Progenitor cells of the first and second heart fields depend on cardiac-specific transcription factors for their differentiation. Using conditional mutagenesis of mouse embryos, we define the hierarchy of signaling events that controls the expression of cardiacspecific transcription factors during differentiation of cardiac progenitors at embryonic day 9.0. Wnt/β-catenin and Bmp act downstream of Notch/RBPJ at this developmental stage. Mutation of Axin2, the negative regulator of canonical Wnt signaling, enhances Wnt and Bmp4 signals and suffices to rescue the arrest of cardiac differentiation caused by loss of RBPJ. Using FACS enrichment of cardiac progenitors in RBPJ and RBPJ/Axin2 mutants, embryo cultures in the presence of the Bmp inhibitor Noggin, and by crossing a Bmp4 mutation into the RBPJ/Axin2 mutant background, we show that Wnt and Bmp4 signaling activate specific and nonoverlapping cardiac-specific genes in the cardiac progenitors: Nkx2-5, Isl1 and Baf60c are controlled by Wnt/β-catenin, and Gata4, SRF, and Mef2c are controlled by Bmp signaling. Our study contributes to the understanding of the regulatory hierarchies of cardiac progenitor differentiation and outflow tract development and has implications for understanding and modeling heart development.cardiogenesis | MesP1-cre | mesoderm patterning | canonical Wnt | progenitor differentiation in culture

The diagnosis of hepatitis C is based on serological testing for antibodies against various epitopes of the hepatitis C virus (HCV) and detection of HCV RNA in serum, because anti-HCV antibodies alone cannot discriminate patients who are infectious from those who have resolved the infection. If HCV RNA is not detected, which is the case in at least 20% of enzyme immunoassay (EIA)-positive patients, diagnosis remains unclear in a state of disease possibly well suited for therapeutic intervention. Therefore, we investigated if detection of HCV antigens or HCV RNA in routinely processed, formalin-fixed and paraffinembedded (ffpe) liver biopsy specimens of patients positive for anti-HCV, but negative for HCV RNA in serum, could confirm diagnosis in this serological constellation. In recent years, chronic hepatitis C has turned out to be one of the most urgent problems in chronic hepatic disease and even in public health, with prevalence rates of hepatitis C virus (HCV) infection at approximately 0.5% to 2% in the general population of Western countries, and higher rates in some African and Southeast Asian countries, including up to 14% in Egypt. 1 Most HCV infections take a chronic course, the estimated rates ranging between 50% and 90%, and at least 20% of these patients will eventually develop cirrhosis. 2-4 Although many patients do not present with clinical signs of active liver disease, consecutive liver biopsies have histologically proven progressive liver damage in more than half of the cases. 3,5 Because liver histology can only suggest, but not prove, chronic hepatitis C, the definite diagnosis relies in general on serological demonstration of anti-HCV antibodies in enzyme immunoassays (EIA) and a confirmatory recombinant immunoblot assay, and/or direct detection of HCV RNA. About 20% of anti-HCV-positive individuals are negative for HCV RNA in serum. 6,7 For these patients, diagnosis remains unclear, because a past infection with elimination of the virus cannot be ruled out. Follow-up testing for alanine transaminase (ALT) and HCV RNA has been suggested in this situation, 4 taking into account the spontaneous fluctuations in the activity of chronic hepatitis C. On the other hand, a low viral load is accepted as a favorable prognostic factor for therapy, 8 so that these patients are likely to benefit from immediate therapy if they actually have chronic hepatitis C. Therefore, we investigated if a direct diagnostic decision can be obtained in patients positive for anti-HCV antibodies, but negative for HCV RNA in serum, by the demonstration of viral proteins or HCV RNA within the routinely processed biopsy itself. PATIENTS AND METHODS Serological AnalysesThe study was performed retrospectively on 44 patients positive for anti-HCV antibodies by a second-generation EIA (HCV 2.0 EIA or AxSym HCV, Abbott Laboratories, Chicago, IL) negative for HCV RNA in blood serum. The sample-to-cutoff values of the antibody tests ranged from 1.3 to 97. Confirmatory assays (Matrix HCV, Abbott) were performed if sample-to-cutoff...

Highlights d High Wnt/b-catenin and Mll1 are linked to high H3K4me3 at promoters in mouse tumors d Mll1 is required for the initiation and maintenance of salivary gland tumors d SET domain mutations of Mll1 reduce the self-renewal of tumor-propagating cells d Genetic Mll1 ablation reduces tumor initiation of human head and neck cancer cells

Analysis of lambda light chain use in normal mice is made difficult by the dominant chi light chain repertoire. We produced mice rendered deficient in chi light chain expression by gene targeting and focused on questions concerned with the generation of lambda light chain diversity. Whilst these mice compensate the chi deficiency with increased lambda liters, and their Ig level is therefore not significantly reduced, they show major differences in immunization titers, germinal center (GC) development and somatic hypermutation. After immunization, using antigens that elicit a restricted IgL response in normal mice, we obtained in the chi-/- mice elevated primary antibody titers but a subsequent lack in titer increase after repeated antigen challenge. Analysis of the Peyer's patches (PP) revealed a dramatically reduced cell content with rather small but highly active GC. Flow cytometric analysis showed different cell populations in the PP with enriched peanut agglutinin (PNA)hi/CD45R(B220)+ B cells, implying that the apparent compensation for the lack of lambda light chain expression involves the GC microenvironment in cell selection, the initiation of hypermutation and high affinity expansion. The three V lambda genes, V1, V2 and Vx, are mutated in the GC B cells, but show no junctional diversity. In contrast, a reduced rate of V lambda hypermutation is found in the hybridoma antibodies, which appears to reflect a selection bias rather than structural constraints. However, mechanisms of somatic mutation and specificity selection can operate with equal efficiency on the few V lambda genes.

Lung adenocarcinoma (LUAD) is the most prevalent subtype of non‐small cell lung cancer. Despite the development of novel targeted and immune therapies, the 5‐year survival rate is still only 21%, indicating the need for more efficient treatment regimens. Lysine‐specific demethylase 1 (LSD1) is an epigenetic eraser that modifies histone 3 methylation status, and is highly overexpressed in LUAD. Using representative human cell culture systems and two autochthonous transgenic mouse models, we investigated inhibition of LSD1 as a novel therapeutic option for treating LUAD. The reversible LSD1 inhibitor HCI‐2509 significantly reduced cell growth with an IC 50 of 0.3–5 μm in vitro, which was linked to an enhancement of histone 3 lysine methylation. Most importantly, growth arrest, as well as inhibition of the invasion capacities, was independent of the underlying driver mutations. Subsequent expression profiling revealed that the cell cycle and replication machinery were prominently affected after LSD1 inhibition. In addition, our data provide evidence that LSD1 blockade significantly interferes with EGFR downstream signaling. Finally, our in vitro results were confirmed by preclinical therapeutic approaches, including the use of two autochthonous transgenic LUAD mouse models driven by either EGFR or KRAS mutations. Importantly, LSD1 inhibition resulted in significantly lower tumor formation and a strong reduction in tumor progression, which were independent of the underlying mutational background of the mouse models. Hence, our findings provide substantial evidence indicating that tumor growth of LUAD can be markedly decreased by HCI‐2509 treatment, suggesting its use as a single agent maintenance therapy or combined therapeutical application in novel concerted drug approaches.