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Aberrant activation of the Wnt signalling pathway is required for tumour initiation and survival in the majority of colorectal cancers. The development of inhibitors of Wnt signalling has been the focus of multiple drug discovery programs targeting colorectal cancer and other malignancies associated with aberrant pathway activation. However, progression of new clinical entities targeting the Wnt pathway has been slow. One challenge lies with the limited predictive power of 2D cancer cell lines because they fail to fully recapitulate intratumoural phenotypic heterogeneity. In particular, the relationship between 2D cancer cell biology and cancer stem cell function is poorly understood. By contrast, 3D tumour organoids provide a platform in which complex cell-cell interactions can be studied. However, complex 3D models provide a challenging platform for the quantitative analysis of drug responses of therapies that have differential effects on tumour cell subpopulations. Here, we generated tumour organoids from colorectal cancer patients and tested their responses to inhibitors of Tankyrase (TNKSi) which are known to modulate Wnt signalling. Using compounds with 3 orders of magnitude difference in cellular mechanistic potency together with image-based assays, we demonstrate that morphometric analyses can capture subtle alterations in organoid responses to Wnt inhibitors that are consistent with activity against a cancer stem cell subpopulation. Overall our study highlights the value of phenotypic readouts as a quantitative method to asses drug-induced effects in a relevant preclinical model.

Tcf7l2 mediates Wnt/β-Catenin signalling during development and is implicated in cancer and type-2 diabetes. The mechanisms by which Tcf7l2 and Wnt/β-Catenin signalling elicit such a diversity of biological outcomes are poorly understood. Here, we study the function of zebrafish tcf7l2 alternative splice variants and show that only variants that include exon five or an analogous human tcf7l2 variant can effectively provide compensatory repressor function to restore eye formation in embryos lacking tcf7l1a/tcf7l1b function. Knockdown of exon five specific tcf7l2 variants in tcf7l1a mutants also compromises eye formation, and these variants can effectively repress Wnt pathway activity in reporter assays using Wnt target gene promoters. We show that the repressive activities of exon5-coded variants are likely explained by their interaction with Tle co-repressors. Furthermore, phosphorylated residues in Tcf7l2 coded exon5 facilitate repressor activity. Our studies suggest that developmentally regulated splicing of tcf7l2 can influence the transcriptional output of the Wnt pathway.

Transforming growth factor-beta1 (TGF-beta 1) is a pluripotent cytokine that can inhibit epithelial proliferation and induce apoptosis, but is also widely implicated in breast cancer progression. Understanding its biological action in mammary development is critical for understanding its role in cancer. TGF-beta 1 is produced as a latent complex that requires extracellular activation before receptor binding. To better understand the spatial and temporal regulation of its action during mammary gland development, we examined the pattern of activation in situ using antibodies selected to distinguish between latent and active TGF-beta. Activation was highly restricted. TGF-beta 1 activation was localized primarily to the epithelium, and within the epithelium it was restricted to luminal epithelial cells but absent from either cap or myoepithelial cells. Within the luminal epithelium, we noted a further restriction. During periods of proliferation (ie, puberty, estrus and pregnancy), which are stimulated by ovarian hormones, TGF-beta 1 activation decreased in some cells, consistent with preparation for proliferation. Paradoxically, other cells simultaneously increase TGF-beta 1 immunoreactivity, which suggests that TGF-beta 1 differentially restrains epithelial subpopulations from responding to hormonal signals to proliferate. These data suggest that endogenous TGF-beta 1 activation and thus activity are regulated by ovarian hormones. To determine the specific consequences of TGF-beta 1 activity, we manipulated TGF-beta 1 levels in vivo using Tgfbeta 1 knockout mice and undertook tissue recombination experiments with heterozygous tissue. In Tgfbeta 1 heterozygous mice, which have <10% wild-type levels of TGF-beta1, ductal development during puberty and alveolar development during pregnancy were accelerated, consistent with its role as a growth inhibitor. The proliferative index of Tgfbeta 1+/- epithelium was increased approximately twofold in quiescent tissue and fourfold in proliferating tissue but both ducts and alveoli were grossly and histologically normal. To test whether epithelial TGF-beta1 was critical to the proliferative phenotype, Tgfbeta 1+/+ and +/- epithelium were transplanted into +/+ mammary stroma. The outgrowth of Tgfbeta 1+/- epithelium was accelerated in wild-type hosts, indicating that the phenotype was intrinsic to the epithelium. Moreover, proliferation was 15-fold greater in Tgfbeta 1+/- than wild-type mice after ovariectomy and treatment with estrogen and progesterone, suggesting that TGF-beta 1 acts in an autocrine or juxtacrine manner to regulate epithelial proliferation. Together these data indicate that ovarian hormones regulate TGF-beta 1 activation, which in turn restricts proliferative response to hormone signaling.

