Mice carrying a complete deletion of the talin2 coding sequence are viable and fertile

AbstractMice homozygous for several Tln2 gene targeted alleles are viable and fertile. Here we show that although the expression of talin2 protein is drastically reduced in muscle from these mice, other tissues continue to express talin2 albeit at reduced levels. We therefore generated a Tln2 allele lacking the entire coding sequence (Tln2cd). Tln2cd/cd mice were viable and fertile, and the genotypes of Tln2cd/+ intercrosses were at the expected Mendelian ratio. Tln2cd/cd mice showed no major difference in body mass or the weight of the major organs compared to wild-type, although they displayed a mildly dystrophic phenotype. Moreover, Tln2cd/cd mouse embryo fibroblasts showed no obvious defects in cell adhesion, migration or proliferation. However, the number of Tln2cd/cd pups surviving to adulthood was variable suggesting that such mice have an underlying defect

Talin1 and Rap1 are critical for osteoclast function

To determine talin1's role in osteoclasts, we mated TLN1(fl/fl) mice with those expressing cathepsin K-Cre (CtsK-TLN1) to delete the gene in mature osteoclasts or with lysozyme M-Cre (LysM-TLN1) mice to delete TLN1 in all osteoclast lineage cells. Absence of TLN1 impairs macrophage colony-stimulating factor (M-CSF)-stimulated inside-out integrin activation and cytoskeleton organization in mature osteoclasts. Talin1-deficient precursors normally express osteoclast differentiation markers when exposed to M-CSF and receptor activator of nuclear factor κB (RANK) ligand but attach to substrate and migrate poorly, arresting their development into mature resorptive cells. In keeping with inhibited resorption, CtsK-TLN1 mice exhibit an ∼5-fold increase in bone mass. Osteoclast-specific deletion of Rap1 (CtsK-Rap1), which promotes talin/β integrin recognition, yields similar osteopetrotic mice. The fact that the osteopetrosis of CtsK-TLN1 and CtsK-Rap1 mice is substantially more severe than that of those lacking αvβ3 is likely due to added failed activation of β1 integrins. In keeping with osteoclast dysfunction, mice in whom talin is deleted late in the course of osteoclastogenesis are substantially protected from ovariectomy-induced osteoporosis and the periarticular osteolysis attending inflammatory arthritis. Thus, talin1 and Rap1 are critical for resorptive function, and their selective inhibition in mature osteoclasts retards pathological bone loss

Talin is required for integrin-mediated platelet function in hemostasis and thrombosis

Integrins are critical for hemostasis and thrombosis because they mediate both platelet adhesion and aggregation. Talin is an integrin-binding cytoplasmic adaptor that is a central organizer of focal adhesions, and loss of talin phenocopies integrin deletion in Drosophila. Here, we have examined the role of talin in mammalian integrin function in vivo by selectively disrupting the talin1 gene in mouse platelet precursor megakaryocytes. Talin null megakaryocytes produced circulating platelets that exhibited normal morphology yet manifested profoundly impaired hemostatic function. Specifically, platelet-specific deletion of talin1 led to spontaneous hemorrhage and pathological bleeding. Ex vivo and in vitro studies revealed that loss of talin1 resulted in dramatically impaired integrin αIIbβ3-mediated platelet aggregation and β1 integrin–mediated platelet adhesion. Furthermore, loss of talin1 strongly inhibited the activation of platelet β1 and β3 integrins in response to platelet agonists. These data establish that platelet talin plays a crucial role in hemostasis and provide the first proof that talin is required for the activation and function of mammalian α2β1 and αIIbβ3 integrins in vivo

Altered regulation and expression of genes by BET family of proteins in COPD patients

