The Mongolian gerbil as an advanced model to study cone system physiology

Area of Science:

• Ophthalmology and Vision Science
• Comparative Physiology
• Retinal Biology

Background:

• The cone system is crucial for high-acuity and color vision, making its impairment in retinal disorders highly disabling.
• Mice, despite their nocturnal nature, are widely used for cone-related disease research due to genetic model availability, but significant retinal differences limit translational potential.
• Diurnal rodents, like the Mongolian gerbil (Meriones unguiculatus), possess a higher proportion of cones and a macula-like visual streak, suggesting better suitability for cone research.

Purpose of the Study:

• To evaluate the Mongolian gerbil (MG) as an alternative model for studying retinal cone system physiology and pathophysiology.
• To compare the cone system functionality and retinal morphology of MGs with those of mice.

Main Methods:

• Full-field electroretinography (ERG) to assess cone system functionality.
• Angiography, optical coherence tomography (OCT), and photoreceptor immunohistochemistry for morphological assessment of retinal and visual streak organization.

Main Results:

• MG cone system responses were significantly larger, more sensitive, and faster than murine counterparts, with identifiable ON and OFF ERG components.
• Morphologically, MGs exhibited even cone opsin distribution and single opsin expression per cone, unlike the M- and S-opsin gradients and co-expression in mice.
• The MG visual streak showed a higher cone density, elongated photoreceptor outer segments, and thicker retinal layers compared to peripheral regions.

Conclusions:

• The Mongolian gerbil (Meriones unguiculatus) is a superior model for investigating cone system physiology and pathophysiology.
• MGs provide a more translatable model for validating therapeutic strategies for cone-related retinal disorders.
• The unique retinal features of MGs, particularly in the visual streak, enhance their utility in vision research.