ABSTRACT
Introduction .......................................................................................................279 RA Receptors Have Pleiotropic and Mostly Redundant
Developmental Functions.............................................................................281 Retinoic Acid Synthesis Is Enzymatically Regulated in Embryonic Tissues.....282 Differential Expression Patterns of Murine Retinaldehyde Dehydrogenases.....283 RALDH2 Is Mainly Responsible for RA Synthesis at Early
Embryonic Stages.........................................................................................285 RA-Rescue of Null Mutant Embryos Unveils Additional RALDH2
Developmental Functions.............................................................................286 Decreased RALDH2-Mediated RA Synthesis Leads to a DiGeorge
Syndromelike Phenotype..............................................................................288 Conditional Mutagenesis: An Alternative Approach to Investigate
Tissue-Specific RALDH2 Functions............................................................289 Acknowledgments .............................................................................................291 References .........................................................................................................291
The lipophilic vitamin A (retinol) and its derivatives, the retinoids, have long been known to be essential for proper embryonic and fetal development. Maternal vitamin A deficiency (VAD) in mice or rats leads to a well-defined spectrum of fetal abnormalities affecting many organ systems.1 Most severe VAD conditions can lead to earlier embryonic defects in rodents, although such experiments require a retinoid supplementation to be performed during early pregnancy, in
