Aberrant protein expression in the placenta of cloned mouse derived from embryonic stem cell

Placentomegaly is a common phenotype in cloned mice. To assess differences in protein expression between placentae of cloned and uncloned mice, we used a proteomic approach involving 2-dimensional electrophoresis (DE) and MALDI-TOF MS. Proteins within isoelectric point range of 4–11 separately were analyzed in 2-DE with 3 replications of each sample. A total of approximately 3500 spots were detected in placental 2-DE stained with Coomassie blue. In the comparison of normal and cloned samples, a total of 41 spots were identified as differentially expressed proteins, of which 25 spots were up-regulated proteins such as TIMP-2, glutamate-ammonia, and esterase 10, while 16 spots were down-regulated proteins such as PBEF and annexin A1. The TIMP-2, which is related to extracellular matrix degradation and tissue remodeling processes, is an inhibitor of MMP-2. The PBEF is related to inhibition of apoptosis and induction of spontaneous labor. Western blot analysis confirmed increased TIMP-2 expression and decreased PBEF expression in cloned placentae compared with normal controls. Our results demonstrated composite profiles of key proteins involved in abnormal hypertrophic placenta derived from cloned mice and suggested that the reason for the placentomegaly may be due to abnormal gene expression in cloned mice.