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The development of retinal ganglion cells deprived of their targets
1Department of Biological Sciences, State University of New York, Albany 12222.
Abstract:
The influence of central targets on the morphological differentiation of retinal ganglion cells was investigated in Xenopus laevis. Since the ganglion cells mature into distinct morphological subtypes after their axons have reached their central targets, it is possible that the target tissues may influence or specify this aspect of neuronal cell development. To test this idea, Xenopus eyebuds were target-deprived by transplantation to the flank region of host embryos where they developed ectopically. The grafted eyes grew at normal rates, but could not make any projections into the central nervous system. To examine the morphological differentiation of the retinal ganglion cells their structures were revealed using an in vitro retinal preparation and intracellular injections of the dye Lucifer yellow. The elaboration and maturation of ganglion cell dendrites were found to be indistinguishable between control and transplanted eyes throughout development. Thus, the development of retinal ganglion cells into distinct morphological classes can occur even when their axons do not interact with the appropriate central targets.
Insights
Central targets do not influence retinal ganglion cell differentiation. Even when deprived of central nervous system connections, these neurons develop normal morphological subtypes, demonstrating intrinsic developmental programs.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- Retinal ganglion cells (RGCs) differentiate into distinct morphological subtypes.
- Axon guidance to central targets is a critical step in neuronal development.
- The role of central targets in RGC morphological differentiation remains unclear.
Purpose of the Study:
- To investigate whether central targets influence the morphological differentiation of Xenopus laevis RGCs.
- To determine if RGCs can develop distinct morphological subtypes in the absence of central connections.
Main Methods:
- Xenopus laevis eyebuds were ectopically transplanted to the flank, creating a target-deprived condition.
- Grafted eyes developed without central nervous system projections.
- In vitro retinal preparations and intracellular Lucifer yellow injections were used to visualize RGC morphology.
Main Results:
- Transplanted eyes grew normally but lacked central projections.
- Morphological differentiation of RGC dendrites in transplanted eyes was indistinguishable from control eyes.
- RGCs achieved mature morphological subtypes despite the absence of target interaction.
Conclusions:
- Central targets are not necessary for the morphological differentiation of RGCs.
- RGCs possess intrinsic mechanisms for subtype specification.
- Axon-target interactions do not appear to specify RGC morphological classes.