Variation in gene expression and aberrantly regulated chromosomal regions in cloned mice

DNA microarray analysis has been carried out to know the precise genome-wide gene expression profiles of somatic cloned mice derived from Sertoli or cumulus cells. It demonstrated unexpectedly large epigenetic diversity in neonatal cloned mice, despite their normal appearance and genetic identity. In three neonatal tissues of the cloned mice, a total of 9–40% of the examined genes exhibited more than two times higher or lower levels in donor cell-dependent or -independent manner compared to those in normal controls. Relatively few (0.4–4%) of the genes exhibited up- or down-regulation in the same manner in both types of clones. Cluster analysis of the variations in gene expression led to identification of several chromosomal regions in which gene expression was aberrantly controlled in the somatic clones. These results provide a more complete understanding of how somatic clones differ from each other and from normal individuals produced by sexual reproduction and indicate the significant difficulties that exist for the application of somatic cloning in regenerative medicine. Keywords: clone mouse Neonatal tissues of four Sertoli cell-derived clones, four cumulus cell-derived clones, and four normal controls (two males and two females) were analysed by DNA microarray. Cloning by nuclear transfer was performed according to the method developed by Wakayama et al., with slight modifications. Immature Sertoli and cumulus cells were collected from newborn male (0-8 days after birth) and mature female (2-3 months old) C57BL/6 x DBA/2 F1(BDF1) mice, respectively, and used as nuclear donor cells. Cloned pups were obtained from the recipients at term (day 19.5) by caesarean section. All control mice were genetically identical to the somatic cell clones, e.g., BDF1. The control neonates were produced by in vitro fertilization.