Research Fellows Directory
Dr Helen White-Cooper
How do flies make sperm? Specifically, what genes are used in the sperm production process, either as components of the final product, or as tools during the manufacturing process? How is the expression of these genes in testes controlled to ensure the protein products are produced exclusively at the right time and in the right place?
Sperm are probably the most specialised of all differentiated cell types, and testes have the most atypical gene expression profile of all organs. All cells in an individual animal have the same complement of genes in their genome; differences between cells depends on differential expression of the genes. A little over half of all the genes in the genome are expressed in testes. Many of the genes expressed in the sperm precursor cells are not expressed in any other cell type in the body. We study sperm production in the fruit fly, using this a model system to answer a fundamental biological question - "how do cells decide which genes to express, and which genes to keep silent?".
Genetic analysis has proved very powerful in addressing this question. We can deplete flies of a single gene function and analyse the resulting defects. In my lab we have a set of such mutant flies, which are male sterile due to defects in sperm production. Specifically, the defect is in the activation of the testis-specific gene expression programme. By tagging the proteins we are able to follow where they are in the cell, how they interact with each other and with genomic DNA, and thus can infer how they carry out their biological function.
There is strong evolutionary conservation of our mutant genes, thus what we learn from insects is likely to be relevant to studying the counterpart genes in mammals. The human equivalents of our genes are also expressed highly in testes and might function in activating gene expression to facilitate normal sperm production in men.