Our data revealed differences between hESC and phESC during propagation and differentiation, as well as molecular differences in imprinting and expression of ECM genes.
Differences in imprinting among alleles tied to differences in DNA methylation could be due to genetic or epigenetic differences.
Thus, we currently know very little about the likelihood and patterns of differences in imprinting effects in males and females.
The differences in imprinting methylation described here are also relevant to observations linking breast cancer susceptibility to early development [ 10].
Amongst others, another possible explanation for these contrasting observations could be differences in imprinting of IGF-1 axis genes, reflecting historical differences in maternal nutrition between generations [ 32].
Additionally, morphological and physiological differences are evident between mouse and human placenta, consistent with differences in imprinting between these two species.
Identifying imprinted DMRs in humans is complicated by species- and tissue-specific differences in imprinting status and the presence of multiple regulatory regions associated with a particular gene, only some of which may be imprinted.
As suggested in the summary review statement above, we have focused on methylation variation being casual for differences in imprinting rather than focusing on whether or not this variation is purely epigenetic or whether it has a genetic basis.
Further experimentation exploring the function of these genes during seed development in each genetic background will be required to determine if differences in imprinting among strains contribute to seed phenotypes.
At first, it was suggested that the variable phenotypic expression of 1p36 deletions might be caused by a parent-of-origin effect in which deletions of the paternally-derived copy of 1p36 were not equivalent to deletions of the maternally-derived copy due to differences in imprinting.
