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Increased apoptosis of myoblasts in Drosophila model for the Walker-Warburg syndrome.

Ueyama M, Akimoto Y, Ichimiya T, Ueda R, Kawakami H, Aigaki T, Nishihara S - PLoS ONE (2010)

Bottom Line: We demonstrated that expression of RNA interference (RNAi) for the rt gene and the tw mutant was almost completely lethal and semi-lethal, respectively.Flies expressing RNAi had reduced lifespans.We then observed a high density of myoblasts with an enhanced degree of apoptosis in the tw mutant, which completely lost enzymatic activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioinformatics, Soka University, Hachioji, Tokyo, Japan.

ABSTRACT
Walker-Warburg syndrome, a progressive muscular dystrophy, is a severe disease with various kinds of symptoms such as muscle weakness and occasional seizures. The genes of protein O-mannosyltransferases 1 and 2 (POMT1 and POMT2), fukutin, and fukutin-related protein are responsible for this syndrome. In our previous study, we cloned Drosophila orthologs of human POMT1 and POMT2 and identified their activity. However, the mechanism of onset of this syndrome is not well understood. Furthermore, little is known about the behavioral properties of the Drosophila POMT1 and POMT2 mutants, which are called rotated abdomen (rt) and twisted (tw), respectively. First, we performed various kinds of behavioral tests and described in detail the muscle structures by using these mutants. The mutant flies exhibited abnormalities in heavy exercises such as climbing or flight but not in light movements such as locomotion. Defective motor function in mutants appeared immediately after eclosion and was exaggerated with aging. Along with motor function, muscle ultrastructure in the tw mutant was altered, as seen in human patients. We demonstrated that expression of RNA interference (RNAi) for the rt gene and the tw mutant was almost completely lethal and semi-lethal, respectively. Flies expressing RNAi had reduced lifespans. These findings clearly demonstrate that Drosophila POMT mutants are models for human muscular dystrophy. We then observed a high density of myoblasts with an enhanced degree of apoptosis in the tw mutant, which completely lost enzymatic activity. In this paper, we propose a novel mechanism for the development of muscular dystrophy: POMT mutation causes high myoblast density and position derangement, which result in apoptosis, muscle disorganization, and muscle cell defects.

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Related in: MedlinePlus

Climbing ability in flies expressing RNAi for the rt gene.The climbing ability of whole-body knockdown flies using Act5C-Gal4 (A), that of neuron-specific knockdown flies using elav-Gal4 (B), and that of glial cell-specific knockdown flies using repo-Gal4 (C). Error bars indicate standard error. Results of the statistical analyses in (A), (B), and (C) are shown in Table 3. The climbing ability of flies expressing RNAi for the rt gene driven by Act5C-Gal4 was significantly less than that of control flies at all ages. Neither neuron- nor glial cell-specific knockdown of the rt gene resulted in a distinct reduction in climbing ability at any age except at 1 day after eclosion in neuron-specific knockdown flies.
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pone-0011557-g002: Climbing ability in flies expressing RNAi for the rt gene.The climbing ability of whole-body knockdown flies using Act5C-Gal4 (A), that of neuron-specific knockdown flies using elav-Gal4 (B), and that of glial cell-specific knockdown flies using repo-Gal4 (C). Error bars indicate standard error. Results of the statistical analyses in (A), (B), and (C) are shown in Table 3. The climbing ability of flies expressing RNAi for the rt gene driven by Act5C-Gal4 was significantly less than that of control flies at all ages. Neither neuron- nor glial cell-specific knockdown of the rt gene resulted in a distinct reduction in climbing ability at any age except at 1 day after eclosion in neuron-specific knockdown flies.

Mentions: We examined in which tissue the expression of the rt and tw genes affects motor function. We used tissue-specific knockdown flies produced by the Gal4-UAS-IR technique [32], the tissue-specific gene knockdown technique that uses the Gal4-UAS system and RNA interference (RNAi) methods. Tissue-specific rt gene knockdown was induced when flies had both Gal4 driver and UAS-rt-IR, whereas gene knockdown was not induced when flies had only Gal4 driver or UAS-rt-IR (Fig. S2). The climbing ability of flies with ubiquitous expression of RNAi for the rt gene as driven by Act5C-Gal4 was significantly lower than that of control flies at all ages (Fig. 2A, Table 3). We also examined the climbing ability of neuron- and glial cell-specific knockdown flies by using elav-Gal4 and repo-Gal4, respectively, since it has been reported that there are some defects in the efficacy of synaptic transmission and changes in the subunit composition of postsynaptic glutamate receptors at the larval neuromuscular junction of rt mutants [24]. Neither neuron- nor glia-specific knockdown of the rt gene resulted in a distinct reduction in climbing ability at any age, except at the age of 1 day after eclosion in neuron-specific knockdown flies (Figs. 2B and C, Table 3). It was noted that the presence of elav-Gal4 or repo-Gal4 has a deteriorative effect on climbing ability for unknown reasons. These data indicated that the climbing ability of adult flies is not mainly influenced by knockdown of the rt gene in neurons or glial cells, and that the expression of this gene in muscles should be relevant to climbing ability.


