Exploring RNA Expression in Spermatozoa

Al-Gazi, Maha K.A. (2019) Exploring RNA Expression in Spermatozoa. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Spermatozoa are known to be a carrier of genetic materials and serve no other function; However, it appears that it has a complex population of RNA including small noncoding RNA (sncRNA) that can deliver to the oocyte during fertilization. sncRNAs contribute to cellular gene regulation, in terms of their role in pre and post-fertilization genomic code, which in turn participate in the embryonic development process and any deviations in the gene expression pattern may lead to development retardation or early embryonic death. Moreover, phenotypic or environmental changes of parents can alter the phenotype of the next generation via specific miRNA expression regulation changes. The present research investigated the profile of sperm mRNA and miRNA expression in both motile and immotile human sperm, in order to understand the role of sperm epigenetics in regulating genes that are involved in spermatogenesis and sperm function, in specific sperm motility, that has an impact on male fertility. Semen samples were collected from normo-spermic participants. RNA was extracted, and the mRNA profile in motile and non-motile sperm was investigated by Next Generation Sequencing. Results found that most transcripts expressed in motile sperm belonged to ribosomal mRNA. Secondly, the thesis investigated and the miRNA expression changes in motile and immotile sperm. Preamplification of miRNAs with miscript PreAmp PCR kit before quantitative RT-PCR was performed using misprint PCR custom plate for 84 different sperm-specific miRNAs, in order to establish the miRNA profile in different motility grades. 2 The results suggested that miRNAs were differentially expressed in different sperm activity groups of the same sample and confirmed the role of miRNA in the physiological process of the spermatozoa. Data revealed that the miRNA expression profile in the sperm could serve as biomarkers for male fertility assessment. To further, elucidate the relative expression and the epigenetic control of the sperm specific microRNAs in high-fat diet (HFD) mice and age-matched controls (AMC) by study the miRNA expression via qRT-PCR and DNA methylation of the most significant miRNA through finding its promoter region. The aim of this study was to explore the link between obesity and miRNA profile expression in a mouse model. We found that sperm-specific microRNAs from HFD mice were upregulated, with miR-21a-5p expression being highly significant and was regulated by methylation of the CpG islands on VMP1 promoter. In conclusion, the current study demonstrated a differential expression of miRNA in sperm from motile and immotile populations. In addition, this study revealed links with obesity and altered expression of sperm miRNAs in a mouse model. There was a change in the methylation status and expression of miR-21a-5p, which may indicate the impact that paternal high fat diet has on sperm miRNA expression and DNA methylation.