Doctor of Philosophy
Singh, Shiva M.
Fetal alcohol spectrum disorders (FASD) are caused by prenatal alcohol exposure (PAE) and affect 1‑5% of the North American population. Children born with FASD often face maternal separation throughout childhood. How this early life stress (ELS) affects the severity of FASD-related deficits is poorly understood. Using a mouse model, this dissertation establishes that behavioural deficits accumulate following prenatal alcohol exposure and early life stress, assessed using tests for activity, anxiety-like behaviour as well as learning and memory. Hippocampal gene expression was evaluated using RNA-seq followed by clustering of expression profiles through weighted gene co-expression network analysis (WGCNA). A set of transcripts are associated with anxiety-like behaviour (r = 0.79, p = 0.002) and treatment (r = 0.68, p = 0.015). Genes in this module are overrepresented by transcriptional regulation and neurodevelopment genes. One member of this module, Polr2a, is downregulated by the combination of treatments. Hippocampal promoter DNA methylation was assessed using methylated DNA immunoprecipitation sequencing (MeDIP-Seq). Methylation at different genes is affected by each treatment independently, and a unique set of genes are affected by the combination of treatments. PAE leads to altered promoter DNA methylation at genes important for transcriptional regulation and ELS leads to changes at genes important for histone methylation and immune response. The combination of treatments results in DNA methylation changes at genes important for neuronal migration and immune response. The results from the same samples show that genes with altered expression and promoter methylation are critical in brain development and function. Also, there is minimal complementarity between changes in promoter DNA methylation and gene expression. Mechanisms beyond promoter DNA methylation are likely involved in lasting gene expression changes leading to behavioural deficits seen in FASD. Although further research is required to elucidate the mechanism, the results included may be valuable towards early and reliable diagnosis, together with the development of novel strategies for the amelioration of FASD-related deficits.
Summary for Lay Audience
Fetal alcohol spectrum disorders (FASD) result from maternal alcohol consumption during pregnancy. Children born with FASD have a range of behavioural problems that include anxiety and hyperactivity alongside learning and memory deficits. Unfortunately, children born with FASD often face early life stress through maternal separation, various home placements and other adversity. To investigate molecular changes that may explain behavioural problems in children born with FASD, a mouse model was developed. Pregnant mice were exposed to alcohol, then the offspring were subjected to maternal separation as early life stress. Behavioural tests demonstrated FASD-related problems, including anxiety-like behaviour and hyperactivity, as well as learning and memory deficits resulting from each treatment. Behaviours are a result of protein interactions in the brain that are the product of gene expression. Changes in gene expression and promoter DNA methylation (involved in turning genes on or off) were assessed in the hippocampus region of the brain that is critical for behaviour. Gene expression results show that genes involved in immune response and brain maturation are affected by prenatal alcohol exposure and early life stress. Promoter DNA methylation is also affected by prenatal alcohol exposure and early life stress. Interestingly, not all changes in gene expression were directly related to promoter DNA methylation, suggesting the involvement of other regulatory mechanisms in FASD. This research is important for pushing the field of FASD forward by refining an animal model of FASD to include the developmental period after birth. It demonstrates that brain development continues after birth and provides a postnatal window for further negative or positive intervention. Understanding how the still-developing brain responds to the postnatal environment at the molecular level is valuable for the development of potential treatments.
Alberry, Bonnie, "Behavioural And Molecular Consequences Of Postnatal Stress In A Mouse Model Of Fetal Alcohol Spectrum Disorder" (2020). Electronic Thesis and Dissertation Repository. 7600.
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Appendix C - Genes implicated by transcripts in module 19
Appendix D - DE Genes (sleuth).xlsx (261 kB)
Appendix D - Differentially expressed genes (sleuth)
Appendix E - DE Genes (DESeq2).xlsx (32 kB)
Appendix E - Differentially expressed genes (DESeq2)
Appendix F - Promoter DMRs.xlsx (543 kB)
Appendix F - Differentially methylated regions in gene promoters