US-AUSTRALIAN ACADEMIES JOINT WORKSHOP
US-AUSTRALIAN ACADEMIES JOINT WORKSHOP ON VERTEBRATE COMPARATIVE GENOMICS
Beckman Conference Centre, Irvine, California, 23-25 May 2007
Genome organisation, sex chromosomes and epigenetics in monotremes, birds and bovine hybrids
by Frank Grützner
Frank Grützner is an Australian Research Fellow funded by the Australian Research Council. His lab at the School for Molecular and Biomedical Science at the University of Adelaide is investigating the evolution and organisation of genomes in different cell types (e.g. mitotic, meiotic cells and sperm) in mammals and reptiles. In addition his lab is working on meiotic sex chromosome inactivation, sex determination in monotremes. In collaboration with Dr Stefan Hiendleder (JS Davies Epigenetics Group, University of Adelaide) we are investigating if epigenetic changes like genomic imprinting and X inactivation are contributing to the phenotype in bovine intersubspecies hybrids.
Vertebrate genomes can differ considerably in size, chromosome number and morphology, sex chromosome system and epigenetics. Our research interest is to understand how these differences have evolved and how they influence genome function and organisation in different organism and in hybrids where different genomes are forced to interact.
Mammalian genomes are organised in gene-rich and gene-poor regions with a XY male, XX female sex chromosome system. In female somatic cells one X chromosomes is inactivated, while in male meiotic cells both the X and Y chromosome undergo meiotic sex chromosome inactivation. Birds have gene-rich microchromosomes and gene-poor macrochromosomes, and a ZW female, ZZ male sex chromosome system. Chromosome arrangement in mammalian sperm is non-random. Chicken sperm showed a random distribution of chromosomes, although a more central localisation of microchromosomes has been reported.
Monotremes (platypus and echidna) are the most diverged mammals and ideal to study mammalian genome evolution. Platypus has tiny microchromosome like chromosomes as well as a unique ten sex chromosome system that shows homology with the chicken Z. We are using a candidate-gene and candidate-region (Y specific BAC clones) approach to identify and characterise sex-determining genes in platypus. We are also investigating how meiotic sex chromosome inactivation occurs in male meiosis.
Chromosome specific BAC clones are used to determine the chromosome arrangement in bird and monotreme sperm in more detail. Platypus sperm clearly showed non-random arrangement and a clustering of Y chromosomes in the posterior part of the sperm nucleus. In chicken sperm our preliminary results show random and non-random chromosome arrangement.
Specific hybrid phenotypes have been explained by sex-specific gene interactions and differences in genomic imprinting. We are using a comprehensive resource collection of intersubspecies hybrids between Bos taurus (Angus) and Bos indicus (Brahman) cattle to investigate the epigenetic basis of
hybrid phenotypes.
Contact details:
Frank Grützner, Australian Research Council Research Fellow
School of Molecular & Biomedical Science
The University of Adelaide, 5005 SA, Australia
Tel: +61 8 8303 4812
Fax: +61 8 8303 4362
Email: frank.grutzner@adelaide.edu.au
