Cell segregation caused by collective cell migration (CCM) is crucial for morphogenesis, functional development of tissue parts, and is an important aspect in other diseases such as cancer and its metastasis process. Efficiency of the cell segregation depends on the interplay between: (1) biochemical processes such as cell signaling and gene expression and (2) physical interactions between cells. Despite extensive research devoted to study the segregation of various co-cultured systems, we still do not understand the role of physical interactions in cell segregation. Cumulative effects of these physical interactions appear in the form of physical parameters such as: (1) tissue surface tension, (2) viscoelasticity caused by CCM, and (3) solid stress accumulated in multicellular systems. These parameters primarily depend on the interplay between the state of cell-cell adhesion contacts and cell contractility. The role of these physical parameters on the segregation efficiency is discussed on model systems such as co-cultured breast cell spheroids consisting of two subpopulations that are in contact. This review study aims to: (1) summarize biological aspects related to cell segregation, mechanical properties of cell collectives, effects along the biointerface between cell subpopulations and (2) describe from a biophysical/mathematical perspective the same biological aspects summarized before. So that overall it can illustrate the complexity of the biological systems that translate into very complex biophysical/mathematical equations. Moreover, by presenting in parallel these two seemingly different parts (biology vs. equations), this review aims to emphasize the need for experiments to estimate the variety of parameters entering the resulting complex biophysical/mathematical models.

Different experimental models reveal that malignant cancer cells can be induced to change their phenotype into a benign one. This phenotypic transformation, confirmed both in vitro and in vivo, currently is known as \'tumor reversion\'. This evidence raises a radical question among current cancer models: Is cancer reversible? How do genetic and epigenetic alterations hierarchically relate? Understanding the mechanisms of \'tumor reversion\' represents a key point in order to evolve the actual cancer models and develop new heuristic models that can possibly lead to drugs that target epigenetic mechanisms, for example epigenetic drugs. Even though evidence of tumor reversion dates back to the 1950s, this remains a completely new field of research recently re‑discovered thanks to the interest in cell reprogramming research, developmental biology and the increasing understanding of epigenetic mechanisms. In the current review, a comprehensive review of all the main experimental models on tumor reversion was presented.

The gilthead seabream, one of the most important species in Mediterranean aquaculture, with an increasing status of exploitation in terms of production volume and aquafarming technologies, has become an important research topic over the years. The accumulation of knowledge from several studies conducted during recent decades on their functional and biological characteristics has significantly improved their aquacultural aspects, namely their reproductive success, survival, and growth. Despite the remarkable progress in the aquaculture industry, hatchery conditions are still far from ideal, resulting in frequent abnormalities at the beginning of intensive culture, entailing significant economic losses. Those deformities are induced during the embryonic and post-embryonic periods of life, and their development is still poorly understood. In the present review, we created a comprehensive synthesis that covers the various aspects of skeletal morphogenesis and anomalies in the gilthead seabream, highlighting the genetic, environmental, and nutritional factors contributing to bone deformities and emphasized the potential of the gilthead seabream as a model organism for understanding bone morphogenesis in both aquaculture and translational biological research. This review article addresses the existing lack in the literature regarding gilthead seabream bone deformities, as there are currently no comprehensive reviews on this subject.

The so-called extra-embryonic tissues are important for embryonic development in many animals, although they are not considered to be part of the germ band or the embryo proper. They can serve a variety of functions, such as nutrient uptake and waste removal, protection of the embryo against mechanical stress, immune response and morphogenesis. In insects, a subgroup of arthropods, extra-embryonic tissues have been studied extensively and there is increasing evidence that they might contribute more to embryonic development than previously thought. In this review, we provide an assessment of the occurrence and possible functions of extra-embryonic tissues in the closest arthropod relatives, onychophorans (velvet worms) and tardigrades (water bears). While there is no evidence for their existence in tardigrades, these tissues show a remarkable diversity across the onychophoran subgroups. A comparison of extra-embryonic tissues of onychophorans to those of arthropods suggests shared functions in embryonic nutrition and morphogenesis. Apparent contribution to the final form of the embryo in onychophorans and at least some arthropods supports the hypothesis that extra-embryonic tissues are involved in organogenesis. In order to account for this role, the commonly used definition of these tissues as \'extra-embryonic\' should be reconsidered. This article is part of the theme issue \'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom\'.

