Coco is a dual activity modulator of TGFβ signaling

The Role of Small Molecules and Their Effect on the Molecular Mechanisms of Early Retinal Organoid Development

Early in vivo embryonic retinal development is a well-documented and evolutionary conserved process. The specification towards eye development is temporally controlled by consecutive activation or inhibition of multiple key signaling pathways, such as the Wnt and hedgehog signaling pathways. Recently, with the use of retinal organoids, researchers aim to manipulate these pathways to achieve better human representative models for retinal development and disease. To achieve this, a plethora of different small molecules and signaling factors have been used at various time points and concentrations in retinal organoid differentiations, with varying success. Additions differ from protocol to protocol, but their usefulness or efficiency has not yet been systematically reviewed. Interestingly, many of these small molecules affect the same and/or multiple pathways, leading to reduced reproducibility and high variability between studies. In this review, we make an inventory of the key signaling pathways involved in early retinogenesis and their effect on the development of the early retina in vitro. Further, we provide a comprehensive overview of the small molecules and signaling factors that are added to retinal organoid differentiation protocols, documenting the molecular and functional effects of these additions. Lastly, we comparatively evaluate several of these factors using our established retinal organoid methodology.

Identification and characterization of Fbxl22, a novel skeletal muscle atrophy-promoting E3 ubiquitin ligase

Muscle-specific E3 ubiquitin ligases have been identified in muscle atrophy-inducing conditions. The purpose of the current study was to explore the functional role of F-box and leucine-rich protein 22 (Fbxl22), and a newly identified splice variant (Fbxl22-193), in skeletal muscle homeostasis and neurogenic muscle atrophy. In mouse C₂C₁₂ muscle cells, promoter fragments of the Fbxl22 gene were cloned and fused with the secreted alkaline phosphatase reporter gene to assess the transcriptional regulation of Fbxl22. The tibialis anterior muscles of male C57/BL6 mice (12-16 wk old) were electroporated with expression plasmids containing the cDNA of two Fbxl22 splice variants and tissues collected after 7, 14, and 28 days. Gastrocnemius muscles of wild-type and muscle-specific RING finger 1 knockout (MuRF1 KO) mice were electroporated with an Fbxl22 RNAi or empty plasmid and denervated 3 days posttransfection, and tissues were collected 7 days postdenervation. The full-length gene and novel splice variant are transcriptionally induced early (after 3 days) during neurogenic muscle atrophy. In vivo overexpression of Fbxl22 isoforms in mouse skeletal muscle leads to evidence of myopathy/atrophy, suggesting that both are involved in the process of neurogenic muscle atrophy. Knockdown of Fbxl22 in the muscles of MuRF1 KO mice resulted in significant additive muscle sparing 7 days after denervation. Targeting two E3 ubiquitin ligases appears to have a strong additive effect on protecting muscle mass loss with denervation, and these findings have important implications in the development of therapeutic strategies to treat muscle atrophy.

Cancer stem cells and their unique role in metastatic spread

Cancer stem cells (CSC) possess abilities generally associated with embryonic or adult stem cells, especially self-renewal and differentiation, but also dormancy and cellular plasticity that allow adaption to new environmental circumstances. These abilities are ideal prerequisites for the successful establishment of metastasis. This review highlights the role of CSCs in every step of the metastatic cascade from cancer cell invasion into blood vessels, survival in the blood stream, attachment and extravasation as well as colonization of the host organ and subsequent establishment of distant macrometastasis.

Rapid changes in morphogen concentration control self-organized patterning in human embryonic stem cells

During embryonic development, diffusible signaling molecules called morphogens are thought to determine cell fates in a concentration-dependent way. Yet, in mammalian embryos, concentrations change rapidly compared to the time for making cell fate decisions. Here, we use human embryonic stem cells (hESCs) to address how changing morphogen levels influence differentiation, focusing on how BMP4 and Nodal signaling govern the cell-fate decisions associated with gastrulation. We show that BMP4 response is concentration dependent, but that expression of many Nodal targets depends on rate of concentration change. Moreover, in a self-organized stem cell model for human gastrulation, expression of these genes follows rapid changes in endogenous Nodal signaling. Our study shows a striking contrast between the specific ways ligand dynamics are interpreted by two closely related signaling pathways, highlighting both the subtlety and importance of morphogen dynamics for understanding mammalian embryogenesis and designing optimized protocols for directed stem cell differentiation.

Editorial note

This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

TGF-β Family Signaling in Early Vertebrate Development

TGF-β family ligands function in inducing and patterning many tissues of the early vertebrate embryonic body plan. Nodal signaling is essential for the specification of mesendodermal tissues and the concurrent cellular movements of gastrulation. Bone morphogenetic protein (BMP) signaling patterns tissues along the dorsal-ventral axis and simultaneously directs the cell movements of convergence and extension. After gastrulation, a second wave of Nodal signaling breaks the symmetry between the left and right sides of the embryo. During these processes, elaborate regulatory feedback between TGF-β ligands and their antagonists direct the proper specification and patterning of embryonic tissues. In this review, we summarize the current knowledge of the function and regulation of TGF-β family signaling in these processes. Although we cover principles that are involved in the development of all vertebrate embryos, we focus specifically on three popular model organisms: the mouse Mus musculus, the African clawed frog of the genus Xenopus, and the zebrafish Danio rerio, highlighting the similarities and differences between these species.

