Additionally, an increased level of osteopontin (OPN), a recently described biomarker of DMD [36,37,38], was detected in the serum (Figure S1f) and in the gastrocnemius, where its transcript (Spp1) was upregulated almost 150-fold in comparison to WT mice (Figure S1g). The gene discussed is SPP1; the disease is Duchenne muscular dystrophy.