In vivolineage conversion of vertebrate muscle into early endoderm-like cells

Abstract

The extent to which differentiated cells, while remaining in their native microenvironment, can be reprogrammed to assume a different identity will reveal fundamental insight into cellular plasticity and impact regenerative medicine. To investigate in vivo cell lineage potential, we leveraged the zebrafish as a practical vertebrate platform to determine factors and mechanisms necessary to induce differentiated cells of one germ layer to adopt the lineage of another. We discovered that ectopic co-expression of Sox32 and Oct4 in several non-endoderm lineages, including skeletal muscle, can specifically trigger an early endoderm genetic program in a cell-autonomous manner.Gene expression, live imaging, and functional studies reveal that the endoderm-induced muscle cells lose muscle gene expression and morphology, while specifically gaining endoderm organogenesis markers, such as the pancreatic specification genes, hhex and ptf1a, via a mechanism resembling normal development. Endoderm induction by a pluripotent defective form of Oct4, endoderm markers appearing prior to loss of muscle cell morphology, a lack of dependence on cell division, and a lack of mesoderm, ectoderm, dedifferentiation, and pluripotency gene activation, together, suggests that reprogramming is endoderm specific and occurs via direct lineage conversion. Our work demonstrates that within a vertebrate animal, stably differentiated cells can be induced to directly adopt the identity of a completely unrelated cell lineage, while remaining in a distinct microenvironment, suggesting that differentiated cells in vivo may be more amenable to lineage conversion than previously appreciated. This discovery of possibly unlimited lineage potential of differentiated cells in vivo challenges our understanding of cell lineage restriction and may pave the way towards a vast new in vivo supply of replacement cells for degenerative diseases such as diabetes.

The Eupentacta fraudatrix transcriptome provides insights into regulation of cell transdifferentiation

“…In vertebrates, it is a marker of the formation of the endoderm and gut 61,62 . According to Campbell et al 23 , SOX17 is involved in the transdifferentiation of muscle cells into enterocytes in zebrafish. In E. fraudatrix, the sox17 homolog is expressed as early as the first stage of regeneration, and subsequently the number of its transcripts increases (see Supplementary Table S5).…”

“…Until recently, E. fraudatrix was the only species for which transdifferentiation of mesodermal cells into enterocytes was reported 7 . Recently, the ability of muscle cells to transform into enterocytes has been found in zebrafish 23 . It is not yet clear how similar the mechanisms of transdifferentiation in holothurians and fish actually are.…”

“…It is not yet clear how similar the mechanisms of transdifferentiation in holothurians and fish actually are. One of the key genes that trigger transdifferentiation in zebrafish is oct4 23 . The holothurian ortholog of this gene, oct-1/2/11, does not show noticeable expression during intestinal regeneration in Holothuria glaberrima 24 .…”