Mutation analysis of left-right axis determining genes in NOD and ICR, strains susceptible to maternal diabetes

Background: Genetic background of the fetus contributes to the pathogenesis of congenital malformation after teratogen exposure. Such contribution is illustrated in left-right axis malformations observed in the Fl offspring o f nonobese diabetic (NOD) mouse dams and sires from different strains. When sires of the NOD, ICR, or C57BL/6J were mated with NOD darns, incidence va ried depending on the fetal genotype, with 65% in NOD x NOD, 24% in NOD x I CR, and 7% in NOD x C57BL/6J. Methods: As a first step in elucidating the molecular basis of the interstr ain differences in susceptibility to situs defects, we compared genomic seq uences of six genes HNF3beta, Acvr2b, Nodal, ZIC3, Lefty1, and Smad2, which are involved in the normal development of left-right axis among NOD, ICR, and C57BL/6J strains. Results: The outbred strain ICR had 1) a 0.2-kb insertion in the putative p romoter region of the isoform E of HNF3beta together with a G to A change t hat could create a potential splice acceptor in the exon 3 of HNF3beta (gen e frequency P = 0.36), 2) five single base substitutions within the 5' cont rolling element and a proline to serine substitution (P2S) of Lefty1 (P 0.7 7), and 3) a tyrosine to histidine substitution within the prodomain of Nod al(P = 0.48). The inbred strain NOD had the same G to A change as ICR and a three-base deletion in the putative promoter of isoform E of HNF3 beta. Conclusions: We suggest that sequence variations in HNF3 beta, Lefty1, and Nodal might account, in part, for the interstrain differences in susceptibi lity to situs abnormalities among the offspring of diabetic dams.