Mechanisms of monozygotic (MZ) twinning: a possible role for the cell adhesion molecule, E-cadherin

Monozygotic (MZ) twins account for about one-third of all twins. Most MZ twins arise sporadically but there are familial occurrences. The causes of MZ twinning are largely speculative but involve both genetic and environmental factors. Genetic factors could include cell adhesion molecules and factors involved in growth and differentiation of the placenta and fetus. In this study, we examine the possible role of E-cadherin, a cell adhesion molecule, in the causation of twinning. A common polymorphism in the E-cadherin gene reduces expression of E-cadherin by up to 68%. We examined the E-cadherin polymorphism in DNA extracted from placental tissue from 121 MZ twins, 99 DZ twins, and 93 singletons. There was no significant difference in the distribution of the E-cadherin polymorphism in MZ twins although there was a slight over-representation of homozygotes for the polymorphism in MZ twins. We conclude that there is insufficient evidence to suggest that decreased E-cadherin expression alone is a causative factor in MZ twinning but it could be a contributory factor along with other genetic and environmental influences.