Cynthia Bayer - Academia.edu (original) (raw)

Papers by Cynthia Bayer

Research paper thumbnail of Genetic interactions between the RhoA and Stubble-stubbloid loci suggest a role for a type II transmembrane serine protease in intracellular signaling during Drosophila imaginal disc morphogenesis

Genetics, 2003

The Drosophila RhoA (Rho1) GTPase is essential for postembryonic morphogenesis of leg and wing im... more The Drosophila RhoA (Rho1) GTPase is essential for postembryonic morphogenesis of leg and wing imaginal discs. Mutations in RhoA enhance leg and wing defects associated with mutations in zipper, the gene encoding the heavy chain of nonmuscle myosin II. We demonstrate here that mutations affecting the RhoA signaling pathway also interact genetically with mutations in the Stubble-stubbloid (Sb-sbd) locus that encodes an unusual type II transmembrane serine protease required for normal leg and wing morphogenesis. In addition, a leg malformation phenotype associated with overexpression of Sb-sbd in prepupal leg discs is suppressed when RhoA gene dose is reduced, suggesting that RhoA and Sb-sbd act in a common pathway during leg morphogenesis. We also characterized six mutations identified as enhancers of zipper mutant leg defects. Three of these genes encode known members of the RhoA signaling pathway (RhoA, DRhoGEF2, and zipper). The remaining three enhancer of zipper mutations interac...

Research paper thumbnail of Contributors

Research paper thumbnail of The Drosophila Broad-CompZex Encodes a Family of Related Proteins Containing Zinc Fingers

The Broad-Complex (BR-C) is essential for metamorphosis in Drosophila melanogaster. This locus is... more The Broad-Complex (BR-C) is essential for metamorphosis in Drosophila melanogaster. This locus is coextensive with the 2B5 ecdysone-responsive early puff and is necessary for puffing and transcription of many subsequently activated late genes in the developing salivary gland. Mapping of 31 cDNA clones indicates that approximately 100 kb of the genome is devoted to the synthesis of many BR-C RNAs.

Research paper thumbnail of Relationships between Protein Isoforms and Genetic Functions Demonstrate Functional Redundancy at theBroad-ComplexduringDrosophilaMetamorphosis

Developmental Biology, 1997

reproductive, adult form. At the onset of metamorphosis ecdysone induces a set of early genes whi... more reproductive, adult form. At the onset of metamorphosis ecdysone induces a set of early genes which coordinate tissuespecific responses to hormone. The Broad-Complex (BR-C) early gene, which acts as a global regulator of tissue-specific responses to ecdysone, encodes a family of zinc-finger DNA binding proteins known as Z1, Z2, Z3, and Z4. Genetically the BR-C encodes three complementing functions, br, rbp, and 2Bc, and a class of npr1 alleles that fail to complement any of the other genetic functions. The effects of BR-C mutations on metamorphic development are highly pleiotropic, yet little is known about the roles of individual BR-C proteins in directing the required responses to ecdysone. Because the BR-C is a vital regulator of metamorphosis it is essential to establish the relationships between BR-C genetic functions and protein products. We present here the first general and definitive study of these relationships. Using heat-inducible transgenes we have rescued lethality associated with each of the complementing genetic functions and have restored transcriptional activity of tissue-specific BR-C / -dependent target genes. Our data lead us to conclude that br / function is only provided by the Z2 isoform. We find that Z1 transgenes provide full rbp / function, while Z4 provides partial function. Likewise, while Z3 provides full 2Bc / function, Z2 also provides partial function. These results indicate possible functional redundancy or regulatory dependence (via autoregulation) associated with the rbp / and 2Bc / functions. The establishment of these relationships between BR-C genetic functions and protein isoforms is an important step toward understanding the roles of BR-C proteins in directing metamorphic responses to ecdysone. ᭧ 1997 Academic Press 2 To whom correspondence should be addressed. Fax

Research paper thumbnail of TheDrosophila Broad-ComplexEarly Gene Directly Regulates Late Gene Transcription during the Ecdysone-Induced Puffing Cascade

Developmental Biology, 1996

The ensemble of tissue-specific changes that drivesDrosophilametamorphosis is initiated by the st... more The ensemble of tissue-specific changes that drivesDrosophilametamorphosis is initiated by the steroid hormone ecdysone and proceeds through a transcriptional cascade comprised of primary response transcriptional regulators and secondary response structural genes. TheBroad-Complex(BR-C) primary response early gene is composed of several distinct genetic functions and encodes a family of related transcription factor isoforms. Our objective in this study was to determine

