Development of the asymmetric
human
L E W I S W O L P E R T
Anatomy and Developmental Biology, University College, London WC1E
6BT, UK. E-mail: l.wolpert@ucl.ac.uk
Symmetry across the midline is present in many animals, together with the
left/right asymmetry of several organs, such as the heart in vertebrates. The
development of such asymmetries during embryonic development requires
first the specification of the midline and then specification of left/right. One
model proposes the transfer of molecular asymmetry to the multicellular
level. Nodal expression on the left side in mammals and chicks is a key
event, and is due to the release of calcium on the left possibly involving an
ion pump and the Notch pathway