Evolutionary Developmental Biology: the Interaction of Developmental Biology,Evolutionary Biology,Paleontology, and Genomics

Paleontological Journal - Evolutionary developmental biology (evo-devo) formed due to the interactions of evolutionary biology, paleontology, and comparative genomics, analyzes the interrelations...     

Ecological Developmental Biology: Developmental Biology Meets the Real World1

The production of phenotype is regulated by differential gene expression. However, the regulators of gene expression need not all reside within the embryo. Environmental factors, such as temperature, photoperiod, diet, population density, or the presence of predators, can produce specific phenotypes, presumably by altering gene-expression patterns. The field of ecological developmental biology seeks to look at development in the real world of predators, competitors, and changing seasons. Ecological concerns had played a major role in the formation of experimental embryology, and they are returning as the need for knowledge about the effects of environmental change on embryos and larvae becomes crucial. This essay reviews some of the areas of ecological developmental biology, concentrating on new studies of Amphibia and Homo.     

Evolutionary Developmental Biology (Evo-Devo): Past, Present, and Future

Evolutionary developmental biology (evo–devo) is that part of biology concerned with how changes in embryonic development during single generations relate to the evolutionary changes that occur between generations. Charles Darwin argued for the importance of development (embryology) in understanding evolution. After the discovery in 1900 of Mendel’s research on genetics, however, any relationship between development and evolution was either regarded as unimportant for understanding the process(es) of evolution or as a black box into which it was hard to see. Research over the past two decades has opened that black box, revealing how studies in evo–devo highlight the mechanisms that link genes (the genotype) with structures (the phenotype). This is vitally important because genes do not make structures. Developmental processes make structures using road maps provided by genes, but using many other signals as well—physical forces such as mechanical stimulation, temperature of the environment, and interaction with chemical products produced by other species—often species in entirely different kingdoms as in interactions between bacteria and squid or between leaves and larvae (Greene Science 243:643–666, 1989). Not only do genes not make structures (the phenotype), but new properties and mechanisms emerge during embryonic development: genes are regulated differentially in different cells and places; aggregations of similar cells provide the cellular resources (modules) from which tissues and organs arise; modules and populations of differently differentiated cells interact to set development along particular tracks; and organisms interact with their environment and create their niche in that environment. Such interactions are often termed “epigenetic,” meaning that they direct gene activity using mechanisms that are not encoded in the DNA of the genes. This paper reviews the origins of evo–devo, how the field has changed over the past 30 years, evaluates the recognition of the importance for development and evolution of mechanisms that are not encoded in DNA, and evaluates what the future might bring for evo–devo. Although impossible to know, history tells us that we might expect more of the same; expansion of evo–devo into other areas of biology (ecology, physiology, behavior); absorption of evo–devo by evolution or a unification of biology in which evo–devo plays a major role.     

Ecological Developmental Biology: Interpreting Developmental Signs

Developmental biology is a theory of interpretation. Developmental signals are interpreted differently depending on the previous history of the responding cell. Thus, there is a context for the reception of a signal. While this conclusion is obvious during metamorphosis, when a single hormone instructs some cells to proliferate, some cells to differentiate, and other cells to die, it is commonplace during normal development. Paracrine factors such as BMP4 can induce apoptosis, proliferation, or differentiation depending upon the history of the responding cells. In addition, organisms have evolved to alter their development in response to differences in temperature, diet, the presence of predators, or the presence of competitors. This allows them to develop the phenotype, within the limits imposed by the genotype, best suited for the immediate habitat of the organism. Most developing organisms have also evolved to expect developmental signals from symbionts, and these organisms develop abnormally if the symbiont signals are not present. Thus Hoffmeyer’s “vertical semiotic system” of genetic communication and “horizontal semiotic system” of ecological communication are integrated during development.     

Deconstructing Pancreas Developmental Biology

The relentless nature and increasing prevalence of human pancreatic diseases, in particular, diabetes mellitus and adenocarcinoma, has motivated further understanding of pancreas organogenesis. The pancreas is a multifunctional organ whose epithelial cells govern a diversity of physiologically vital endocrine and exocrine functions. The mechanisms governing the birth, differentiation, morphogenesis, growth, maturation, and maintenance of the endocrine and exocrine components in the pancreas have been discovered recently with increasing tempo. This includes recent studies unveiling mechanisms permitting unexpected flexibility in the developmental potential of immature and mature pancreatic cell subsets, including the ability to interconvert fates. In this article, we describe how classical cell biology, genetic analysis, lineage tracing, and embryological investigations are being complemented by powerful modern methods including epigenetic analysis, time-lapse imaging, and flow cytometry-based cell purification to dissect fundamental processes of pancreas development.     

Diachronic Biology Meets Evo-Devo: C. H. Waddington's Approach to Evolutionary Developmental Biology

Conrad Hal Waddington (1905–1975) did not respect thetraditional boundaries established between genetics, embryology,and evolutionary biology. Rather, he viewed them together asa "diachronic biology." In this diachronic biology, evolutionarychange was caused by heritable alterations in development. Stabilizingselection within the embryo was followed by normative selectionon the adult. To explain evolution, Waddington had to inventmany concepts and terms, some of which have retained their usageand some of which have not. In this paper I seek to explicateWaddington's ideas and evaluate their usefulness for contemporaryevolutionary developmental biology.     

Developmental Biology and Human Concerns

There is a large natural loss of human embryos in early gestation.Most conceptual losses occur before pregnancy has been diagnosedin the woman. It is now acknowledged that chromosomal aberrationsare the major etiologic agents responsible for spontaneous abortions.Fully 50 percent of naturally aborted embryos in the first trimesterhave an abnormal karyotype. Most of the chromosomal errors thathave been identified in abortuses are only rarely seen in livebirths.Natural in utero selection is relentless in eliminating 99 percentof the chromosomally abnormal conceptuses through spontaneousabortion. The birth of affected offspring that escape nature'sscreening mechanism can be averted by the option of prenataldiagnosis. The thrust of prenatal diagnosis is to prevent thetragic impact of debilitating genetic disorders. But notallat-risk parents wish to avail themselves of prenatal diagnosisbecause they are unwilling to accept the choice of therapeuticabortion. Prevention of a genetic disorder before implantationwould obviate the necessity of an abortion at a later stageof pregnancy. With this perspective, the correction of the basicgenetic flaw by replacing the faulty gene with a functioningallele is an attractive alternative. Notwithstanding the imprecisetechnology that presently serves to caution against immediateapplication, gene therapy is a reasonable and natural extensionof efforts to ameliorate the effects of severe inherited disorders.     

History of Evolutionary Developmental Biology

Russian Journal of Developmental Biology - Foundations of evolutionary developmental biology (evo-devo) were laid by K. von Baer, the author of the law of embryonic similarity in various animal...