Fig. 7: Fusion and myonuclear accrual is needed for pre-existing myonuclei to transcriptionally respond to muscle overload.

a Schematic diagram of the bulk nuclei RNA-seq methodology for analyzing pre-existing myonuclei adapting to muscle overload (MOV) in the absence of myonuclear accretion. Myomaker^loxP/loxP; Pax7^CreER mice were treated with tamoxifen to generate fusion-incompetent mice (Mymk^scKO). Note that three sham mice were Pax7^rtTA; TRE^H2B-GFP (+Dox) and one sham animal was Mymk^loxP/loxp (+tamoxifen). b Principal component analysis of bnRNA-seq from Mymk^scKO myonuclei isolated from plantaris muscle 1 week after muscle overload, myonuclei (GFP⁺ and GFP⁻) derived from control mice that underwent the same surgery, and myonuclei from sham mice. c Scatter plot highlighting genes upregulated in both control muscle overload (MOV) (GFP⁻ pre-existing myonuclei) and Mymk^scKO MOV myonuclei (peach dots, fusion independent) or upregulated in only GFP⁻ pre-existing myonuclei (maroon dots, fusion dependent). Gene Ontology analysis of the genes upregulated that are fusion-dependent (maroon dots) is shown on the right. d Scatter plot highlighting genes downregulated in both control muscle overload (MOV) (GFP⁻ pre-existing myonuclei) and Mymk^scKO MOV myonuclei (green dots) or downregulated in only Mymk^scKO MOV myonuclei (pink dots). Gene Ontology analysis of both sets of genes is shown on the right.