Non-overlapping expression of CRBP I and CRABP I during pattern formation of limbs and craniofacial structures in the early mouse embryo

The distribution of cellular retinoic acid-binding protein I during odontogenesis in the rat incisor

Retinoids are important molecules in various aspects of embryological development. Here the distribution of cellular retinoic acid-binding protein I (CRABPI) was studied in the continuously growing incisor of adult rats using an affinity-purified rabbit polyclonal antibody. CRABPI was present throughout the presecretory and secretory ameloblast layer. The protein disappeared from that layer during its maturation phase. The adjacent dental mesenchyme of the developing pulp stained positively for CRABPI, especially in the layer immediately beneath the fully differentiated odontoblasts. Little CRABPI was present in the odontoblast layer itself. The distribution of CRABPI, both in the undifferentiated basal region of the incisor tooth and associated with the cells during hard-tissue formation, suggests a role for this molecule during differentiation and hard-tissue genesis.

Retinoic acid induction and regional differentiation prefigure olfactory pathway formation in the mammalian forebrain

We have used an in vitro assay to identify sources of retinoic acid (RA) and transgenic mice to identify target domains in the developing forebrain. RA participates in a sequence of events that leads to the establishment of the olfactory pathway. First, the lateral cranial mesoderm activates an RA-inducible transgene in neuroepithelial cells in the olfactory placode and the ventrolateral forebrain. Then, neurons and neurites begin to differentiate in these two regions. Finally, olfactory axons grow specifically into the ventrolateral forebrain and subsequently are limited to the olfactory bulb rudiment. The coordination of these events, perhaps by common signals, implies that retinoid induction and retinoid-activated region-specific transcriptional regulation may help to define a forebrain subdivision and the peripheral neurons that provide its primary innervation.