Objective
Mutations in low-density lipoprotein receptor (
LDLR
), which encodes a critical protein for cholesterol homeostasis and lipid metabolism in mammals, are involved in cardiometabolic diseases, such as familial hypercholesterolemia in pigs. Whereas microRNAs (miRNAs) can control
LDLR
regulation, their involvement in circulating cholesterol and lipid levels with respect to cardiometabolic diseases in pigs is unclear. We aimed to identify and analyze
LDLR
as a potential target gene of
SSC
-miR-20a.
Methods
Bioinformatic analysis predicted that porcine
LDLR
is a target of
SSC
-miR-20a. Wild-type and mutant
LDLR
3′-untranslated region (UTR) fragments were generated by polymerase chain reaction (PCR) and cloned into the pGL3-Control vector to construct pGL3 Control LDLR wild-3′-UTR and pGL3 Control LDLR mutant-3
′
-UTR recombinant plasmids, respectively. An miR-20a expression plasmid was constructed by inserting the porcine pre-miR-20a-coding sequence between the
Hind
III and
Bam
HI sites in pMR-mCherry, and constructs were confirmed by sequencing. HEK293T cells were co-transfected with the miR-20a expression or pMR-mCherry control plasmids and constructs harboring the corresponding 3′-UTR, and relative luciferase activity was determined. The relative expression levels of miR-20a and LDLR mRNA and their correlation in terms of expression levels in porcine liver tissue were analyzed using reverse-transcription quantitative PCR.
Results
Gel electrophoresis and sequencing showed that target gene fragments were successfully cloned, and the three recombinant vectors were successfully constructed. Compared to pMR-mCherry, the miR-20a expression vector significantly inhibited wild-type LDLR-3′-UTR-driven (p<0.01), but not mutant LDLR-3′-UTR-driven (p>0.05), luciferase reporter activity. Further, miR-20a and
LDLR
were expressed at relatively high levels in porcine liver tissues. Pearson correlation analysis revealed that porcine liver miR-20a and
LDLR
levels were significantly negatively correlated (r = −0.656, p<0.05).
Conclusion
LDLR
is a potential target of miR-20a, which might directly bind the
LDLR
3′-UTR to post-transcriptionally inhibit expression. These results have implications in understanding the pathogenesis and progression of porcine cardiovascular diseases.