Modelling post-implantation human development to yolk sac blood emergence.

Implantation of the human embryo begins a critical developmental stage that comprises profound events including axis formation, gastrulation and the emergence of haematopoietic system1,2. Our mechanistic knowledge of this window of human life remains limited due to restricted access to in vivo samples for both technical and ethical reasons3-5. Stem cell models of human embryo have emerged to help unlock the mysteries of this stage6-16. Here we present a genetically inducible stem cell-derived embryoid model of early post-implantation human embryogenesis that captures the reciprocal codevelopment of embryonic tissue and the extra-embryonic endoderm and mesoderm niche with early haematopoiesis. This model is produced from induced pluripotent stem cells and shows unanticipated self-organizing cellular programmes similar to those that occur in embryogenesis, including the formation of amniotic cavity and bilaminar disc morphologies as well as the generation of an anterior hypoblast pole and posterior domain. The extra-embryonic layer in these embryoids lacks trophoblast and shows advanced multilineage yolk sac tissue-like morphogenesis that harbours a process similar to distinct waves of haematopoiesis, including the emergence of erythroid-, megakaryocyte-, myeloid- and lymphoid-like cells. This model presents an easy-to-use, high-throughput, reproducible and scalable platform to probe multifaceted aspects of human development and blood formation at the early post-implantation stage. It will provide a tractable human-based model for drug testing and disease modelling.

Generative models of morphogenesis in developmental biology.

Understanding the mechanism by which cells coordinate their differentiation and migration is critical to our understanding of many fundamental processes such as wound healing, disease progression, and developmental biology. Mathematical models have been an essential tool for testing and developing our understanding, such as models of cells as soft spherical particles, reaction-diffusion systems that couple cell movement to environmental factors, and multi-scale multi-physics simulations that combine bottom-up rule-based models with continuum laws. However, mathematical models can often be loosely related to data or have so many parameters that model behaviour is weakly constrained. Recent methods in machine learning introduce new means by which models can be derived and deployed. In this review, we discuss examples of mathematical models of aspects of developmental biology, such as cell migration, and how these models can be combined with these recent machine learning methods.

The term "caline" in plant developmental biology.

In the 1930s, Frits Warmolt Went conducted a number of seminal studies on pea seedlings that had been germinated in the dark and assessed their growth when either the apical parts, cotyledons, or roots were cut off or grafted, to assess whether coplant growth factors assisted auxin in the development of these organs. Went assigned the term "calines" to all auxin-assisting substances, specifically rhizocaline, caulocaline, and phyllocaline in root, shoot (and axillary buds) and leaf development, respectively. Those experiments were based exclusively on growth assays, and no supplementary biochemical or physiological analyses were ever conducted, and additional proof was only provided by Went using pea or tomato. The lack of independent reproducibility by other groups, combined with the fact that the hormonal control of these developmental events in plants is now fairly well-studied event, even at the molecular level, suggests that these growth factors that Went observed 80 years ago either do not exist or are known by some other term in modern plant development. The terms related to "calines" should thus no longer be used in plant developmental biology.

Non-model systems in mammalian forelimb evo-devo.

Mammal forelimbs are highly diverse, ranging from the elongated wing of a bat to the stout limb of the mole. The mammal forelimb has been a long-standing system for the study of early developmental patterning, proportional variation, shape change, and the reduction of elements. However, most of this work has been performed in mice, which neglects the wide variation present across mammal forelimbs. This review emphasizes the critical role of non-model systems in limb evo-devo and highlights new emerging models and their potential. We discuss the role of gene networks in limb evolution, and touch on functional analyses that lay the groundwork for further developmental studies. Mammal limb evo-devo is a rich field, and here we aim to synthesize the findings of key recent works and the questions to which they lead.

Evolution of organoid technology: Lessons learnt in Co-Culture systems from developmental biology.

In recent years, the development of 3D organoids has opened new avenues of investigation into development, physiology, and regenerative medicine. Organoid formation and the process of organogenesis share common developmental pathways; thus, our knowledge of developmental biology can help model the complexity of different organs to refine organoids into a more sophisticated platform. The developmental process is strongly dependent on complex networks and communication of cell-cell and cell-matrix interactions among different cell populations and their microenvironment, during embryogenesis. These interactions affect cell behaviors such as proliferation, survival, migration, and differentiation. Co-culture systems within the organoid technology were recently developed and provided the highly physiologically relevant systems. Supportive cells including various types of endothelial and stromal cells provide the proper microenvironment, facilitate organoid assembly, and improve vascularization and maturation of organoids. This review discusses the role of the co-culture systems in organoid generation, with a focus on how knowledge of developmental biology has directed and continues to shape the development of more evolved 3D co-culture system-derived organoids.

