Diversity and Complexity of the Mouse Saa1 and Saa2 genes Diversity and Complexity of the Mouse <i>Saa1</i> and <i>Saa2</i> genes
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Mouse strains show polymorphisms in the amino acid sequences of serum amyloid A 1 (SAA1) and serum amyloid A 2 (SAA2). Major laboratory mouse strains are classified based on the sequence as carrying the <i>A</i> haplotype (e.g., BALB/c) or <i>B</i> haplotype (e.g., SJL/J) of the <i>Saa1</i> and <i>Saa2</i> gene unit. We attempted to elucidate the diversity of the mouse <i>Saa1</i> and <i>Saa2</i> family genes at the nucleotide sequence level by a systematic survey of 6 inbred mouse strains from 4 <i>Mus</i> subspecies, including <i>Mus musculus domesticus</i>, <i>Mus musculus musculus</i>, <i>Mus musculus castaneus</i>, and <i>Mus spretus</i>. <i>Saa1</i> and <i>Saa2</i> genes were obtained from the mouse genome by PCR amplification, and each full-length nucleotide sequence was determined. We found that <i>Mus musculus castaneus</i> mice uniquely possess 2 divergent <i>Saa1</i> genes linked on chromosome 7. Overall, the mouse strains had distinct composite patterns of amino acid substitutions at 9 positions in SAA1 and SAA2 isoforms. The mouse strains also had distinct composite patterns of 2 polymorphic upstream regulatory elements that influenced gene transcription in <i>in vitro</i> reporter assays. <i>B</i> haplotype mice were revealed to possess an LTR insertion in the downstream region of <i>Saa1</i>. Collectively, these results indicate that the mouse <i>Saa</i> genes hold broader diversity and greater complexity than previously known, and these characteristics were likely attained through gene duplication and repeated gene conversion events in the <i>Mus</i> lineage.
- Experimental Animals
Experimental Animals 63(1), 99-106, 2014
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