While hiking through an oak savannah with the dogs yesterday, we heard plenty of rodent vocalizations. Though we only saw one, we recognized the vocalizations as those of chipmunks, Tamias sp. The pitch and staccato of the vocalizations made them easily recognizable as warning calls. And since we were interfering with the chipmunks’ acorn gathering on a lovely, fall-like day, there was no doubt that the dogs and I were really annoying the chippies.
Warnings are not the only reason for vocalizations in wild rodents. Mate selection is influenced by Scotinomys’ (Alston’s singing mice) singing as well. And where mate selection is at play, can hormones be far behind?
Bret Pasch at the University of Florida-Gainesville published a report in the journal Hormones and Behavior in 2010 (1), showing the influence of androgen hormones on vocalization in male Alston’s singing mice, Scotinomys teguina, of Central America. Pasch et al. studied laboratory-reared offspring of wild Scotinomys, which were altered so as to experimentally manipulate the circulating levels of androgen.
The researchers studied the effects of androgens on singing behavior, song characteristics and related aggressive behavior in singing mice. Seriously; these mice not only sing, but vary their songs in length, frequency and structure.
The studies showed that androgens made a measurable effect on song structure, including rate, song length and power, as measured in frequency. They found that neutered male Scotinomys without androgen hormone had less power and more variability in their songs, suggesting that androgens affect the larynx in terms of size and/or musculature that controls this organ. This work was interesting in part because it demonstrated larnyx changes post adolescence.
Pasch et al. found the effect of androgens on aggression behavior was significant, but more subtle and more difficult to measure and control for in a laboratory setting.
A collaborator on the Pasch studies, Steven Phelps and his laboratory, now at the University of Texas-Austin, are looking into genetic components that underlie and influence singing behavior. In particular, they are interested in the FOXP2 gene (2).
The discovery of the FOXP2 gene has caused much excitement as the only gene to so far be connected to deficits of speech in humans (3). These deficits include stuttering, articulation disorders, verbal dyspraxia. Some of these disorders have been shown to cluster in families and modern genetic methods have enabled genetic analysis of large families with multiple affected persons, which lead to the identification of the FOXP2 gene.
FOXP2 functions in the regulation of transcription (is a transcription factor), so that mutations in this gene could result in changes of expression for a number of other genes.
Phelps and his laboratory are studying FOXP2 expression, its activators and the genes expressed once FOXP2 has done its work as a transcription factor. To accomplish this work they study gene expression in Scotinomys that have listened to recordings of other Scotinomys singing, as well as recordings of vocalizations from other species. One finding is that of expression of the neurons that carry FOXP2 when songs from other mice are played.
In addition, Phelps’ lab is studying whether DNA undergoes sequence changes associated with listening to singing mice, and whether specific DNA sequences are interacting with FOXP2.
Phelps et al. use powerful next generation sequencing (NGS) to determine if and how FOXP2 acts to regulate other DNA. And they rely on the supercomputing power of Texas Advanced Computing Center, which can run in only hours the amount of data that used to take days on a lab computer.
FOXP2 has been found not only in singing mice and humans, but birds and a number of other species such as bats. And even if the number of vocalization disorders with a genetic component turns out to be small, significant improvements in these conditions are possible once the genetic contributions to the disorder are understood.
Singing mice may lead the way.
- Pasch B, George AS, Hamlin HJ, Guillette LJ Jr, & Phelps SM (2011). Androgens modulate song effort and aggression in Neotropical singing mice. Hormones and behavior, 59 (1), 90-7 PMID: 21035450
- University of Texas at Austin, Texas Advanced Computing Center (2012, August 10). Of mice and melodies: Research on language gene seeks to uncover the origins of the singing mouse. ScienceDaily. Retrieved August 13, 2012
- Kang C, & Drayna D (2011). Genetics of speech and language disorders. Annual review of genomics and human genetics, 12, 145-64 PMID: 21663442