Abstract

• We study the genetics of aging using the fruitfly Drosophila as a model

• Since aging is a complex trait, influenced both by genetics and the environment, the genetic background of all our fly strains must be rendered genetically uniform

• We have subjected specific genetic fly strains to twelve generations of back crossing to an established isogenic control strain (homozygous at every point in the genome)

• We have tested the functionality of our newly isogenized fly lines by using fluorescence microscopy.

Manipulating gene expression with the UAS-GAL4 system in Drosophila

• “driver” flies contain engineered genes (transgenes) that express the yeast GAL4 transcription factor in tissue-specific patterns

• “responder” flies express target genes that are sensitive to the yeast GAL4 transcription factor

• When driver and responder flies are crossed together, the progeny flies express target genes in tissue specific patterns

Gal4 GFP

Tissue specific promoter

GAL4 sensitive promoter

XDriver strain parent Responder parent

Gal4

Tissue specific promoter

GFP

GAL4 sensitive promoter

Using the UAS-GAL4 system to study aging in Drosophila

• Research in yeast, worms and mice have revealed specific genetic pathways that can regulate life span

• Certain genes play pivotal roles in these pathways, and in very particular tissues

• Two tissues in which regulated gene expression can lead to life span extension in many different animal models include fat tissue and the nervous system

• We plan to use fat body and nervous system, drivers in Drosophila to manipulate genes involved in aging specifically in these tissues.

Backcrossing scheme

• In each generation, a female heterozygous for the driver genetic background and the control isogenic background makes gametes of which ~50% have undergone recombination

• Both the driver line and the isogenic control line are mutant for the eye color gene (no red eye pigment from the native gene), but the driver transgenes also carry a red eye color reporter, which is dominant (visible when present only in one copy, as in a heterozygote)

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Gametes

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Genetic background function I

• After n generations, the non uniform background constitutes (1/2)n of the new, isogenic background

• Has recombination disrupted the driver transgene?

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Genetic background function II

• Argument based on close linkage

pic of chromos with color coding to show concern about disrupting driver transgene

Test for driver functionality

• Cross newly isogenized driver to GFP reporter

Picture GFP? Dissections of tissue? Picture of cross

Fluorescence analysis: Nervous system driver functionality

Non isoIso

Gal4

Tissue specific promoter

GFP

GAL4 sensitive promoter

Fluorescence analysis: Fat body driver functionality

• legend

Non isoIso

Conclusions and future work

• The expression of GFP in the fat bodies, salivary glands, and nervous system tissues in the final fly generation confirmed that driver and responder was not separated by a recombination event during isogenization.

• Once fly lines containing the GAL4 drivers are isogenized, more specific aging experiments can be conducted.

• Aging is a complex trait and can interact with many background genes, the homogenization of driver and responder fly lines prevents undocumented background interactions.

• In future work we can use isogenized Drosophila stock in aging studies, with the GAL4 driver initiating the transcription of an aging specific responder protein.