From Aedes to Zeugodacus: a review of dipteran body coloration studies regarding evolutionary developmental biology, pest control, and species discovery.

Over the past two decades, evo-devo (evolution of development) studies have elucidated genetic mechanisms underlying novel dipteran body color patterns. Here we review the most recent developments, which show some departure from the model organism Drosophila melanogaster, leading the field into the investigation of more complex color patterns. We also discuss how the robust application of transgenic techniques has facilitated the study of many non-model pest species. Furthermore, we see that subtle pigmentation differences guide the discovery and description of new dipterans. Therefore, we argue that the existence of new field guides and the prevalence of pigmentation studies in non-model flies will enable scientists to adopt uninvestigated species into the lab, allowing them to study novel morphologies.

Virtual meeting, real and sound science: report of the 17th Meeting of the Spanish Society for Developmental Biology (SEBD-2020).

The Spanish Society for Developmental Biology (SEBD) organized its 17th meeting in November 2020 (herein referred to as SEBD2020). This meeting, originally programmed to take place in the city of Bilbao, was forced onto an online format due to the SARS-CoV2, COVID-19 pandemic. Although, we missed the live personal interactions and missed out on the Bilbao social scene, we were able to meet online to present our work and discuss our latest results. An overview of the activities that took place around the meeting, the different scientific sessions and the speakers involved are presented here. The pros and cons of virtual meetings are discussed.

Changes in Cardiomyocyte Cell Cycle and Hypertrophic Growth During Fetal to Adult in Mammals.

The failure of adult cardiomyocytes to reproduce themselves to repair an injury results in the development of severe cardiac disability leading to death in many cases. The quest for an understanding of the inability of cardiac myocytes to repair an injury has been ongoing for decades with the identification of various factors which have a temporary effect on cell-cycle activity. Fetal cardiac myocytes are continuously replicating until the time that the developing fetus reaches a stage of maturity sufficient for postnatal life around the time of birth. Recent reports of the ability for early neonatal mice and pigs to completely repair after the severe injury has stimulated further study of the regulators of the cardiomyocyte cell cycle to promote replication for the remuscularization of injured heart. In all mammals just before or after birth, single-nucleated hyperplastically growing cardiomyocytes, 1X2N, undergo ≥1 additional DNA replications not followed by cytokinesis, resulting in cells with ≥2 nuclei or as in primates, multiple DNA replications (polyploidy) of 1 nucleus, 2X2(+)N or 1X4(+)N. All further growth of the heart is attributable to hypertrophy of cardiomyocytes. Animal studies ranging from zebrafish with 100% 1X2N cells in the adult to some strains of mice with up to 98% 2X2N cells in the adult and other species with variable ratios of 1X2N and 2X2N cells are reviewed relative to the time of conversion. Various structural, physiologic, metabolic, genetic, hormonal, oxygenation, and other factors that play a key role in the inability of post-neonatal and adult myocytes to undergo additional cytokinesis are also reviewed.

Early and late stages of Developmental Biology in Argentina.

The history of science in Argentina is based on the enormous contribution that the great immigration of the 19th and 20th centuries produced in the country. The scientific and philosophical ideas and the role played especially by Italian scientists who arrived in the country produced a great impact on the different disciplines including Development Biology in emerging universities. The University of Tucumán pioneered the study of experimental biology, making important contributions to reproductive biology and to the early development of amphibians. The contribution of the Italian embryologist Armando Pisanó and the Argentinian Francisco D. Barbieri expanded the field to other universities and research centers located in Córdoba, La Plata, Bahía Blanca and Rosario. Given its strategic position, laboratories located in the city of Buenos Aires reached technological advances faster than others. Indeed, these laboratories saw the evolution from experimental biology to developmental genetics, renewing interest in this area. Currently, Developmental Biology brings together young researchers eager to consolidate regional and global collaboration networks that seek to help solve specific problems such as fertility, epigenetics, stem cells and tissue engineering.

UNESCO Chair of Developmental Biology: how an initiative that fostered careers in Developmental Biology impacted Brazilian Science.

