Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2003
Publication Date: May 1, 2003
Citation: Poch, S.M., Richards, M.P., Clarke, S.M., McMurtry, J.P. 2003. Insulin-like growth factor gene expression in turkey liver and brain during embryonic and post hatch development [abstract]. BARC Poster Day. Abstract No. 20.
Insulin-like growth factor (IGF) genes are thought to play important roles in growth and development in avian species. Therefore, our objective in this study was to examine changes in the expression of IGF-I, IGF-II, and IGF-I receptor genes during embryonic and post hatch development of the turkey (Meleagris gallopavo) and also to determine the sequence of the cDNA corresponding to the IGF-II mRNA. A molecular cloning strategy was used after gene specific primers were designed to sequence 1300 bp of a turkey liver cDNA for IGF-II including the complete coding region and portions of the 3' and 5' untranslated regions. The sequenced cDNA encoded a 187 amino acid pre-proprotein which showed greater than 96% homology to chicken at both the amino acid and nucleotide level. Preliminary IGF-II gene mapping studies have indicated the presence of 4 exons and 3 introns. We sequenced intron 3 which consisted of 712 bp. Liver and brain RNA were extracted and reverse transcription/polymerase chain reaction was used to quantify the expression of IGF-I, IGF-II, and IGF-I receptor genes relative to an 18s ribosomal RNA internal standard at days 14-28 of embryonic development (ED), and at 3 weeks post hatch (PH). Liver and brain tissues showed an increase in IGF-I gene expression PH compared to ED levels. Liver IGF-I gene expression (due to low levels throughout ED) increased dramatically compared to brain PH. Liver IGF-II gene expression increased at day 24 prior to hatch and remained at high levels to PH. Brain IGF-II gene expression, which was relatively unchanged during ED, exhibited a gradual decline PH. IGF-I receptor gene expression in liver was variable. Brain exhibited higher IGF-I receptor gene expression than liver with a gradual decline in expression starting after day 20 and continuing toward PH. Linear regression analysis of gene expression data indicated an inverse correlation between IGF-I and IGF-I receptor levels in brain. Our data would support differential IGF gene regulation during embryonic and post hatch development in liver and brain.