Tcf7l2 mediates Wnt/β-Catenin signalling during development and is implicated in cancer and type-2 diabetes. The mechanisms by which Tcf7l2 and Wnt/β-Catenin signalling elicits such a diversity of biological outcomes are poorly understood. Here, we study alternatively spliced tcf7l2 in zebrafish and show that only splice variants that include exon 5 and an analogous human tcf7l2 variant can effectively provide compensatory repressor function to restore eye formation in embryos lacking tcf7l1a/tcf7l1b function. Knockdown of exon 5 specific tcf7l2 variants in tcf7l1a mutants also compromises eye formation and these variants can effectively repress Wnt pathway activity in reporter assays using Wnt target gene promoters. We show that the repressive activities of exon5-coded variants are likely explained by their interaction with Tle co-repressors. Furthermore, phosphorylated residues in Tcf7l2 coded exon5 facilitate repressor activity. Our studies suggest that developmentally regulated splicing of tcf7l2 can influence the transcriptional output of the Wnt pathway.

Aberrant activation of the Wnt signalling pathway is required for tumour initiation and survival in the majority of colorectal cancers. The development of inhibitors of Wnt signalling has been the focus of multiple drug discovery programs targeting colorectal cancer and other malignancies associated with aberrant pathway activation. However, progression of new clinical entities targeting the Wnt pathway has been slow. One challenge lies with the limited predictive power of 2D cancer cell lines because they fail to fully recapitulate intratumoural phenotypic heterogeneity. In particular, the relationship between 2D cancer cell biology and cancer stem cell function is poorly understood. By contrast, 3D tumour organoids provide a platform in which complex cell-cell interactions can be studied. However, complex 3D models provide a challenging platform for the quantitative analysis of drug responses of therapies that have differential effects on tumour cell subpopulations. Here, we generated tumour organoids from colorectal cancer patients and tested their responses to inhibitors of Tankyrase (TNKSi) which are known to modulate Wnt signalling. Using compounds with 3 orders of magnitude difference in cellular mechanistic potency together with image-based assays, we demonstrate that morphometric analyses can capture subtle alterations in organoid responses to Wnt inhibitors that are consistent with activity against a cancer stem cell subpopulation. Overall our study highlights the value of phenotypic readouts as a quantitative method to asses drug-induced effects in a relevant preclinical model.

