Editing the mouse genome to understand the regulation of milk proteins

Abstract

Dairy industries not only contribute to global food security but also have a major economic role worldwide. Milk is an important source of proteins, lactose, fat, and minerals, as such, understanding the genetic regulation of milk components is crucial to improve dairy production and livestock health. The Caseins, the predominant milk proteins, consist of four components (αS1, αS2, β and κ casein) that exhibit different functions during lactation. Recently a comparative analysis of the casein locus identified an evolutionarily conserved region (ECR) in the mouse genome, predicted to be a potential regulatory and element. CRISPRs are programmable molecular scissors that generate targeted double stranded breaks in DNA which are subsequently repaired by non-homologous end joining or homology directed repair. To understand the role of ECR in regulation of casein locus, an ECR knockout mouse has been generated using CRISPRs. Similarly, the entire casein locus of mouse was attempted to be removed in order to redesign this locus with proteins of interest. Lactose is a milk sugar, the concentration of which is regulated by α lactalbumin which in turn is controlled by a transcription activator protein called STAT5, which binds to α lactalbumin promoter at a consensus binding site resulting in transcription activation. The STAT5 binding site the mouse α lactalbumin promoter have been altered to check its expression in mouse mammary epithelial (HC11) cells using the reporter assay. The mouse lalba promoter without a STAT5 binding site showed the maximum luciferase activity suggesting its role as a limiting factor in the lalba gene regulation.