Limits...
Dystroglycan and mitochondrial ribosomal protein L34 regulate differentiation in the Drosophila eye.

Zhan Y, Melian NY, Pantoja M, Haines N, Ruohola-Baker H, Bourque CW, Rao Y, Carbonetto S - PLoS ONE (2010)

Bottom Line: Overexpression of DG in R cells results in a small but significant increase in their size.We conclude that DG does not affect neuronal commitment but functions R cell autonomously to regulate neuronal elongation during differentiation in the pupa.We discuss these findings in view of recent work implicating DG as a regulator of cell metabolism and its genetic interaction with mRpL34, a member of a class of mitochondrial genes essential for normal metabolic function.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Neuroscience, McGill University Health Centre, Montreal, Quebec, Canada.

ABSTRACT
Mutations that diminish the function of the extracellular matrix receptor Dystroglycan (DG) result in muscular dystrophies, with associated neuronal migration defects in the brain and mental retardation e.g. Muscle Eye Brain Disease. To gain insight into the function of DG in the nervous system we initiated a study to examine its contribution to development of the eye of Drosophila melanogaster. Immuno-histochemistry showed that DG is concentrated on the apical surface of photoreceptors (R) cells during specification of cell-fate in the third instar larva and is maintained at this location through early pupal stages. In point mutations that are for DG we see abortive R cell elongation during differentiation that first appears in the pupa and results in stunted R cells in the adult. Overexpression of DG in R cells results in a small but significant increase in their size. R cell differentiation defects appear at the same stage in a deficiency line Df(2R)Dg(248) that affects Dg and the neighboring mitochondrial ribosomal gene, mRpL34. In the adult, these flies have severely disrupted R cells as well as defects in the lens and ommatidia. Expression of an mRpL34 transgene rescues much of this phenotype. We conclude that DG does not affect neuronal commitment but functions R cell autonomously to regulate neuronal elongation during differentiation in the pupa. We discuss these findings in view of recent work implicating DG as a regulator of cell metabolism and its genetic interaction with mRpL34, a member of a class of mitochondrial genes essential for normal metabolic function.

Show MeSH

Related in: MedlinePlus

Large mosaic clones of Df(2R)Dg248 results in disruption of the adult eye.Light and scanning EM micrographs of the wild type fly eye (A–F) show the classical ommatidial facets and bristles of the external eye. A′–F′, show the equivalent micrographs of fly eyes of Df(2R)Dg248 clones generated by the ey, FLP/FRT system. The Df(2R)Dg248 tissue in A′ is white while tissue with heterozygous expression of the wild type gene is red. The Df(2R)Dg248 (white) regions appear flattened and glossy (A′). Cross sections of the internal eye reveal that the normal (B) array of R-cells with central rhabdomeres is disrupted (B′ arrows) and there appears to be cell debris (B′ arrowhead) in these regions. Electron micrographs reveal regions where the external eye has collapsed and the facets have been obliterated (C′, D′). A transverse section through the eyes reveals the normal length (E, double arrow head) of the retina and its ordered array of ommatidia (arrow). The Df(2R)Dg248 (white) region appears disrupted (arrow) and the retinal thickness is shorter (double arrow head). The lenses, which normally (F) form a biconvex disc, are flattened on their external, but not internal, faces though the cuticle that forms the external boundary is visible within a flattened and partially “empty” lens (arrow, F′). (G) ERGs were recorded after a 5 min dark adaptation followed by a 2 sec bright-light pulses (top trace). The bottom trace shows representative ERGs of wild type (left) and Df(2R)Dg248 regions (white) of mosaic eyes. In Df(2R)Dg248 regions the 9-14 mV R cell depolarization (left) was greatly diminished and the early and late synaptic transients (left) completely abolished. Quantification of ERG parameters in wild type and Df(2R)Dg248 patches showed significant differences (P<0.01) between wild type and Df(2R)Dg248 eyes.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2864756&req=5

pone-0010488-g004: Large mosaic clones of Df(2R)Dg248 results in disruption of the adult eye.Light and scanning EM micrographs of the wild type fly eye (A–F) show the classical ommatidial facets and bristles of the external eye. A′–F′, show the equivalent micrographs of fly eyes of Df(2R)Dg248 clones generated by the ey, FLP/FRT system. The Df(2R)Dg248 tissue in A′ is white while tissue with heterozygous expression of the wild type gene is red. The Df(2R)Dg248 (white) regions appear flattened and glossy (A′). Cross sections of the internal eye reveal that the normal (B) array of R-cells with central rhabdomeres is disrupted (B′ arrows) and there appears to be cell debris (B′ arrowhead) in these regions. Electron micrographs reveal regions where the external eye has collapsed and the facets have been obliterated (C′, D′). A transverse section through the eyes reveals the normal length (E, double arrow head) of the retina and its ordered array of ommatidia (arrow). The Df(2R)Dg248 (white) region appears disrupted (arrow) and the retinal thickness is shorter (double arrow head). The lenses, which normally (F) form a biconvex disc, are flattened on their external, but not internal, faces though the cuticle that forms the external boundary is visible within a flattened and partially “empty” lens (arrow, F′). (G) ERGs were recorded after a 5 min dark adaptation followed by a 2 sec bright-light pulses (top trace). The bottom trace shows representative ERGs of wild type (left) and Df(2R)Dg248 regions (white) of mosaic eyes. In Df(2R)Dg248 regions the 9-14 mV R cell depolarization (left) was greatly diminished and the early and late synaptic transients (left) completely abolished. Quantification of ERG parameters in wild type and Df(2R)Dg248 patches showed significant differences (P<0.01) between wild type and Df(2R)Dg248 eyes.

