Robert C. King: an appreciation of his work.

THE advance of scientific knowledge is a combined early differentiation of the Drosophila egg chamber in product of both the contributions of the individual the 1960s. Through painstaking three-dimensional (3D) scientist and the acceptance and authentication of his reconstructions of serially sectioned egg chambers, they or her work over time by the larger scientific community. deciphered the pattern of cystocyte divisions and the Robert C. King is one of the most distinguished contribformation of the ring canal system (Brown and King utors to advancements in genetics, cell biology, and 1964; Koch and King 1966, 1969; Koch et al. 1967). developmental biology. In honor of Bob’s seventy-fifth During the following two decades, the formation of the birthday, it seems appropriate to highlight some of his fusome was unraveled (King 1979; King and Storto abundant accomplishments. 1988; Storto and King 1989). The determination of Among geneticists, Bob King is widely known as a the spatial relationship between the cells of the egg distinguished author and editor of genetics books, but chamber and their interconnecting organelles was an cell and developmental biologists also know him as an enormous undertaking involving multiple arduous steps: accomplished, often ground-breaking researcher. As a plastic embedded egg chambers were serially sectioned researcher, Bob is perhaps most widely recognized for and photographed at the light and electron microscope his definitive characterization of the 14 developmental levels, composites were made from overlapping microstages of Drosophila oogenesis (see King 1970), his graphs of each section, morphological information beloved experimental system. It is largely through his from serial composites was meticulously traced by hand early cytological work that we know about the origin on diffusion paper, and information from stacked tracand development of the egg chamber, the basic structural ings was then used to construct 3D plastic models of and functional unit of the Drosophila ovary. Briefly, cell clusters. the egg chamber is composed of 16 interconnected In electron microscope studies involving painstakgermline cells, the cystocytes, 15 of which differentiate ingly reconstructed germaria, the regions of germline as nurse cells and support the growth of the sixteenth cell, cyst formation, Bob and colleagues identified the develthe oocyte, through cytoplasmic transfer via intercellular opmental stages in the formation of the 16-cell cluster bridges, or ring canals (King 1970). Such oocyte-nurse (Koch and King 1966; Koch et al. 1967). They deduced cell syncytia are present in a majority of orders of higher from their observations that in the anterior region of insects. In Drosophila (and presumably in other insects the germarium reside a small number of single cells, possessing polytrophic meroistic ovaries), a cytoskeletal, the stem cells. Each of these divides asymmetrically to membranous structure known as the fusome extends form two daughter cells, one of which proliferates inthrough the ring canals during the early stages of oogendefinitely as another stem cell, while the other functions esis and is thought to regulate the division patterns and as a cystoblast, which undergoes four synchronous incomdifferentiation of the germline cells (reviewed by De plete cytokineses to produce a complex, branched patCuevas et al. 1997; McKearin 1997). Complex interactern of 16 interconnected cystocytes (Koch and King tions between these cells and the somatic follicle cells 1966; Koch et al. 1967). that surround them result in the formation of a mature In a previous ovarian reconstruction study, Bob King oocyte (reviewed by Lasko 1994). had coined the term ring canals to describe the “cytoBob and co-workers described the formation and plasmic pores” that interconnect sister cystocytes (Brown and King 1964). Subsequently, he described the formation of the ring canal system at the ultrastructural level in several insect species (Cassidy and King 1Author e-mail: [email protected]