Milena Pellikka | University of Toronto (original) (raw)
Uploads
Papers by Milena Pellikka
To better understand the consequences of retinal disease causing missense mutations in human CRB1... more To better understand the consequences of retinal disease causing missense mutations in human CRB1 we have recreated 4 mutations in Drosophila crb. Analysis of these mutations identifies domains within the Crb extracellular region that control protein level and distribution, and suggests that CRB1 missense mutations affect rhodopsin trafficking, a known cause of retinal disease.
The Journal of Cell Biology, 2005
American Journal of Ophthalmology, 2002
87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude... more 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 V, gave a useful indication of visual field loss. The authors conclude that field-specific VEPs are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.-Nancy J. Newman • Crumbs, the Drosophila homologue of human CRB1/ RP12, is essential for photoreceptor morphogenesis.
a-catenin associates the cadherin–catenin complex with the actin cytoskeleton. a-catenin binds to... more a-catenin associates the cadherin–catenin complex with the actin cytoskeleton. a-catenin binds to b-catenin, which links it to the
cadherin cytoplasmic tail, and F-actin, but also to a multitude of actin-associated proteins. These interactions suggest a highly complex
cadherin–actin interface. Moreover, mammalian aE-catenin has been implicated in a cadherin-independent cytoplasmic function in
Arp2/3-dependent actin regulation, and in cell signaling. The function and regulation of individual molecular interactions of a-catenin,
in particular during development, are not well understood. We have generated mutations in Drosophila a-Catenin (a-Cat) to investigate
a-Catenin function in this model, and to establish a setup for testing a-Catenin-related constructs in a-Cat-null mutant cells in vivo. Our
analysis of a-Cat mutants in embryogenesis, imaginal discs and oogenesis reveals defects consistent with a loss of cadherin function.
Compromising components of the Arp2/3 complex or its regulator SCAR ameliorate the a-Cat loss-of-function phenotype in embryos
but not in ovaries, suggesting negative regulatory interactions between a-Catenin and the Arp2/3 complex in some tissues. We also show
that the a-Cat mutant phenotype can be rescued by the expression of a DE-cadherin::a-Catenin fusion protein, which argues against an
essential cytosolic, cadherin-independent role of Drosophila a-Catenin.
The linkage of adherens junctions to the actin cytoskeleton is essential for cell adhesion. The c... more The linkage of adherens junctions to the actin cytoskeleton is essential for cell adhesion. The contribution of the cadherincatenin
complex to the interaction between actin and the adherens junction remains an intensely investigated subject that centres on the
function of -catenin, which binds to cadherin through -catenin and can bind F-actin directly or indirectly. Here, we delineate
regions within Drosophila -Catenin ( -Cat) that are important for adherens junction performance in static epithelia and dynamic
morphogenetic processes. Moreover, we address whether persistent -catenin-mediated physical linkage between cadherin and
F-actin is crucial for cell adhesion and characterize the functions of -catenin monomers and dimers at adherens junctions. Our
data support the view that monomeric -catenin acts as an essential physical linker between the cadherin -catenin complex and
the actin cytoskeleton, whereas -catenin dimers are cytoplasmic and form an equilibrium with monomeric junctional -catenin.
European Journal of Cell Biology, Jan 1, 2009
The Immortal Strand Hypothesis proposes that asymmetrically dividing stem cells cosegregate chrom... more The Immortal Strand Hypothesis proposes that asymmetrically dividing stem cells cosegregate chromatids to retain ancestral DNA templates. Using both pulse-chase and label retention assays, we show that non-random partitioning of DNA occurs in germline stem cells (GSCs) in the Drosophila ovary as these divide asymmetrically to generate a new GSC and a differentiating cystoblast. This process is disrupted when GSCs are forced to differentiate through the overexpression of Bag of Marbles, a factor that impels the terminal differentiation of cystoblasts. When Decapentaplegic, a ligand which maintains the undifferentiated state of GSCs, is expressed ectopically the non-random partitioning of DNA is similarly disrupted. Our data suggest asymmetric chromatid segregation is coupled to mechanisms specifying cellular differentiation via asymmetric stem cell division.
