A Tale of a Whale: De Novo Assembly and Annotation of the Humpback Whale Genome to Provide Insight Into the Evolution of Cancer Suppression Mechanisms

Aleah Caulin, University of Pennsylvania

The humpback whale may hold the key to cancer prevention. If all mammals were equally susceptible to oncogenic mutations and had identical tumor suppressor mechanisms, one would expect that the rate of cancer would be proportional to a species’ body size and lifespan. This is because a greater number of cells and a greater number of cell divisions over a lifetime would increase the chance of accumulating mutations that result in malignant transformation. Even though theory predicts cancer incidence should increase with body size and lifespan, this correlation has not been observed across species and is known as Peto’s Paradox. We are interested in revealing how evolution has increased the ability of large, long-lived animals (e.g. whales) to suppress cancer.

Few genomes of large, long-lived organisms have been sequenced, greatly limiting our ability to analyze possible tumor suppression mechanisms on a genome-wide level that may explain how these organisms have dealt with the risk of cancer. We chose to sequence the genome of the humpback whale using next-generation sequencing (NGS). The highly repetitive genome has proven difficult to assemble with short reads, so we have made use of numerous types of sequencing data and performed a hybrid de novo assembly in order to complete the draft genome. We have also predicted and annotated gene sequences and are analyzing cancer-associated genes for evidence of strong selective pressures. Understanding how evolution has solved the problem of cancer in large, long-lived animals should provide insight into new cancer prevention methods for humans.

Abstract Author(s): Aleah F. Caulin, John St. John, Dent Earl, R. Edward Green, Per J. Palsboll, Nader Pourmand, Shane T. Jensen, Carlo C. Maley