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Cell-type specific roles for PTEN in establishing a functional retinal architecture.

Cantrup R, Dixit R, Palmesino E, Bonfield S, Shaker T, Tachibana N, Zinyk D, Dalesman S, Yamakawa K, Stell WK, Wong RO, Reese BE, Kania A, Sauvé Y, Schuurmans C - PLoS ONE (2012)

Bottom Line: Furthermore, while Pten mutant RGC axons targeted appropriate brain regions, optokinetic spatial acuity was reduced in Pten mutant animals.We conclude that Pten regulates somal positioning and neurite arborization patterns of a subset of retinal cells that form mosaics, likely functioning independently of Dscam, at least during the embryonic period.Our findings thus reveal an unexpected level of cellular specificity for the multi-purpose phosphatase, and identify Pten as an integral component of a novel cell positioning pathway in the retina.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.

ABSTRACT

Background: The retina has a unique three-dimensional architecture, the precise organization of which allows for complete sampling of the visual field. Along the radial or apicobasal axis, retinal neurons and their dendritic and axonal arbors are segregated into layers, while perpendicular to this axis, in the tangential plane, four of the six neuronal types form patterned cellular arrays, or mosaics. Currently, the molecular cues that control retinal cell positioning are not well-understood, especially those that operate in the tangential plane. Here we investigated the role of the PTEN phosphatase in establishing a functional retinal architecture.

Methodology/principal findings: In the developing retina, PTEN was localized preferentially to ganglion, amacrine and horizontal cells, whose somata are distributed in mosaic patterns in the tangential plane. Generation of a retina-specific Pten knock-out resulted in retinal ganglion, amacrine and horizontal cell hypertrophy, and expansion of the inner plexiform layer. The spacing of Pten mutant mosaic populations was also aberrant, as were the arborization and fasciculation patterns of their processes, displaying cell type-specific defects in the radial and tangential dimensions. Irregular oscillatory potentials were also observed in Pten mutant electroretinograms, indicative of asynchronous amacrine cell firing. Furthermore, while Pten mutant RGC axons targeted appropriate brain regions, optokinetic spatial acuity was reduced in Pten mutant animals. Finally, while some features of the Pten mutant retina appeared similar to those reported in Dscam-mutant mice, PTEN expression and activity were normal in the absence of Dscam.

Conclusions/significance: We conclude that Pten regulates somal positioning and neurite arborization patterns of a subset of retinal cells that form mosaics, likely functioning independently of Dscam, at least during the embryonic period. Our findings thus reveal an unexpected level of cellular specificity for the multi-purpose phosphatase, and identify Pten as an integral component of a novel cell positioning pathway in the retina.

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Interactions between Pten and Dscam.(A,B) Distribution of Dscam transcripts in P7 wild-type (A) and Pten cKO (B) retinae. (C–F) Labeling of E18.5 wild-type and Dscam KO retinae with Pax6 (red)/syntaxin (green; C,D) and calretinin (red; E,F). Blue is DAPI counterstain. (G–I) Western blotting and densitometry for PTEN and pPTENSer380 (G), total Akt and pAktSer473 (H), and total S6 and pS6Ser235/236 (I) in E18.5 wild-type and Dscam mutants. gcl, ganglion cell layer; inl, inner nuclear layer; ipl, inner plexiform layer; onl, outer nuclear layer; opl, outer plexiform layer. Scale bars = 50 µm.
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pone-0032795-g009: Interactions between Pten and Dscam.(A,B) Distribution of Dscam transcripts in P7 wild-type (A) and Pten cKO (B) retinae. (C–F) Labeling of E18.5 wild-type and Dscam KO retinae with Pax6 (red)/syntaxin (green; C,D) and calretinin (red; E,F). Blue is DAPI counterstain. (G–I) Western blotting and densitometry for PTEN and pPTENSer380 (G), total Akt and pAktSer473 (H), and total S6 and pS6Ser235/236 (I) in E18.5 wild-type and Dscam mutants. gcl, ganglion cell layer; inl, inner nuclear layer; ipl, inner plexiform layer; onl, outer nuclear layer; opl, outer plexiform layer. Scale bars = 50 µm.

Mentions: Since PTEN is an intracellular signaling molecule, it seemed likely itself to be regulated by extrinsic signals. For that reason, we were struck by the similarities between Pten and Dscam mutant retinas, both of which develop a markedly thickened IPL and display aberrant fasciculation and mosaic patterning of subsets of amacrine cells [9], [11]. To test for regulatory interactions between Pten and Dscam, we first determined whether retinal expression of Dscam was altered in the absence of Pten expression. Dscam is expressed in amacrine cells and RGCs in the INL and GCL [9], [11], as shown here in P7 wild-type retinas (Figure 9A). In P7 Pten cKO retinas, Dscam transcripts were similarly detected in the INL and GCL, but expression was also detected in ectopic cells in the IPL (Figure 9B). Thus, the maintenance of Dscam expression in Pten cKO retinas was not itself sufficient to prevent amacrine cells and/or RGCs from aberrantly migrating into the IPL. Moreover, DSCAM does not prevent amacrine cell processes from fasciculating in the IPL in Pten cKO retinas, even though DSCAM is thought to prevent such homotypic adhesion [10].


