Article
- The EMBO Journal (2003) 22, 5304 - 5312
- doi:10.1093/emboj/cdg507
Subject Categories:
Pluripotency deficit in clones overcome by clone–clone aggregation: epigenetic complementation?
Michele Boiani1, Sigrid Eckardt2, N. Adrian Leu2, Hans R. Schöler1 and K. John McLaughlin2
- Germline Development, Center for Animal Transgenesis and Germ Cell Research, New Bolton Center, University of Pennsylvania, Kennett Square, PA 19348, USA
- Developmental Epigenetics Groups, Center for Animal Transgenesis and Germ Cell Research, New Bolton Center, University of Pennsylvania, Kennett Square, PA 19348, USA
Correspondence to:
K. John McLaughlin, E-mail: kjmclaug@vet.upenn.edu
Received 10 June 2003; Accepted 13 August 2003; Revised 6 August 2003
Abstract
Abnormal gene expression patterns in somatic cell clones and their attrition in utero are commonly considered a consequence of errors in nuclear reprogramming. We observe that mouse clone blastocysts have less than half the normal cell number, and that higher cell number correlates with correct expression of Oct4, a gene essential for peri-implantation development and embryonic pluripotency. To increase the cell number, we aggregated genetically identical clones at the 4-cell stage. Clone–clone aggregates did not form more blastocysts, but the majority expressed Oct4 normally and had higher rates of fetal and postnatal development. Fertilized blastocysts with low cell numbers, induced by removal of two blastomeres at the 4-cell stage, did not exhibit abnormal Oct4 expression, indicating that improved gene expression and post-implantation development of clone–clone aggregates is not a consequence of increased cell number. Rather, we propose that complementation of non-cell-autonomous defects of genetically identical, but epigenetically different, embryos results in improved gene expression in clone–clone aggregates.
Keywords:
- aggregation,
- cloning,
- mouse chimera,
- nuclear transfer,
- pluripotency
