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Cone and rod cells have different target preferences in vitro as revealed by optical tweezers.

Clarke RJ, Högnason K, Brimacombe M, Townes-Anderson E - Mol. Vis. (2008)

Bottom Line: Cell orientation of the photoreceptor also did not affect preferences: Cells oriented away from dendritic processes could reorient their axonal pole toward the target cell.Cone cells preferred normal partners, and rod cells preferred novel partners.Further,these differences may help explain the patterns of photoreceptor sprouting seen in retinal degeneration in which rod, but not cone, cells invade the inner retinal layers where third-order neurons are located.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology and Neuroscience, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103, USA.

ABSTRACT

Purpose: When neural circuits are damaged in adulthood, regenerating and sprouting processes must distinguish appropriate targets to recreate the normal circuitry. We tested the ability of adult nerve cells to target specific cells in culture using the retina as a model system.

Methods: Under sterile culture conditions, retinal cells, isolated from tiger salamander retina, were micromanipulated with optical tweezers to create pairs of first-order photoreceptor cells with second- or third-order retinal neurons. The development of cell contact and presynaptic varicosities, the direction and amount of neuritic growth, and nerve cell polarity were assessed after seven days in vitro. Cultures were labeled for rod opsin to distinguish rod from cone cells and for the alpha subunit of the trimeric G protein Go (Go alpha) to identify cone-dominated and mixed rod-cone ON bipolar cells.

Results: Quantitative analysis of growth demonstrated that target preferences were cell-specific: Cone cells preferred second-order bipolar cells, whereas rod cells grew toward third-order neurons, which include amacrine and ganglion cells. In addition, when rod cells grew toward bipolar cells, they chose an abnormally high number of Go alpha-positive bipolar cells. These growth patterns were not affected by tweezers manipulation or the amount of growth. Cell orientation of the photoreceptor also did not affect preferences: Cells oriented away from dendritic processes could reorient their axonal pole toward the target cell.

Conclusions: Cone cells preferred normal partners, and rod cells preferred novel partners. These intrinsic preferences indicate that adult nerve cells can have differing capacities for targeting even if they come from the same cell class. Further,these differences may help explain the patterns of photoreceptor sprouting seen in retinal degeneration in which rod, but not cone, cells invade the inner retinal layers where third-order neurons are located.

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Analysis of attraction and repulsion between photoreceptors and their target cells. A: Cell pairs were classed as either showing attraction, repulsion, or undetermined, which means showing neither attraction nor repulsion. There were 89 pairs with cone cells and 114 pairs with rod cells. Cone cells were significantly more attracted than repulsed by bipolar cells. Rod cells were significantly more attracted than repulsed by bipolar cells and, when paired with multipolar cells, were also significantly more attracted than repulsed by them. Significance (asterisk denotes p<0.05) was tested with the exact binomial test. B: The net percent of attraction or repulsion was computed by subtracting the percent of repulsed pairs from the percent of attracted pairs. Although rods were attracted to both multipolar and bipolar cells, they were significantly more attracted to multipolar cells than bipolar cells. Cones, on the other hand, were more attracted to bipolar than multipolar cells. Significance (asterisk denotes p<0.05) was determined with the Pearson χ2 test.
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f3: Analysis of attraction and repulsion between photoreceptors and their target cells. A: Cell pairs were classed as either showing attraction, repulsion, or undetermined, which means showing neither attraction nor repulsion. There were 89 pairs with cone cells and 114 pairs with rod cells. Cone cells were significantly more attracted than repulsed by bipolar cells. Rod cells were significantly more attracted than repulsed by bipolar cells and, when paired with multipolar cells, were also significantly more attracted than repulsed by them. Significance (asterisk denotes p<0.05) was tested with the exact binomial test. B: The net percent of attraction or repulsion was computed by subtracting the percent of repulsed pairs from the percent of attracted pairs. Although rods were attracted to both multipolar and bipolar cells, they were significantly more attracted to multipolar cells than bipolar cells. Cones, on the other hand, were more attracted to bipolar than multipolar cells. Significance (asterisk denotes p<0.05) was determined with the Pearson χ2 test.