Transforming growth factor-β1 (TGF-β1) is a pluripotent cytokine that can inhibit epithelial proliferation and induce apoptosis, but is also widely implicated in breast cancer progression. Understanding its biological action in mammary development is critical for understanding its role in cancer. TGF-β1 is produced as a latent complex that requires extracellular activation before receptor binding. To better understand the spatial and temporal regulation of its action during mammary gland development, we examined the pattern of activation in situ using antibodies selected to distinguish between latent and active TGF-β. Activation was highly restricted. TGF-β1 activation was localized primarily to the epithelium, and within the epithelium it was restricted to luminal epithelial cells but absent from either cap or myoepithelial cells. Within the luminal epithelium, we noted a further restriction. During periods of proliferation (ie, puberty, estrus and pregnancy), which are stimulated by ovarian hormones, TGF-β1 activation decreased in some cells, consistent with preparation for proliferation. Paradoxically, other cells simultaneously increase TGF-β1 immunoreactivity, which suggests that TGF-β1 differentially restrains epithelial subpopulations from responding to hormonal signals to proliferate. These data suggest that endogenous TGF-β1 activation and thus activity are regulated by ovarian hormones. To determine the specific consequences of TGF-β1 activity, we manipulated TGF-β1 levels in vivo using Tgfβ1 knockout mice and undertook tissue recombination experiments with heterozygous tissue. In Tgfβ1 heterozygous mice, which have <10% wild-type levels of TGF-β1, ductal development during puberty and alveolar development during pregnancy were accelerated, consistent with its role as a growth inhibitor. The proliferative index of Tgfβ1 +/− epithelium was increased approximately twofold in quiescent tissue and fourfold in proliferating tissue but both ducts and alveoli were grossly and histologically normal. To test whether epithelial TGF-β1 was critical to the proliferative phenotype, Tgfβ1 +/+ and +/− epithelium were transplanted into +/+ mammary stroma. The outgrowth of Tgfβ1 +/− epithelium was accelerated in wild-type hosts, indicating that the phenotype was intrinsic to the epithelium. Moreover, proliferation was 15-fold greater in Tgfβ1 +/− than wild-type mice after ovariectomy and treatment with estrogen and progesterone, suggesting that TGF-β1 acts in an autocrine or juxtacrine manner to regulate epithelial proliferation. Together these data indicate that ovarian hormones regulate TGF-β1 activation, which in turn restricts proliferative response to hormone signaling.

Due to their fast evolution and large natural variability in macro- and microphysical properties, the accurate representation of boundary layer clouds in current climate models remains a challenge. One of the regions with large intermodel spread in the Coupled Model Intercomparison Project Phase 6 ensemble is the western North Atlantic Ocean. Here, statistically representative in situ measurements can help to develop and constrain the parameterization of clouds in global models. To this end, we performed comprehensive measurements of boundary layer clouds, aerosol, trace gases, and radiation in the western North Atlantic Ocean during the NASA Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) mission. In total, 174 research flights with 574 flight hours for cloud and precipitation measurements were performed with the HU-25 Falcon during three winter (February–March 2020, January–April 2021, and November 2021–March 2022) and three summer seasons (August–September 2020, May–June 2021, and May–June 2022). Here we present a statistical evaluation of 16 140 individual cloud events probed by the fast cloud droplet probe and the two-dimensional stereo cloud probe during 155 research flights in a representative and repetitive flight strategy allowing for robust statistical data analyses. We show that the vertical profiles of distributions of the liquid water content and the cloud droplet effective diameter (ED) increase with altitude in the marine boundary layer. Due to higher updraft speeds, higher cloud droplet number concentrations (Nliquid) were measured in winter compared to summer despite lower cloud condensation nucleus abundance. Flight cloud cover derived from statistical analysis of in situ data is reduced in summer and shows large variability. This seasonal contrast in cloud coverage is consistent with a dominance of a synoptic pattern in winter that favors conditions for the formation of stratiform clouds at the western edge of cyclones (post-cyclonic). In contrast, a dominant summer anticyclone is concomitant with the occurrence of shallow cumulus clouds and lower cloud coverage. The evaluation of boundary layer clouds and precipitation in the Nliquid ED phase space sheds light on liquid, mixed-phase, and ice cloud properties and helps to categorize the cloud data. Ice and liquid precipitation, often masked in cloud statistics by a high abundance of liquid clouds, is often observed throughout the cloud. The ACTIVATE in situ cloud measurements provide a wealth of cloud information useful for assessing airborne and satellite remote-sensing products, for global climate and weather model evaluations, and for dedicated process studies that address precipitation and aerosol–cloud interactions.

