GSE117382
Human muscle-derived CLEC14A-positive cells regenerate muscle independent of PAX7
Skeletal muscle stem cells, called satellite cells, are responsible for postnatal muscle growth, homeostasis and regeneration. Attempts to utilize the regenerative potential of muscle stem cells for therapeutic purposes so far failed. The transcription factor Pax7 defines satellite cells across species 1-4 . We previously established human PAX7-positive cell colonies with high regenerative potential 5 . We now identified PAX7-negative human muscle-derived cell colonies (PAX7neg) also positive for the myogenic markers desmin and MYF5. These included cells from a unique myopathic patient with rigid spine and respiratory insufficiency due to a homozygous PAX7 c.86-1G>A mutation (PAX7null). Single cell and bulk transcriptome analysis showed high intra- and inter-donor heterogeneity and revealed the endothelial cell marker CLEC14A to be highly expressed in PAX7null cells. All PAX7neg cell populations, including PAX7null, formed myofibers after transplantation into mice, and regenerated muscle after reinjury. Transplanted PAX7neg cells repopulated the satellite cell niche where they re-expressed PAX7. Strikingly, PAX7null cells expressing CLEC14A were also identified below the basal lamina. In summary, transplanted human cells do not depend on PAX7 for muscle regeneration. Thus, Pax7 is not a suitable marker for selection of optimal cells for muscle regenerative therapies. Overall design: Eleven human primary myoblasts cell lines with and without PAX7 expression were analysed using single- cell or bulk RNA-seq. For single-cell experiments we analysed myoblast subpopulations with and without PAX7 expression from the same donor as well as myoblasts from a patient with PAX7 deficiency. Bulk RNA-seq included a PAX7-positive and a PAX7-negative myoblast cell line and myoblasts from the patient with PAX7 deficiency.