Functional genomics of the avian circadian system

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Title: Functional genomics of the avian circadian system
Author: Bailey, Michael J
Abstract: The genetic identification of molecular mechanisms responsible for circadian rhythm generation has advanced tremendously over the past 25 years . However the molecular identities of the avian clock remain largely unexplored . The present studies seek to determine candidate clock components in the avian species Gallus domesticus . Construction and examination of the transcriptional profiles of the pineal gland and retina using DNA microarray analysis provided a clear view into the avian clock mechanism . Investigation of the pineal and retina transcriptomes determined the mRNA profiles of several thousand genes over the course of one day in LD (daily ) and one day in DD (circadian ) conditions . Several avian orthologs of mammalian clock genes were identified and many exhibited oscillating patterns of mRNA abundance including several of the putative avian clock genes . Comparison of the pineal transcriptional profile to that of the retina revealed several intriguing candidate genes that may function as core clock components . Including the putative avian clock genes and several others implicated in phototransduction , metabolism , and immune response . A more detailed examination of several candidate photoisomerase /photopigment genes identified from our transcriptional profiling was conducted . These include peropsin (rrh ) , RGR -opsin (rgr ) , melanopsin (opn4 ) and cryptochrome 2 (cry2 ) genes . This analysis revealed several interesting patterns of mRNA distribution and regulation for these genes in the chick . First , the mRNA of all 4 genes is located within the Inner Nuclear Layer (INL ) and Retinal Ganglion cell Layers (RGL ) of the ocular retina , where circadian photoreception is present . Second , opn4 and cry2 mRNA is expressed in the photoreceptor layer of the chick retina where melatonin biosynthesis occurs . Lastly , the mRNA for all 4 candidate photopigment genes is regulated on a circadian basis in the pineal gland . As a whole these data yield significant insight into the mechanisms of the avian circadian system and present several candidate genes that may function to integrate photic information , and /or regulate circadian rhythm generation in birds .
URI: http : / /hdl .handle .net /1969 .1 /3318
Date: 2006-04-12

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Functional genomics of the avian circadian system. Available electronically from http : / /hdl .handle .net /1969 .1 /3318 .

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