Linking sperm genotype to phenotype: exploring the underlying mechanisms of haploid gametic selection

Marcu, Daniel (2024) Linking sperm genotype to phenotype: exploring the underlying mechanisms of haploid gametic selection. Doctoral thesis, University of East Anglia.

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Abstract

Sperm are one of the most specialised and phenotypically diverse cell types in animals. They vary not only across species but also between and within individuals. Sperm counts have been declining in recent years and defects in the male germline are amongst the most common causes of human infertility. Much of the observed variation within an ejaculate was previously believed to be mainly due to differences in male condition. However, much less is known about the contribution of genetic variation in sperm to sperm phenotypic performance. Furthermore, whilst sperm within an ejaculate experience intense selection prior to fertilisation, the traits that make sperm competitive and influence male fertility and reproductive outcomes remain to be determined. This thesis presents three distinct projects that contribute to our understanding of the genetic determinants of sperm performance and the traits under selection in two model species, zebrafish Danio rerio and humans Homo sapiens. These projects used state-of-the-art genomics and transcriptomics technologies, combined with robust phenotypic assessment to characterise the signatures of haploid selection in sperm. In Chapter 2, I used single-cell genome and transcriptome sequencing to characterise the haploid stage of spermatogenesis and provide evidence for transcriptional activity and haploid selection in post-meiotic male germ cells in zebrafish. In Chapter 3, I integrated whole-genome sequencing with bioinformatics algorithms to systematically explore the signatures of haploid selection in zebrafish and human sperm pools and uncover the degree of molecular homology between sperm from the two species. Finally, in Chapter 4, I investigated the phenotypic dynamics of haploid selection within an ejaculate and uncovered the phenotypic traits under selection in human sperm. Collectively, the results of this thesis provide significant insights into the mechanisms shaping the evolution of sperm and have the potential to guide future experimental work aimed at identifying new interventions to improve reproductive health.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Zoe White
Date Deposited:	28 Jun 2024 14:02
Last Modified:	28 Jun 2024 14:02
URI:	https://ueaeprints.uea.ac.uk/id/eprint/95705
DOI:

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