Differential isoform expression and selective muscle involvement in muscular dystrophies

To test the hypothesis that different muscles may express variable amounts of different isoforms of muscle genes, we applied a custom-designed exon microarray containing probes for 57 muscle-specific genes to assay the transcriptional profiles in sets of human adult, lower limb skeletal muscles. Muscle biopsies from 15 individuals were selected for analysis dissected from 21 anatomically different muscles collected from eight men and seven women, ranging from 61 to 91 years The muscle tissue samples collected included samples from 11 different thigh muscles––vastus medialis, vastus lateralis, vastus intermedialis, sartorius, gracilis, semimembranosus, semitendinosus, biceps femoris, adductor magnus, adductor longus, and rectus femoris––and 10 lower leg muscles––flexor digitorum longus, extensor digitorum longus, tibialis posterior, tibialis anterior, peroneus longus/brevis, extensor hallucis longus, gastrocnemius lateralis, gastrocnemius medialis, flexor hallucis longus, and soleus. Approximately five to seven muscle pieces were collected from each individual muscle sampled. The muscle sample pieces obtained for histological analysis measured roughly 10 mm x 5 mm, and the pieces for RNA isolation 5 mm x 5 mm. The samples were obtained directly from the proximal vital parts of the amputated limbs and processed immediately following their removal to avoid tissue degradation.To test the hypothesis that different muscles may express variable amounts of different isoforms of muscle genes, we applied a custom-designed Agilent exon microarray containing probes for 57 muscle-specific genes to assay the transcriptional profiles in sets of human adult, lower limb skeletal muscles