Glowing Green Sperm Point Way Forward for Infertility Research
A new way of studying sperm function has been developed which will aid research into male infertility.
In work published in this month's edition of the journal Biology of Reproduction, an international team led by Oxford researchers has shown for the first time that it is possible to introduce a synthetic gene (a transgene) directly into a normal, live animal in such a way that the gene is expressed in mature sperm.
The new method could be extremely important for fertility research because it allows many different aspects of gene function in sperm to be studied. This means that scientists can begin to understand the details of how the sperm works and how infertility may result when things go wrong.
The new approach is particularly important because although many cells of the body can be cultured in a petri dish and genetically modified there, this is not possible for sperm cells because of their small size and unusual shape, and because they only live for a short time outside the body.
The study showed that the gene coding for a fluorescent green protein, originally taken from a jellyfish, could be introduced into sperm precursor cells within the testicles of a hamster, resulting in green, glowing sperm. Hamsters were used in the study because their sperm have many attributes in common with those of humans, and thus offer an excellent model for studying human sperm development and how defects in this process might result in infertility.
The scientist leading the study, Dr John Parrington of the Department of Pharmacology in Oxford, said: 'We created green sperm to show this approach could work. But our real aim is to use this technique to study the function of genes that are important during fertilization and that may cause infertility if they become defective. That's an important goal given that a recent study found that one in seven British couples have fertility problems and a third of these have an unknown cause.'
One of the areas that Dr Parrington's team in Oxford are studying is the mechanism by which sperm activate eggs; that is, how a sperm by entering an egg triggers it to develop into an embryo rather than remaining in a state of suspended animation. This method of creating genetically modified sperm will aid their research, with important implications for understanding male infertility. It is also likely to be widely used by other scientists working in the field of gene function in sperm.
The technique may also offer the possibility of a new way of creating genetically modified animals for all sorts of other research. Currently, genetically modified mice are created by introducing transgenes into an egg. However, this method is relatively inefficient, and so far attempts to use it to create genetically modified versions of important model species such as hamsters and guinea pigs have failed.
Creating the transgenic animals from transgenic sperm (in other words genetically modifying the sperm and then fertilizing a normal egg with it) might on the one hand help to reduce the numbers of mice used in medical research, and on the other hand, open up the possibility of studying gene function in species that are better models than mice for studying certain human diseases.