A century of cell adhesion: from the blastomere to the clinic part 1: conceptual and experimental foundations and the pre-molecular era

From Entomological Research to Culturing Tissues: Aron Moscona's Investigative Pathway

Aron Arthur Moscona (1921-2009) was an Israeli-American developmental biologist whose name is associated with research on cell interactions during embryonic development. His appearance on the international scene dates back to a paper published in 1952, while he was working, together with his wife Haya Sobel Moscona, at the Strangeways Research Laboratory of Cambridge. Together they demonstrated that cells from previously dissociated chick tissues undergo histiotypical and organotypical aggregation in vitro. From 1952 to 1997, Moscona focused his research on cell recognition mechanisms, ultimately demonstrating the role of transmembrane proteins in cellular adhesiveness, tissue segregation, and organ tridimensional assemblage during development. However, who was Aron Moscona before 1952 and what brought him to developmental biology? A Polish Jew who immigrated to Mandatory Palestine in 1933, Moscona belonged to the first generation of biologists formed in the newly established Zoology Department of the Hebrew University. With a particular focus on the Israeli context, the paper reconstructs the evolution of Moscona's scientific thought by emphasizing the cultural and experimental context of his training and early research at the Hebrew University. The aim is to investigate how local scientific traditions influenced Moscona's eventual research as well as enabled the relevant experimental innovation he contributed to the field of developmental biology and pathology. The paper can be read both as a scientific biography of Aron Moscona and as a preliminary contribution to the historiography of embryology in the Mandatory Palestine/Israeli context.

E. E. Just and Creativity in Science. The Importance of Diversity

Renowned biologist Ernest Everett Just (1883-1941) was an outspoken advocate for the classical embryologist's view of the cell; he believed that all the parts of the cell, but especially the cytoplasm, have important roles to play in the process of development, whereby a one-celled zygote becomes a many-celled animal. In opposition to geneticist Thomas Hunt Morgan, Just formulated a hypothesis for how the cell works in development, one that gave a more dominant role to cytoplasmic (instead of nuclear) factors. This paper argues that, in creating his hypothesis, Just applied insights from the African American intellectual community in which he was immersed, much as Charles Darwin applied insights from British political economist Thomas R. Malthus in formulating his theory of evolution by natural selection. This in no way diminishes the scientific validity of Just's (or Darwin's) hypothesis. Rather, it highlights Just's creativity and, as such, points to the importance of having diversity in science.

Ernest Everett Just: Egg and embryo as excitable systems

Ernest Everett Just (1883-1941) was an African American embryologist of international standing whose research interests lay in the area of fertilization and early development in marine invertebrates. Perhaps best known for his discovery of the dynamical and structural blocks to polyspermy that sweep over the egg upon fertilization, E. E. Just also was the first to associate cell surface changes with stages of embryonic development. He was deeply familiar with the natural history of the animals whose eggs he studied, and his knowledge of natural settings led him to emphasize the importance of using laboratory conditions that closely match those in nature. Based on more than 30 years of work, he came to believe that it was the cell surface that played the most critical role in development, heredity, and evolution. He promoted a holistic view of cells and organisms in opposition to the gene-centric view that was becoming more prevalent with the rise of genetics, but rejected the vitalism espoused by some biologists of his era, calling instead for "a physics and chemistry in a new dimension …superimposed upon the now known physics and chemistry" to account for biological phenomena. Just's incisive critique of genetic reductionism finds echoes in contemporary multiscale, systems approaches in biology. His speculations on the relationship between developmental and evolutionary mechanisms resonate with today's evolutionary developmental biology. After a brief biographical sketch, this paper outlines and discusses some of Just's scientific contributions, and shows how his ideas remain relevant today.