RT Journal Article SR Electronic T1 A new mechanism for a familiar mutation – bovine DGAT1 K232A modulates gene expression through multi-junction exon splice enhancement JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.02.04.934562 DO 10.1101/2020.02.04.934562 A1 Tania Fink A1 Thomas J Lopdell A1 Kathryn Tiplady A1 Renee Handley A1 Thomas JJ Johnson A1 Richard J Spelman A1 Stephen R Davis A1 Russell G Snell A1 Mathew D Littlejohn YR 2020 UL http://biorxiv.org/content/early/2020/02/05/2020.02.04.934562.abstract AB The DGAT1 gene encodes an enzyme responsible for catalysing the terminal reaction in mammary triglyceride synthesis, and underpins a well-known pleiotropic quantitative trait locus (QTL) with a large influence on milk composition phenotypes. Since first described over 15 years ago, a protein-coding variant K232A has been assumed as the causative variant underlying these effects, following in-vitro studies that demonstrated differing levels of triglyceride synthesis between the two protein isoforms. In the current study, we used a large RNAseq dataset to re-examine the underlying mechanisms of this large milk production QTL, and hereby report novel expression-based functions of the chr14 g.1802265AA>GC variant that encodes the DGAT1 K232A substitution. Using expression QTL (eQTL) mapping, we demonstrate a highly-significant mammary eQTL for DGAT1, where the K232A mutation appears as one of the top associated variants for this effect. By conducting in vitro expression and splicing experiments in bovine mammary cell culture, we further show modulation of splicing efficiency by this mutation, likely through disruption of an exon splice enhancer as a consequence of the allele encoding the 232A variant. Although the relative contributions of the enzymatic and transcription-based mechanisms now attributed to K232A remain unclear, these results suggest that transcriptional impacts contribute to the diversity of lactation effects observed at this locus.