1. Genomic Instability and the Evolution of the Erythrocyte-Null
Condition of Antarctic Icefishes

Evolutionary processes have created organisms and communities that are as stunning in their beauty and complexity as they are unexpected by and novel to biological scientists. Indeed, the evolution of the erythrocyteless icefishes, the most derived of the eight families of the largely Antarctic perciform suborder Notothenioidei, has long presented evolutionary biologists with a conundrum: how is it possible for organisms that lack functional erythrocytes and the oxygen transport protein hemoglobin, which are presumably essential to vertebrate life, to evolve at all? We are investigating the mechanisms by which the erythrocyte-null condition of the icefishes evolved. Preliminary evidence suggests that genomic instability mediated by mobile genetic elements and repetitive DNA sequences was an important evolutionary driver that led to this unusual phenotype.

2. Comparative Genomics in Erythropoietic Gene Discovery

We have developed a multi-model, comparative genomics strategy, which exploits the erythrocyte-null condition of the Antarctic icefishes, to scan the vertebrate genome for new genes involved in erythropoiesis. These natural “knockouts” of the erythroid lineage are a unique resource for analyzing the genetic program of erythropoiesis by subtractive genomic strategies. However, due to their long generation times (many years to reproductive maturity), Antarctic fishes are not suitable subjects for functional analysis of the genes so discovered. The zebrafish Danio rerio , our second model system, reproduces rapidly with high fecundity and is widely used for analysis of gene function during vertebrate development. Thus, our overall strategy is to use Antarctic icefishes to isolate potential erythropoietic genes, to clone the zebrafish orthologs of these novel genes, and then to determine the functions of the genes in zebrafish embryos using reverse genetic technologies.

3. Regulation of Tubulin and Globin Gene Expression in
Antarctic Fishes

We seek to understand the modifications to the transcriptional apparatus that maintain efficient gene expression at low temperatures. Our objectives include the functional analysis of the promoter elements of tubulin and globin genes and the characterization of the transcription factors that regulate the expression of these genes. In a related project, we are characterizing the inactive globin genes that are present in the genomes of the hemoglobinless Antarctic icefishes.