Tbx1/Ripply3/retinoic acid signal network that regulates pharyngeal arch development

Abstract

The main feature of the developing pharynx of the vertebrate embryo is the transient appearance of a series of segmental pharyngeal arches. These arches are divided by internal pouches (endoderm) and external clefts (ectoderm) that together comprise the pharyngeal apparatus. The formation of the pharyngeal arches is essential for the development of many organs at later stages, and the pouches give rise to the rudiments of the thymus, parathyroid glands, and ultimobranchial body. During the development of the arches occur the sequential formation of pharyngeal arch arteries and the precise ingrowth of the axons of cranial nerves. Neural crest cells also migrate through each arch to differentiate in appropriate locations. Therefore, defects in pharyngeal arch development lead to deficits of pharyngeal arch arteries and mislocation or cell death of neural crest cells, which cause later malformations in the derivative organs. This chapter first overviews pharyngeal arch development, and then discusses our present knowledge regarding the genetic factors (Tbx1 and Ripply3) and signaling molecules (retinoic acid) that regulate the formation of the pharyngeal arches and their organ derivatives.