A New Use for a Common Model Organism

Mus Musculus, or the House Mouse, Joins a Long List of Feathered Friends That are Studied for Their Vocalization and Hearing.

Small, furry and stinky, the common mouse, which is notorious for scaring both elephants and housewives, has a new trick up its sleeve...er..paw. That's right, the rodent that worked its way through the proverbial maze to become the most popular mammalian model organism has recently been discovered to be quite the virtuoso.

New studies suggest that mice possess a singing ability that rivals the songbird's. This revelation increases the biodiversity of organisms studied for vocalization and allows mammals to be used in a new sector of biomedical research. The study also shows that experimenting with a diverse set of mice has the possibility to advance human health, a notion that differs from the historical use of model organisms.

The article “Spectrographic Analyses Reveal Signals of Individuality and Kinship in the Ultrasonic Courtship Vocalizations of Wild House Mice” by Frauke Hoffman, Kerstin Musolf, and Dustin J Pen, was published in last February's Physiology & Behavior, and has garnered a fair amount of attention from ornithologists and neurobiologists alike.

In essence, the study found that wild male mice produce ultrasonic vocalizations that appear to help coordinate mating, wild females are not only attracted to these vocalizations but use them to discriminate between males based on relatedness and compatibility.

To carry out the study, Hoffman, Musolf, and Penn placed the progeny of wild mice into a sound proof recording chamber and introduced pooled female urine to induce the male's mating vocalizations. Once the ultrasonic sounds were recorded, they were separated by syllables, and each syllable was compared against the others in terms of kinship via spectrograph analysis. The results show that, depending on the type of syllable uttered, the sounds between kin could be matched with anywhere from 87% to 99% reliability. According to the study, this fact proves that the mating vocalizations of wild mice contain signatures of both individuality and kinship. When combined with the group's previous assays, this data points to vocalizations as a source of female preference and genetic discrimination.

This figure shows the similarity of the same syllable uttered by two related male mice (Hoffman, Musolf, Penn).

While this treatment of mouse vocalization may sound like news to you, the fact that mouse squeaks are melodic was discovered all the way back in 2005. In a PLoS article entitled “Ultrasonic Songs of Male Mice,” Timothy E. Holly and Zhongsheng Gou show that the vocalizations of male laboratory mice have many characteristics of song. After the initial breakthrough, Holly and Gou allowed the research to sit for around six years until Hoffman, Musolf, and Penn picked up where they left off.

Despite a niche topic, soon after the Hoffman, Musolf, and Penn article was published, it gained a significant amount of attention for its unique investigation into mice vocalization. On January 27, 2012, Rebecca Sears wrote a short article for the Huffington Post's science section titled “Mice Sing To Attract Mates, Courtship Study Reveals.” And another, longer article titled “From Squeaks to Songs” by Hannah Waters was published around four months later by The Scientist. .

What makes this study so intriguing, arguably more so than the Holly and Gou paper, is the fact that it proves that mouse songs function much like bird vocalizations. Water's The Scientist article cites ornithologist Pam Rasmussen saying, “If they weren't up there so high I wouldn’t know that they weren't bird songs.” The two creatures' songs are similar in more than just tune. The vocalizations of male birds are known to attract mates and are used by females to aid in genetic discrimination just like in wild mice.

Similarities aside, there are still many questions left to be answered. The most obvious of which is: nature vs. nurture. It is still unknown if the unique songs are genetic or due to imprinting at infancy, like birds. It is also unknown if complexity or length has any effect on female attraction.

Even though the study was far from exhaustive, phrases like 'new model organism' are already being thrown around. Co-author Dr. Dustin Pen writes this in a statement, “It seems as though house mice might provide a new model organism for the study of song in animals.” 

If this becomes a reality it could have drastic effects on the study of mammalian, even human, vocalization and sound perception.

Studying bird calls has already resulted in a significant amount of information about basal ganglia (a lower part of the brain associated with diseases like Parkinson’s and Huntington’s) according Terra Barnes, who was interviewed for Water's article. But a bird's brain is far from a human's, which makes it hard to carry over results. Mice on the other hand have a long history of being studied for human health. The ability to study a type of communication as unique as bird song in a mammal would produce a wealth of new and interesting data that could be applied to human health. Also, if it is proven that mouse songs are as complex as those of birds, there's a possibility that a large portion of the work invested in the study of bird song can be applied to mice, and perhaps by extension, humans.

The Hoffman, Musman, and Penn article also raises questions about biodiversity in the field of biomedical research. This unique type of research often relies on a small set of model organisms that are breed and selected to have a very limited range of phenotypes. This is required to control genetic variables, but it also limits the amount of bio-diversity in typical studies.

The work done by Hoffman, Musman and Penn is important because it has significant medical implications and requires the use of genetically diverse subjects, the songs of laboratory mice were too similar. While it may not instantly change paradigms, their article may inspire more biomedical researchers to consider investigating a more bio-diverse model of experimentation, even if that diversity is merely genetic.

Academic Work Cited:

Holy TE, Guo Z (2005) Ultrasonic Songs of Male Mice. PLoS Biol 3(12): e386.doi: 10.1371/journal.pbio.0030386

Frauke Hoffmann, Kerstin Musolf, Dustin J. Penn, Spectrographic analyses reveal signals of individuality and kinship in the ultrasonic courtship vocalizations of wild house mice, Physiology & Behavior, Volume 105, Issue 3, 1 February 2012, Pages 766-771, ISSN 0031-9384, 10.1016/j.physbeh.2011.10.011.