Developmental Cell, Jan 1, 2006
The Crumbs (Crb) complex is a key regulator of epithelial cell architecture where it promotes api... more The Crumbs (Crb) complex is a key regulator of epithelial cell architecture where it promotes apical membrane formation. Here, we show that binding of the FERM protein Yurt to the cytoplasmic domain of Crb is part of a negative-feedback loop that regulates Crb activity. Yurt is predominantly a basolateral protein but is recruited by Crb to apical membranes late during epithelial development. Loss of Yurt causes an expansion of the apical membrane in embryonic epithelia and photoreceptor cells similar to Crb overexpression and in contrast to loss of Crb. Analysis of yurt crb double mutants suggests that these genes function in one pathway and that yurt negatively regulates crb. We also show that the mammalian Yurt orthologs YMO1 and EHM2 bind to mammalian Crb proteins. We propose that Yurt is part of an evolutionary conserved negative-feedback mechanism that restricts Crb complex activity in promoting apical membrane formation.
Developmental Cell, Jan 1, 2006
The formation of epithelial lumina is a fundamental process in animal development. Each ommatidiu... more The formation of epithelial lumina is a fundamental process in animal development. Each ommatidium of the Drosophila retina forms an epithelial lumen, the interrhabdomeral space, which has a critical function in vision as it optically isolates individual photoreceptor cells. Ommatidia containing an interrhabdomeral space have evolved from ancestral insect eyes that lack this lumen, as seen, for example, in bees. In a genetic screen, we identified eyes shut (eys) as a gene that is essential for the formation of matrix-filled interrhabdomeral space. Eys is closely related to the proteoglycans agrin and perlecan and secreted by photoreceptor cells into the interrhabdomeral space. The honeybee ortholog of eys is not expressed in photoreceptors, raising the possibility that recruitment of eys expression has made an important contribution to insect eye evolution. Our findings show that the secretion of a proteoglycan into the apical matrix is critical for the formation of epithelial lumina in the fly retina.
Nature, Jan 1, 2002
87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude... more 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 V, gave a useful indication of visual field loss. The authors conclude that field-specific VEPs are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.-Nancy J. Newman • Crumbs, the Drosophila homologue of human CRB1/ RP12, is essential for photoreceptor morphogenesis.
To better understand the consequences of retinal disease causing missense mutations in human CRB1... more To better understand the consequences of retinal disease causing missense mutations in human CRB1 we have recreated 4 mutations in Drosophila crb. Analysis of these mutations identifies domains within the Crb extracellular region that control protein level and distribution, and suggests that CRB1 missense mutations affect rhodopsin trafficking, a known cause of retinal disease.
The Journal of Cell Biology, 2005
American Journal of Ophthalmology, 2002
87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude... more 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 V, gave a useful indication of visual field loss. The authors conclude that field-specific VEPs are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.-Nancy J. Newman • Crumbs, the Drosophila homologue of human CRB1/ RP12, is essential for photoreceptor morphogenesis.
a-catenin associates the cadherin–catenin complex with the actin cytoskeleton. a-catenin binds to... more a-catenin associates the cadherin–catenin complex with the actin cytoskeleton. a-catenin binds to b-catenin, which links it to the
cadherin cytoplasmic tail, and F-actin, but also to a multitude of actin-associated proteins. These interactions suggest a highly complex
cadherin–actin interface. Moreover, mammalian aE-catenin has been implicated in a cadherin-independent cytoplasmic function in
Arp2/3-dependent actin regulation, and in cell signaling. The function and regulation of individual molecular interactions of a-catenin,
in particular during development, are not well understood. We have generated mutations in Drosophila a-Catenin (a-Cat) to investigate
a-Catenin function in this model, and to establish a setup for testing a-Catenin-related constructs in a-Cat-null mutant cells in vivo. Our
analysis of a-Cat mutants in embryogenesis, imaginal discs and oogenesis reveals defects consistent with a loss of cadherin function.
Compromising components of the Arp2/3 complex or its regulator SCAR ameliorate the a-Cat loss-of-function phenotype in embryos
but not in ovaries, suggesting negative regulatory interactions between a-Catenin and the Arp2/3 complex in some tissues. We also show
that the a-Cat mutant phenotype can be rescued by the expression of a DE-cadherin::a-Catenin fusion protein, which argues against an
essential cytosolic, cadherin-independent role of Drosophila a-Catenin.
