Transient Inactivation of Rb and ARF Yields Regenerative Cells from Postmitotic Mammalian Muscle

SummaryAn outstanding biological question is why tissue regeneration in mammals is limited, whereas urodele amphibians and teleost fish regenerate major structures, largely by cell cycle reentry. Upon inactivation of Rb, proliferation of postmitotic urodele skeletal muscle is induced, whereas in mammalian muscle this mechanism does not exist. We postulated that a tumor suppressor present in mammals but absent in regenerative vertebrates, the Ink4a product ARF (alternative reading frame), is a regeneration suppressor. Concomitant inactivation of Arf and Rb led to mammalian muscle cell cycle reentry, loss of differentiation properties, and upregulation of cytokinetic machinery. Single postmitotic myocytes were isolated by laser micro-dissection-catapulting, and transient suppression of Arf and Rb yielded myoblast colonies that retained the ability to differentiate and fuse into myofibers upon transplantation in vivo. These results show that differentiation of mammalian cells is reversed by inactivation of Arf and Rb and support the hypothesis that Arf evolved at the expense of regeneration.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (155 K)Download as PowerPoint slideHighlights4Inactivation of Rb and ARF induces cell cycle reentry of mammalian muscle 4Single postmitotic myocytes give rise to clones after transient loss of Rb and ARF 4Myocyte-derived clones differentiate and fuse to mature muscle fibers in vivo 4Regeneration by reversal of differentiation is possible in mammalian cells