Fetal ethanol exposure activates protein kinase A and impairs Shh expression in prechordal mesendoderm cells in the pathogenesis of holoprosencephaly.
BACKGROUND
In humans, fetal ethanol exposure can cause holoprosencephaly (HPE), one of the most common birth defects that is characterized by brain, facial, and oral abnormalities. However, the pathogenesis of HPE is not clear. In the present study, we investigated the teratogenic mechanism of ethanol-induced brain and facial malformations in mice.


METHODS
Pregnant C57BL/6J mice were administered ethanol on E7 and facial and brain malformations were characterized on E10.5. We examined the effect of fetal ethanol exposure on Shh expression and activation of protein kinase A (PKA) because mutations in the human Shh gene are the most frequent cause of autosomal-dominant inherited HPE and PKA is a potent endogenous antagonist of Shh signaling.


RESULTS
Fetal ethanol exposure on E7 induced severe midline defects characteristic of HPE. Ethanol exposure impaired Shh expression and induced excessive apoptosis only along the anterior edge of the prechordal mesendoderm (PME). In addition, ethanol activated PKA in anterior PME cells. Pretreatment of embryos with antioxidants, such as vitamins C or E, prevented the development of ethanol-induced HPE.


CONCLUSIONS
Shh expression in PME cells is involved in the pathogenesis of ethanol-induced HPE. Ethanol may impair Shh expression indirectly by activating PKA. The inhibition of excessive apoptosis in PME cells by antioxidants implies that oxidative stress may underlie the teratogenic actions of ethanol. Thus, antioxidant treatment may be a simple preventative measure that could reduce the incidence of HPE following fetal ethanol exposure.
Aoto
Kazushi
K
Molecular Neuropathology Group, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198.
Shikata
Yayoi
Y
Higashiyama
Daisuke
D
Shiota
Kohei
K
Motoyama
Jun
J
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001205:Ascorbic Acid / Q000494:pharmacology; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004707:Endoderm / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D000431:Ethanol / Q000633:toxicity*; D005145:Face / Q000196:embryology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D016142:Holoprosencephaly / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism; D018811:Maternal Exposure; D033261:Maternal-Fetal Relations; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009672:Notochord / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D011247:Pregnancy; D013687:Telencephalon / Q000187:drug effects / Q000196:embryology; D014810:Vitamin E / Q000494:pharmacology
D053823:Hedgehog Proteins; C465570:Shh protein, mouse; D014810:Vitamin E; D000431:Ethanol; D017868:Cyclic AMP-Dependent Protein Kinases; D001205:Ascorbic Acid