Fish Teeth Findings Hold The Key To Genetic Discovery

February 24, 2009 News, General Dentistry, News

This week sees the publication in the “PLoS Biology journal” of research highlighting a breakthrough discovery in the field of genetics. The paper, produced by Dr Gareth Fraser and his research team from the Georgia Tech School of Biology has identified a common set of genes within living organisms that play a key role in the development of teeth in terms of their arrangement, character and number. This common set of genes are also known as a gene regulatory circuit, a collection of genes that when put together effect the genetic expression and development of each other.

The findings are based on research carried out at Lake Malawi in Africa. The lake was chosen because of its population of Cichlid fish. Cichlid fish are known for having a pharyngeal jaw, a set of teeth deep inside their throats. These teeth were similar to those found in Conodonts, an extinct eel like jawless fish.  This fish was the first vertebrate to have teeth, which also ran along the lining of the throat or pharynx. In addition to these, Cichlids possess a set of teeth within their oral jaw, much like humans. However, it was the rapid rate of evolution amongst Cichlids that made them the perfect specimen for Dr. Fraser’s tooth formation study. 

Dr. Fraser recalls how he initially “thought there wouldn’t be a correlation” between the numbers of teeth found in the oral and pharyngeal jaws of Cichlids. He had pointed to “the developmental differences and the evolutionary distinction between the two jaw regions,” as reasons for doubt. However Darrin Hulsey, a co author of the paper, soon discovered a positive correlation.  According to Dr Fraser, the research indicated “fish that have fewer oral teeth also have fewer pharyngeal teeth.” For Dr Fraser this suggested that “on some level there’s a genetic control that governs the number of teeth in both regions.”   

The next step was identifying the “genetic control” at the centre of tooth development.  The team studied cells using a technique known as “situ hybridization.” This technique sought to localize and identify the gene expression of the cells during the development of teeth.  It was here that a common genetic network, controlling tooth development, was discovered in the oral and pharyngeal jaws. For co author J. Todd Streelman, these findings establish that “regardless of where you grow a tooth, whether it’s in the jaw or the pharynx, you use the core set of genes to do it.” Dr Fraser also concludes that “every tooth made throughout the evolution of vertebrates has used this core set of genes,” a view backed up by the findings of the Malawi Cichlids study.

Yet, Streelman goes further, suggesting that potentially “this network is not just acting in teeth but also in other similarly patterned structures like hair and feathers.” While this study certainly represents a breakthrough in identifying controlling gene networks within tooth development, it may have more far reaching consequences within the study of genetics.