Mentions: Mitochondrial dysfunction results in a subset of neurodegenerative diseases because of the function of this organelle in apoptosis. Other mitochondrial diseases have been linked to mutations in genes encoding respiratory chain proteins and, more recently, nuclear genes like mRpL34, that are responsible for mitochondrial ribosomal translation [23], [32]. Mitochondrial diseases typically affect brain and muscle [23] similar to dystroglycanopathies [11]. For mitochondrial diseases this is thought to reflect the high metabolic activity of muscle and brain. Recently, Mirouse et al., [24] have reported that DG regulates cell polarity during development via AMP Kinase, a central regulator of metabolic homeostasis in cells [33]. In this context, we asked whether a similar pathway might function in CNS development by comparing R cell differentiation in Df(2R)Dg248 with Dg point mutants. Since the Df(2R)Dg248 homozygotes die as immature larvae we examined mosaic eyes generated using ey-FLP/FRT system [30]. In the adult Df(2R)Dg248 tissue can be recognized by a lack of pigment granules and appear as white patches (Fig. 4A′). Mosaic eyes are irregularly shaped and appear glossy (Fig. 4A′). Electron micrographs show regions where the external eye has collapsed and the facets have been obliterated (Fig. 4C′, D′). Histology of the eye reveals flattening of the external aspect of the lens (Fig. 4E′–F′), which is normally a biconvex disc (Fig. 4E–F). Areas containing Df(2R)Dg248 ommatidia, marked by the absence of brown pigment granules, appear disorganized (black arrowhead, Fig. 4B′). Importantly, the R cells are disrupted in this deficiency to an extent greater than the Dg point mutants where the R cells were simply stunted.


Dystroglycan and mitochondrial ribosomal protein L34 regulate differentiation in the Drosophila eye.

Zhan Y, Melian NY, Pantoja M, Haines N, Ruohola-Baker H, Bourque CW, Rao Y, Carbonetto S - PLoS ONE (2010)

Large mosaic clones of Df(2R)Dg248 results in disruption of the adult eye.Light and scanning EM micrographs of the wild type fly eye (A–F) show the classical ommatidial facets and bristles of the external eye. A′–F′, show the equivalent micrographs of fly eyes of Df(2R)Dg248 clones generated by the ey, FLP/FRT system. The Df(2R)Dg248 tissue in A′ is white while tissue with heterozygous expression of the wild type gene is red. The Df(2R)Dg248 (white) regions appear flattened and glossy (A′). Cross sections of the internal eye reveal that the normal (B) array of R-cells with central rhabdomeres is disrupted (B′ arrows) and there appears to be cell debris (B′ arrowhead) in these regions. Electron micrographs reveal regions where the external eye has collapsed and the facets have been obliterated (C′, D′). A transverse section through the eyes reveals the normal length (E, double arrow head) of the retina and its ordered array of ommatidia (arrow). The Df(2R)Dg248 (white) region appears disrupted (arrow) and the retinal thickness is shorter (double arrow head). The lenses, which normally (F) form a biconvex disc, are flattened on their external, but not internal, faces though the cuticle that forms the external boundary is visible within a flattened and partially “empty” lens (arrow, F′). (G) ERGs were recorded after a 5 min dark adaptation followed by a 2 sec bright-light pulses (top trace). The bottom trace shows representative ERGs of wild type (left) and Df(2R)Dg248 regions (white) of mosaic eyes. In Df(2R)Dg248 regions the 9-14 mV R cell depolarization (left) was greatly diminished and the early and late synaptic transients (left) completely abolished. Quantification of ERG parameters in wild type and Df(2R)Dg248 patches showed significant differences (P<0.01) between wild type and Df(2R)Dg248 eyes.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2864756&req=5

