Taken collectively, these reports suggest that cigarette smoke may elicit some of its downstream consequences on the placental epigenome in both a global- and site-specific fashion (Suter, et al., 2010; Suter, et al., 2011). Moreover, repetitive elements may have specific methylation patterns influenced by environmental exposures, underscoring the need to carefully consider how “globally-representative” a particular repetitive element’s methylation pattern may be without utilizing a representative genome-wide methylation assessment as comparison (Wilhelm-Benartzi, et al., 2011). These findings in the human placenta build on work described by Breton and colleagues in human buccal cells whereby they described that in utero exposure to tobacco smoke is associated with alterations to global and gene-specific methylation (Breton et al., 2009).
