Summary Embryonic stem (ES) cells are derived from blastocyst stage embryos and are believed to be functionally equivalent to the inner cell mass, which lacks the ability to produce all extraembryonic tissues. Here we report the identification of a rare transient cell population within mouse ES and induced pluripotent stem (iPS) cell cultures that express high levels of transcripts found in two-cell (2C) embryos in which the blastomeres are totipotent. We genetically tagged these 2C-like ES cells and show that they lack the ICM pluripotency proteins Oct4, Sox2, and Nanog and have acquired the ability to contribute to both embryonic and extraembryonic tissues. We show that nearly all ES cells cycle in and out of this privileged state, which we find is partially controlled by histone modifying enzymes. Transcriptome sequencing and bioinformatic analyses revealed that a significant number of 2C-transcripts are initiated from long terminal repeats derived from murine endogenous retroviruses, suggesting this foreign sequence has helped to drive cell fate regulation in placental mammals.

Despite a significant improvement in the availability of therapeutic options to treat lung diseases, pulmonary disease still remains a major cause of morbidity and mortality around the world. Currently there are limited opportunities to study human lung disease either in vivo and in vitro. Using induced pluripotent stem cells (iPSC) we have generated a reproducible differentiation protocol to make mature post‐mitotic multiciliated cells in a functional airway epithelium. iPSC were generated from human skin biopsies and differentiated via FOXA2+SOX17+ definitive endoderm (>90% efficiency) to FOXA2+NKx2.1+ anterior foregut endoderm, FOXA2+NKx2.1+SOX2+ (~50% efficiency) pulmonary endoderm and then matured in an air liquid interface. Robust multiciliogenesis occurred when Notch signaling was inhibited and was confirmed by; i) the assembly of multiple pericentrin stained centrioles at the apical surface, ii) expression of transcription factor FOXJ1 and iii) presence of multiple acetylated tubulin labeled cilia projections in individual cells. The presence of NKx2.1+CC10+ Clara cells, MUC5A/C+ goblet cells and FOXA2+p63+ basal cells was also confirmed showing we are generating a complete polarized epithelial cell layer comprised of all relevant cell types. Functional cAMP activated and CFTRinh‐172 sensitive CFTR currents were recorded in isolated epithelial cells by whole cell patch clamp technique. Furthermore, we have corrected the deltaF508 mutation in the CFTR gene (>80% of all cases of CF) using a combination of CRISPR‐Cas9 endonuclease‐mediated genome editing and piggyBac transposase technologies, in the CF patient‐derived iPSC. The generation of mature multiciliated cells in a human iPSC differentiated respiratory epithelium and the ability to correct disease causing mutations provides a significant advancement toward modeling a number of human respiratory diseases in vitro. Grant Funding Source: Supported in part by CIRM and the Berger Foundation

SUMMARY Lung disease is a major cause of death in the USA, with current therapeutic approaches only serving to manage symptoms. The most common chronic and life-threatening genetic disease of the lung is Cystic fibrosis (CF) caused by mutations in the cystic fibrosis transmembrane regulator (CFTR). We have generated induced pluripotent stem cells (iPSC) from CF patients carrying a homozygous deletion of F508 in the CFTR gene, which results in defective processing of CFTR to the cell membrane. This mutation was precisely corrected using CRISPR to target corrective sequences to the endogenous CFTR genomic locus, in combination with a completely excisable selection system which significantly improved the efficiency of this correction. The corrected iPSC were subsequently differentiated to mature airway epithelial cells where recovery of normal CFTR expression and function was demonstrated. This isogenic iPSC-based model system for CF could be adapted for the development of new therapeutic approaches.

Background-Adenylyl cyclases (ACs) are a family of effector molecules for G-protein-coupled receptors. The 2 ACs most abundantly expressed in cardiac myocytes are types 5 (AC5) and 6 (AC6), which have 65% amino acid homology. It has been speculated that coexpression of 2 AC types in cardiac myocytes represents redundancy, but the specific role of AC6 in cardiac physiology and its differences from AC5 remain to be defined. Methods and Results-We generated transgenic mice with targeted deletion of AC6. Deletion of AC6 was associated with reduced left ventricular contractile function (Pϭ0.026) and relaxation (Pϭ0.041). The absence of AC6 was associated with a 48% decay in ␤-adrenergic receptor-stimulated cAMP production in cardiac myocytes (Pϭ0.003) and reduced protein kinase A activity (Pϭ0.015). In addition, phospholamban phosphorylation was reduced (Pϭ0.015), sarcoplasmic reticulum Ca 2ϩ -ATPase activity was impaired (PϽ0.0001), and cardiac myocytes showed marked abnormalities in calcium transient formation (Pϭ0.001). Conclusions-The

