The common fruit fly, Drosophila melanogaster, is one of the most studied organisms in biological research, with a history of use going back to the early 1900s. The first person known to have cultured Drosophila in quantity is Charles W. Woodworth, who suggested to colleagues that this organism be used for genetic work. Shortly after, Drosophila was introduced to Thomas Hunt Morgan, who made significant advances in genetics using this organism, leading him to win a Nobel Prize in Physiology or Medicine in 1933.
Drosophila is a convenient model organism in laboratories because it is easy to culture, inexpensive, available with a highly homogeneous genetic background, and has high reproductive capacity and a short lifespan. The system has traditionally been used in genetics, but more recently has become a staple in developmental biology. Furthermore, it has proven a useful model on which to study basic physiology such as circadian rhythms, learning, and memory. It even provides a genetic model for human neurodegenerative diseases including
Huntington's disease, Alzheimer's disease, and Parkinson's disease. A potential new field may be the use in nociception research (Manev and Dimitrijevic, 2005), since there are no serious ethical considerations for insects like there are for higher model organisms.
The sequencing and annotation of the entire eukary-otic component of the Drosophila genome (about 13,600 genes) was completed in March 2000. Humans have about twice as many genes as flies, but the extra genes rarely represent novel functions; they simply allow for more complex regulation of fundamental molecular pathways. This is one of the main reasons the Drosophila model has implications for biological understandings of higher organisms.
Drosophila has also been one of the major model organisms on which to study fundamental mechanisms of aging. Although aging has been studied in various model organisms, a unique feature the Drosophila model has relative to other organisms is the wealth of resources already available. Its embryonic development, physiology, and behavior have all been studied by experts in these areas, and experimental techniques including advanced genetic tools are readily accessible. Furthermore, different stocks are available from stock centers around the world, and related information is publicly available on the Internet. Thus, although there are merits to working on novel animals, working with well-characterized organisms like Drosophila can facilitate research immensely. In addition, there are some biological characteristics that may be useful in aging studies. First, the period of growth and development (egg, larva and pupa) is clearly distinguishable from adult phase, where aging manifests. The transition to adult phase is not always so discrete in some animals. Next, the adult fly consists of mostly postmitotic cells, except for a few cells in the gonads and gut. Thus, the changes that occur during aging in cells and tissues are readily measurable.
The purpose of this chapter is to introduce Drosophila as a model organism for the study of aging. It includes a description of Drosophila life history, Drosophila as an aging organism, types of studies that can be done, and a brief review of aging research on Drosophila. Basic fly culturing techniques are also outlined. From this, one might consider whether Drosophila is a suitable model for a particular question to be investigated and whether it is feasible to culture flies in a given laboratory. Although Drosophila is often associated with genetic approaches, a detailed explanation of genetic techniques is beyond the scope of this chapter. More detailed laboratory protocols and experimental procedures as well as genetic technologies available are described elsewhere. See the Recommended Resources section at the end of this chapter for many excellent review articles, books and Internet resources on Drosophila.
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