The ability to repair injuries among reptiles, i.e., ectothermic amniotes, is similar to that of mammals with some noteworthy exceptions. While large wounds in turtles and crocodilians are repaired through scarring, the reparative capacity involving the tail derives from a combined process of wound healing and somatic growth, the latter being continuous in reptiles. When the tail is injured in juvenile crocodilians, turtles and tortoises as well as the tuatara (Rhynchocephalia: Sphenodon punctatus, Gray 1842), the wound is repaired in these reptiles and some muscle and connective tissue and large amounts of cartilage are regenerated during normal growth. This process, here indicated as \"regengrow\", can take years to produce tails with similar lengths of the originals and results in only apparently regenerated replacements. These new tails contain a cartilaginous axis and very small (turtle and crocodilians) to substantial (e.g., in tuatara) muscle mass, while most of the tail is formed by an irregular dense connective tissue containing numerous fat cells and sparse nerves. Tail regengrow in the tuatara is a long process that initially resembles that of lizards (the latter being part of the sister group Squamata within the Lepidosauria) with the formation of an axial ependymal tube isolated within a cartilaginous cylinder and surrounded by an irregular fat-rich connective tissue, some muscle bundles, and neogenic scales. Cell proliferation is active in the apical regenerative blastema, but much reduced cell proliferation continues in older regenerated tails, where it occurs mostly in the axial cartilage and scale epidermis of the new tail, but less commonly in the regenerated spinal cord, muscles, and connective tissues. The higher tissue regeneration of Sphenodon and other lepidosaurians provides useful information for attempts to improve organ regeneration in endothermic amniotes.

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Melatonin (N-acetyl-5-methoxy-tryptamine) is a mammalian neurohormone, antioxidant and signaling molecule that was first discovered in plants in 1995. The first studies investigated plant melatonin from a human perspective quantifying melatonin in foods and medicinal plants and questioning whether its presence could explain the activity of some plants as medicines. Starting with these first handful of studies in the late 1990s, plant melatonin research has blossomed into a vibrant and active area of investigation and melatonin has been found to play critical roles in mediating plant responses and development at every stage of the plant life cycle from pollen and embryo development through seed germination, vegetative growth and stress response. Here we have utilized a systematic approach in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) protocols to reduce bias in our assessment of the literature and provide an overview of the current state of melatonin research in plants, covering 1995-2021. This review provides an overview of the biosynthesis and metabolism of melatonin as well as identifying key themes including: abiotic stress responses, root development, light responses, interkingdom communication, phytohormone and plant signaling. Additionally, potential biases in the literature are investigated and a birefringence in the literature between researchers from plant and medical based which has helped to shape the current state of melatonin research. Several exciting new opportunities for future areas of melatonin research are also identified including investigation of non-crop and non-medicinal species as well as characterization of melatonin signaling networks in plants.

Centaurium erythraea (centaury) is a traditionally used medicinal plant, with a spectrum of secondary metabolites with confirmed healing properties. Centaury is an emerging model in plant developmental biology due to its vigorous regenerative potential and great developmental plasticity when cultured in vitro. Hereby, we review nearly two decades of research on somatic embryogenesis (SE) in centaury. During SE, somatic cells are induced by suitable culture conditions to express their totipotency, acquire embryogenic characteristics, and eventually give rise to somatic embryos. When SE is initiated from centaury root explants, the process occurs spontaneously (on hormone-free medium), directly (without the callusing phase), and the somatic embryos are of unicellular origin. SE from leaf explants has to be induced by plant growth regulators and is indirect (preceded by callusing). Histological observations and culture conditions are compared in these two systems. The changes in antioxidative enzymes were followed during SE from the leaf explants. Special focus is given to the role of arabinogalactan proteins during SE, which were analyzed using a variety of approaches. The newest and preliminary results, including centaury transcriptome, novel potential SE markers, and novel types of arabinogalactan proteins, are discussed as perspectives of centaury research.

Cilia are cellular organelles that project from the cell. They occur in nearly all non-hematopoietic tissues and have different functions in different tissues. In mesenchymal tissues primary cilia play a crucial role in the adequate morphogenesis during embryological development. In mature articular cartilage, primary cilia fulfil chemo- and mechanosensitive functions to adapt the cellular mechanisms on extracellular changes and thus, maintain tissue homeostasis and morphometry. Ciliary abnormalities in osteoarthritic cartilage could represent pathophysiological relationships between ciliary dysfunction and tissue deformation. Nevertheless, the molecular and pathophysiological relationships of \'Primary Cilia\' (PC) in the context of osteoarthritis is not yet fully understood. The present review focuses on the current knowledge about PC and provide a short but not exhaustive overview of their role in cartilage.

In nature, gene regulatory networks are a key mediator between the information stored in the DNA of living organisms (their genotype) and the structural and behavioral expression this finds in their bodies, surviving in the world (their phenotype). They integrate environmental signals, steer development, buffer stochasticity, and allow evolution to proceed. In engineering, modeling and implementations of artificial gene regulatory networks have been an expanding field of research and development over the past few decades. This review discusses the concept of gene regulation, describes the current state of the art in gene regulatory networks, including modeling and simulation, and reviews their use in artificial evolutionary settings. We provide evidence for the benefits of this concept in natural and the engineering domains.