoMet tertiary complex revealed large conformational differences at the cofactor-binding site in fibrillarin.

Functional requirement for symmetric assembly of archaeal box C/D small ribonucleoprotein particles.

Box C/D small ribonucleoprotein particles (sRNPs) are archaeal homologs of small nucleolar ribonucleoprotein particles (snoRNPs) in eukaryotes that are responsible for site specific 2'-O-methylation of ribosomal and transfer RNAs. The function of box C/D sRNPs is characterized by step-wise assembly of three core proteins around a box C/D RNA that include fibrillarin, Nop5p, and L7Ae. The most distinct structural feature in all box C/D RNAs is the presence of two conserved box C/D motifs accompanied by often a single, and sometimes two, antisense elements located immediately upstream of either the D or D' box.

Structure and function of archaeal box C/D sRNP core proteins.

Nop56p and Nop58p are two core proteins of the box C/D snoRNPs that interact concurrently with fibrillarin and snoRNAs to function in enzyme assembly and catalysis. Here we report the 2.9 A resolution co-crystal structure of an archaeal homolog of Nop56p/Nop58p, Nop5p, in complex with fibrillarin from Archaeoglobus fulgidus (AF) and the methyl donor S-adenosyl-L-methionine.