Copyright Ó 2006 by the Genetics Society of America The 2006 GSA Honors and Awards The Genetics Society of America annually honors members who have made outstanding contributions to genetics. The Thomas Hunt Morgan Medal recognizes a lifetime contribution to the science of genetics. The Genetics Society of America Medal recognizes particularly outstanding contributions to the science of genetics within the past 15 years. The George W. Beadle Medal recognizes distinguished service to the field of genetics and the community of geneticists. We are pleased to announce the 2006 awards. The 2006 Thomas Hunt Morgan Medal Masatoshi Nei Masatoshi Nei ASATOSHI Nei has been a major contributor to elegant statistic involving allele frequencies from two M population and evolutionary genetics theory populations that, under the infinite alleles mutation throughout his career. He is one of a select group to model, had an expected value proportional to the time have a statistic named for him: ‘‘Nei’s genetic distance’’ since those populations had diverged from an ancestral is a cornerstone of population genetic analyses. His body population. The measure therefore provided a natural of work includes two influential textbooks and a remark- basis for reconstructing phylogenies and it was quickly able 55 (of nearly 300) articles with over 100 citations adopted for distance-based methods for building evo- each, 9 of which have over 1100 citations and 1 of which lutionary trees. Nei provided further discussion of the has over 12,000. sampling properties of his distance statistic in Genetics When Nei received the International Prize for Biology in 1978. His most widely cited work is his 1987 article in 2002, the Japan Society for the Promotion of Science with Saitou in Molecular Biology and Evolution, said: ‘‘Through these achievements, Dr. Nei has not only which introduced the ‘‘neighbor-joining method’’ for made the latest findings at the molecular level available phylogeny reconstruction. This method starts with a to evolutionary biologists, but has contributed greatly star-like tree and produces a unique tree by minimizing to the birth of molecular evolutionary biology and its the sum of branch lengths at each stage of a recursive establishment as a positive science in which hypotheses clustering of the taxonomic units. can be verified quantitatively, rather than being dis- Nei’s early work came at the height of the selection vs. cussed solely on a conceptual level.’’ neutrality debate that followed the discovery, by starch- Nei’s work on genetic distances began with an gel electrophoresis, of large amounts of genetic varia- American Naturalist article in 1972. He presented an tion for protein variants. Nei and his students devised Genetics 172: 719–725 (February 2006) 720 Honors and Awards and applied several tests of the neutral hypothesis and moving to the United States. He had postdoctoral so contributed to an acceptance of this theory in many training at the University of California at Davis and at situations. His 1975 book Molecular Population Genetics North Carolina State University and was on the faculty laid out much of the theory known at that time and was briefly at Brown University. For 18 years, from 1972 to followed by the masterly Molecular Evolutionary Genetics 1990, he was at the heart of a very productive group at in 1987 and three other jointly written books. the Center for Demographic and Population Genetics Although Nei has produced a great body of work in of the University of Texas at Houston. In 1990 Nei statistical genetics, he was trained as a biologist and has moved to Penn State University to become Director of been able to translate his data analyses into increasing the Institute of Molecular Evolutionary Genetics and our understanding of the mechanisms of evolution. He later also became the Evan Pugh Professor of Biology. posited an African origin of modern humans in a 1974 Nei has been honored by election to the National article in the American Journal of Human Genetics and Academy of Sciences of the United States of America has provided details on the geographic pathways of and by fellowship in the American Academy of Arts and human expansion in several subsequent articles. He has Sciences and the American Association for the Advance- had a particular interest in the generation and mainte- ment of Science. Among his many other honors, he nance of variation in the vertebrate immune system. His received the 2002 International Prize for Biology, pre- 1988 Nature article on patterns of nucleotide diversity at sented in the presence of the Emperor and Empress of MHC class I loci suggested the action of overdominant Japan. In his remarks at the ceremony, the Emperor said selection. Nei’s work on MHC multigene families led that he himself had used neighbor-joining to construct a him to formulate a ‘‘birth-and-death evolution’’ model phylogenetic tree for the gobioid fishes that he studies. for the fate of members of a multigene family after gene In what must be at least as satisfying a recognition from duplication. His thinking over the past 40 years has led his peers, the Society for Molecular Biology and Evolu- him to a view of evolution that he terms ‘‘neomuta- tion, of which Nei is the cofounder, has established the tionism,’’ whereby the driving force of evolution is Masatoshi Nei Annual Lecture. mutation, with natural selection being secondary. This Masatoshi Nei is a long-time member of the Genetics view is argued very clearly in a 2005 review article in Society of America and a frequent publisher in Genetics. Molecular Biology and Evolution that is likely to become He has served on the Editorial Board of this journal. a major reference for future workers. The Society is pleased to present him with the 2006 Masatoshi Nei has played many leading roles in Thomas Hunt Morgan Medal, and I know that Masa- population and evolutionary genetics. He has trained toshi is proud to receive the award: in Chapter 14 of .40 graduate and postdoctoral students, who them- his Molecular Population Genetics he quotes a passage selves read like a Who’s Who in the field. In addition to from Morgan’s The Scientific Basis of Evolution, which his publications, he and his group have written and shows both Morgan’s deep understanding of evolution distributed software packages, including MEGA and and the consistency of Nei’s own work with that of MEP. Morgan’s. Nei received his formal training at Miyazaki and Kyoto universities in Japan and held positions in Japan before Bruce Weir Honors and Awards 721 The 2006 Genetics Society of America Medal Victor Ambros Victor Ambros In 1990, Victor Ambros faced a conundrum. The search lular organism, but also hinted at how mutations in key for the heterochronic gene lin-4 had led him to a 700-bp genes might underlie heterochronic variation between DNA fragment. This fragment could rescue a lin-4 mutant species (Ambros and Horvitz 1984). but contained no apparent open reading frame (ORF). The few small ORFs that could be detected were either In 1985, Victor joined the faculty in the Department not conserved in other nematodes or not essential for of Cellular and Developmental Biology at Harvard rescue. Two years and several RNAse protection experi- University. Taking advantage of the opposite pheno- ments later, Victor Ambros was forced to conclude that types of retarded and precocious mutants, Victor set out the lin-4 gene product was not a protein at all, but a very to dissect the epistatic relationships among lin-4, lin-14, small 20-base RNA—the first microRNA! Geraldine Seydoux lin-28, and lin-29. With keen insight, he focused his analysis on a single, easy-to-score, stage-specific event: HE 2006 GSA Medal is awarded to Victor Ambros the larval-to-adult switch (L/A switch). At the transition T in recognition of his seminal discovery of micro- between the last larval stage and adulthood, certain cells RNAs and his many contributions to the field since. in the skin of the worm cease division, fuse with one Victor did his graduate work at MIT with David another, and produce a characteristic ridged structure Baltimore, where he studied mechanisms of poliovirus in the cuticle (alae). Victor constructed double, triple, replication. In 1979, Victor joined the lab of Bob and quadruple mutants and scored the L/A switch in Horvitz, who had recently returned to MIT after 5 years each combination. The results were published in a at the MRC where he had helped launch Sydney single-author article (Ambros 1989), now renowned as Brenner’s new model system, Caenorhabditis elegans. a classic ‘‘epistasis’’ study, a favorite among teachers of Among the many mutants that Bob Horvitz brought genetics! This publication laid out the core hierarchy of back from the MRC was lin-4(e912). lin-4 mutants have the C. elegans heterochronic pathway: lin-4 negatively complex lineage defects with many cells repeating regulates lin-14 and lin-28, lin-14 and lin-28 inhibit lin- division patterns characteristic of early larval stages. 29, and lin-29 activates the L/A switch (Ambros 1989). lin-4 mutants cannot lay eggs, so Victor decided to With the genetics sorted out, it was time to determine screen other egg-laying defective mutants for similar the molecular identities of the heterochronic genes. ‘‘heterochronic’’ defects. The screen yielded mutations Cloning in the pregenomic era was not an easy task and in three new loci: lin-14, lin-28, and lin-29. Remarkably, the article reporting the cloning of lin-14 (a collabora- while some mutations caused ‘‘retarded’’ phenotypes tion among Gary Ruvkun, Victor Ambros, Bob Horvitz, similar to lin-4, others caused ‘‘precocious’’ phenotypes, and the future leaders of the C.