Document Type

Thesis - University Access Only

Award Date

2004

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Nels H. Granholm

Abstract

The agouti-related protein (agrp) gene encodes a protein that acts on melanocortin-4 receptors (MC4-Rs) within appetite-controlling neurons in the hypothalamus. Thus, agrp plays an important role in appetite regulation and other aspects of energy homeostasis in mammals. We believe that variations in this gene (alleles), if they exist, could be important determinants of appetite, basal metabolic rate (BMR), body composition, and other metabolic activities in livestock. Therefore, identification and selection of optimal "production alleles" of agrp could be of great benefit to livestock producers. In a previous study in our laboratory, we isolated and characterized the agrp gene in 16 domestic pig breeds and breed combinations. Our results showed that the coding regions of the agrp gene are highly conserved among domestic pigs. Two explanations were put forward for this observation: 1) considering the important role agrp plays in appetite regulation, it is possible that pigs with mutations in the co1ing region of this gene do not survive long enough to produce offspring; 2) due to intense selective breeding during the domestication process, agrp alleles may either have been lost from the domestic pig genepool or become very rare. Therefore, we hypothesized that wild or undomesticated pigs and pig relatives may carry agrp alleles and exhibit polymorphisms in the coding regions of the gene. We tested this hypothesis by sequencing the agrp gene in several members of the pig family (Suborder Suiformes), selected on their phylogenetic relationship to domestic pigs and to each other. A 978 bp region of the agrp gene in each pig was amplified using the polymerase chain reaction (PCR) and sequenced. Analysis of the sequence results has shown that polymorphisms exist within the coding regions of the agrp gene in wild pigs. Some of these polymorphisms cause changes to the amino acid sequence of the agouti-related protein (AGRP). Therefore, these nucleotide variations could alter the functionality of AGRP and cause major physiological changes in appetite, BMR, and body composition. We believe that characterization of the agrp gene in pigs is an important step in identifying agrp alleles that may produce animals with greater production efficiency and optimal carcass traits.

Library of Congress Subject Headings

Swine -- Genetics.
Proteins.
Appetite.

Publisher

South Dakota State University

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Rights Statement

In Copyright