Egg chambers with nuage and germ plasm.
Molecular functions of germline proteins A protein called Oskar is essential to the assembly of the germ plasm, the material that induces the formation of germ cells in some animals, and its absence has a major impact on development. We spoke to Dr Mandy Jeske about how she is combining a range of different techniques to investigate this area, alongside research into other fundamental questions around germ cell development. LOTUS domains are found in a group of proteins known to play important roles in animal development. Based at the Biochemistry Centre at Heidelberg University, Dr Mandy Jeske leads a research group which is investigating the molecular mechanisms behind the function of these proteins. “In my group we focus on questions related to germ cell development,” she explains. One part of this research is centred on the function of these LOTUS domain proteins in animals. “In animals there are only four proteins that carry LOTUS domains. I previously studied a germline protein called Oskar that is known to carry a LOTUS domain,” says Dr Jeske. “It is wellknown that the absence of this protein leads to marked developmental defects in flies.”
Development in Drosophila There are essentially two phenotypes to consider here, with researchers looking at the early stages of development in flies lacking Oskar. Researchers have found that eggs laid by these flies develop into embryos showing severe developmental issues. “The germ cell precursors are not produced, they are missing. Without germ cell precursors there are no germ cells, and if a larva would then develop into an adult it would be infertile,” outlines Dr Jeske. The second phenotype is that the abdominal segments usually seen on larvae
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Figure 1: Molecular functioin of germline proteins A) Drosophila egg chamber with maturing oocyte and nurse cells (NC). Nuage surrounds the NC nuclei. Germ plasm assembles at the posterior pole of the oocyte. B) Crystal structure of the Vasa-LOTUS protein complex.
are missing, resulting in developmental arrest and ultimately death. “Normally there are eight segments, and in this phenotype some or even all of them are missing,” continues Dr Jeske. “So, the function of this protein is associated with two developmental aspects, which in flies are genetically coupled – fertility and embryonic patterning.” A lot of attention in Dr Jeske’s group is devoted to investigating how LOTUS domain proteins function during the early stages of development. It is known that Oskar is very important in assembling the germ plasm, but
its molecular role is rather unclear, a topic of great interest to Dr Jeske. “We are still trying to understand the function of Oskar. We know that at the pole of the developing egg it’s required to assemble the germ plasm, and that if Oskar is missing, we see infertility and patterning defects. But beyond that, its function is not really clear,” she says. Researchers are using biochemistry techniques and X-ray crystallography to probe deeper in this area. “We need to do more biochemical studies and structural studies, using crystallography for example, to get a deeper
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