Kidney collecting duct cell type composition is regulated by Notch signaling via modulation of mTORC1.

The plasticity and diversity of cell types with specialized functions likely defines the capacity of multicellular organisms to adapt to physiologic stressors. The kidney collecting ducts contribute to water, electrolyte, and pH homeostasis and are composed of mature intermingled epithelial cell types that are susceptible to transdifferentiate. The conversion of kidney collecting duct principal cells to intercalated cells is actively inhibited by Notch signaling to ensure urine concentrating capability.

Comprehensive analysis of the proximity-dependent nuclear interactome for the oncoprotein NOTCH1 in live cells.

Notch signaling plays a critical role in cell fate decisions in all cell types. Furthermore, gain-of-function mutations in NOTCH1 have been uncovered in many human cancers. Disruption of Notch signaling has recently emerged as an attractive disease treatment strategy.

Hdac1 and Hdac2 positively regulate Notch1 gain-of-function pathogenic signaling in committed osteoblasts of male mice.

Background: Skeletal development requires precise extrinsic and intrinsic signals to regulate processes that form and maintain bone and cartilage. Notch1 is a highly conserved signaling receptor that regulates cell fate decisions by controlling the duration of transcriptional bursts. Epigenetic molecular events reversibly modify DNA and histone tails by influencing the spatial organization of chromatin and can fine-tune the outcome of a Notch1 transcriptional response.

Selective Targeting of Class I Histone Deacetylases in a Model of Human Osteosarcoma.

Dysregulation of histone deacetylases (HDACs) is associated with the pathogenesis of human osteosarcoma, which may present an epigenetic vulnerability as well as a therapeutic target. Domatinostat (4SC-202) is a next-generation class I HDAC inhibitor that is currently being used in clinical research for certain cancers, but its impact on human osteosarcoma has yet to be explored. In this study, we report that 4SC-202 inhibits osteosarcoma cell growth in vitro and in vivo.

Precise detection of a murine germline mutation of the gene associated with kyphosis and developmental disorders.

Objective: Humpback () mice harbor a pathogenic mutation in the gene and can serve as a beneficial animal model for investigating human myopathy, kyphosis, and developmental disorders, including lateral meningocele syndrome. Detection of the point mutation in mice is important for maintaining strains and scrutinizing genetic rescues, especially considering that homozygous mice are infertile and indistinguishable from their littermates at a young age. This study aimed for the development of a novel, precise, and time-saving genotyping method to identify the mutation in mice.

Development and characterization of the novel human osteosarcoma cell line COS-33 with sustained activation of the mTOR pathway.

Outcomes have not improved for metastatic osteosarcoma for several decades. In part, this failure to develop better therapies stems from a lack of understanding of osteosarcoma biology, given the rarity of the disease and the high genetic heterogeneity at the time of diagnosis. We report here the successful establishment of a new human osteosarcoma cell line, COS-33, from a patient-derived xenograft and demonstrate retention of the biological features of the original tumor.

Statin-mediated cholesterol depletion exerts coordinated effects on the alterations in rat vascular smooth muscle cell biomechanics and migration.

Key Points: This study demonstrates and evaluates the changes in rat vascular smooth muscle cell biomechanics following statin-mediated cholesterol depletion. Evidence is presented to show correlated changes in migration and adhesion of vascular smooth muscle cells to extracellular matrix proteins fibronectin and collagen. Concurrently, integrin α5 expression was enhanced but not integrin α2.

Targeting the Wnt/β-catenin pathway in human osteosarcoma cells.

Aberrant activation of Wnt signaling has been implicated in human osteosarcoma, which may provide a genetic vulnerability that can be targeted in osteosarcoma treatment. To test whether Wnt activation is necessary for osteosarcoma growth, colony formation, invasion, and metastasis, we treated human osteosarcoma cells with a small molecule inhibitor of Wnt/β-catenin, PRI-724, which suppresses Wnt/β-catenin-mediated transcription. We found increased protein levels of endogenous active-β-catenin in five human osteosarcoma cell lines.

Functionalization of PCL-3D Electrospun Nanofibrous Scaffolds for Improved BMP2-Induced Bone Formation.

Bone morphogenic protein 2 (BMP2) is a key growth factor for bone regeneration, possessing FDA approval for orthopedic applications. BMP2 is often required in supratherapeutic doses clinically, yielding adverse side effects and substantial treatment costs. Considering the crucial role of materials for BMPs delivery and cell osteogenic differentiation, we devote to engineering an innovative bone-matrix mimicking niche to improve low dose of BMP2-induced bone formation.

MicroRNA miR-23a cluster promotes osteocyte differentiation by regulating TGF-β signalling in osteoblasts.

Osteocytes are the terminally differentiated cell type of the osteoblastic lineage and have important functions in skeletal homeostasis. Although the transcriptional regulation of osteoblast differentiation has been well characterized, the factors that regulate differentiation of osteocytes from mature osteoblasts are poorly understood. Here we show that miR-23a∼27a∼24-2 (miR-23a cluster) promotes osteocyte differentiation.

Hypoxia-Mimicking Nanofibrous Scaffolds Promote Endogenous Bone Regeneration.

Utilizing biomimetic materials to potentiate endogenous cell growth or signaling is superior to relying on exogenous cells or signals for bone formation. Desferoxamine (DFO), which is a hypoxia-mimetic agent that chelates iron (Fe), mimics hypoxia to encourage bone healing. However, high cytotoxicity, off-target effects, and the short half-life of DFO have significantly impeded its further applications.