Quantifying the degree of coupling between marine boundary layer (MBL) clouds and the surface is critical for understanding the evolution of low clouds and explaining the vertical distribution of aerosols and microphysical cloud properties. Previous work has characterized the boundary layer as either coupled or decoupled, but this study rather considers four degrees of coupling, ranging from strongly to weakly coupled. We use aircraft data from the NASA Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) to assess aerosol and cloud characteristics for the following four regimes, quantified using differences in liquid water potential temperature (θℓ) and total water mixing ratio (qt) between flight data near the surface level (∼150 m) and directly below cloud bases: strong coupling (Δθℓ≤1.0 K, Δqt≤0.8 g kg−1), moderate coupling with high Δθℓ (Δθℓ>1.0 K, Δqt≤0.8 g kg−1), moderate coupling with high Δqt (Δθℓ≤1.0 K, Δqt>0.8 g kg−1), and weak coupling (Δθℓ>1.0 K, Δqt>0.8 g kg−1). Results show that (i) turbulence is greater in the strong coupling regime compared to the weak coupling regime, with the former corresponding to more vertical homogeneity in 550 nm aerosol scattering, integrated aerosol volume concentration, and giant aerosol number concentration (Dp>3 µm) coincident with increased MBL mixing; (ii) cloud drop number concentration is greater during periods of strong coupling due to the greater upward vertical velocity and subsequent activation of particles; and (iii) sea salt tracer species (Na+, Cl−, Mg2+, K+) are present in greater concentrations in the strong coupling regime compared to weak coupling, while tracers of continental pollution (Ca2+, non-sea-salt (nss) SO42-, NO3-, oxalate, and NH4+) are higher in mass fraction for the weak coupling regime. Additionally, pH and Cl-:Na+ (a marker for chloride depletion) are consistently lower in the weak coupling regime. There were also differences between the two moderate regimes: the moderate with high Δqt regime had greater turbulent mixing and sea salt concentrations in cloud water, along with smaller differences in integrated volume and giant aerosol number concentration across the two vertical levels compared. This work shows value in defining multiple coupling regimes (rather than the traditional coupled versus decoupled) and demonstrates differences in aerosol and cloud behavior in the MBL for the various regimes.

The NASA North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) ship and aircraft field campaign deployed to the western subarctic Atlantic between the years 2015 and 2018. One of the primary goals of NAAMES is to improve the understanding of aerosol–cloud interaction (ACI) over the Atlantic Ocean under different seasonal regimes. ACIs currently represent the largest source of uncertainty in global climate models. During three NAAMES field campaigns (NAAMES-1 in November 2015, NAAMES-2 in May 2016, and NAAMES-3 in September 2017), multiple 10 h science flights were conducted using the NASA C-130 aircraft to measure marine boundary layer aerosol and cloud properties. The standard flight pattern includes vertical spirals where the C-130 transitioned from high altitude to low altitude (and vice versa), collecting in situ measurements of aerosols, trace gases, clouds, and meteorological parameters as a function of altitude. We examine the data collected from 37 spirals during the three NAAMES field campaigns, and we present a comprehensive characterization of the vertical profiles of aerosol properties under different synoptic conditions and aerosol regimes. The vertical distribution of submicron aerosol particles exhibited strong seasonal variation, as well as elevated intra-seasonal variability depending on emission sources and aerosol processes in the atmospheric column. Pristine marine conditions and new particle formation were prevalent in the wintertime (NAAMES-1) due to low biogenic emissions from the surface ocean and reduced continental influence. Higher concentrations of submicron aerosol particles were observed in the spring (NAAMES-2) due to strong phytoplankton activity and the arrival of long-range-transported continental plumes in the free troposphere with subsequent entrainment into the marine boundary layer. Biomass burning from boreal wildfires was the main source of aerosol particles in the region during the late summer (NAAMES-3) in both the marine boundary layer and free troposphere.