As a Ph.D. candidate at the University of California, Los Angeles, Mark Phuong accompanied Australian Museum Mollusc expert, Francesco Criscione, on a field trip to the Lizard Island Research Station in August, 2014. During the course of 5 days, Mark collected 32 species of cone snails.
Cone snails are a hyper-diverse family of carnivorous marine gastropods, with over 700 species known world-wide. They are typically well known to reef visitors because of the strong warnings not to touch them. Cone snails are molluscs that hunt by harpooning prey, injecting them with a highly toxic chemical cocktail of proteins and peptides. Cone snails are easily recognised by reef visitors because they are common, active during the day, and have a clearly recognisable cone-shaped shell.
Different species of cone snails specialise in different prey species. The molecular structure of the peptides (a kind of protein) in their venom is adapted to be effective in hunting target prey species.
Mark, specialising in evolutionary biology, needed to collect a wide variety of samples as part of a genetic sequencing study. This study has enhanced our capacity to discover the specific gene sequences responsible for the venom differences between various species. Quoting directly from Mark’s article, with co-author Gusti Mahardika:
“Animal venoms provide an excellent opportunity to study the interplay between genetics and adaptation because of the relatively simple relationship between genotype, phenotype, and ecology. Venoms have evolved multiple times throughout the tree of life (e.g., spiders, snakes, and snails) and play a direct role in prey capture and survival.”
It is this simple relationship that makes the discovery of venom-related gene sequences of such great interest to evolutionary biologists exploring the molecular basis for adaptation and species diversity.
The Lizard Island Research Station was particularly suitable for Mark’s fieldwork because there are records of over 60 species of cone snails from Lizard Island and the nearby reefs. 44 of those species have been documented in the Lizard Island Field Guide. Mark collected specimens of 32 different species while at Lizard Island.
Back in the laboratory, Mark designed 800 different probes to perform targeted gene sequencing to focus in on venom-related gene sequences. The targeted sequencing approach enabled Mark to describe several key features of cone-snail toxin genes, including their genetic architecture, their molecular evolution, their expression patterns, and changes in gene superfamily size.
Cone snails collectively harbour tens of thousands of peptides in their venoms that have potential value for pharmacology. The peptides that enrich cone-snail venoms have considerable therapeutic potential and biomedical research utility. In particular, they offer avenues for discovery of protein-binding ligands, molecules that bind to a specific site on a target protein. Being able to target specific sites on target proteins is critical in designing effective treatments for diseases related to target proteins.
Traditional techniques, developed over the previous three decades have barely begun to uncover and characterise the diversity of peptides in cone-snail venoms. The targeted sequencing technique applied by Mark proves the value of targeted sequencing as a tool for biologists to accelerate the discovery of new venom peptides. Importantly, Mark’s successful application of the targeted sequencing technique will allow DNA sequencing of genetic samples housed in museum collections. These collections often contain a large proportion of the species diversity for venomous taxonomic groups that have been amassed through several decades of intensive field expeditions. For example, the Australian Museum’s collection includes about 400 different species. Some of the specimens are just shell material, unsuitable for DNA analysis but the collection does contain material suitable for DNA analysis for about 60 species.
Geoff Shuetrim, LIRRF Trustee