Methylation is one of the main epigenetic markers, which can change during the course of life according to age and environmental factors, like smoking, and may be even expressed differently in different tissues. New research shows methylation patterns could also hold a life-long record of such dramatic events as preterm birth.
Preterm birth is known to be associated with such long-term factors as impaired physical and cognitive development and susceptibility to chronic conditions, including cardiovascular, respiratory, visual, auditory disorders and others. However, the underlying molecular mechanisms of these health effects are unclear.
A new study (PDF), which was published in Genome Medicine, suggests that methylation patterns could hold a clue to the molecular signature of preterm birth.
DNA methylation patterns of babies born before 31 weeks of gestation and matched full-term controls at birth and 18 years of age were compared to prove this hypothesis. It should be noted that most observed differences in methylation patterns were shown to resolve by the age of 18. These were suggested to be related to gestational age and cell composition, which is expected to be different in extremely preterm babies. However, ten genomic loci were found to hold persistent methylation differences even after the age of 18.
Due to premature transition from safe uterine environment to outside world, preemies are exposed to a variety of environmental factors, which would otherwise be milder or at all absent. Premature infants experience dramatic change in temperature and nutrition, are exposed to external toxins, oxygen deprivation and other stressors. Most of these might only have short-time effects; however, some factors leave a permanent molecular legacy. In fact, studies in mice have demonstrated that full-term in utero nutrition and post-natal maternal care leave permanent epigenetic markers on DNA.
Further research in the area is likely to reveal even more epigenetic variability between premature and term babies, which could explain some of the long-term health effects experienced by preterm babies during infancy and later life.