Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Dr. Shiva Singh

Abstract

Fetal Alcohol Spectrum Disorder (FASD) is an umbrella term referring to a range of physical, behavioural, and cognitive deficits resulting from prenatal alcohol exposure. The resulting abnormalities are heterogeneous and often attributed to timing and dosage of alcohol exposure. However, the specific effects of developmental timing are not well-known.

This research used C57BL/6J (B6) as an animal model for early (human trimester one) and mid-gestation (human trimester two) alcohol exposure. Pregnant B6 mice were injected with 2.5 g/kg ethanol on gestational day (GD) 8 and 11 (trimester one equivalent), or on GD 14 and 16 (trimester two equivalent). Resulting pups were followed from birth to adulthood using FASD-relevant behavioural tests. At postnatal day (PD) 70, whole brain tissues were extracted. A third group of dams were injected on GD 16 (short-term). Two hours post injection, fetal brains were removed. Brains were used for genome-wide expression analysis, including microRNAs. Downstream analyses were completed using software packages and online databases.

All ethanol-treated pups showed motor skill delays, increased activity, and spatial learning deficits. Gene expression analysis resulted in altered expression of 48 short-term genes between ethanol and control mice treated during the second trimester. Fifty-five and 68 genes were differentially-expressed in the long-term analyses of mice treated during trimester one and two, respectively. Genes involved in immune system response were disrupted across all treatments. Disrupted short-term processes included cytoskeleton development and immunological functions. Processes altered in long-term exposures included stress signaling, DNA stability, and cellular proliferation. MicroRNA analyses returned eight and 20 differentially-expressed miRNAs in trimesters one and two, respectively. Target filtering of trimester one microRNAs and mRNAs resulted in inverse relationships between miR-532-5p and Atf1, Itpripl2, and Stxbp6. Trimester two target filtering resulted in miR-302c targeting Ccdc6.

Gene expression and microRNA results demonstrate the stage-specific genes and processes altered during neurodevelopment upon ethanol exposure. Certain cellular processes are disrupted no matter the timing of ethanol exposure. Given that microRNAs are fine-tuners of gene expression, they may play an important role in the maintenance of FASD. Furthermore, transcriptomic changes in the brain may explain the observed behavioural effects of prenatal ethanol exposure.


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