Genes involved in the formation of neurons of hearing and balance
Close your eyes and imagine you are in a darkened Carnegie Hall. Eventhough it is pitch black, you know you are getting closer to the stage as the music gets louder. If you have been there before, you have a sense of the location of the seats and aisles. You remain upright because you somehow know where your legs, arms and feet are. Your head remains upright.
A variety of neurons or nerve cells make it possible for you to approach the stage and even find a seat without sight. Several of those neurons migrate from an embryonic structure called the rhombic lip, and a number of of these in the auditory, vestibular and proprioreceptive (sense of position in space) systems come into being because of a single gene called Math1, said scientists from Baylor College of Medicine in a report in the current issue of the journal Neuron.
"These three systems all seem to have a similar function. They help us coordinate body perception and movement in space. Now we know that one gene specifies the majority of these neurons - that this one gene has been conserved during evolution to execute this task," said Dr. Huda Zoghbi, BCM professor of pediatrics and molecular and human genetics as well as a Howard Hughes Medical Institute investigator.
Zoghbi led the team that found the Math1 gene a few years ago and at that time, determined that it was important for the formation of hair cells in the inner ear and some neurons in the cerebellum and intestine.
Now, mouse studies carried out by her and two graduate students, Matthew Rose and Vincent Y. Wang, demonstrate that Math1 plays a pivotal role in the formation of a number of of the neurons important in carrying hearing and vestibular and balance signals after they have been received and transmitted by the inner ear hair cells. The gene also specifies neurons that coordinate balance of body parts.
These nerve cells all arise in the rhombic lip, an embryonic structure not known to produce some of these various neurons previously, said Rose.
"Here is a neuronal network that coordinates a number of different types of sensations, and Math1 is mandatory for a number of components of it," said Zoghbi. "It is involved in the formation of a number of neurons that form key hubs for these senses. This is really very interesting. When one thinks of genes, one thinks of them specifying certain type of cells, but here is a gene that specifies a number of different types of cells in a network designed to help us keep our balance find our position in space both by being aware of the position of our body parts and by hearing.".
In a more prosaic sense, "This is the gene that make the neurons you use when you get up in the night to get a drink of water and manage to do so in the dark," said Rose.
This research was supported by the Howard Hughes Medical Institute, National Research Service Award Kirschtein Predoctoral Fellowships, a Baylor Research Advocates for Students Researchers Scholarship and a McNair Scholarship.