(A) Schematic representation of the expected gene replacement at the PG locus. loxP sites are represented by triangles. The rectangles represent FRT sites. The combination of PG floxed allele (FN) containing a neomycin cassette (neo) with the germline null allele (Δ) resulted in a PG hypomorph (PG FN/Δ). (B) Quantification of PG mRNA expression in PG +/+, PG Δ/+, and PG FN/Δ hearts (n=4 for each genotype) at 3 months of age. (C) Representative Western blot of heart lysates from 1 month old PG +/+, PG FN/+ and PG FN/Δ mice (n=6 for each genotype) were immunoblotted for PG and GAPDH. *, p<0.05; ***, p<0.001.