Mentions: Observation of the pairs throughout the seven days in vitro showed that retraction of neurites after process outgrowth was rare, suggesting that intercellular effects were relatively stable over time. Cone cells grew an average of 6.4±0.3 processes per cell and formed on average 1.4±0.1 presynaptic varicosities. From analysis of growth patterns, cone cells were found to be attracted to and repulsed by both bipolar and multipolar cells but in distinctly different proportions (Figure 3A). In cone-bipolar cell pairs (n=55), 53% showed attraction and 27% showed repulsion with the remaining pairs classed as undetermined; cones, therefore, showed an overall attraction to appropriate second-order targets. For pairs with third-order cells (n=43), 38% showed attraction and 56% showed repulsion, with 11% undetermined, suggesting a repulsion of cone cells to inappropriate multipolar targets. Rod cells grew an average of 35.3±1.5 processes and formed 5.8±0.6 varicosities per cell. For rod cells (Figure 3A), 52% were attracted and 28% were repulsed by their bipolar partner (n=74); like cone cells, rod cells showed an attraction to normal second-order targets. However, 65% of rod cells were attracted but only 10% were repulsed by multipolar partners (n=40), indicating an additional attraction to novel third-order cells. Of the pairs between rod and multipolar neurons showing attraction, 25% had formed broad cell-to-cell contact compared to 13% of attracted cone-multipolar cell pairs. This broad cell-cell contact was not due to fortuitous close pairing of cells: there was no statistical difference at day of plating in the intercellular distance between cells that subsequently showed attraction compared to those that subsequently showed repulsion. Moreover, pairs with broad contact were observed equally often in rod-bipolar and cone-bipolar cells (28% and 29% of attracted cell pairs, respectively), indicating that cone cells had the ability to make broad cell contacts. Attraction to multipolar cells by rod cells appeared to be strong both on the basis of the number of pairs showing attraction and the number of attracted pairs showing broad cell-cell contact. With chi-square analysis, the attraction of rod cells to multipolar cells was significantly greater than rod cells to bipolar cells (p=0.027, Figure 3B). Thus, there was an obvious difference in the effect of multipolar cells on growth and varicosity formation of cone and rod cells. This comparison between photoreceptor cell types is particularly striking when looking at the net effects of partners (% attraction minus % repulsion; see Figure 3B).


Cone and rod cells have different target preferences in vitro as revealed by optical tweezers.

Clarke RJ, Högnason K, Brimacombe M, Townes-Anderson E - Mol. Vis. (2008)

Analysis of attraction and repulsion between photoreceptors and their target cells. A: Cell pairs were classed as either showing attraction, repulsion, or undetermined, which means showing neither attraction nor repulsion. There were 89 pairs with cone cells and 114 pairs with rod cells. Cone cells were significantly more attracted than repulsed by bipolar cells. Rod cells were significantly more attracted than repulsed by bipolar cells and, when paired with multipolar cells, were also significantly more attracted than repulsed by them. Significance (asterisk denotes p<0.05) was tested with the exact binomial test. B: The net percent of attraction or repulsion was computed by subtracting the percent of repulsed pairs from the percent of attracted pairs. Although rods were attracted to both multipolar and bipolar cells, they were significantly more attracted to multipolar cells than bipolar cells. Cones, on the other hand, were more attracted to bipolar than multipolar cells. Significance (asterisk denotes p<0.05) was determined with the Pearson χ2 test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2383278&req=5