The UNESCO Chair in Developmental Biology started in 1998, at the Institute of Biomedical Sciences of the Federal University of Rio de Janeiro, in Brazil. This Chair was a Brazilian-French initiative led by Professor Vivaldo Moura Neto and Professor Nicole Le Douarin, one of the most inspiring Developmental Biologists of the 20th and 21st centuries. The UNESCO Chair wanted to stimulate interest in Developmental Biology among Brazilian students and scientists by organizing annual international courses on Evolution and Developmental Biology at an advanced level. At the Federal University of Rio de Janeiro, the UNESCO Chair established an international laboratory for the permanent training of researchers and the development of research programs in Developmental Biology and related areas. Moreover, the program aimed at establishing an international network connecting Brazilian Universities and research centers in Latin America and Europe. The advanced hands-on courses, symposiums, and workshops promoted by this Chair inspired the careers of many young scientists. They generated new lines of research in Developmental Biology using a variety of animal models. This review does not intend to bring up all the historical events that marked the beginning of Developmental Biology in Brazil. Instead, it will be dedicated to highlighting one specific initiative that inspired a new generation of Developmental Biologists who established important research lines and contributed to the advance of this scientific field in Brazil.

Developmental Biology in México.

Contemporary scientific endeavor in México emanates from two great public institutions: the Universidad Nacional Autónoma de México (UNAM) and the Instituto Politécnico Nacional (IPN), founded in 1929 and 1936, respectively. Here, the first research institutes and centers dedicated to various scientific areas were created. Thus, the origin of most laboratories of Developmental Biology in México was like that of other scientific fields. In this article, I have attempted to describe the establishment of a specialized community involved in the understanding of organism development during ontogeny. The use of chick embryos to study heart development was among the first experimental approaches developed in México. Then, a younger group employed chick embryos to study the mechanisms underlying limb development. Various laboratory animal models have been employed, including mouse, rat, rabbit, and recently the naked mole-rat, as well as some wild species, such as sea turtles and bats. Two classical invertebrates, Drosophila melanogaster, and Caenorhadbitis elegans, also form part of the multilayered complex models used by Mexican developmental biologists. My use of animals brought me closer to the pioneer developmental biologists who worked with animal models. Their academic trajectory was more detailed than that of investigators using plant models. However, the pioneering merit and bright contributions of the two groups are on a par, regardless of the biological model. As current scientific knowledge is the sum of individual contributions throughout human history, here I have attempted to describe my suitable experience as a witness to the birth of the fascinating field of developmental biology in my country.

Building the embryo of Developmental Biology in Uruguay.

In Uruguay, a country with a small population, and hence a small scientific community, there were no classical embryologists as such in the past. However, in the decade of the 1950s, a cumulus of favorable conditions gave rise to highly active and modern research groups in the fields of cytology and physiology, which eventually contributed to developmental biology. The advent of a long dictatorship between the 1970's and 1980's caused two things: a strong lag in local research and the migration of young investigators who learned abroad new disciplines and technologies. The coming back to democracy allowed for the return of some, now as solid researchers, and together with those who stayed, built a previously inexistent postgraduate training program and a globally-integrated academy that fostered diversity of research disciplines, including developmental biology. In this paper, we highlight the key contributions of pioneer researchers and the significant role played by academic and funding national institutions in the growth and consolidation of developmental biology in our country.

Developmental Biology in Chile: historical perspectives and future challenges.

Developmental Biology is a growing discipline in Chile. It started in the 1950s when Luis Izquierdo challenged the traditional descriptive perspective of embryology and comparative anatomy to explore the mechanisms underlying the origin of form. After this initial drive, Claudio Barros, beginning in the late 1960s and Juan Fernández, in the late 1970s, contributed with unique and complementary facets to the early growth of the discipline. In the 1980s, the community of developmental biologists created its first forms of association together with the reproduction biology community, and in 1993 the first international course of developmental biology was organised. During the 1990s and 2000s, a group of young investigators arrived in Chile after postdocs in Europe and the US to build the first research centres of developmental biology, fostering the discipline to an unprecedented level. In the 2010s, as these centres consolidated, a stream of young developmental biologists established new labs at several institutions, expanding the community size and broadening its scope. The recent organisation of developmental biology meetings fostered the sense of community and nurtured the need of formal organisation, setting the bases for the foundation of the Chilean Society for Developmental Biology. Today, the community of developmental biologists is a mix of young and experienced investigators working in a variety of geographical locations, institutions, topics and model organisms. These characteristics are a strength of an active community that is pushing the discipline to the next level, aiming to make it a relevant actor in national and international settings.

Developmental Biology in Central America, the northern region of South America and the Caribbean.

This review highlights the history of Developmental Biology studies in Latin-American countries of Central America, the northern region of South America and the Caribbean and their impact on the field. For this, we have compiled the contributions made by investigators in various institutions of the region, including universities, as well as agricultural, research and health centers. Most of the contributions focus on particular fields, among them, Evo-Devo, regenerative biology, nervous system development and health related issues. A large share of the contributions originates from a subset of countries, primarily, Colombia, Costa Rica, Ecuador, Panama and Puerto Rico. In addition, we underscore the new investigators and the ongoing research in the region.