217 PROMOTER-SPECIFIC EXPRESSION OF THE IMPRINTED Igf2 GENE IN CATTLE
C. Curchoe A , S. Zhang B , Y. Bin B , L. Yang A and X.C. Tian AA Department of Animal Science, Center for Regenerative Biology, University of Connecticut, Storrs, CT 06269, USA
B College of Animal Science, South China Agricultural University, Guangzhou 510642, China. Email: carolcurls@hotmail.com
Reproduction, Fertility and Development 17(2) 259-259 https://doi.org/10.1071/RDv17n2Ab217
Submitted: 1 August 2004 Accepted: 1 October 2004 Published: 1 January 2005
Abstract
Insulin-like growth factor II (Igf2) is an imprinted gene crucial to fetal development and maternal/fetal nutrient transfer. Studies in the pig have demonstrated that this quantitative trait locus controls muscle growth, fat deposition, and heart size. Additionally, studies have shown that four splice variants transcribed from promoters (P1–P4) regulate the complex temporal and spatial expression of Igf2 in mice, humans, pigs, and horses. Cattle have a cotyledonary placenta and therefore a distinct type of maternal/fetal interaction. Here we have studied for the first time the promoter-specific expression of Igf2 in cattle, an economically valuable livestock species. Five naturally reproduced animals obtained from an abattoir were used in this study (2 mid-gestation fetuses, 1 calf, and 2 adults) of which all major internal organs were tested. Here we used RT-PCR to show that, like that of the pig and the human, the bovine Igf2 is expressed from four different promoters in a temporal and spatial manner. However, unlike for pigs and humans, we have found that transcripts from promoter P1 were present in several bovine fetal and adult tissues including the liver, heart, kidney, lung, placenta, and spleen. Promoter P2 was expressed only in mid-gestation fetal tissues including the liver, bladder, lung, and kidney. Promoter P2 was not detected in the brain. Promoter P3 was expressed ubiquitously throughout fetal and adult life; however, expression appears to be lower in the heart. Promoter P4 was expressed in all mid-gestation fetal tissues. Transcription from P4 decreased with age until transcripts were detected only in the kidney, lung, heart, and spleen. Using single-stranded conformational polymorphism polyacrylamide gel electrophoresis and a single nucleotide polymorphism in exon 10 of Igf2, we have confirmed that a loss of imprinting occurs with age from all transcripts (P1–P4) and biallelic expression is observed in most adult tissues studied.
This work was funded by a grant from the USDA.
