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Mech Dev 2014 Aug 01;133:91-104. doi: 10.1016/j.mod.2014.05.004.
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Retinoic acid induced-1 (Rai1) regulates craniofacial and brain development in Xenopus.

Tahir R , Kennedy A , Elsea SH , Dickinson AJ .

Retinoic acid induced-1 (RAI1) is an important yet understudied histone code reader that when mutated in humans results in Smith-Magenis syndrome (SMS), a neurobehavioral disorder accompanied by signature craniofacial abnormalities. Despite previous studies in mouse and human cell models, very little is known about the function of RAI1 during embryonic development. In the present study, we have turned to the model vertebrates Xenopus laevis and Xenopus tropicalis to better understand the developmental roles of Rai1. First we demonstrate that the Rai1 protein sequence is conserved in frogs, especially in known functional domains. By in situ hybridization we revealed expression of rai1 in the developing craniofacial tissues and the nervous system. Knockdown of Rai1 using antisense morpholinos resulted in defects in the developing brain and face. In particular, Rai1 morphants display midface hypoplasia and malformed mouth shape analogous to defects in humans with SMS. These craniofacial defects were accompanied with aberrant neural crest migration and reduction in the size of facial cartilage elements. Rai1 morphants also had defects in axon patterns and decreased forebrain ventricle size. Such brain defects correlated with a decrease in the neurotrophic factor, bdnf, and increased forebrain apoptosis. Our results emphasize a critical role of Rai1 for normal neural and craniofacial development, and further the current understanding of potential mechanisms that cause SMS.

PubMed ID: 24878353
Article link: Mech Dev

Species referenced: Xenopus tropicalis Xenopus laevis
Genes referenced: bdnf eef1a1 grap2 rab40b rai1 sms tfap2a
GO keywords: brain development [+]
Antibodies: Neuronal Ab4
Morpholinos: rai1 MO1 rai1 MO2

Disease Ontology terms: Smith-Magenis syndrome

Article Images: [+] show captions