Detection of differential splicing of Abcg8 in liver of lactating rats compared to virgin controls using exon arrays

Lactating dams have an increased demand for cholesterol for secretion into milk, bile acid synthesis and incorporation into cellular membranes. We used Affymetrix Rat Exon 1.0ST® analysis to investigate mRNA expression in liver of lactating (L) vs female control (C) rats. Analysis of splicing variance (ANOSVA) revealed 59 differentially alternatively spliced genes (p<0.001). Abcg5 and Abcg8 function as a heterodimer to export cholesterol into bile, creating a major pathway for cholesterol clearance. Exon array analysis indicated reduced mRNA of Abcg5 and Abcg8 in L vs C, and demonstrated differential alternative splicing of Abcg8 (ANOSVA p=0.0002), but not Abcg5. Screening of calculated expression levels for each exon indicated that exons 6 and 10 were alternatively spliced in L; RT‐PCR confirmed differential splicing. One splice variant detected in L, but not C, showed deletion of part of exons 4 and 9 and all intervening exons by sequencing the RT‐PCR products from the splice variant. Loss of Abcg5/g8 would provide a mechanism for controlling cholesterol loss in bile during lactation. (DK46923)