Document Type

Thesis - University Access Only

Award Date

2001

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

Abstract

In mice, melanogenesis and weight homeostasis are linked by two mutant genes at two different genetic loci -Agouti and Attractin. The Lethal Yellow (AY) allele ectopically expresses agouti protein (AP), which affects signal transduction of melanogenesis within melanocytes by antagonizing the melanocortin-1 receptor resulting in phaeomelanin (yellow pigment production). Meanwhile, AP simultaneously disrupts satiety within neurons of the hypothalamus by blocking the melanocortin-4 receptor causing obesity. Overall, the ubiquitous overproduction of AP promotes a condition called Lethal Yellow Syndrome (L YS) in mice that is characterized by obesity, diabetes, tumor susceptibility, infertility, and yellow coat color (Ollmann et al., 1997). Compound mutant mice possessing both Lethal Yellow and Attractin exhibit significant alterations in melanogenesis, weight, activity level, and basal metabolic rate (BMR). Mutant Attractin encodes a single transmembrane cell receptor also located on melanocytes and hypothalamic neurons. The function of Attract in has been proposed to reverse the aberrant effects of AP shifting melanogenesis from phaeomelanin to eumelanin (black pigment) and suppressing obesity (Gunn et al., 1999, Nagle et al., 1999). Attractin plays major roles in energy homeostasis, which affects fat concentration. Cattle producers search for favorable traits to increase carcass quality, production efficiency, and overall vigor. The identification of beneficial genes would assist cattle production. The overall hypothesis to be evaluated is that mice and humans possess the Attractin gene along with four distinctive alleles that affect weight homeostasis. Therefore, it is proposed that cattle also possess the Attract in gene and possibly other mutations similar to mouse and human alleles. Utilizing reverse transcription polymerase chain reaction (RT-PCR), bovine Attractin cDNA (487 bp) was amplified from total mRNA from bovine brain, liver, and lung. Tissue was extracted from four different crossbred cows and one purebred cow. A bovine Attractin cDNA fragment from each cow exhibited 100% homology to mouse Attractin sequence while 91 % homology to human Attractin sequence. Humans possess a unique alteration within the Attractin gene. Due to a LINE-retrotransposon within exon 25 and differential splicing during DNA processing, humans construct two dissimilar mRNA transcripts. One transcript possessing exons 1-24,26-30 produces a cell receptor while another transcript possessing exon 1-25 produces a soluble secreted protein. Exon 25, the LINE-retrotransposon, introduces a STOP codon, thus ending translation and resulting in a slightly truncated protein. Exon 25 has yet to be characterized within mice. The bovine cDNA fragment amplified in this study possessed exons 24, 26-29. These data implicate that cattle produce a cell receptor. similar to mice and humans. Experimentation to determine if cattle also possess exon 25 has yet to be performed. Overall, these results suggest that cattle possess the Attractin gene and its sequence and DNA processing is similar to both mouse and human.

Library of Congress Subject Headings

Cattle -- Genetics
Mutation (Biology)

Format

application/pdf

Number of Pages

100

Publisher

South Dakota State University

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