Wdr5 is required for chick skeletal development

Measuring transcription factor function with cell type-specific somatic transgenesis in chicken embryos

Retroviral-mediated misexpression in chicken embryos has been a powerful research tool for developmental biologists in the last two decades. In the RCASBP retroviral vectors that are widely used for in vivo somatic transgenesis, a coding sequence of interest is under the transcriptional control of a strong viral promoter in the long terminal repeat. While this has proven to be effective for studying secreted signalling proteins, interpretation of the mechanisms of action of nuclear factors is more difficult using this system since it is not clear whether phenotypic effects are cell-autonomous or not, and therefore whether they represent a function of the endogenous protein. Here, we report the consequences of retroviral expression using the RCANBP backbone, in which the transcription factor Dlx5 is expressed under the control of chondrocyte-specific regulatory sequences from the Col2a1 gene. To our knowledge, this is the first demonstration of a tissue-specific phenotype in the chicken embryo.

Targeting WD Repeat-Containing Protein 5 (WDR5): A Medicinal Chemistry Perspective

WD repeat-containing protein 5 (WDR5) is a member of the WD40 protein family, and it is widely involved in various biological activities and not limited to epigenetic regulation in vivo. WDR5 is also involved in the initiation and development of many diseases and plays a key role in these diseases. Since WDR5 was discovered, it has been suggested as a potential disease treatment target, and a large number of inhibitors targeting WDR5 have been discovered. In this review, we discussed the development of inhibitors targeting WDR5 over the years, and the biological mechanisms of these inhibitors based on previous mechanistic studies were explored. Finally, we describe the development potential of inhibitors targeting WDR5 and prospects for further applications.

RAIN Is a Novel Enhancer-Associated lncRNA That Controls RUNX2 Expression and Promotes Breast and Thyroid Cancer

Enhancer (ENH)-associated long noncoding RNAs (lncRNA) are a peculiar class of RNAs produced by transcriptionally active ENHs, owning potential gene-regulatory function. Here, we characterized RAIN, a novel ENH-associated lncRNA. Analysis of RAIN expression in a retrospective cohort of human thyroid cancers showed that the expression of this lncRNA is restricted to cancer cells and strongly correlates with the expression of the cancer-promoting transcription factor RUNX2. We showed that RAIN, serving as a cis-regulatory element, promotes RUNX2 expression by two mechanisms. Binding WDR5 and facilitating its localization on the RUNX2 promoter, RAIN modifies the transcriptional status of the RUNX2 locus facilitating transcription initiation. In parallel, RAIN acts as decoy for negative elongation factor complex, restraining its inhibitory function on transcription elongation. In both thyroid and breast cancer cells, RAIN promotes oncogenic features. Using RNA-sequencing profiling, we showed that RAIN orchestrates the expression of a network of cancer-promoting transcription regulators, suggesting that RAIN affects cancer cell phenotype by coordinating the expression of a complex transcriptional network. IMPLICATIONS: Our data contribute to understand lncRNA function in gene regulation and to consolidate their role in cancer.

Moonlighting with WDR5: A Cellular Multitasker

WDR5 is a highly conserved WD40 repeat-containing protein that is essential for proper regulation of multiple cellular processes. WDR5 is best characterized as a core scaffolding component of histone methyltransferase complexes, but emerging evidence demonstrates that it does much more, ranging from expanded functions in the nucleus through to controlling the integrity of cell division. The purpose of this review is to describe the current molecular understandings of WDR5, discuss how it participates in diverse cellular processes, and highlight drug discovery efforts around WDR5 that may form the basis of new anti-cancer therapies.

INO80 is Required for Osteogenic Differentiation of Human Mesenchymal Stem Cells

Bone marrow derived human mesenchymal stem cells (MSC) are a great source in bone tissue engineering. However, how to improve the efficiency of MSC osteogenesis remains a big challenge in bone regenerative medicine. Here, we characterized the role of INO80 chromatin remodeling complex in osteogenic differentiation of MSC. We showed that silencing of subunits of INO80 reduced the mineral deposition of MSC in osteogenic condition. Moreover, INO80-silencing MSC cultured in osteogenic condition expressed lower mRNA levels of osteoblast-specific genes, including Runx2, Osx, Col1α1 and OCN. INO80 can interact with Wdr5 in MSC and positively regulates the canonical Wnt signaling transduction. Importantly, the mice implanted with INO80-silencing MSC displayed less bone formation. Overall, our study provides a new mechanism regarding osteogenic differentiation of MSC and could potentially be applied in clinical tissue engineering and treatment of osteoporosis.

Growth plate biology: new insights

PURPOSE OF REVIEW

To discuss the most recent findings of growth plate regulation and physiology. The mechanism of endochondrial bone growth is incompletely understood and continues to be an active area of research.

RECENT FINDINGS

In this review, new understandings of growth plate chondrocyte regulation of proliferation, differentiation and ossification are discussed. Through genetic studies potential signaling pathways are proposed and new insights into hormonal influences on growth are offered. New potential genetic pathways regulating growth are suggested and finally skeletal dysplasia and potential emerging treatment are considered.

SUMMARY

The findings discussed here continue to build the understanding of the mechanisms of growth. As our knowledge increases potential treatments for growth inhibiting conditions can be developed.