Correction: PLoS One 2018 12 (4): 0175997Background BET proteins (BRD2, BRD3, BRDT and BRD4) belong to the family of bromodomain containing proteins, which form a class of transcriptional co-regulators. BET proteins bind to acetylated lysine residues in the histones of nucleosomal chromatin and function either as co-activators or co-repressors of gene expression. An imbalance between HAT and HDAC activities resulting in hyperacetylation of histones has been identified in COPD. We hypothesized that pan-BET inhibitor (JQ1) treatment of BET protein interactions with hyperacety-lated sites in the chromatin will regulate excessive activation of pro-inflammatory genes in key inflammatory drivers of alveolar macrophages (AM) in COPD. Methods and findings Transcriptome analysis of AM from COPD patients indicated up-regulation of macrophage M1 type genes upon LPS stimulation. Pan-BET inhibitor JQ1 treatment attenuated expression of multiple genes, including pro-inflammatory cytokines and regulators of innate and adaptive immune cells. We demonstrated for the first time that JQ1 differentially modulated LPS-induced cytokine release from AM or peripheral blood mononuclear cells (PBMC) of COPD patients compared to PBMC of healthy controls. Using the BET regulated gene signature, we identified a subset of COPD patients, which we propose to benefit from BET inhibition. Conclusions This work demonstrates that the effects of pan-BET inhibition through JQ1 treatment of inflammatory cells differs between COPD patients and healthy controls, and the expression of BET protein regulated genes is altered in COPD. These findings provide evidence of histone hyperacetylation as a mechanism driving chronic inflammatory changes in COPD.Peer reviewe

Murine Wnt-11 and Wnt-12 have temporally and spatially restricted expression patterns during embryonic development

The Wnt gene family encodes a set of signalling molecules implicated in the development of a wide range of organisms. We have recently cloned partial cDNA sequences of murine Wnt-11 and Wnt-12. Here, we describe the spatio-temporal expression patterns of both genes during mouse embryogenesis. Wnt-11 expression is first detected within the truncus arteriosus from 8.25 dpc. By 9.5 dpc, Wnt-11 expression is detected in the somites at the medial junction of the dermatome and the myotome. Wnt-11 transcripts are also detected in limb bud mesenchyme from the time the bud is first visible. Wnt-12 is detected in the apical ectodermal ridge from 10.5 dpc. The implications of these expression patterns are discussed

Endothelial cell talin1 is essential for embryonic angiogenesis

Using Tln1fl/fl;CreER mice, we show that tamoxifen-induced inactivation of the talin1 gene throughout the embryo produces an angiogenesis phenotype that is restricted to newly forming blood vessels. The phenotype has a rapid onset in early embryos, resulting in vessel defects by 48 h and death of the embryo within 72 h. Very similar vascular defects were obtained using a Tie2-Cre endothelial cell-specific Tln1 knockout, a phenotype that was rescued by expression of a Tln1 mini-gene in endothelial cells. We show that endothelial cells, unlike most other cell types, do not express talin2, which can compensate for loss of talin1, and demonstrate for the first time that endothelial cells in vivo lacking talin1 are unable to undergo the cell spreading and flattening required to form vessels

Talin-dependent integrin activation is required for fibrin clot retraction by platelets

Talin functions both as a regulator of integrin affinity and as an important mechanical link between integrins and the cytoskeleton. Using genetic deletion of talin, we show for the first time that the capacity of talin to activate integrins is required for fibrin clot retraction by platelets. To further dissect which talin functions are required for this process, we tested clot retraction in platelets expressing a talin1(L325R) mutant that binds to integrins, but exhibits impaired integrin activation ascribable to disruption of the interaction between talin and the membrane-proximal region (MPR) in the β-integrin cytoplasmic domain. Talin-deficient and talin1(L325R) platelets were defective in retracting fibrin clots. However, the defect in clot retraction in talin1(L325R) platelets, but not talin-deficient platelets, was rescued by extrinsically activating integrins with manganese, thereby proving that integrin activation is required and showing that talin1(L325R) can form functional links to the actin cytoskeleton