Molecular genetics of osteosarcoma.

Osteosarcoma is the predominant form of bone cancer, affecting mostly adolescents. Recent progress made in molecular genetic studies of osteosarcoma has changed our view on the cause of the disease and ongoing therapeutic approaches for patients. As we draw closer to gaining more complete catalogs of candidate cancer driver genes in common forms of cancer, the landscape of somatic mutations in osteosarcoma is emerging from its first phase.

The osteogenic niche promotes early-stage bone colonization of disseminated breast cancer cells.

Breast cancer bone micrometastases can remain asymptomatic for years before progressing into overt lesions. The biology of this process, including the microenvironment niche and supporting pathways, is unclear. We find that bone micrometastases predominantly reside in a niche that exhibits features of osteogenesis.

RECQL4 Regulates p53 Function In Vivo During Skeletogenesis.

RECQ DNA helicases play critical roles in maintaining genomic stability, but their role in development has been less well studied. Rothmund-Thomson syndrome, RAPADILINO, and Baller-Gerold syndrome are rare genetic disorders caused by mutations in the RECQL4 gene. These patients have significant skeletal developmental abnormalities including radial ray, limb and craniofacial defects.

Notch activation as a driver of osteogenic sarcoma.

Osteogenic sarcoma (OS) is a deadly skeletal malignancy whose cause is unknown. We report here a mouse model of OS based on conditional expression of the intracellular domain of Notch1 (NICD). Expression of the NICD in immature osteoblasts was sufficient to drive the formation of bone tumors, including OS, with complete penetrance.

A spontaneous Fatp4/Scl27a4 splice site mutation in a new murine model for congenital ichthyosis.

Congenital ichthyoses are life-threatening conditions in humans. We describe here the identification and molecular characterization of a novel recessive mutation in mice that results in newborn lethality with severe congenital lamellar ichthyosis. Mutant newborns have a taut, shiny, non-expandable epidermis that resembles cornified manifestations of autosomal-recessive congenital ichthyosis in humans.

Notch gain of function inhibits chondrocyte differentiation via Rbpj-dependent suppression of Sox9.

Notch signaling plays a critical role during development by directing the binary cell fate decision between progenitors and differentiated cells. Previous studies have shown sustained Notch activation in cartilage leads to chondrodysplasia. Genetic evidence indicates that Notch regulates limb bud mesenchymal stem cell differentiation into chondrocytes via an Rbpj-dependent Notch pathway.

miRNA-34c regulates Notch signaling during bone development.

During bone homeostasis, osteoblast and osteoclast differentiation is coupled and regulated by multiple signaling pathways and their downstream transcription factors. Here, we show that microRNA 34 (miR-34) is significantly induced by BMP2 during osteoblast differentiation. In vivo, osteoblast-specific gain of miR-34c in mice leads to an age-dependent osteoporosis due to the defective mineralization and proliferation of osteoblasts and increased osteoclastogenesis.

One NOTCH Further: Jagged 1 in Bone Metastasis.

The outgrowth of metastatic cells to bone depends on the interaction between multiple intrinsic and host factors. In this issue of Cancer Cell, Sethi and colleagues report Notch signaling in bone cells as responsible for promoting this outgrowth and provide evidence for a beneficial treatment effect of NOTCH inhibitors.

E-selectin ligand-1 regulates growth plate homeostasis in mice by inhibiting the intracellular processing and secretion of mature TGF-beta.

The majority of human skeletal dysplasias are caused by dysregulation of growth plate homeostasis. As TGF-beta signaling is a critical determinant of growth plate homeostasis, skeletal dysplasias are often associated with dysregulation of this pathway. The context-dependent action of TFG-beta signaling is tightly controlled by numerous mechanisms at the extracellular level and downstream of ligand-receptor interactions.

Osteosclerosis owing to Notch gain of function is solely Rbpj-dependent.

Osteosclerosis is a pathologic bone disease characterized by an increase in bone formation over bone resorption. Genetic factors that contribute to the pathogenesis of this disease are poorly understood. Dysregulation or mutation in many components of the Notch signaling pathway results in a wide range of human developmental disorders and cancers, including bone diseases.

Alteration of Notch signaling in skeletal development and disease.

Notch signaling is an evolutionarily conserved mechanism for specifying and regulating organogenesis and tissue renewal. Human and mouse genetic studies have demonstrated mutations in many components of the Notch signaling pathway that cause skeletal patterning defects. More recently, the in vivo effects of Notch signaling on osteoblast specification, proliferation, and differentiation have been demonstrated in addition to its regulation of osteoclast activity.

BMP4-dependent expression of Xenopus Grainyhead-like 1 is essential for epidermal differentiation.

Morphogen-dependent epidermal-specific transacting factors have not been defined in vertebrates. We demonstrate that a member of the grainyhead transcription factor family, Grainyhead-like 1 (XGrhl1) is essential for ectodermal ontogeny in Xenopus laevis. Expression of this factor is restricted to epidermal cells.

A highly conserved novel family of mammalian developmental transcription factors related to Drosophila grainyhead.

The Drosophila transcription factor Grainyhead regulates several key developmental processes. Three mammalian genes, CP2, LBP-1a and LBP-9 have been previously identified as homologues of grainyhead. We now report the cloning of two new mammalian genes (Mammalian grainyhead (MGR) and Brother-of-MGR (BOM)) and one new Drosophila gene (dCP2) that rewrite the phylogeny of this family.