To date the etiology of the association called VACTERL remains a mystery. Interestingly, clues as to the origin of this collection of defects may reside in an old hypothesis concerning the midline as a developmental field as postulated by Dr. John Opitz. This theory suggested that the midline was not a separate entity, but could be influenced by other developmental signals. With new information concerning the origin of the left-right axis (laterality) and the importance of communications between this axis and the cranio-caudal (anterior-posterior) axis for normal development, it has become clear that coordination of the molecular signals responsible for specification of these domains is essential for normal development. In fact, if the signals regulating laterality are disrupted, then midline and other defects can occur as has been observed in cases of heterotaxy, presumably because of a disruption in this coordinated signaling effort. Thus, the origins of the defects commonly observed in the VACTERL association may be due to altered signaling responsible for establishing the left-right axis.
Keywords: VACTERL; ZIC3; heterotaxy; laterality; left-right axis; midline.
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