Retinoic acid signaling in development: Tissue‐specific functions and evolutionary origins

Abstract

Summary: Retinoic acid (RA) is a vitamin A-derived morphogen important for axial patterning and organ formation in developing vertebrates and invertebrate chordates (tunicates and cephalochordates). Recent analyses of genomic data have revealed that the molecular components of the RA signaling cascade are also present in other invertebrate groups, such as hemichordates and sea urchins. In this review, we reassess the evolutionary origins of the RA signaling pathway by examining the presence of key factors of this signaling cascade in different metazoan genomes and by comparing tissue-specific roles for RA during development of different animals. This discussion of genomic and developmental data suggests that RA signaling might have originated earlier in metazoan evolution than previously thought. On the basis of this hypothesis, we conclude by proposing a scenario for the evolution of RA functions during development, which highlights functional gains and lineage-specific losses during metazoan diversification. genesis 46:640-656,

Structural shifts of aldehyde dehydrogenase enzymes were instrumental for the early evolution of retinoid-dependent axial patterning in metazoans

“…The resulting comprehensive data set was complemented with information on developmental gene expression of ALDH1/2s in the cephalochordate amphioxus (Branchiostoma floridae) and the ascidian tunicate Ciona intestinalis. These two invertebrate chordate models possess functional RA signaling cascades and are pivotal models for understanding vertebrate origins from both a genomic and a developmental perspective (4,(23)(24)(25)(26). Together, this work provides support for the hypothesis that some intercellular signaling mechanisms evolved from cellular detoxification pathways.…”

Retinoic acid and dexamethasone induce differentiation and maturation of somatotroph cells at different stages in vitro

“…RA is an active metabolic product of vitamin A and plays an important role in the growth, development and cell differentiation of vertebrates, particularly during embryonic development [3]. The expression of RA and its activating enzyme, type 2 retinal dehydrogenase, in embryonic pituitary cells occurs earlier than expression of Pit-1 and GH [4,6].…”

“…Retinoic acid (RA) promotes the differentiation of numerous types of cells during vertebrate embryogenesis [3]. Some reports indicate that RA plays an important role in the early differentiation of GH cells [4,5].…”

Development of the Immune System - Early Nutrition and Consequences for Later Life

“…In absence of this enzyme proper lymphoid follicles are not developed. Retinoic acid is the active form of vitamin A and is important during embryogenesis, when axial patterning and organ formation take place (Campo-Paysaa, Marletaz et al 2008). RA is involved in nerve development and expression of RALDH is found in nerve fibers near the lymph node anlagen, where RA can influence stromal cells to produce specific chemokines.…”