Cell-type specific roles for PTEN in establishing a functional retinal architecture.

Cantrup R, Dixit R, Palmesino E, Bonfield S, Shaker T, Tachibana N, Zinyk D, Dalesman S, Yamakawa K, Stell WK, Wong RO, Reese BE, Kania A, Sauvé Y, Schuurmans C - PLoS ONE (2012)

Interactions between Pten and Dscam.(A,B) Distribution of Dscam transcripts in P7 wild-type (A) and Pten cKO (B) retinae. (C–F) Labeling of E18.5 wild-type and Dscam KO retinae with Pax6 (red)/syntaxin (green; C,D) and calretinin (red; E,F). Blue is DAPI counterstain. (G–I) Western blotting and densitometry for PTEN and pPTENSer380 (G), total Akt and pAktSer473 (H), and total S6 and pS6Ser235/236 (I) in E18.5 wild-type and Dscam mutants. gcl, ganglion cell layer; inl, inner nuclear layer; ipl, inner plexiform layer; onl, outer nuclear layer; opl, outer plexiform layer. Scale bars = 50 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3293905&req=5

pone-0032795-g009: Interactions between Pten and Dscam.(A,B) Distribution of Dscam transcripts in P7 wild-type (A) and Pten cKO (B) retinae. (C–F) Labeling of E18.5 wild-type and Dscam KO retinae with Pax6 (red)/syntaxin (green; C,D) and calretinin (red; E,F). Blue is DAPI counterstain. (G–I) Western blotting and densitometry for PTEN and pPTENSer380 (G), total Akt and pAktSer473 (H), and total S6 and pS6Ser235/236 (I) in E18.5 wild-type and Dscam mutants. gcl, ganglion cell layer; inl, inner nuclear layer; ipl, inner plexiform layer; onl, outer nuclear layer; opl, outer plexiform layer. Scale bars = 50 µm.
Mentions: Since PTEN is an intracellular signaling molecule, it seemed likely itself to be regulated by extrinsic signals. For that reason, we were struck by the similarities between Pten and Dscam mutant retinas, both of which develop a markedly thickened IPL and display aberrant fasciculation and mosaic patterning of subsets of amacrine cells [9], [11]. To test for regulatory interactions between Pten and Dscam, we first determined whether retinal expression of Dscam was altered in the absence of Pten expression. Dscam is expressed in amacrine cells and RGCs in the INL and GCL [9], [11], as shown here in P7 wild-type retinas (Figure 9A). In P7 Pten cKO retinas, Dscam transcripts were similarly detected in the INL and GCL, but expression was also detected in ectopic cells in the IPL (Figure 9B). Thus, the maintenance of Dscam expression in Pten cKO retinas was not itself sufficient to prevent amacrine cells and/or RGCs from aberrantly migrating into the IPL. Moreover, DSCAM does not prevent amacrine cell processes from fasciculating in the IPL in Pten cKO retinas, even though DSCAM is thought to prevent such homotypic adhesion [10].

Bottom Line: Furthermore, while Pten mutant RGC axons targeted appropriate brain regions, optokinetic spatial acuity was reduced in Pten mutant animals.We conclude that Pten regulates somal positioning and neurite arborization patterns of a subset of retinal cells that form mosaics, likely functioning independently of Dscam, at least during the embryonic period.Our findings thus reveal an unexpected level of cellular specificity for the multi-purpose phosphatase, and identify Pten as an integral component of a novel cell positioning pathway in the retina.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.

ABSTRACT

Background: The retina has a unique three-dimensional architecture, the precise organization of which allows for complete sampling of the visual field. Along the radial or apicobasal axis, retinal neurons and their dendritic and axonal arbors are segregated into layers, while perpendicular to this axis, in the tangential plane, four of the six neuronal types form patterned cellular arrays, or mosaics. Currently, the molecular cues that control retinal cell positioning are not well-understood, especially those that operate in the tangential plane. Here we investigated the role of the PTEN phosphatase in establishing a functional retinal architecture.

Methodology/principal findings: In the developing retina, PTEN was localized preferentially to ganglion, amacrine and horizontal cells, whose somata are distributed in mosaic patterns in the tangential plane. Generation of a retina-specific Pten knock-out resulted in retinal ganglion, amacrine and horizontal cell hypertrophy, and expansion of the inner plexiform layer. The spacing of Pten mutant mosaic populations was also aberrant, as were the arborization and fasciculation patterns of their processes, displaying cell type-specific defects in the radial and tangential dimensions. Irregular oscillatory potentials were also observed in Pten mutant electroretinograms, indicative of asynchronous amacrine cell firing. Furthermore, while Pten mutant RGC axons targeted appropriate brain regions, optokinetic spatial acuity was reduced in Pten mutant animals. Finally, while some features of the Pten mutant retina appeared similar to those reported in Dscam-mutant mice, PTEN expression and activity were normal in the absence of Dscam.

Conclusions/significance: We conclude that Pten regulates somal positioning and neurite arborization patterns of a subset of retinal cells that form mosaics, likely functioning independently of Dscam, at least during the embryonic period. Our findings thus reveal an unexpected level of cellular specificity for the multi-purpose phosphatase, and identify Pten as an integral component of a novel cell positioning pathway in the retina.

Show MeSH
Related in: MedlinePlus