Species variation in ABCG1 isoform expression: Implications for the use of animal models in elucidating ABCG1 function

The ATP-binding cassette transporter G1 (ABCG1) plays an important role in reverse cholesterol transport by exporting cholesterol to high density lipoproteins (HDL). Two major ABCG1 isoforms exist in humans, which differ by the presence or absence of twelve amino acids between the ATP cassette and the transmembrane domains. Previously, the longer isoform was thought to be expressed only in humans. However, here we have sequenced mRNA from various cell lines and tissues and demonstrate that primates and several other species, including dog, cow and cat, also express both isoforms. Furthermore, we confirm that rodents, including mice, express only the short isoform of ABCG1. Considering that murine models are used extensively in ABCG1-related research, this report highlights that there are limitations in extrapolating results from murine models to humans.