Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 11, 2004
Publication Date: June 10, 2004
Citation: Mccormack, B.L., Agca, C., Chase, C.C., Olson, T.A., Elsasser, T.H., Hammond, A.C., Welsh Jr., T.H., Lucy, M.C. 2004. A miniature condition in brahman cattle is associated with a single nucleotide mutation within the growth hormone gene. Journal of Animal Science. 82(Suppl-1). (Journal Dairy Science. 87(Suppl.1)/ Poultry Science. 83(Suppl.1)).
Miniature Brahman cattle at the USDA, ARS in Brooksville, FL have normal proportioned growth but are approximately 70% of normal mature height and weight. Pedigree analyses suggest that the condition is inherited as a recessive gene. The objective was to clone the GH cDNA from miniature cattle and compare its sequence to normal cattle. Messenger RNA was isolated from pituitary and a cDNA for the protein coding region of the GH gene was amplified by reverse transcription PCR from each of two miniature cattle. The cDNA were cloned into plasmid vectors and top and bottom strands were sequenced by automated DNA sequencing. Both cDNA clones contained a nucleotide polymorphism in which base number 641 of GenBank AF034386 (Bos indicus GH) was mutated from a cytosine (C) to a thymine (T). The C to T change encodes a mutation (threonine to methionine) at amino acid 200. The threonine is located in the fourth alpha helix of GH and is one of nine amino acids that participate directly in binding of GH to the GH receptor. Amino acid mutations at this location are associated with dwarfism in humans. Four miniature and four normal stature cattle from the Brooksville herd were tested for the polymorphism by using restriction fragment length polymorphism (RFLP) analysis of PCR-amplified GH gene with BsmBI restriction enzyme (specific for mutated nucleotide). The four miniature cattle were homozygous for the mutation (-/-). Two of the normal stature cattle were homozygous for the wild type allele (+/+) and two were heterozygous (+/-) (P<.05). Miniature Brahman cattle were homozygous for a single nucleotide polymorphism that encodes a mutation in an amino acid involved in binding of GH to the GH receptor. Normal stature cattle had at least one copy of the normal GH allele. We conclude that threonine 200 in bovine GH is required for normal growth in cattle.