Spontaneous induction of an homologous robertsonian translocation, Rb(11.11) in a murine embryonic stem cell line.

Karyotype analysis of a series of established mouse embryonic stem cell (MESC) lines showed that the majority were aneuploid by the 7th and 9th passage and that all lines contained a single Robertsonian (Rb) translocation chromosome with a symmetrical, homologous, arm composition Rb(11.11). Although the chromosomal imbalance makes these MESC lines unsuitable for genetic manipulation in vitro and hence for subsequent production of transgenic animals, the spontaneous occurrence and stable retention of the homologous Rb(11.11) as the only metacentric chromosome in an otherwise all acrocentric karyotype, provides potentially useful cell lines for gene assignment and recombinant DNA studies.