No abstract

Keratin expression dynamically changes in airway basal cells (BCs) following acute and chronic injury, yet the functional consequences of these changes on BC behavior remain unknown. In Bronchiolitis Obliterans (BO) following lung transplantation, BC clonogenicity declines which is associated with a switch from keratin15 (Krt15) to keratin14 (Krt14). We investigated the roles of these keratins using Crispr-KO in vitro and in vivo and found that Krt14-KO and Krt15-KO produce contrasting phenotypes in terms of differentiation and clonogenicity. Primary mouse Krt14-KO BCs failed to differentiate into club and ciliated cells, but had enhanced clonogenicity.By contrast, Krt15-KO did not alter BC differentiation, but impaired clonogenicity in vitro and reduced the number of label-retaining BCs in vivo following injury. Krt14, but not Krt15, bound the tumor suppressor stratifin (Sfn). Disruption of Krt14, but not of Krt15, reduced Sfn protein abundance and increased expression of the oncogene dNp63a during BC differentiation, while dNp63a levels were reduced in Krt15-KO BCs. Overall, the phenotype of Krt15-KO BCs contrasts that of Krt14-KO and resembles the phenotype in BO with decreased clonogenicity, increased Krt14 and decreased dNp63a expression. This work demonstrates that Krt14 and Krt15 functionally regulate BC behavior which is relevant in chronic disease states like BO.

Background: The mesenchymal transcription factor Forkhead Box C1 (FOXC1), derepressed in hematopoietic stem progenitor cells (HSPCs) in the setting of acute myeloid leukemia (AML), but not in normal HSPCs, was recently demonstrated to play an important role in AML disease onset and progression by blocking myeloid lineage differentiation and enhancing clonogenic potential. Herein we sought to further examine the prognostic value of FOXC1 in AML and whether FOXC1 expression is a potential predictor of disease relapse and/or lack of response to induction chemotherapy in AML. Methods: Expression of FOXC1 mRNA in mixed karyotype AML bone marrow samples was examined using publicly available microarray datasets (n=521, n=244). The clinical significance of FOXC1 gene expression as a prognostic biomarker was evaluated using censored overall survival (OS) and event-free survival (EFS) data. Degree of statistical significance in the univariate and multivariate analyses performed was assessed using log-rank test and Cox regression model, respectively. Results: FOXC1 mRNA expression was a significant predictor of OS on univariate (hazard ratio [HR] 1.592 95% confidence interval [CI] 1.263-2.007, P = 0.0001) and multivariate (HR 1.755 95% CI 1.355-2.273, P < 0.0001) analyses. This effect on OS could be attributed to disease relapse and/or lack of response to induction chemotherapy as FOXC1 mRNA expression also proved to be a significant predictor of EFS on univariate analysis (hazard ratio [HR] 1.539 95% confidence interval [CI] 1.208-1.961, P = 0.0002) and multivariate analysis (HR 1.678 95% CI 1.280-2.201, P = 0.0001), independent of age, FLT3 ITD status, NPM1 status or cytogenetic risk status. Compared to patients who experienced disease remission, FOXC1 expression was significantly elevated in patients experiencing disease relapse following induction chemotherapy (P<0.02), and in patients who were non-responders to induction chemotherapy (P<0.002) Conclusions: FOXC1 expression in AML is an independent prognostic predictor of decreased OS and EFS and is significantly associated with disease relapse and/or refractoriness to induction chemotherapy. A risk of relapse/non-response score that incorporates FOXC1 expression status may prove to be of value in identifying patients at the time of initial diagnosis who are likely to fail induction chemotherapy. Further studies are warranted to explore the prognostic and predictive utility of FOXC1 expression in the clinical management of AML. Figure Figure. Disclosures Ray: Onconostic Technologies, Inc.: Employment. Shah:Onconostic Technologies, Inc.: Employment. Ray:Onconostic Technologies, Inc.: Consultancy, Equity Ownership; 3N Diagnostics Ltd.: Consultancy, Equity Ownership.

Reprogramming somatic cells to pluripotency by repressing lineage-instructive transcription factors (TFs) alone has not been pursued because lineage specification is thought to be regulated by transcriptional regulatory networks (TRNs) comprising of multiple TFs rather than by single pivotal "gatekeeper" TFs. Utilizing an intra-species somatic cell hybrid model, we identified Snai2 and Prrx1 as the most critical determinants of mesenchymal commitment in rat embryonic fibroblasts (REFs) and demonstrate that siRNA-mediated knockdown of either of these master regulators is adequate to convert REFs into functional adipocytes, chondrocytes or osteocytes without requiring exogenous TFs or small molecule cocktails. Furthermore, knockdown of Snai2 alone proved sufficient to transform REFs to dedifferentiated pluripotent stem-like cells (dPSCs) that formed embryoid bodies capable of triple germ-layer differentiation.These findings suggest that inhibition of a single gatekeeper TF in a lineage committed cell is adequate for acquisition of cell plasticity and reprogramming without requiring permanent genetic modification.

In all eukaryotic cell types, the unfolded protein response (UPR) upregulates factors that promote protein folding and misfolded protein clearance to help alleviate endoplasmic reticulum (ER) stress. Yet ER stress in the liver is uniquely accompanied by the suppression of metabolic genes, the coordination and purpose of which is largely unknown. Here, we used unsupervised machine learning to identify a cluster of correlated genes that were profoundly suppressed by persistent ER stress in the liver. These genes, which encode diverse functions including metabolism, coagulation, drug detoxification, and bile synthesis, are likely targets of the master regulator of hepatocyte differentiation HNF4α. The response of these genes to ER stress was phenocopied by liver-specific deletion of HNF4α. Strikingly, while deletion of HNF4α exacerbated liver injury in response to an ER stress challenge, it also diminished UPR activation and partially preserved ER ultrastructure, suggesting attenuated ER stress. Conversely, pharmacological maintenance of hepatocyte identity in vitro enhanced sensitivity to stress. Several pathways potentially link HNF4α to ER stress sensitivity, including control of expression of the tunicamycin transporter MFSD2A; modulation of IRE1/XBP1 signaling; and regulation of Pyruvate Dehydrogenase. Together, these findings suggest that HNF4α activity is linked to hepatic ER homeostasis through multiple mechanisms.