Retinoids control anterior and dorsal properties in the developing forebrain
Aida Halilagic1, Vanessa Ribes, Norbert B Ghyselinck
1MRC Centre for Developmental Neurobiology, King's College London, Guy's Campus, London SE1 1UL, UK.
Developmental Biology
|December 23, 2006
Summary
Retinoids, crucial for forebrain development, regulate cell signaling pathways. This study reveals their role in restricting anterior and dorsal identities in the developing brain and eye.
Area of Science:
- Developmental Biology
- Neuroscience
- Molecular Biology
Background:
- Retinoic acid (RA) synthesized by retinaldehyde dehydrogenase 2 (RALDH2) is vital for forebrain development.
- RA deficiency leads to abnormal forebrain morphogenesis.
- Retinoids regulate cell proliferation and survival in the ventral forebrain via SHH and FGF8 signaling.
Purpose of the Study:
- To investigate the role of retinoids in craniofacial and forebrain development.
- To elucidate the mechanisms by which retinoids modulate signaling pathways in the developing brain and eye.
- To examine the effects of combined RALDH2 and RALDH3 deficiency on embryonic development.
Main Methods:
- Utilized double Raldh2/Raldh3 mouse mutants and vitamin-A-deficient (VAD) quail models.
- Analyzed craniofacial and forebrain phenotypes, including nasal process truncation and eye abnormalities.
- Investigated the impact of retinoids on FGF8, WNT, and BMP4 signaling pathways.
- Examined gene expression patterns (Pax6, Tbx5, Bmp4, Otx2, Mitf) during optic cup development.
Main Results:
- Double Raldh2/Raldh3 mutants exhibit more severe craniofacial defects than single mutants, with truncated nasal processes and exacerbated eye abnormalities.
- In VAD quails, retinoids maintain forebrain anterior and dorsal boundaries by modulating FGF8 and WNT signaling.
- BMP4 and FGF8 signaling are altered in the nasal region, and BMP4 expands ventrally in the optic vesicle.
- Ectopic expression of Pax6, Tbx5, and Bmp4 in the presumptive RPE, with lack of Otx2 and Mitf induction, leads to dorsal transdifferentiation of RPE to neural retina.
Conclusions:
- Retinoids are essential for the survival of ventral forebrain structures.
- Retinoids restrict anterior identity in the telencephalon and dorsal identity in the diencephalon and retina.
- Combined RALDH2 and RALDH3 deficiency results in severe craniofacial and developmental abnormalities.
- Retinoid signaling plays a critical role in patterning the developing brain and eye through modulation of key signaling pathways.
