Maturation-dependent alcohol resistance in the developing mouse: cerebellar neuronal loss and gene expression during alcohol-vulnerable and -resistant periods.
BACKGROUND
Alcohol abuse during pregnancy injures the fetal brain. One of alcohol's most important neuroteratogenic effects is neuronal loss. Rat models have shown that the cerebellum becomes less vulnerable to alcohol-induced neuronal death as it matures. We determined if maturation-dependent alcohol resistance occurs in mice and compared patterns of gene expression during the alcohol resistant and sensitive periods.


METHODS
Neonatal mice received alcohol daily over postnatal day (PD) 2 to 4 or PD8 to 10. Purkinje cells and granule cells were quantified on PD25. The temporal expression patterns of 4 neuro-developmental genes and 3 neuro-protective genes in the cerebellum were determined daily over PD0 to 15 to determine how gene expression changes as the cerebellum transitions from alcohol-vulnerable to alcohol-resistant. The effect of alcohol on expression of these genes was determined when the cerebellum is alcohol sensitive (PD4) and resistant (PD10).


RESULTS
Purkinje and granule cells were vulnerable to alcohol-induced death at PD2 to 4, but not at PD8 to 10. Acquisition of maturation-dependent alcohol resistance coincided with changes in the expression of neurodevelopmental genes. The vulnerability of cerebellar neurons to alcohol toxicity declined in parallel with decreasing levels of Math1 and Cyclin D2, markers of immature granule cells. Likewise, the rising resistance to alcohol toxicity paralleled increasing levels of GABA alpha-6 and Wnt-7a, markers of mature granule neurons. Expression of growth factors and genes with survival promoting function (IGF-1, BDNF, and cyclic AMP response element binding protein) did not rise as the cerebellum transitioned from alcohol-vulnerable to alcohol-resistant. All 3 were expressed at substantial levels during the vulnerable period and were not expressed at higher levels later. Acute alcohol exposure altered the expression of neurodevelopmental genes and growth factor genes when administered either during the alcohol vulnerable period or resistant period. However, the patterns in which gene expression changed varied among the genes and depended on timing of alcohol administration.


CONCLUSIONS
Mice have a temporal window of vulnerability in the first week of life, during which cerebellar neurons are more sensitive to alcohol toxicity than during the second week. Expression of genes governing neuronal maturation changes in synchrony with the acquisition of alcohol resistance. Growth factors do not rise as the cerebellum transitions from alcohol-vulnerable to alcohol-resistant. Thus, a process intrinsic to neuronal maturation, rather than rising levels of growth factors, likely underlies maturation-dependent alcohol resistance.
Division of Child Neurology, Department of Pediatrics, 200 Hawkins Dr., University of Iowa College of Medicine, Iowa City, IA 52242, USA. bahri-karacay@uiowa.edu
Bahri
B
Karaçay
Shenglan
S
Li
Daniel J
DJ
Bonthius
D000375:Aging / Q000378:metabolism / Q000473:pathology*; D000428:Alcohol Drinking / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics / Q000378:metabolism; D002492:Central Nervous System Depressants / Q000494:pharmacology; D002531:Cerebellum / Q000187:drug effects / Q000473:pathology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D056742:Cyclin D2; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D000431:Ethanol / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000473:pathology*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D019208:Brain-Derived Neurotrophic Factor; D002492:Central Nervous System Depressants; D017362:Cyclic AMP Response Element-Binding Protein; D056742:Cyclin D2; D016213:Cyclins; D000431:Ethanol; D007334:Insulin-Like Growth Factor I; D051153:Wnt Proteins; C500943:Atoh1 protein, mouse; C486196:Ccnd2 protein, mouse; C492004:Creb1 protein, mouse; C490508:Wnt7a protein, mouse