Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2015
Publication Date: 9/1/2014
Citation: Miska, K.B., Fetterer, R.H., Wong, E.A. 2014. The mRNA expression of amino acid transporters, aminopeptidase N, and the di- and tri- peptide transporter PepT1 in the embryo of the domesticated chicken (Gallus gallus) shows developmental regulation. Comparative Biochemistry and Physiology. 2014 Sep;93(9):2262-70. Interpretive Summary: Producing robust chicks at hatch is essential for efficient poultry production. The development of the chicken requires that the embryo within the egg must survive to hatch on the nutrients contained within the egg. This is much different than observed in mammalian embryos that are constantly provided nutrients from the mother via the placenta. The purpose of the current study was to determine when during embryonic development do chick embryos start expressing genes which code for proteins that are involved in breaking down nutrients i.e. to amino acids and transporting them into and out of cells for energy needs. The results indicate that the liver, the most metabolically active organ in the embryo, expressed these genes throughout development. Gene expression in the intestine at day 9 of development was low, but by day 11 expression of genes that code for proteins that transport amino acids from the intestinal cell were detected. By day 15 of embryo development all genes were expressed in three regions of the gut: duodenum, mid-gut, and the ceca. The results indicate that a 15 day-old chick embryo is capable of processing, uptake, and transport of amino acids. It is possible that extra protein could be provided for the chick while still in the egg. Feeding of developing chicks in the egg has recently gained some popularity and our results indicate that such methods may be useful in producing more robust chicks at hatch.
Technical Abstract: The mRNA expression profile for ten amino acid transporters (AAT), the di-and tri- peptide transporter (Pept1), and aminopeptidase N (APN) during chick embryogenesis was determined. Fertilized eggs were sampled at days 9, 11, 15, 17, 19, and 20, post fertilization. Three to four embryos were sampled at each time period. At days 9 and 11, the entire intestine was taken due to its undifferentiated appearance. The ceca, duodenum, mid-gut, and liver were sampled at days 15, 17, 19 and 20. Gene expression was measured using absolute quantitation qRT-PCR. In the liver, all genes except for PepT1 were expressed at most time points. At day 9, the expression of all genes in the intestine was barely detectable, and by day 11, only genes associated with the basolateral surface were expressed. By day 15, most of the genes were expressed in the intestine at high levels that remained relatively constant until day 20. At day 9 and 11, the gut may not function in amino acid (AA) uptake from the lumen and possibly relies on other structures like the yolk sac. As the gut matures and protein becomes available, AATs become highly expressed in all parts of the intestine.