pone-0010488-g004: Large mosaic clones of Df(2R)Dg248 results in disruption of the adult eye.Light and scanning EM micrographs of the wild type fly eye (A–F) show the classical ommatidial facets and bristles of the external eye. A′–F′, show the equivalent micrographs of fly eyes of Df(2R)Dg248 clones generated by the ey, FLP/FRT system. The Df(2R)Dg248 tissue in A′ is white while tissue with heterozygous expression of the wild type gene is red. The Df(2R)Dg248 (white) regions appear flattened and glossy (A′). Cross sections of the internal eye reveal that the normal (B) array of R-cells with central rhabdomeres is disrupted (B′ arrows) and there appears to be cell debris (B′ arrowhead) in these regions. Electron micrographs reveal regions where the external eye has collapsed and the facets have been obliterated (C′, D′). A transverse section through the eyes reveals the normal length (E, double arrow head) of the retina and its ordered array of ommatidia (arrow). The Df(2R)Dg248 (white) region appears disrupted (arrow) and the retinal thickness is shorter (double arrow head). The lenses, which normally (F) form a biconvex disc, are flattened on their external, but not internal, faces though the cuticle that forms the external boundary is visible within a flattened and partially “empty” lens (arrow, F′). (G) ERGs were recorded after a 5 min dark adaptation followed by a 2 sec bright-light pulses (top trace). The bottom trace shows representative ERGs of wild type (left) and Df(2R)Dg248 regions (white) of mosaic eyes. In Df(2R)Dg248 regions the 9-14 mV R cell depolarization (left) was greatly diminished and the early and late synaptic transients (left) completely abolished. Quantification of ERG parameters in wild type and Df(2R)Dg248 patches showed significant differences (P<0.01) between wild type and Df(2R)Dg248 eyes.
Mentions: Mitochondrial dysfunction results in a subset of neurodegenerative diseases because of the function of this organelle in apoptosis. Other mitochondrial diseases have been linked to mutations in genes encoding respiratory chain proteins and, more recently, nuclear genes like mRpL34, that are responsible for mitochondrial ribosomal translation [23], [32]. Mitochondrial diseases typically affect brain and muscle [23] similar to dystroglycanopathies [11]. For mitochondrial diseases this is thought to reflect the high metabolic activity of muscle and brain. Recently, Mirouse et al., [24] have reported that DG regulates cell polarity during development via AMP Kinase, a central regulator of metabolic homeostasis in cells [33]. In this context, we asked whether a similar pathway might function in CNS development by comparing R cell differentiation in Df(2R)Dg248 with Dg point mutants. Since the Df(2R)Dg248 homozygotes die as immature larvae we examined mosaic eyes generated using ey-FLP/FRT system [30]. In the adult Df(2R)Dg248 tissue can be recognized by a lack of pigment granules and appear as white patches (Fig. 4A′). Mosaic eyes are irregularly shaped and appear glossy (Fig. 4A′). Electron micrographs show regions where the external eye has collapsed and the facets have been obliterated (Fig. 4C′, D′). Histology of the eye reveals flattening of the external aspect of the lens (Fig. 4E′–F′), which is normally a biconvex disc (Fig. 4E–F). Areas containing Df(2R)Dg248 ommatidia, marked by the absence of brown pigment granules, appear disorganized (black arrowhead, Fig. 4B′). Importantly, the R cells are disrupted in this deficiency to an extent greater than the Dg point mutants where the R cells were simply stunted.

Bottom Line: Overexpression of DG in R cells results in a small but significant increase in their size.We conclude that DG does not affect neuronal commitment but functions R cell autonomously to regulate neuronal elongation during differentiation in the pupa.We discuss these findings in view of recent work implicating DG as a regulator of cell metabolism and its genetic interaction with mRpL34, a member of a class of mitochondrial genes essential for normal metabolic function.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Neuroscience, McGill University Health Centre, Montreal, Quebec, Canada.

ABSTRACT
Mutations that diminish the function of the extracellular matrix receptor Dystroglycan (DG) result in muscular dystrophies, with associated neuronal migration defects in the brain and mental retardation e.g. Muscle Eye Brain Disease. To gain insight into the function of DG in the nervous system we initiated a study to examine its contribution to development of the eye of Drosophila melanogaster. Immuno-histochemistry showed that DG is concentrated on the apical surface of photoreceptors (R) cells during specification of cell-fate in the third instar larva and is maintained at this location through early pupal stages. In point mutations that are for DG we see abortive R cell elongation during differentiation that first appears in the pupa and results in stunted R cells in the adult. Overexpression of DG in R cells results in a small but significant increase in their size. R cell differentiation defects appear at the same stage in a deficiency line Df(2R)Dg(248) that affects Dg and the neighboring mitochondrial ribosomal gene, mRpL34. In the adult, these flies have severely disrupted R cells as well as defects in the lens and ommatidia. Expression of an mRpL34 transgene rescues much of this phenotype. We conclude that DG does not affect neuronal commitment but functions R cell autonomously to regulate neuronal elongation during differentiation in the pupa. We discuss these findings in view of recent work implicating DG as a regulator of cell metabolism and its genetic interaction with mRpL34, a member of a class of mitochondrial genes essential for normal metabolic function.

Show MeSH
Related in: MedlinePlus