(P10-027-23) Identification of Bidirectional Regulatory Regions for FADS1 and FADS2

Objectives: Long-chain polyunsaturated fatty acids (LC-PUFAs) play important roles in human health, and the FADS1 and FADS2 genes are critical in the biosynthesis of these fatty acids. The two genes are located adjacent to each other in a head-to-head orientation, suggesting a potentially shared regulatory region. Using GTEx data, many eQTLs in this region were found to be associated in opposite directions with FADS1 and FADS2 expression levels. We aim to identify the bi-directional regulatory variants and the underlying mechanism for FADS genes.

Methods: Two regions containing two causal variants for FADS1 and FADS2, respectively, were tested for their effects on the other gene. We performed bi-directional luciferase reporter assay, whose results were further confirmed with bi-directional fluorescent reporter assay. ChIP-seq data from HepG2 were used to reveal the transcription factor binding sites for FADS genes. CRISPR-Cas9-based prime editing was used in HepG2 cells to verify how these two variants influences FADS genes simultaneously.

Results: None of two regions showed bi-directional regulatory activity in bi-directional luciferase and fluorescent reporter assay. However, these regions may compete for certain TFs since they both located in the binding sites for SREBP-1c and SP1 according to the ChIP-seq data. Overexpression of SREBP1c promotes enhancer activities of the regulatory region harboring rs174557-A more than rs174557-G, while overexpression of SP1 only significantly increases enhancer activity of the regulatory region containing rs968567. By examining the frequencies of these two variants in different human populations, we found that certain combinations of alleles were associated with higher expression of either FADS1 or FADS2, but not both at the same time.

Conclusions: This study explores the bi-directional regulation for FADS1 and FADS2 and provides a possible explanation for the opposite effects of regulatory variants on these genes. Overall, this study sheds new light on the complex regulation of FADS1 and FADS2 and may help pave the way for more personalized approaches to preventing complex diseases through personalized supplementation of LC-PUFAs.

Funding Sources: This study was supported by the University of Georgia Research Foundation.