Divergent and overlapping hippocampal and cerebellar transcriptome responses following developmental ethanol exposure during the secondary neurogenic period

• Published in: Alcoholism, clinical and experimental research Vol. 45; no. 7; pp. 1408 - 1423
• Main Authors: Pinson, Marisa R., Holloway, Kalee N., Douglas, James C., Kane, Cynthia J. M., Miranda, Rajesh C., Drew, Paul D.
• Format: Journal Article
• Language: English
• Published: Austin Wiley Subscription Services, Inc 01-07-2021; John Wiley and Sons Inc
• Subjects: Adaptation; Alcohol use; Alcoholism; Cell cycle; Cerebellum; Divergence; Ethanol; fetal alcohol spectrum disorders; Gene expression; Hedgehog protein; Hippocampus; Juveniles; Mitosis; Neonates; Neurogenesis; Neuroscience; Original; postnatal ethanol; RNA‐seq; Transcriptomes; Transcriptomics
• ISSN: 0145-6008; 1530-0277
• DOI: 10.1111/acer.14633

Background
The developing hippocampus and cerebellum, unique among brain regions, exhibit a secondary surge in neurogenesis during the third trimester of pregnancy. Ethanol (EtOH) exposure during this period is results in a loss of tissue volume and associated neurobehavioral deficits. However, mechanisms that link EtOH exposure to teratology in these regions are not well understood. We therefore analyzed transcriptomic adaptations to EtOH exposure to identify mechanistic linkages.
Methods
Hippocampi and cerebella were microdissected at postnatal day (P)10, from control C57BL/6J mouse pups, and pups treated with 4 g/kg of EtOH from P4 to P9. RNA was isolated and RNA‐seq analysis was performed. We compared gene expression in EtOH‐ and vehicle‐treated control neonates and performed biological pathway‐overrepresentation analysis.
Results
While EtOH exposure resulted in the general induction of genes associated with the S‐phase of mitosis in both cerebellum and hippocampus, overall there was little overlap in differentially regulated genes and associated biological pathways between these regions. In cerebellum, EtOH additionally induced gene expression associated with the G2/M‐phases of the cell cycle and sonic hedgehog signaling, while in hippocampus, EtOH‐induced the pathways for ribosome biogenesis and protein translation. Moreover, EtOH inhibited the transcriptomic identities associated with inhibitory interneuron subpopulations in the hippocampus, while in the cerebellum there was a more pronounced inhibition of transcripts across multiple oligodendrocyte maturation stages.
Conclusions
These data indicate that during the delayed neurogenic period, EtOH may stimulate the cell cycle, but it otherwise results in widely divergent molecular effects in the hippocampus and cerebellum. Moreover, these data provide evidence for region‐ and cell‐type‐specific vulnerability, which may contribute to the pathogenic effects of developmental EtOH exposure.
Comparative RNAseq analyses of developing mouse cerebellum and hippocampus identified common and unique actions of ethanol during their shared secondary neurogenic period for granule cell formation. In both regions, ethanol significantly induced cell‐cycle genes associated with S‐phase. However, ethanol preferentially altered oligodendrocyte lineage and microglia transcripts in cerebellum, while inhibiting inhibitory interneuron lineage genes in hippocampus. These effects, accompanied by effects on divergent molecular pathways, suggest significant region and cell‐type specific vulnerabilities to ethanol which may contribute to neurodevelopmental disorders.