Tgf-β superfamily and limb regeneration: Tgf-β to start and Bmp to end

The development and the genetic diseases of the ciliary body

The ciliary body, located at the junction of the choroid and iris, is crucial in the development of the embryonic eye. Notch2 signalling, Wnt signalling, transforming growth factor β (TGF-β) signalling, and Pax6 signalling are critical for coordinating the ciliary body formation. These signalling pathways are coordinated with each other and participate in the ciliary body development, ensuring the precise formation and optimal functioning of the eye structure. Although rare, ciliary body hypoplasia, ciliary tumours, and genetic-related iritis indicate the intricate nature of ciliary body development. Given the ciliary body's important biological significance and potential medical relevance, we aim to provide a comprehensive overview of the developmental molecular mechanisms governing ciliary body formation and function. Here, we focus on the intricate signalling pathways governing ciliary body development and corresponding genetic ciliary diseases.

The ctenophore Mnemiopsis leidyi deploys a rapid injury response dating back to the last common animal ancestor

Regenerative potential is widespread but unevenly distributed across animals. However, our understanding of the molecular mechanisms underlying regenerative processes is limited to a handful of model organisms, restricting robust comparative analyses. Here, we conduct a time course of RNA-seq during whole body regeneration in Mnemiopsis leidyi (Ctenophora) to uncover gene expression changes that correspond with key events during the regenerative timeline of this species. We identified several genes highly enriched in this dataset beginning as early as 10 minutes after surgical bisection including transcription factors in the early timepoints, peptidases in the middle timepoints, and cytoskeletal genes in the later timepoints. We validated the expression of early response transcription factors by whole mount in situ hybridization, showing that these genes exhibited high expression in tissues surrounding the wound site. These genes exhibit a pattern of transient upregulation as seen in a variety of other organisms, suggesting that they may be initiators of an ancient gene regulatory network linking wound healing to the initiation of a regenerative response.

Genome-wide analysis of BMP/GDF family and DAP-seq of YY1 suggest their roles in Cynoglossus semilaevis sexual size dimorphism

Sexual size dimorphism (SSD) characterized by different body size between females and males have been reported in various animals. Gonadectomy experiments have implied important regulatory roles of the gonad in SSD. Among multiple factors from the gonad, TGF-β superfamily (especially BMP/GDF family) attracted our interest due to its pleiotropy in growth and reproduction regulations. Thus, whether BMP/GDF family members serve as crucial regulators for SSD was studied in a typically female-biased SSD flatfish named Chinese tongue sole (Cynoglossus semilaevis). Firstly, a total of 26 BMP/GDF family members were identified. The PPI network analysis showed that they may interact with ACVR2a, ACVR2b, ACVR1, BMPR2, SMAD3, BMPR1a, and other proteins. Subsequently, DAP-seq was employed to reveal the binding sites for yin yang 1 (yy1), a transcription factor involved in gonad function and cell growth partly by regulating TGF-β superfamily. The results revealed that two yy1 homologues yy1a and yy1b in C. semilaevis could regulate Hippo signaling pathway, mTOR signaling pathway, and AMPK signaling pathway. Moreover, BMP/GDF family genes including bmp2, bmp4, bmp5, gdf6a, and gdf6b were important components of Hippo pathway. In future, the crosstalk among yy1a, yy1b, and TGF-β family would provide more insight into sexual size dimorphism in C. semilaevis.

From injury to patterning—MAPKs and Wnt signaling in Hydra

Hydra has a regenerative capacity that is not limited to individual organs but encompasses the entire body. Various global and integrative genome, transcriptome and proteome approaches have shown that many of the signaling pathways and transcription factors present in vertebrates are already present in Cnidaria, the sister group of Bilateria, and are also activated in regeneration. It is now possible to investigate one of the central questions of regeneration biology, i.e., how does the patterning system become activated by the injury signals that initiate regeneration. This review will present the current data obtained in Hydra and draw parallels with regeneration in Bilateria. Important findings of this global analysis are that the Wnt signaling pathway has a dual function in the regeneration process. In the early phase Wnt is activated generically and in a second phase of pattern formation it is activated in a position specific manner. Thus, Wnt signaling is part of the generic injury response, in which mitogen-activated protein kinases (MAPKs) are initially activated via calcium and reactive oxygen species (ROS). The MAPKs, p38, c-Jun N-terminal kinases (JNKs) and extracellular signal-regulated kinases (ERK) are essential for Wnt activation in Hydra head and foot regenerates. Furthermore, the antagonism between the ERK signaling pathway and stress-induced MAPKs results in a balanced induction of apoptosis and mitosis. However, the early Wnt genes are activated by MAPK signaling rather than apoptosis. Early Wnt gene activity is differentially integrated with a stable, β-Catenin-based gradient along the primary body axis maintaining axial polarity and activating further Wnts in the regenerating head. Because MAPKs and Wnts are highly evolutionarily conserved, we hypothesize that this mechanism is also present in vertebrates but may be activated to different degrees at the level of early Wnt gene integration.

