Arrested Hematopoiesis and Vascular Relaxation Defects in Mice with a Mutation in Dhfr

Julie A. I. Thoms, Kathy Knezevic, Jia Jenny Liu, Elias N. Glaros, Thuan Thai, Qiao Qiao, Heather Campbell, Deborah Packham, Yizhou Huang, Peter Papathanasiou, Robert Tunningley, Belinda Whittle, Amanda W. S. Yeung, Vashe Chandrakanthan, Luke Hesson, Vivien Chen, Jason W. H. Wong, Louise E. Purton, Robyn L. Ward, Shane R. Thomas, John E. Pimanda

Dihydrofolate reductase (DHFR) is a critical enzyme in the folate metabolism pathway, and also plays a role in regulating nitric oxide (NO) signalling in endothelial cells. Although both coding and non-coding mutations with phenotypic effects have been identified in the human DHFR gene, no mouse model is currently available to study the consequences of perturbing DHFR in vivo. In order to identify genes involved in definitive hematopoiesis, we performed a forward genetic screen and produced a mouse line, hereafter referred to as Orana, with a point mutation in the Dhfr locus leading to a Thr136Ala substitution in the DHFR protein. Homozygote Orana mice initiate definitive hematopoiesis but expansion of progenitors in the fetal liver is compromised, and animals die between E13.5 and E14.5. Heterozygote Orana mice survive to adulthood but have tissue specific alterations in folate abundance and distribution, perturbed stress erythropoiesis, and impaired endothelial-dependent relaxation of the aorta consistent with the role of DHFR in regulating NO signalling. Orana mice provide insight into the dual roles of DHFR, and are a useful model for investigating the role of environmental and dietary factors in the context of vascular defects caused by altered NO signalling.