Pulmonary and systemic arterial hypertension are associated with profound alterations in Ca(2+) homeostasis and smooth muscle cell proliferation. A novel class of non-selective cation channels, the transient receptor potential (TRP) channels, have emerged at the forefront of research into hypertensive disease states. TRP channels are identified as molecular correlates for receptor-operated and store-operated cation channels in the vasculature. Over 10 TRP isoforms are identified at the mRNA and protein expression levels in the vasculature. Current research implicates upregulation of specific TRP isoforms to be associated with increased Ca(2+) influx, characteristic of vasoconstriction and vascular smooth muscle cell proliferation. TRP channels are implicated as Ca(2+) entry pathways in pulmonary hypertension and essential hypertension. Caveolae have recently emerged as membrane microdomains in which TRP channels may be co-localized with the endoplasmic reticulum in both smooth muscle and endothelial cells. Such enhanced expression and function of TRP channels and their localization in caveolae in pathophysiological hypertensive disease states highlights their importance as potential targets for pharmacological intervention.

Platelet-derived growth factor (PDGF) and its receptor are known to be substantially elevated in lung tissues and pulmonary arterial smooth muscle cells (PASMC) isolated from patients and animals with pulmonary arterial hypertension. PDGF has been shown to phosphorylate and activate Akt and mammalian target of rapamycin (mTOR) in PASMC. In this study, we investigated the role of PDGF-mediated activation of Akt signaling in the regulation of cytosolic Ca(2+) concentration and cell proliferation. PDGF activated the Akt/mTOR pathway and, subsequently, enhanced store-operated Ca(2+) entry (SOCE) and cell proliferation in human PASMC. Inhibition of Akt attenuated the increase in cytosolic Ca(2+) concentration due to both SOCE and PASMC proliferation. This effect correlated with a significant downregulation of stromal interacting molecule (STIM) and Orai, proposed molecular correlates for SOCE in many cell types. The data from this study present a novel pathway for the regulation of Ca(2+) signaling and PASMC proliferation involving activation of Akt in response to upregulated expression of PDGF. Targeting this pathway may lead to the development of a novel therapeutic option for the treatment of pulmonary arterial hypertension.

Rationale: Alveolar epithelial cell (AEC) injury and dysregulated repair are implicated in the pathogenesis of pulmonary fibrosis. Endoplasmic reticulum (ER) stress in AEC has been observed in idiopathic pulmonary fibrosis (IPF), a disease of aging.Objectives: To investigate a causal role for ER stress in the pathogenesis of pulmonary fibrosis (PF) and therapeutic potential of ER stress inhibition in PF.Methods: The role of ER stress in AEC dysfunction and fibrosis was studied in mice with tamoxifen (Tmx)-inducible deletion of ER chaperone Grp78, a key regulator of ER homeostasis, in alveolar type II (AT2) cells, progenitors of distal lung epithelium, and in IPF lung slice cultures.Measurements and Main Results: Grp78 deletion caused weight loss, mortality, lung inflammation, and spatially heterogeneous fibrosis characterized by fibroblastic foci, hyperplastic AT2 cells, and increased susceptibility of old and male mice, all features of IPF. Fibrosis was more persistent in more severely injured Grp78 knockout (KO) mice. Grp78 KO AT2 cells showed evidence of ER stress, apoptosis, senescence, impaired progenitor capacity, and activation of TGF-b (transforming growth factor-b)/SMAD signaling. Glucose-regulated protein 78 is reduced in AT2 cells from old mice and patients with IPF, and ER stress inhibitor tauroursodeoxycholic acid ameliorates ER stress and fibrosis in Grp78 KO mouse and IPF lung slice cultures.Conclusions: These results support a causal role for ER stress and resulting epithelial dysfunction in PF and suggest ER stress as a potential mechanism linking aging to IPF. Modulation of ER stress and chaperone function may offer a promising therapeutic approach for pulmonary fibrosis.

Motile cilia are characterized by dynein motor units, which preassemble in the cytoplasm before trafficking into the cilia. Proteins required for dynein preassembly were discovered by finding human mutations that result in absent ciliary motors, but little is known about their expression, function, or interactions. By monitoring ciliogenesis in primary airway epithelial cells and MCIDAS-regulated induced pluripotent stem cells, we uncovered two phases of expression of preassembly proteins. An early phase, composed of HEATR2, SPAG1, and DNAAF2, preceded other preassembly proteins and was independent of MCIDAS regulation. The early preassembly proteins colocalized within perinuclear foci that also contained dynein arm proteins. These proteins also interacted based on immunoprecipitation and Förster resonance energy transfer (FRET) studies. FRET analysis of HEAT domain deletions and human mutations showed that HEATR2 interacted with itself and SPAG1 at multiple HEAT domains, while DNAAF2 interacted with SPAG1. Human mutations in HEATR2 did not affect this interaction, but triggered the formation of p62/Sequestosome-1-positive aggregates containing the early preassembly proteins, suggesting that degradation of an early preassembly complex is responsible for disease and pointing to key regions required for HEATR2 scaffold stability. We speculate that HEATR2 is an early scaffold for the initiation of dynein complex assembly in motile cilia.