f3: Analysis of attraction and repulsion between photoreceptors and their target cells. A: Cell pairs were classed as either showing attraction, repulsion, or undetermined, which means showing neither attraction nor repulsion. There were 89 pairs with cone cells and 114 pairs with rod cells. Cone cells were significantly more attracted than repulsed by bipolar cells. Rod cells were significantly more attracted than repulsed by bipolar cells and, when paired with multipolar cells, were also significantly more attracted than repulsed by them. Significance (asterisk denotes p<0.05) was tested with the exact binomial test. B: The net percent of attraction or repulsion was computed by subtracting the percent of repulsed pairs from the percent of attracted pairs. Although rods were attracted to both multipolar and bipolar cells, they were significantly more attracted to multipolar cells than bipolar cells. Cones, on the other hand, were more attracted to bipolar than multipolar cells. Significance (asterisk denotes p<0.05) was determined with the Pearson χ2 test.
Mentions: Observation of the pairs throughout the seven days in vitro showed that retraction of neurites after process outgrowth was rare, suggesting that intercellular effects were relatively stable over time. Cone cells grew an average of 6.4±0.3 processes per cell and formed on average 1.4±0.1 presynaptic varicosities. From analysis of growth patterns, cone cells were found to be attracted to and repulsed by both bipolar and multipolar cells but in distinctly different proportions (Figure 3A). In cone-bipolar cell pairs (n=55), 53% showed attraction and 27% showed repulsion with the remaining pairs classed as undetermined; cones, therefore, showed an overall attraction to appropriate second-order targets. For pairs with third-order cells (n=43), 38% showed attraction and 56% showed repulsion, with 11% undetermined, suggesting a repulsion of cone cells to inappropriate multipolar targets. Rod cells grew an average of 35.3±1.5 processes and formed 5.8±0.6 varicosities per cell. For rod cells (Figure 3A), 52% were attracted and 28% were repulsed by their bipolar partner (n=74); like cone cells, rod cells showed an attraction to normal second-order targets. However, 65% of rod cells were attracted but only 10% were repulsed by multipolar partners (n=40), indicating an additional attraction to novel third-order cells. Of the pairs between rod and multipolar neurons showing attraction, 25% had formed broad cell-to-cell contact compared to 13% of attracted cone-multipolar cell pairs. This broad cell-cell contact was not due to fortuitous close pairing of cells: there was no statistical difference at day of plating in the intercellular distance between cells that subsequently showed attraction compared to those that subsequently showed repulsion. Moreover, pairs with broad contact were observed equally often in rod-bipolar and cone-bipolar cells (28% and 29% of attracted cell pairs, respectively), indicating that cone cells had the ability to make broad cell contacts. Attraction to multipolar cells by rod cells appeared to be strong both on the basis of the number of pairs showing attraction and the number of attracted pairs showing broad cell-cell contact. With chi-square analysis, the attraction of rod cells to multipolar cells was significantly greater than rod cells to bipolar cells (p=0.027, Figure 3B). Thus, there was an obvious difference in the effect of multipolar cells on growth and varicosity formation of cone and rod cells. This comparison between photoreceptor cell types is particularly striking when looking at the net effects of partners (% attraction minus % repulsion; see Figure 3B).

Bottom Line: Cell orientation of the photoreceptor also did not affect preferences: Cells oriented away from dendritic processes could reorient their axonal pole toward the target cell.Cone cells preferred normal partners, and rod cells preferred novel partners.Further,these differences may help explain the patterns of photoreceptor sprouting seen in retinal degeneration in which rod, but not cone, cells invade the inner retinal layers where third-order neurons are located.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology and Neuroscience, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103, USA.

ABSTRACT

Purpose: When neural circuits are damaged in adulthood, regenerating and sprouting processes must distinguish appropriate targets to recreate the normal circuitry. We tested the ability of adult nerve cells to target specific cells in culture using the retina as a model system.

Methods: Under sterile culture conditions, retinal cells, isolated from tiger salamander retina, were micromanipulated with optical tweezers to create pairs of first-order photoreceptor cells with second- or third-order retinal neurons. The development of cell contact and presynaptic varicosities, the direction and amount of neuritic growth, and nerve cell polarity were assessed after seven days in vitro. Cultures were labeled for rod opsin to distinguish rod from cone cells and for the alpha subunit of the trimeric G protein Go (Go alpha) to identify cone-dominated and mixed rod-cone ON bipolar cells.

Results: Quantitative analysis of growth demonstrated that target preferences were cell-specific: Cone cells preferred second-order bipolar cells, whereas rod cells grew toward third-order neurons, which include amacrine and ganglion cells. In addition, when rod cells grew toward bipolar cells, they chose an abnormally high number of Go alpha-positive bipolar cells. These growth patterns were not affected by tweezers manipulation or the amount of growth. Cell orientation of the photoreceptor also did not affect preferences: Cells oriented away from dendritic processes could reorient their axonal pole toward the target cell.

Conclusions: Cone cells preferred normal partners, and rod cells preferred novel partners. These intrinsic preferences indicate that adult nerve cells can have differing capacities for targeting even if they come from the same cell class. Further,these differences may help explain the patterns of photoreceptor sprouting seen in retinal degeneration in which rod, but not cone, cells invade the inner retinal layers where third-order neurons are located.

Show MeSH
Related in: MedlinePlus