We note with sadness the passing of Dr. Larry R. Rohrschneider of the Fred Hutchinson Cancer Research Center’s Basic Sciences Division, who died Sunday, Oct. 28, of a stroke. He was 68.
Larry obtained his bachelor’s degree in chemistry from the University of Minnesota and doctorate in oncology from the McArdle Laboratory of the University of Wisconsin-Madison in 1972, where he worked with Dr. R.K. Boutwell studying the effects of phorbol esters, the tumor- promoting chemicals in croton oil, using a mouse skin model. For his postdoctoral work, he studied with Dr. Heinz Bauer, first at the Robert Koch Institut in Berlin and then at the Institut for Virologie in Giessen, Germany. The Koch laboratory used antibodies from model organisms bearing oncorna-virus cancers as tools to identify transformation antigens. Rohrschneider focused initially on cell-surface proteins in cells infected with avian oncorna viruses, identifying the envelope and group-specific antigens (gag proteins). The isolation of temperature-sensitive transformation-defective mutants of Rous sarcoma virus led to the hypothesis that the viral protein or proteins should be temperature-sensitive in its expression or function, and Dr. John Wyke and Rohrschneider found that expression of some of the cell-surface tumor antigens correlated with transformation, suggesting that they were under control of the transforming gene.
In 1976, he joined the tumor virology laboratory at the newly opened Fred Hutchinson Cancer Research Center on Columbia Street near Swedish Hospital. The transforming protein of Rous sarcoma virus, Src, had just been identified by Dr. Ray Erikson's group using antibodies from tumor-bearing model organisms. Rohrschneider generated similar antisera and used them to good effect, performing some of the first immunoprecipitation and immunofluorescence experiments to identify the Src protein in Rous sarcoma virus-infected model organisms and to localize the protein to the cytoplasm. Those first immunoprecipitation experiments also revealed a related protein in uninfected cells, one of the first sightings of the Src proto-oncogene product. Using improved immunofluorescence microscopy, Rohrschneider soon realized that most of the Src oncoprotein is actually concentrated in small regions of the cell membrane where the internal cytoskeleton sticks to the external matrix that makes up the glue of connective tissue. This first identification of an oncoprotein interacting with adhesion sites had a major impact on the field, since it provided an explanation for how Src and other oncoproteins could have such dramatic effects on cell morphology. Indeed, in less than a year, proteins interacting with Src in adhesion plaques were found to contain phosphotyrosine, a signature of Src activity.
Rohrschneider's strengths in raising antibodies and skillful immunofluorescence soon led him to investigate the subcellular localizations of the oncoproteins of other oncorna viruses, by then known by the current name of retroviruses. He found that adhesion plaques also contained the oncoproteins of Abelson leukemia virus (Abl, now best known at the cause of chronic myelogenous leukemia) and the Susan McDonough and Gardner-Rasheed strains of feline sarcoma virus (Fms and Fgr), while, with colleague Dr. Bob Eisenman, the Myc oncoprotein was found in the nucleus. He also went proto-oncogene hunting, cloning out the normal cell version of the Fms oncogene and identifying the mutations that make it oncogenic. Around this time, Dr. Chuck Sherr at St. Jude's and Dr. Richard Stanley at Albert Einstein identified the normal cellular Fms protein as the cell surface receptor for a growth factor known as the macrophage colony-stimulating factor or M-CSF. This was one of the initial discoveries that mutations in a cell surface receptor could initiate oncogenesis, just one year after the avian erythroblastosis virus oncogene was found to be a mutant EGF receptor.
Rohrschneider became fascinated by the challenge of working on the normal function of the M-CSF receptor and understanding how it regulates macrophage function. He and wife, Jean, and young children, Reuben and Monica, spent an enjoyable sabbatical year in Melbourne, Australia, working with Dr. Don Metcalf at the Walter and Eliza Hall Institute, the world center for research into hematopoietic regulatory factors. The family formed strong ties with the family of Dr. Ashley Dunn, the person who cloned the first colony stimulation factor. Rohrschneider returned to the Hutchinson Center and recrafted his laboratory to study M-CSF functions, and particularly the signal transduction pathways used by the M-CSF receptor to regulate the proliferation and differentiation of myeloid cells. One key molecule he identified is now known as SHIP, the SH2 domain containing inositol phosphatase. Rohrschneider showed that SHIP is recruited to active M-CSF receptors and turns down phospholipid signaling. SHIP is multifunctional, forming signaling complexes with protein phosphatases and other signaling proteins, as well as hydrolyzing selected phosphoinositides. It is also subject to alternative splicing and alternative transcription start sites, and different forms are expressed in different tissues.
His discovery that a specific form of SHIP is expressed in hematopoietic stem cells led Rohrschneider into his last shift in research focus, again helped by a sabbatical, this time working side-by-side with his former fellow, Dr. Roland Bourette in Lyon, France. Rohrschneider realized that an alternative promoter in the SHIP gene is utilized in only a small subset of cell types, including stem cells. He worked at the bench to generate transgenic mice that would express a fluorescent protein from the SHIP alternative promoter, and used these to graphic and dramatic effect to confirm expression in stem cells and some intermediate progenitors in various tissue types, including mammary gland and skin.
For the past decade Rohrschneider and postdoctoral fellow Dr. Lixia Bai have been using these transgenic mice to explore the relationship between stem cells, intermediate progenitors and mature cell types in normal and malignant mouse mammary gland. The overriding hypothesis is that expression of the SHIP alternative promoter will allow the prospective identification of cells with stem cell properties, which can be tested by sorting of the fluorescent cells and transplantation into other mice. This work is a technical tour de force, with a need for numerous replicate sorting and transplantation experiments from mice at puberty and in pregnancy, and detailed characterization of the reconstituted mammary glands. The group succeeded in demonstrating an extraordinary degree of purification of mammary stem cells from normal mice and has since been working with mammary cancer stem cells from mice with various genetically defined tumors.
Larry was married to Jean Rohrschneider, another virologist who also worked with Bauer in Giessen, for 41 years. Son Reuben studied engineering at Georgia Tech and is currently employed by Ball Aerospace in Colorado. Daughter Monica studied developmental biology at the University of Chicago, in Dr. Victoria Prince's lab, using zebrafish, an organism she first worked with as an intern at Fred Hutch. She is currently a postdoctoral fellow with Hutch alumnus Dr. Jeremy Nance at New York University, researching zebrafish, an organism she first worked with as an intern at the Hutchinson Center.
Larry's research continually met and exceeded the highest standards. He worked at the bench throughout his life, running gels, sitting at the tissue culture hood, poring over the microscope and working with model organisms. Always interested in the science, wherever it might lead, he followed some unlikely paths, such as trying to develop an AIDS drug from the seeds of the Catinospermum tree. He was enormously productive, with more than 90 publications, nearly all of them primary research papers from his own small lab. He made an impact on his colleagues with his wry sense of humor and particularly visual puns. An elegant cardboard palm tree, whimsical doodles, experiments in solarization and a copy of “Jabberwocky” graced his office. One year, when his turn to present his research to other faculty coincided with the first day of the fourth month, he started out with a multislide exposition on the mysterious growth of dark spots on mouse pads. Science has lost an original thinker and creative researcher.