il\VOLVEMENT OF RETII\OIC ACID II{ - MSpace at the University of ...

and a number of transcription factors which will ultimately lead to the transcription of
targeted genes (Mehta et al. 2003; Nagy et al. 1997). The activation of RXR and RAR
receptors will cause the activation of early response and secondary response genes' The
activation of early response genes will result in the transcription of gene regulation
products that have a potential to initiate the activation of secondary response genes.
Secondary response genes can also be directly activated by the ligand-bound retinoic acid
receptors. The activation of secondary response genes will mediate the regulation of the
processes ofcell differentiation and cell death.
IV.d.Retinoic acid functions
IV.d.l.The role of Retinoic acid in CV system: The critical role of retinoic acid
signaling pathway in vertebrate embryogenesis is supported by a wide distribution of
retinoic acid receptors in embryonic tissue. The expression pattern of RAR and RXR
receptors during mouse development has been described in detail by a number of studies
(Dotle et al. 1989; Dolle et al. 1990; Mangelsdorf et al. 1992; Ruberte et al. 1993;
Ruberte et al. 1992; Ruberte et al. 1990; Ruberte et al. 1991).
IV.d.2.Prenatal life: Retinoic acid is involved in the development of the cardiovascular
system (Morriss-Kay and Ward 1999). Vitamin A depletion is found to cause severe
abnormalities in the development of the aortic arch and cardiac chambers (WILSON and
V/arakany J 1947), which can be prevented by the supplementation of retinol (V/ILSON
et al. 1953). A number of studies have shown that retinoic acid is essential in the early
phases of heart formation (heart tube formation). The fact that CRBP, RBP and retinol
dehydrogenase enzymes are highly expressed in a embryonic heart indicates that the heart
itself may be a one of the most important producers of retinoic acid in embryonic tissue
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