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Phenytoin-induced alterations in craniofacial gene expression
J Gelineau-van Waes1, G D Bennett, R H Finnell
1Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station 77843-4458, USA.
Insights
Phenytoin exposure during pregnancy disrupts embryonic development, causing Fetal Hydantoin Syndrome. This study reveals phenytoin alters gene expression, particularly retinoic acid receptors, impacting craniofacial development.
Area of Science:
- Developmental Biology
- Teratology
- Molecular Genetics
Background:
- In utero exposure to phenytoin, an anticonvulsant, causes Fetal Hydantoin Syndrome, characterized by developmental abnormalities.
- The molecular mechanisms underlying phenytoin-induced embryopathy, especially craniofacial malformations, are not fully understood.
Purpose of the Study:
- To investigate the impact of phenytoin exposure on gene expression during critical periods of mouse craniofacial development.
- To identify specific genes and molecular pathways affected by phenytoin that may contribute to Fetal Hydantoin Syndrome.
Main Methods:
- Pregnant SWV mice received phenytoin from gestational day 6.5.
- Craniofacial tissues from exposed and control embryos were analyzed at various developmental time points.
- Gene expression levels of 36 candidate genes were quantitatively assessed using in situ transcription and reverse Northern blot hybridization.
Main Results:
- Phenytoin exposure significantly altered the expression of several genes during craniofacial morphogenesis.
- Increased expression of retinoic acid receptors (RAR alpha, beta, gamma) was observed.
- Elevated gene expression of laminin beta 1 and growth factors (IGF-2, TGF alpha, TGF beta 1) was noted in phenytoin-exposed embryos.
Conclusions:
- Phenytoin-induced alterations in RAR isoform expression may disrupt downstream gene regulation essential for normal craniofacial development.
- Coordinated changes in gene expression during critical developmental windows likely contribute to the dysmorphogenesis seen in Fetal Hydantoin Syndrome.
- This study provides insights into the molecular pathogenesis of phenytoin embryopathy, highlighting the role of retinoic acid signaling pathways.
Abstract:
In utero exposure to the anticonvulsant drug phenytoin has been shown to alter normal embryonic development, leading to a pattern of dysmorphogenesis known as the Fetal Hydantoin Syndrome. This embryopathy is characterized by growth retardation, microcephaly, mental deficiency, and craniofacial malformations, although the precise mechanism(s) by which phenytoin alters normal developmental pathways remains unknown. To better understand the molecular events involved in the pathogenesis of phenytoin-induced congenital defects, alterations in gene expression were examined during critical periods of craniofacial development. Pregnant SWV mice were administered phenytoin (60 mg/kg/day) from gestational day 6.5 until they were sacrificed at selected developmental time points. Tissue from the craniofacial region of control and exposed embryos was isolated, and samples were subjected to in situ transcription, antisense RNA amplification, and hybridization on reverse Northern blots to quantitatively assess expression of 36 candidate genes. Chronic phenytoin exposure significantly altered expression of several genes at distinct times during morphogenesis. Results of these studies show that expression of the retinoic acid receptors (RAR) alpha, beta, and gamma were significantly increased by phenytoin exposure. Elevations in gene expression of laminin beta 1, and the growth factors IGF-2, TGF alpha, and TGF beta 1, were also demonstrated in the craniofacial region of phenytoin-exposed embryos. As several of these genes are transcriptionally regulated by retinoic-acid-responsive elements in their promoter regions, phenytoin-induced alterations in expression of the RAR isoforms may have severe downstream consequences in the regulation of events necessary for normal craniofacial development. Such alterations occurring coordinately at critical times during craniofacial development may account for the dysmorphogenesis often associated with phenytoin exposure.