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Unraveling Platypus Genes

  • Title: Lecturer and Research Fellow (Australian Research Council), The University of Adelaide
  • Education: PhD, Max-Planck Institute of Molecular Genetics, Berlin, 2001; Postdoc, Australian National University, Canberra
  • Recommended by: Jenny Graves

Frank Grützner was introduced to lab research and chromosome evolution earlier than most. Even before going to college, Grützner had a chance to dive into research on human and animal chromosomes at a human genetics institute in his native Germany. By the time he was an undergrad in Freiburg, he was already hooked on studying the evolution of chromosomes.

From that point, Grützner went on to do a doctoral degree at the Max-Planck Institute of Molecular Genetics in Berlin. It was a fairly young institute then, and the interactive environment fostered Grützner's interest in “comparing evolutionary with pathological aspects of genome change.” As a grad student, he was also fascinated by interspecific hybrids, by which he could view the results of two divergent genomes conflicting in one animal. His main project involved pufferfish chromosomes, for which Grützner set up a technique called chromosome microdissection to physically isolate DNA and recover clones and genes for regions of interest.

Doctorate in hand and comparative genomics specialty in place, Grützner felt the call of Canberra. He had met Jenny Graves at a seminar in Freiburg and, knowing well her comparative genomics work, decided to get in touch for a postdoc position. Graves took him on at her lab at the Australian National University. There he imported the chromosome microdissection technique, and also mastered the art of chromosome painting for taking a closer look at platypus chromosomes, which he says were “difficult to distinguish and [remain] unresolved.” The technique helped the researchers uncover a “complex sex chromosome system” in platypus, and also allowed them to follow those chromosomes through stages of meiotic cell division.

Grützner's newly minted lab is now extending this chromosome work by focusing on the sex determination and embryology of the platypus. It's not easy work, Grützner says, as “things just don't work as easily in more distantly related species as they do in human or mouse.” But when things finally do come together, Grützner says, “you normally discover something new” — and that's as good a payoff as anyone could want.

Looking ahead

“People are seeing that just having sequence information is not enough,” Grützner says, pointing out that researchers are more eager than ever to peer into nuclei to see how complexity in a genome translates into myriad behaviors on the level of organism. The tools and techniques of comparative genomics may well shed light on these phenomena, he says. It doesn't hurt that evolutionarily divergent species, such as the platypus, are great for “unraveling the conserved functions of individual genes and regulatory elements,” he says.

Publication of note

During his PhD, Grützner was involved in work that showed that chicken and mammalian sex chromosomes are not homologous, suggesting that they evolved independently. This proposal was blown out of the water a couple of years ago, when Grützner's work on platypus essentially provided an evolutionary link between mammals and birds.

Using chromosome paints, Grützner and the Graves-led team tracked male platypus sex chromosomes as they form a meiotic chain — a very rare setup in vertebrates — which sports regions that are homologous to the bird Z chromosome at one end and human X on the other. The full story on the organization of this sex chromosome system is reported in Nature in 2004. Grützner's current work builds on this, which he considers “an amazing system to look at the evolution of sex determination and to possibly identify new sex-determining genes in humans and other mammals.”

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