Pleiotropic phenotypic expression in cybrids derived from mouse teratocarcinoma cells fused with rat myoblast cytoplasts.

Cybrid clones were isolated by fusing mouse embryonal carcinoma (PCC4) cells with cytoplasts of rat myoblastic cells (L6TG X CAPr). Although some clones were similar to PCC4 (Type II), a high proportion (88%) were differentiated; the differentiated cells had a mesh-like arrangement (Type I) or were flat with many projections (Type III). Protein patterns of both Type I and Type III cells changed markedly from that of PCC4 cells. Type III cells lacked alkaline phosphatase and expressed endo A and B proteins predominantly. One Type III clone produced alpha-fetoprotein and plasminogen activator (visceral endoderm-like), while another clone consisted of trophectodermal cell-like giant cells. Therefore it was shown that introduction of the somatic cell cytoplasm induces differentiation of teratocarcinoma stem cells, suggesting a cytoplasmic element (or elements) regulating gene expression.