The linkage of adherens junctions to the actin cytoskeleton is essential for cell adhesion. The c... more The linkage of adherens junctions to the actin cytoskeleton is essential for cell adhesion. The contribution of the cadherincatenin
complex to the interaction between actin and the adherens junction remains an intensely investigated subject that centres on the
function of -catenin, which binds to cadherin through -catenin and can bind F-actin directly or indirectly. Here, we delineate
regions within Drosophila -Catenin ( -Cat) that are important for adherens junction performance in static epithelia and dynamic
morphogenetic processes. Moreover, we address whether persistent -catenin-mediated physical linkage between cadherin and
F-actin is crucial for cell adhesion and characterize the functions of -catenin monomers and dimers at adherens junctions. Our
data support the view that monomeric -catenin acts as an essential physical linker between the cadherin -catenin complex and
the actin cytoskeleton, whereas -catenin dimers are cytoplasmic and form an equilibrium with monomeric junctional -catenin.
European Journal of Cell Biology, Jan 1, 2009
The Immortal Strand Hypothesis proposes that asymmetrically dividing stem cells cosegregate chrom... more The Immortal Strand Hypothesis proposes that asymmetrically dividing stem cells cosegregate chromatids to retain ancestral DNA templates. Using both pulse-chase and label retention assays, we show that non-random partitioning of DNA occurs in germline stem cells (GSCs) in the Drosophila ovary as these divide asymmetrically to generate a new GSC and a differentiating cystoblast. This process is disrupted when GSCs are forced to differentiate through the overexpression of Bag of Marbles, a factor that impels the terminal differentiation of cystoblasts. When Decapentaplegic, a ligand which maintains the undifferentiated state of GSCs, is expressed ectopically the non-random partitioning of DNA is similarly disrupted. Our data suggest asymmetric chromatid segregation is coupled to mechanisms specifying cellular differentiation via asymmetric stem cell division.
Developmental Cell, Jan 1, 2006
The Crumbs (Crb) complex is a key regulator of epithelial cell architecture where it promotes api... more The Crumbs (Crb) complex is a key regulator of epithelial cell architecture where it promotes apical membrane formation. Here, we show that binding of the FERM protein Yurt to the cytoplasmic domain of Crb is part of a negative-feedback loop that regulates Crb activity. Yurt is predominantly a basolateral protein but is recruited by Crb to apical membranes late during epithelial development. Loss of Yurt causes an expansion of the apical membrane in embryonic epithelia and photoreceptor cells similar to Crb overexpression and in contrast to loss of Crb. Analysis of yurt crb double mutants suggests that these genes function in one pathway and that yurt negatively regulates crb. We also show that the mammalian Yurt orthologs YMO1 and EHM2 bind to mammalian Crb proteins. We propose that Yurt is part of an evolutionary conserved negative-feedback mechanism that restricts Crb complex activity in promoting apical membrane formation.
Developmental Cell, Jan 1, 2006
The formation of epithelial lumina is a fundamental process in animal development. Each ommatidiu... more The formation of epithelial lumina is a fundamental process in animal development. Each ommatidium of the Drosophila retina forms an epithelial lumen, the interrhabdomeral space, which has a critical function in vision as it optically isolates individual photoreceptor cells. Ommatidia containing an interrhabdomeral space have evolved from ancestral insect eyes that lack this lumen, as seen, for example, in bees. In a genetic screen, we identified eyes shut (eys) as a gene that is essential for the formation of matrix-filled interrhabdomeral space. Eys is closely related to the proteoglycans agrin and perlecan and secreted by photoreceptor cells into the interrhabdomeral space. The honeybee ortholog of eys is not expressed in photoreceptors, raising the possibility that recruitment of eys expression has made an important contribution to insect eye evolution. Our findings show that the secretion of a proteoglycan into the apical matrix is critical for the formation of epithelial lumina in the fly retina.
Nature, Jan 1, 2002
87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude... more 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 V, gave a useful indication of visual field loss. The authors conclude that field-specific VEPs are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.-Nancy J. Newman • Crumbs, the Drosophila homologue of human CRB1/ RP12, is essential for photoreceptor morphogenesis.