Sugar-eating bat genome could hold clues to treating diabetes
Diabetes is a major threat to human health, and its prevalence has been increasing in recent years in both humans and animals. Poor diet and obesity contribute, yet genetics plays a key part and could represent an important route for treatment. Most of our current knowledge of the genetic mechanisms behind sugar metabolism comes from lab studies in humans and mice, however. Researchers in the CHIROGLU project looked for for clues in the genomes of other animals that have evolved adaptations to thrive on high-sugar diets, to fill in our knowledge gaps on the molecular adaptations these creatures possess. One of these groups is Old World fruit bats, from the family Pteropodidae. These mammals are unique in that they have independently evolved nectar-feeding several times. CHIROGLU aimed to identify specific genes that provide adaptations, looking at around 1 500 genes involved in glucose and carbohydrate metabolism in all of the nectar-feeding lineages of these bats. “The first key aim of the project was to determine the exact number of independent origins of frugivory within the Old World fruit bats family,” says Nicolas Nesi from Queen Mary University of London and CHIROGLU lead researcher. Until now, this hasn’t been well known – in part because of the rarity of many of the bat species. Some live only in remote tropical regions, making access difficult.
Seeking out the genes
To overcome the logistical challenges, Nesi managed to gather samples from museum collections around the world. In total, his team secured around 135 out of about 200 known species, letting them access all nectar-feeding genera of these bat families. “Museum collections, often including specimens collected at the beginning of the 20th century, can still be used for modern genomic studies,” says Nesi, who received support from the EU’s Marie Skłodowska-Curie programme. This avoids the need to collect new samples from threatened species in the wild. Once the samples were collected, the team used state-of-the-art analysis methods to figure out the evolutionary relationships within the family, to shine a light on the origins of nectar-feeding behaviour. Nesi looked for specific protein-coding genes involved in glucose metabolism that are positively selected in nectar-feeding species. “These genes have been selected to produce a different protein in nectar-feeder bats, in theory potentially more efficient, compared to frugivorous bat species and other mammals, including humans,” Nesi says.
A more complete picture
Historically, nectar-feeding species have all been grouped together based on similar morphological features – such as a small body size, long and narrow rostrum, and tongue with specialised papillae. But the genetic data showed the team that this particular morphology and diet evolved independently, several times, outside of these established groups. “We now have a complete picture of the evolutionary history of the Old World fruit bats family,” Nesi says. In the future, the team would like to test more genes to seek new results. “A complementary approach will be to use transcriptomic (RNA) data in order to have access to all protein-coding genes – including those expressed in different organs like the pancreas and intestine,” says Nesi. These first results from the CHIROGLU project will be used in larger projects in the future, which will include other groups of nectarivorous bats, as well as other nectar-feeder vertebrates, like hummingbirds and the honey possum. Other additional techniques such as the gene editing tool CRISPR/Cas9 will be used to test genes’ metabolic efficiency in glucose regulation.
Keywords
CHIROGLU, bats, nectar, diabetes, genome, genes, adaptation, manage