Emerging bone marrow failure syndromes- new pieces to an unsolved puzzle

Inherited bone marrow failure (BMF) syndromes are genetically diverse - more than 100 genes have been associated with those syndromes and the list is rapidly expanding. Risk assessment and genetic counseling of patients with recently discovered BMF syndromes is inherently difficult as disease mechanisms, penetrance, genotype-phenotype associations, phenotypic heterogeneity, risk of hematologic malignancies and clonal markers of disease progression are unknown or unclear. This review aims to shed light on recently described BMF syndromes with sparse concise data and with an emphasis on those associated with germline variants in ADH5/ALDH2, DNAJC21, ERCC6L2 and MECOM. This will provide important data that may help to individualize and improve care for these patients.

Evi5 is required for Xenopus limb and tail regeneration

Amphibians such as salamanders and the African clawed frog Xenopus are great models for regeneration studies because they can fully regenerate their lost organs. While axolotl can regenerate damaged organs throughout its lifetime, Xenopus has a limited regeneration capacity after metamorphosis. The ecotropic viral integrative factor 5 (Evi5) is of great interest because its expression is highly upregulated in the limb blastema of axolotls, but remains unchanged in the fibroblastema of post-metamorphic frogs. Yet, its role in regeneration-competent contexts in Xenopus has not been fully analyzed. Here we show that Evi5 is upregulated in Xenopus tadpoles after limb and tail amputation, as in axolotls. Down-regulation of Evi5 with morpholino antisense oligos (Mo) impairs limb development and limb blastema formation in Xenopus tadpoles. Mechanistically, we show that Evi5 knockdown significantly reduces proliferation of limb blastema cells and causes apoptosis, blocking the formation of regeneration blastema. RNA-sequencing analysis reveals that in addition to reduced PDGFα and TGFβ signaling pathways that are required for regeneration, evi5 Mo downregulates lysine demethylases Kdm6b and Kdm7a. And knockdown of Kdm6b or Kdm7a causes defective limb regeneration. Evi5 knockdown also impedes tail regeneration in Xenopus tadpoles and axolotl larvae, suggesting a conserved function of Evi5 in appendage regeneration. Thus, our results demonstrate that Evi5 plays a critical role in appendage regeneration in amphibians.

Post-amputation reactive oxygen species production is necessary for axolotls limb regeneration

Introduction: Reactive oxygen species (ROS) represent molecules of great interest in the field of regenerative biology since several animal models require their production to promote and favor tissue, organ, and appendage regeneration. Recently, it has been shown that the production of ROS such as hydrogen peroxide (H₂O₂) is required for tail regeneration in Ambystoma mexicanum. However, to date, it is unknown whether ROS production is necessary for limb regeneration in this animal model. Methods: forelimbs of juvenile animals were amputated proximally and the dynamics of ROS production was determined using 2′7- dichlorofluorescein diacetate (DCFDA) during the regeneration process. Inhibition of ROS production was performed using the NADPH oxidase inhibitor apocynin. Subsequently, a rescue assay was performed using exogenous hydrogen peroxide (H₂O₂). The effect of these treatments on the size and skeletal structures of the regenerated limb was evaluated by staining with alcian blue and alizarin red, as well as the effect on blastema formation, cell proliferation, immune cell recruitment, and expression of genes related to proximal-distal identity. Results: our results show that inhibition of post-amputation limb ROS production in the A. mexicanum salamander model results in the regeneration of a miniature limb with a significant reduction in the size of skeletal elements such as the ulna, radius, and overall autopod. Additionally, other effects such as decrease in the number of carpals, defective joint morphology, and failure of integrity between the regenerated structure and the remaining tissue were identified. In addition, this treatment affected blastema formation and induced a reduction in the levels of cell proliferation in this structure, as well as a reduction in the number of CD45⁺ and CD11b + immune system cells. On the other hand, blocking ROS production affected the expression of proximo-distal identity genes such as Aldha1a1, Rarβ, Prod1, Meis1, Hoxa13, and other genes such as Agr2 and Yap1 in early/mid blastema. Of great interest, the failure in blastema formation, skeletal alterations, as well as the expression of the genes evaluated were rescued by the application of exogenous H₂O₂, suggesting that ROS/H₂O₂ production is necessary from the early stages for proper regeneration and patterning of the limb.

Novel Nanoconjugate of Apamin and Ceftriaxone for Management of Diabetic Wounds

Diabetic hyperglycemia delays wound healing, leading to serious consequences. Topical antibiotics can reduce the risk of a wound infection during healing; nevertheless, the microbial fight against antibiotics brings about public health challenges. Anti-microbial peptides (AMPs) belong to a novel class of drug that is used to prevent and treat systemic and topical infections. The aim of the current work was to achieve better wound healing in diabetic rats by conjugating the anti-microbial peptide “apamin” (APA) with the broad-spectrum antibiotic “ceftriaxone” (CTX) to form a nanocomplex. The CTX–APA nanoconjugate formulation was optimized using a Box–Behnken design. The optimized CTX–APA nanoconjugate formulation was evaluated for its size and zeta potential, and was then examined using transmission electron microscopy (TEM). The CTX–APA nanoconjugate was loaded onto a hydroxypropyl methylcellulose (2% w/v)-based hydrogel. It was observed that the application of the CTX–APA nanocomplex on the wounded skin of diabetic rats accelerated the regeneration of the epithelium, granulation tissue formation, epidermal proliferation, and keratinization. The nanocomplex was capable of significantly reducing the expression of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6), while increasing the expression of transforming growth factor beta-1 (TGF-β1) as well as the angiogenic markers: hypoxia-inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF). Conclusively, the application of an ion-paired CTX–APA nanocomplex enhances wound healing in diabetic rats.