|
|
|
|||||
|
|
|
|
|
|
|
|
|
|
|
|
Tetrahymena thermophila is a very useful microbial animal model for fundamental eukaryotic experimental cell and molecular biology, and for experimental comparative genomics. It is a free-living, fresh-water unicellular organism, which has conserved a fairly complete set of ancestral eukaryotic animal biology. Advanced tools for experimental genetic and molecular analysis have been developed in this organism, such as gene knockouts by homologous recombination, gene silencing by RNAi and "antisense ribosomes", high frequency transformation by high or low copy-number vectors, conditional gene promoters, epitope and affinity tagging, genetic tricks to make recessive mutations homozygous in a single generation, and genetic mapping by either deletions or meiotic recombination. These features make it an alternative eukaryotic microbe with excellent credentials for fundamental cellular and molecular investigation of human biology, complementary to multicellular animal model systems. 
Tetrahymena thermophila micrograph (courtesy of Dr. Jacek Gaertig);
computer-generated picture (courtesy of Dr. Paul H. Dear). A major part of our effort in the past decade has been directed to genetically and physically mapping the Tetrahymena thermophila genomes. In addition, on behalf of the ciliate research community, I coordinated a project to sequence the macronuclear genome. This effort was carried out at The Institute for Genome Research (TIGR) under the leadership of Dr. Jonathan Eisen and culminated with the publication of the results of the sequencing project in September 2006 in the open access journal PLoS Biology. The ~104 Mb macronuclear genome assembly is of very high quality and completeness. Closure efforts at TIGR have resulted in nearly 50% of the genome being completely closed. Most of the physical gaps that remain are short (<1 kb).One goal of our current research is to complete comprehensive and robust physical maps of both Tetrahymena genomes, and to relate them to one another and to the genome sequence. This currently includes genetically mapping short tandem repeat polymorphisms identified using the genome sequence, and completing the physical assembly of the Tetrahymena genome sequence by using HAPPY physical mapping in collaboration with Dr. Paul H. Dear at the Laboratory of Molecular Biology at Cambridge University, UK. One of the benefits of this work will be to facilitate forward genetics, an enduring experimental approach in which one starts with mutant expressing an interesting phenotype with relevance to an important mechanism under investigation. Through genetic mapping and the use of genome sequence information, one then proceeds to identify the responsible gene and its protein product, thus opening the way for further research. 
Tetrahymena's two nuclear genomes.
Linking partial chromosome assemblies using HAPPY physical mapping.
More recently, we have initiated a study of Tetrahymena metallothioneins, a group of multi-stress-response proteins capable of binding heavy metals and scavenge reactive oxygen species. Our work, in collaboration with the group of Professors Juan Carlos Gutierrez and Ana Martin-Gonzalez at Universidad Complutense of Madrid, Spain, has shown that Tetrahymena metallothioneins fall into two discrete subfamilies. Some current goals of my research group are to understand the mechanism of regulation of metallothionein gene expression and to construct Tetrahymena cell lines capable of fluorescing in real time in response to environmental toxicants, including heavy metals. 
Striking modular structure of Cd-responsive Tetrahymena metallothioneins.
|
|
| | | | | |
|
