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Development of visual callosal projection in the microphthalmic stain of mice 944
1Paul-Flechsig-Institut für Hirnforschung, Abt. Neuroanatomie Universität Leipzig.
Abstract:
The strain of mice 944 produces a recessive microphthalmy. The microphthalmic mice were compared with phenotypically healthy animals of the same litter and with 944-mice bilaterally enucleated at 1. postnatal day (pd). Comparison was done at the 5., 10., 15. and 20. pd after lesion of the right visual cortex 24 hours before. Therefore Nissl- and Fink-Heimer-series were prepared. The results are the following: At 20. pd microphthalmic mice show both retrograde and anterograde degeneration after lesion. Enucleated and control mice produce destroyed fibres only. This evidence of callosal projection in visual cortex is possible exclusive at pd 20 with satisfying results. The neurons of laminae II and III project in the animals with a normal visus exactly to the contralateral 17/18a borderline. Enucleated mice show in area 18a two or three stripes more reaching laterally. Microphthalmic mice have terminals in both area 17 and 18a.
Insights
Recessive microphthalmy in 944 mice affects visual cortex development. Microphthalmic mice show altered callosal projections compared to healthy and enucleated controls, revealing developmental differences in visual pathways.
Area of Science:
- Neuroscience
- Developmental Biology
- Ophthalmology
Background:
- The 944 mouse strain exhibits recessive microphthalmy, a condition affecting eye development.
- Understanding visual pathway development is crucial for addressing congenital vision disorders.
Purpose of the Study:
- To investigate the impact of microphthalmy on the development of callosal projections in the visual cortex.
- To compare the neuroanatomical changes in microphthalmic mice with healthy and surgically manipulated controls.
Main Methods:
- Histological analysis using Nissl and Fink-Heimer staining techniques.
- Comparative study of microphthalmic, enucleated, and phenotypically healthy mice at various postnatal days (5, 10, 15, 20).
- Lesioning of the right visual cortex to assess axonal degeneration.
Main Results:
- At 20 postnatal days, microphthalmic mice exhibit both retrograde and anterograde degeneration in the visual cortex after lesion.
- Enucleated and control mice show only destroyed fibers, indicating normal pathway integrity.
- Neurons in laminae II and III project to the contralateral 17/18a border in normal mice; enucleated mice show broader projections into area 18a.
- Microphthalmic mice display terminals in both area 17 and 18a, suggesting altered projection patterns.
Conclusions:
- The study provides evidence of callosal projections in the visual cortex, identifiable by postnatal day 20.
- Microphthalmy significantly alters the normal development and targeting of visual cortex projections.
- These findings contribute to understanding the neurodevelopmental consequences of congenital eye abnormalities.