Pluripotent embryonic stem cell lines can be derived from tw5/tw5 blastocysts.

Abstract

Mouse embryos homozygous for tw5, a recessive lethal mutation in the t complex located on chromosome 17, develop normally until the elongated egg cylinder stage, approximately 6.5 days after fertilization. At this time, the endoderm is morphologically abnormal and the embryonic ectoderm begins to show signs of pyknosis. Death of the embryo usually occurs within the next 2 days (ref. 1). A serious difficulty in the study of lethal t-mutant gene expression during embryogenesis has been to obtain appropriate experimental material, particularly during the period immediately following implantation. Recently, a method involving the use of teratocarcinoma-conditioned medium was devised for establishing pluripotent stem cell cultures directly from the inner cell mass (ICM) of a normal mouse blastocyst2. Using this method, we have established three embryonic stem cell lines derived from embryos carrying tw5. We report here that one of the cell lines is homozygous for the mutation (tw5/tw5), whereas the other two are heterozygous (+/tw5). When injected into athymic mice, each cell line is capable of forming tumours that contain differentiated derivatives of all three primary germ layers.