DNA Methylation Errors in Cloned Mice Disappear with Advancement of Aging

Abstract

Cloned animals have various health problems. Aberrant DNA methylation is a possible cause of the problems. Restriction landmark genomic scanning (RLGS) that enabled us to analyze more than 1,000 CpG islands simultaneously demonstrated that all cloned newborns had aberrant DNA methylation. To study whether this aberration persists throughout the life of cloned individuals, we examined genome-wide DNA methylation status of newborn (19.5 dpc, n=2), adult (8-11 months old, n=3), and aged (23-27 months old, n=4) cloned mice using kidney cells as representatives. In the adult and aged groups, cloning was repeated using cumulus cells of the adult founder clone of each group as nucleus donor. Two newborn clones had three with aberrantly methylated loci, which is consistent with previous reports that all cloned newborns had DNA methylation aberrations. Interestingly, we could detect only one aberrantly methylated locus in two of the three adult clones in mid-age and none of four senescent clones, indicating that errors in DNA methylation disappear with advancement of animals' aging.

Quantification of Leukocyte Genomic 5-Methylcytosine Levels Reveals Epigenetic Plasticity in Healthy Adult Cloned Cattle

“…In the future, it will be interesting to compare the success rate of different cloning protocols with respect to healthy animals and their DNA methylation levels and to evaluate the possibility of a breedspecific susceptibility to technical constraints by testing the same conditions in different breeds. Moreover, our data do not confirm a normalization of DNA methylation differences between clones and nonclones with advancement of age, as suggested by a study with a limited number of SCNT cloned mice (Senda et al, 2007). Instead, our data support the alternative hypothesis discussed by Senda et al (2007) that only cloned animals with a more appropriate methylation status can survive to adulthood.…”

“…Moreover, our data do not confirm a normalization of DNA methylation differences between clones and nonclones with advancement of age, as suggested by a study with a limited number of SCNT cloned mice (Senda et al, 2007). Instead, our data support the alternative hypothesis discussed by Senda et al (2007) that only cloned animals with a more appropriate methylation status can survive to adulthood. This assumption is further supported by data from gene-specific analyses that revealed more severely altered epigenetic marks in clones that died soon after birth than in animals that died as juveniles (Lin et al, 2008).…”

“…High rates of embryonic and fetal mortality (Rhind et al, 2003a;Yang et al, 2007a) and an increased incidence of congenital defects (Chavatte-Palmer et al 2002;Rhind et al, 2003aRhind et al, , 2003b have been linked to perturbations in developmentally important epigenetic marks such as DNA methylation and histone modifications (Humpherys et al, 2001;Lin et al, 2008;Liu et al, 2008;Ohgane et al, 2001Ohgane et al, , 2004Santos et al, 2003). Clones that develop into adults have nevertheless been assumed to possess a normalized epigenome that corresponds to their normal phenotype (Lanza et al, 2001;Senda et al, 2007).…”

Treatment with a Histone Deacetylase Inhibitor after Nuclear Transfer Improves the Preimplantation Development of Cloned Bovine Embryos

“…Because such abnormalities of clones are not transmitted to their progenies [7][8][9][10][11][12], most of the developmental problems of clones are believed to be the results of epigenetic defects [13]. In fact, several studies have revealed abnormal epigenetic modifications such as DNA methylation and histone modifications in SCNT embryos [14][15][16][17].A wide variety of histone deacetylase inhibitors (HDACi) of both natural and synthetic origin has been reported [18]. Trichostatin A (TSA), which is a natural product isolated from Streptomyces hygroscopicus [19], is one of the most frequently used drugs for various studies as a selective HDACi.…”

Faithful reprogramming to pluripotency in mammals - what does nuclear transfer teach us?

“…Even if clones that develop into adults have been assumed to possess a normalized epigenome that corresponds to their normal phenotype (Lanza et al, 2001;Senda et al, 2007), it remains generally considered that those animals are survivors of the poorly efficient process of full reprogramming to totipotency (Jouneau and Renard, 2003; see Fig. 1).…”