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Microarray data analysis towards the understanding the role of hzy in the formation of rhabdomeres Ashwini Oke School of Informatics, Indiana University
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Drosophila compound eye 2
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Rhabdomeres carry out the light reaction Montell, C. 1999 3
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Formation ? ? InitiationElongationMaintenance 4
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hzy is required for rhabdomere formation and phototransduction Development 130, 4383-4392 (2003) 5
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hzy is a transcription factor 6
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The phototransduction pathway The EMBO Journal (2001) 20, 4414–4422, doi:10.1093/emboj/20.16.4414 7
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Known targets of hzy 8
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Goals Identify targets of hzy using oligonucleotide expression arrays Determine the stage of rhabdomere formation that requires hzy Identify DNA binding site for hzy Understand the regulation of hzy itself 9
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Identifying regulatory targets of hzy 10
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Microarray design www.scq.ubc.ca/wp-content/cDNAarray.gif DGRC-2 Oligonucleotide Arrays Genotypes: WildType - cnbw Mutant - hzy - otd;hzy Time Points: 48 hr APF 72 hr APF 96 hr APF Replicates: 4 independent samples for each time point 11
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DGRC-2 arrays ooooooooooooooooooo Probes ~14,400 probes representing 93.5% of the genome Negative Controls Blank Spotting_Solution Exogenous targets Positive Controls Housekeeping genes 12
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tiff image from the scanner 13
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GenePix Pro records spot intensities 14
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GenePix Pro creates.gpr file 15
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Analysis workflow R2.5.1 Bioconductor Packages: LIMMA, OLIN, MARRAY 16
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Preprocessing Scanned Image Heat PlotDensity plot 17
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Normalization A = log 2 average intensity for the two channels M = log ratio of intensities for the two channels Genes Blank Spotting Solution Arabidopsis 18
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Normalization within array LOESS Local polynomial regression fit 19
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Normalization between arrays Rawwithin array normalization between arrays normalization LIMMA: Linear models for Microarray Data 20
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Density Plots after normalizations 21
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Differential analysis 22
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Volcano plot 23
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at 72 hr APFat 96 hr APF (12 total)(28 total) GeneMP Gbeta76C-3.750 ninaC-3.650 Arr2-3.410.00002 Trp-2.160.00011 CG8889-2.680 CG31313-2.350.00002 TotB-2.50 nimB2-2.250.00002 CG5172-2.840.00001 PIP82-2.120.00002 Osi18-2.450.00004 CG10953-2.350.00038 24 GeneMP Rh6-4.941.00E-05 Rh2-5.133.00E-05 Arr1-3.257.00E-05 Trp-2.750.00015 Gbeta76C-4.120.00021 CG2650-3.565.00E-05 Ank2-2.210.00018 Trpl-6.513.00E-05 CG8889-2.640.00029 CG42330-10.750.00329 rdga-2.550.00452 Sr-CI-2.650.00028
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Gene Ontology GO Database provides a vocabulary to describe gene and gene products Cellular Component Eg : Cytoplasmic, Nuclear, plasma membrane Molecular Function Eg : Enzyme activity, protein binding Biological Process Eg : Apoptosis, cell adhesion, phototransduction 25
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Classifying genes by GO At 72 hr APF At 96 hr APF 26
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otd : Another transcription factor regulating rhabdomere formation cnbw hzy;otd otdhzy cnbw 27
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Results from microarray analysis of hzy;otd double mutant 28
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hzy is required during elongation 29 Time point48 hr APF72 hr APF96 hr APF # down regulated genes 01228 EM data No difference between cnbw and hzy hzy mutant has irregular rhabdomeres hzy mutant has malformed rhabdomeres
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Identifying DNA binding site for hzy 30
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hzy has been shown to bind to a motif upstream of eyeG Development 130, 4383-4392 (2003) 31 TAATNNNATTA
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MEME MEME is a tool for discovering motifs in a group of related DNA or protein sequences Primary targets of hzy should have a conserved binding site in their promoter region 32
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Motif search : 72 APF targets meme 72.fas -dna -nmotifs 5 -mod zoops -revcomp -minw 3 -maxw 15 Down regulated genes 33
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A true motif should be conserved For each of the hzy targets at 72 hr APF, find orthologs in other groups of Drosophila Retrieve 500 b upstream of each gene Run MEME on promoter regions from each specie 34
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Motif is conserved across orthologs 35
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Understanding the regulation of hzy 36
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Locating the promoter region 1.4 kb 0.8 kb Apitz, H. 2002. Dros.Inf.Serv.85:118-120. 37
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Promoter testing with Gal4-UAS system X Gal4UASReporterPromoter 38 ElementResult 0.8 kb upstream of hzyEye specific GFP expression 1.4 kb upstream of hzyGFP in eye and some other organs
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Conserved regions 39
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Future Directions 40 RT PCR to confirm targets Search hzy promoter region for known TFBS
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Thank you 41 Dr. Andrew Zelhof Dr. Haixu Tang Dr. Qunfeng Dong Monalisa Mishra PhD Andreas Rechsteiner PhD Jacqueline Lopez
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