Summary: A new type of neuron in the mammalian retina has been discovered. The new cell, named the Campana cell, appears to relay visual signals to both rod and cone photoreceptors in the retina, however, their precise purpose is not yet known.
Source: University of Utah
Scientists at the John A. Moran Eye Center at the University of Utah have discovered a new type of nerve cell, or neuron, in the retina.
In the central nervous system a complex circuitry of neurons communicate with each other to relay sensory and motor information; so-called interneurons serve as intermediaries in the chain of communication.
Publishing in the Proceedings of the National Academy of Sciences of the United States of America, a research team led by Ning Tian, PhD, identifies a previously unknown type of interneuron in the mammalian retina.
The discovery marks a notable development for the field as scientists work toward a better understanding of the central nervous system by identifying all classes of neurons and their connections.
“Based on its morphology, physiology, and genetic properties, this cell doesn’t fit into the five classes of retinal neurons first identified more than 100 years ago,” said Tian. “We propose they might belong to a new retinal neuron class by themselves.”
The research team named their discovery the Campana cell after its shape, which resembles a hand bell. Campana cells relay visual signals from both types of light-sensing rod and cone photoreceptors in the retina, but their precise purpose is the subject of ongoing research. Experiments showed Campana cells remain activated for an unusually long time—as long as 30 seconds—in response to a 10 millisecond light flash stimulation.
“In the brain, persistent firing cells are believed to be involved in memory and learning,” said Tian. “Since Campana cells have a similar behavior, we theorize they could play a role in prompting a temporal ‘memory’ of a recent stimulation.”
Authors are: Brent K. Young, Charu Ramakrishnan, Tushar Ganjawala, Ping Wang, Karl Deisseroth, and Ning Tian.
Funding: Funding for the research came from National Institutes of Health grants R01EY012345, R01EY031699, T32EY024234, HHMI. This work was supported by NIH Core Grant (EY014800), and an Unrestricted Grant from Research to Prevent Blindness, New York, NY, to the Department of Ophthalmology & Visual Sciences, University of Utah, and the Department of Ophthalmology of Wayne State University School of Medicine. The work was also supported by Ligon Research Center of Vision, Kresge Eye Institute, and the Dryer Foundation.
An uncommon neuronal class conveys visual signals from rods and cones to retinal ganglion cells
Neurons in the central nervous system (CNS) are distinguished by the neurotransmitter types they release, their synaptic connections, morphology, and genetic profiles.
To fully understand how the CNS works, it is critical to identify all neuronal classes and reveal their synaptic connections. The retina has been extensively used to study neuronal development and circuit formation. Here, we describe a previously unidentified interneuron in mammalian retina.
This interneuron shares some morphological, physiological, and molecular features with retinal bipolar cells, such as receiving input from photoreceptors and relaying visual signals to retinal ganglion cells. It also shares some features with amacrine cells (ACs), particularly Aii-ACs, such as their neurite morphology in the inner plexiform layer, the expression of some AC-specific markers, and possibly the release of the inhibitory neurotransmitter glycine.
Thus, we unveil an uncommon interneuron, which may play an atypical role in vision.