The Little Brown Bat (Myotis lucifugus) is one of the most widely distributed and recognizable species of bats in North America. As their name suggests, they are a small (5-14g), brown-colored bat. They are frequently found roosting in old buildings, taking breaks in trees, and hibernating in caves and mines [1-2].
There are two main reasons why researchers are interested in having good genomic resources for the Little Brown Bat. First, accounting for body size, the Little Brown Bat lives longest of any mammal. Second, a fungus-caused disease known as the White Nose Syndrome is killing off the little brown bat by the millions. We hope that upgrading the current draft genome assembly, created in 2010 by the Broad Institute, to chromosome-length will help address these questions. The upgraded genome assembly is available here. The upgrade is done in collaboration with Vincent J Lynch (University of Buffalo), Juan Manuel Vazquez (University of Chicago) as well as Richard Miller, Bill Kohler and Melissa Han (University of Michigan).
White Nose Susceptibility and Viral Resistance
A major issue affecting bats today is the emergence and rampage of White Nose Syndrome (WNS), caused by the fungus Pseudogymnoascus destructans. Originating from Europe, P. destructans has decimated Eastern and Midwestern bat populations as it has moved westward throughout North America [5]. Little Brown Bat has been severely affected. Interestingly, it appears that some populations of M. lucifugus have shown signs of resistance to WNS relative to other populations [6]. Access to better genomics resources for M. lucifugus can help determine how differences between populations contribute to their resistance or susceptibility to the WNS.
Peto’s Paradox and Longevity in the Little Brown Bat
Generally speaking, life span in mammals is linked with size: bigger animals live longer. According to this general rule, the little brown bat life expectancy is up to 19 years. Yet, the oldest little brown bat on record was 34 years old, almost twice the prediction! Hopefully, understanding how the Little Brown Bat manages to beat the curve will have benefits for human health.
Cancer resistance is of particular importance for longevity research. While nearly all multicellular species are susceptible to cancer, some species should be more susceptible than others. Within a species, for example, cancer risk is positively correlated with increases in body size and lifespan. Between different species, however, there are no correlations between a species’s body size or lifespan, and cancer risk. This observation, known as Peto’s Paradox, can only be explained if species evolve enhanced tumor suppression mechanisms alongside increases in size and lifespan. Many open questions remain in this puzzle, including whether the evolution of enhanced tumor suppression precedes, follows, or evolves in tandem with these two factors; and which molecular and genetic mechanisms do bats and other long-lived species use to suppress their overall cancer risk.
Myotis Lucifugus and Bat Genomics
This is the fourth bat genome assembly at the DNA Zoo, and the first chromosome-length assembly in the microbat suborder (Microchiroptera). Below, we include a few whole-genome alignment plots to help elucidate how the little brown bat genome relates to those previously shared. It is worth noting that even with the recent push in bat genomics over 99% of all bat species remain unsequenced, and there are likely many more unknown bat species which are yet to be discovered [3-4]. We would like to thank Richard Miller, Bill Kohler and Melissa Han, who provided these cell lines to us for sequencing and molecular studies. Working with the DNA Zoo and other collaborators we hope to break the status quo, so stay tuned!
References:
1- Fenton, M., R. Barclay. 1980. Myotis lucifugus. Mammalian Species, 142: 1-8.
2- Barbour, R., W. Davis. 1969. Bats of America. Lexington, Kentucky: The University Press of Kentucky.
3- Simmons, N.B. and A.L. Cirranello. 2019. Bat Species of the World: A taxonomic and geographic database. Accessed on 12/02/2019
4- Agnarsson, Ingi, Carlos M Zambrana-Torrelio, Nadia Paola Flores-Saldana, and Laura J May-Collado. n.d. “A time-calibrated species-level phylogeny of bats (Chiroptera, Mammalia).” PLoS Currents 3: RRN1212. https://doi.org/10.1371/currents.rrn1212.
5- Zukal J, Bandouchova H, Bartonicka T, et al. White-nose syndrome fungus: a generalist pathogen of hibernating bats. PLoS One. 2014;9(5):e97224. Published 2014 May 12. doi:10.1371/journal.pone.0097224
6- Langwig Kate E., Hoyt Joseph R., Parise Katy L., Frick Winifred F., Foster Jeffrey T. and Kilpatrick A. Marm. “Resistance in persisting bat populations after white-nose syndrome invasion.” 372. Phil. Trans. R. Soc. B. http://doi.org/10.1098/rstb.2016.0044
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