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Published on: November 6, 2014
Genetic analysis of RXR alpha developmental function: convergence of RXR and RAR signaling pathways in heart and eye
P Kastner1, J M Grondona, M Mark
1Laboratoire de Génétique Moléculaire des Eucaryotes, Institut de Chimie Biologique, Faculté de Médecine, Strasbourg, France.
Abstract:
A null mutation was generated in the mouse RXR alpha gene by targeted disruption. Growth deficiency occurred in heterozygote mice. Null mutants died in utero and displayed myocardial and ocular malformations. These malformations belong to the fetal vitamin A deficiency syndrome, supporting the idea that RXR alpha is involved in retinoid signaling in vivo. A phenotypic synergy was observed when the RXR alpha mutation was introduced into RAR alpha or RAR gamma mutant backgrounds: RXR alpha null mutants and RXR alpha +/-/RAR gamma-/- double mutants displayed similar ocular defects, which became more severe in RXR alpha-/-/RAR gamma+/- and RXR alpha-/-/RAR gamma-/- mutants. Furthermore, RXR alpha/RAR double mutants exhibited several malformations not seen in single mutants. This functional convergence strongly suggests that RXR alpha/RAR heterodimers mediate retinoid signaling in vivo.
Insights
Retinoid X receptor alpha (RXR alpha) is crucial for embryonic development, as its absence causes severe malformations and in utero death. RXR alpha and RAR heterodimers are essential for retinoid signaling in vivo.
Area of Science:
- Developmental Biology
- Molecular Genetics
- Genomics
Background:
- Retinoids are vital signaling molecules regulating embryonic development.
- Retinoid receptors, including RXR alpha and RARs, mediate these effects.
- The in vivo function of RXR alpha in retinoid signaling remains incompletely understood.
Purpose of the Study:
- To investigate the in vivo role of RXR alpha in embryonic development.
- To elucidate the functional relationship between RXR alpha and RARs in retinoid signaling.
Main Methods:
- Generation of a null mutation in the mouse RXR alpha gene via targeted disruption.
- Analysis of phenotypic consequences in RXR alpha heterozygote and null mutant mice.
- Introduction of RXR alpha mutations into RAR alpha and RAR gamma mutant backgrounds to assess genetic interactions.
Main Results:
- RXR alpha null mutants exhibit embryonic lethality with myocardial and ocular malformations, characteristic of fetal vitamin A deficiency.
- Heterozygote RXR alpha mice display growth deficiency.
- Phenotypic synergy observed in RXR alpha/RAR double mutants suggests functional convergence and interaction between these receptor types.
Conclusions:
- RXR alpha is essential for embryonic development and mediates retinoid signaling in vivo.
- RXR alpha/RAR heterodimers play a critical role in transducing retinoid signals during development.
- Genetic interactions highlight the complex interplay of retinoid receptors in establishing normal development.