Nodal and BMP dispersal during early zebrafish development

The secreted TGF-β superfamily signals Nodal and BMP coordinate the patterning of vertebrate embryos. Nodal specifies endoderm and mesoderm during germ layer formation, and BMP specifies ventral fates and patterns the dorsal/ventral axis. Five major models have been proposed to explain how the correct distributions of Nodal and BMP are achieved within tissues to orchestrate embryogenesis: source/sink, transcriptional determination, relay, self-regulation, and shuttling. Here, we discuss recent experiments probing these signal dispersal models, focusing on early zebrafish development.

Pitx1 regulates cement gland development in Xenopus laevis through activation of transcriptional targets and inhibition of BMP signaling

The cement gland in Xenopus laevis has long been used as a model to study the interplay of cell signaling and transcription factors during embryogenesis. It has been shown that an intermediate level of Bone Morphogenetic Protein (BMP) signaling is essential for cement gland formation. In addition, several transcription factors have been linked to cement gland development. One of these, the homeodomain-containing protein Pitx1, can generate ectopic cement gland formation; however, the mechanisms underlying this process remain obscure. We report here, for the first time, a requirement for Pitx proteins in cement gland formation, in vivo: knockdown of both pitx1 and the closely related pitx2c inhibit endogenous cement gland formation. Pitx1 transcriptionally activates cement gland differentiation genes through both direct and indirect mechanisms, and functions as a transcriptional activator to inhibit BMP signaling. This inhibition, required for the expression of pitx genes, is partially mediated by Pitx1-dependent follistatin expression. Complete suppression of BMP signaling inhibits induction of cement gland markers by Pitx1; furthermore, we find that Pitx1 physically interacts with Smad1, an intracellular transducer of BMP signaling. We propose a model of cement gland formation in which Pitx1 limits local BMP signaling within the cement gland primordium, and recruits Smad1 to activate direct downstream targets.

The BMP inhibitor DAND5 in serum predicts poor survival in breast cancer

Background & Aims

Breast cancer (BC) is prevalent worldwide malignant cancer. Improvements in timely and effective diagnosis and prediction are needed. As reported, secreted DAND5 is contributed to BC metastasis. We aim to assess whether DAND5 in peripheral blood serum could determine BC-specific mortality.

Methods

We used immunohistochemistry staining to detect DAND5 expression in our BC tissue array including 250 samples. Angiogenesis assay and xenograft mice model were used to examine the secreted DAND5 function in BC progression. Serum concentration of DAND5 was examined by ELISA in 1730 BC patients. Kaplan-Meier and adjusted Cox proportional hazards models were utilized to analyze the prognosis and survival of BC patients.

Results

Tissue array results showed that positive DAND5 staining cases displayed a higher likelihood of occurrence of disease events (HR=5.494; 95% CI: 1.008-2.353; P=0.048) in univariate analysis and remained the same trend in multivariate analysis (HR=2.537; 95% CI: 1.056-6.096; P=0.037). DAND5 positive patients exerted generally poor DFS (P=0.041) in the Kaplan-Meier survival analysis. Furthermore, secreted DAND5 promoted tumor growth and angiogenesis in vitro and in vivo. In addition, positive DAND5 in BC patients serum was associated with increased risk of disease events occurrence (univariate: HR=1.58; 95% CI: 1.206-2.070; P=0.001; multivariate: HR=1.4; 95% CI: 1.003-1.954; P=0.048) in univariate and multivariate survival analysis. In the Kaplan-Meier analysis, serum DAND5 positively correlated with poor DFS (P=0.001) and DDFS (P=0.002).

Conclusions

DAND5 was correlated with poor survival and could serve as an easily detectable serum biomarker to predict the survival of breast cancer.

Elevated serum DAND5 is associated with metastasis and predicts poor prognosis in colorectal cancer

BACKGROUND

The biologic and clinical significance of DAND5 remains unknown in colorectal cancer (CRC).

OBJECTIVE

Herein, we investigated the function of DAND5 and evaluated its clinical significance in both serum and matched primary tumors in patients with CRC.

METHODS

The role of DAND5 was explored in CRC cells and clinical significance of DAND5 was investigated in CRC patients (n = 217) and healthy controls (n = 63).

RESULTS

Knockdown of DAND5 significantly decreased CRC cell proliferation, migration and invasion partly associated with epithelial-mesenchymal transition phenotype. Serum DAND5 levels in CRC were significantly higher than in normal controls and accurately distinguished CRC from healthy subjects. High serum DAND5 levels were significantly correlated with tumor differentiation, large tumor size, advanced Tumor Node Metastasis (TNM) stage, lymph node and liver metastasis, high carcinoembryonic antigen level, recurrence, poor overall and disease-free survival. Serum DAND5 level, together with lymph node metastasis, were independent prognostic factors for CRC patients. High DAND5 protein expression in CRC tissues was increased according to TNM stage. A significant positive correlation existed between serum DAND5 levels and matched DAND5 expression in CRC tissues.

CONCLUSION

Our data provide novel evidence for the clinical significance of DAND5 as a potential biomarker for CRC prognosis.