Increased apoptosis of myoblasts in Drosophila model for the Walker-Warburg syndrome.

Ueyama M, Akimoto Y, Ichimiya T, Ueda R, Kawakami H, Aigaki T, Nishihara S - PLoS ONE (2010)

Climbing ability in flies expressing RNAi for the rt gene.The climbing ability of whole-body knockdown flies using Act5C-Gal4 (A), that of neuron-specific knockdown flies using elav-Gal4 (B), and that of glial cell-specific knockdown flies using repo-Gal4 (C). Error bars indicate standard error. Results of the statistical analyses in (A), (B), and (C) are shown in Table 3. The climbing ability of flies expressing RNAi for the rt gene driven by Act5C-Gal4 was significantly less than that of control flies at all ages. Neither neuron- nor glial cell-specific knockdown of the rt gene resulted in a distinct reduction in climbing ability at any age except at 1 day after eclosion in neuron-specific knockdown flies.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2903483&req=5

pone-0011557-g002: Climbing ability in flies expressing RNAi for the rt gene.The climbing ability of whole-body knockdown flies using Act5C-Gal4 (A), that of neuron-specific knockdown flies using elav-Gal4 (B), and that of glial cell-specific knockdown flies using repo-Gal4 (C). Error bars indicate standard error. Results of the statistical analyses in (A), (B), and (C) are shown in Table 3. The climbing ability of flies expressing RNAi for the rt gene driven by Act5C-Gal4 was significantly less than that of control flies at all ages. Neither neuron- nor glial cell-specific knockdown of the rt gene resulted in a distinct reduction in climbing ability at any age except at 1 day after eclosion in neuron-specific knockdown flies.
Mentions: We examined in which tissue the expression of the rt and tw genes affects motor function. We used tissue-specific knockdown flies produced by the Gal4-UAS-IR technique [32], the tissue-specific gene knockdown technique that uses the Gal4-UAS system and RNA interference (RNAi) methods. Tissue-specific rt gene knockdown was induced when flies had both Gal4 driver and UAS-rt-IR, whereas gene knockdown was not induced when flies had only Gal4 driver or UAS-rt-IR (Fig. S2). The climbing ability of flies with ubiquitous expression of RNAi for the rt gene as driven by Act5C-Gal4 was significantly lower than that of control flies at all ages (Fig. 2A, Table 3). We also examined the climbing ability of neuron- and glial cell-specific knockdown flies by using elav-Gal4 and repo-Gal4, respectively, since it has been reported that there are some defects in the efficacy of synaptic transmission and changes in the subunit composition of postsynaptic glutamate receptors at the larval neuromuscular junction of rt mutants [24]. Neither neuron- nor glia-specific knockdown of the rt gene resulted in a distinct reduction in climbing ability at any age, except at the age of 1 day after eclosion in neuron-specific knockdown flies (Figs. 2B and C, Table 3). It was noted that the presence of elav-Gal4 or repo-Gal4 has a deteriorative effect on climbing ability for unknown reasons. These data indicated that the climbing ability of adult flies is not mainly influenced by knockdown of the rt gene in neurons or glial cells, and that the expression of this gene in muscles should be relevant to climbing ability.

Bottom Line: We demonstrated that expression of RNA interference (RNAi) for the rt gene and the tw mutant was almost completely lethal and semi-lethal, respectively.Flies expressing RNAi had reduced lifespans.We then observed a high density of myoblasts with an enhanced degree of apoptosis in the tw mutant, which completely lost enzymatic activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioinformatics, Soka University, Hachioji, Tokyo, Japan.

ABSTRACT
Walker-Warburg syndrome, a progressive muscular dystrophy, is a severe disease with various kinds of symptoms such as muscle weakness and occasional seizures. The genes of protein O-mannosyltransferases 1 and 2 (POMT1 and POMT2), fukutin, and fukutin-related protein are responsible for this syndrome. In our previous study, we cloned Drosophila orthologs of human POMT1 and POMT2 and identified their activity. However, the mechanism of onset of this syndrome is not well understood. Furthermore, little is known about the behavioral properties of the Drosophila POMT1 and POMT2 mutants, which are called rotated abdomen (rt) and twisted (tw), respectively. First, we performed various kinds of behavioral tests and described in detail the muscle structures by using these mutants. The mutant flies exhibited abnormalities in heavy exercises such as climbing or flight but not in light movements such as locomotion. Defective motor function in mutants appeared immediately after eclosion and was exaggerated with aging. Along with motor function, muscle ultrastructure in the tw mutant was altered, as seen in human patients. We demonstrated that expression of RNA interference (RNAi) for the rt gene and the tw mutant was almost completely lethal and semi-lethal, respectively. Flies expressing RNAi had reduced lifespans. These findings clearly demonstrate that Drosophila POMT mutants are models for human muscular dystrophy. We then observed a high density of myoblasts with an enhanced degree of apoptosis in the tw mutant, which completely lost enzymatic activity. In this paper, we propose a novel mechanism for the development of muscular dystrophy: POMT mutation causes high myoblast density and position derangement, which result in apoptosis, muscle disorganization, and muscle cell defects.

Show MeSH
Related in: MedlinePlus