Research paper thumbnail of A Switch inBroad-ComplexZinc-Finger Isoform Expression Is Regulated Posttranscriptionally during the Metamorphosis ofDrosophilaImaginal Discs

Developmental Biology, 1996

The Broad-Complex (BR-C) is a key member of the 20-hydroxyecdysone regulatory hierarchy that coor... more The Broad-Complex (BR-C) is a key member of the 20-hydroxyecdysone regulatory hierarchy that coordinates changes in gene expression during Drosophila metamorphosis. The family of transcription factors encoded by the BR-C share a common amino-terminal domain which is fused by alternative splicing to one of four pairs of C2H2 zinc-finger domains (Z1, Z2, Z3, and Z4). In this study, we examine the temporal expression of transcripts encoding each BR-C zinc-finger isoform-including the newly discovered fourth zinc-finger domain-during the metamorphosis of imaginal discs which form the integumental structures of the adult head and thorax. We find that all BR-C zinc-finger RNA isoforms are induced as a primary response to 20-hydroxyecdysone. However, induced BR-C RNA isoforms exhibit two divergent expression profiles. The Z2, Z3, and Z4 RNA isoforms accumulate to high levels at the beginning of the ecdysone response and abruptly disappear after several hours. In contrast, the Z1 RNA isoform continues to accumulate while the others decline, resulting in a switch in relative isoform levels. Using probes specific to different regions of the BR-C, we show that the switch in BR-C RNA isoform expression appears to be posttranscriptionally regulated, presumably by ecdysone-responsive factors. We propose that this switch results from a change in splice acceptor site choice. Finally, we present a model describing how this temporal switch in isoform expression could mediate changes in BR-C function, from transcriptional activation to repression and vice versa, that are critical for coordinate downstream target gene expression.

Research paper thumbnail of Dynamic Expression of Broad-Complex Isoforms Mediates Temporal Control of an Ecdysteroid Target Gene at the Onset of Drosophila Metamorphosis

Developmental Biology, 2000

Metamorphosis in Drosophila melanogaster is orchestrated by the steroid hormone ecdysone, which t... more Metamorphosis in Drosophila melanogaster is orchestrated by the steroid hormone ecdysone, which triggers a cascade of primary-response transcriptional regulators and secondary effector genes during the third larval instar and prepupal periods of development. The early ecdysone-response Broad-Complex (BR-C) gene, a key regulator of this cascade, is defined by three complementing functions (rbp, br, and 2Bc) and encodes several distinct zinc-finger-containing isoforms (Z1 to Z4). Using isoform-specific polyclonal antibodies we observe in the fat body a switch in BR-C isoform expression from the Z2 to the other three isoforms during the third instar. We show that the 2Bc ؉ function that corresponds presumably to the Z3 isoform is required for the larval fat body-specific expression of a transgenic construct (AE) in which the lacZ gene is under the control of the ecdysone-regulated enhancer and minimal promoter of the fat body protein 1 (Fbp1) gene. Using hs(BR-C) transgenes, we demonstrate that overexpression of Z1, Z3, or Z4, but not Z2, is able to rescue AE activity with faithful tissue specificity in a BR-C null (npr1) genetic context, demonstrating a partial functional redundancy between Z1, Z3, and Z4 isoforms. We also show that continuous overexpression of Z2 during the third instar represses AE, while conversely, expression of Z3 earlier than its normal onset induces precocious expression of the construct. This finding establishes a tight correlation between the dynamic pattern of expression of the BR-C isoforms and their individual repressive or inductive roles in AE regulation. Altogether our results demonstrate that the balance between BR-C protein isoforms in the fat body mediates, in part, the precise timing of the ecdysone activation of the AE construct but does not modulate its tissue specificity.

Research paper thumbnail of Evolution of the Drosophila broad locus: the Manduca sexta broad Z4 isoform has biological activity in Drosophila

Development Genes and Evolution, 2003

The Drosophila melanogaster broad locus is essential for normal metamorphic development. Broad en... more The Drosophila melanogaster broad locus is essential for normal metamorphic development. Broad encodes three genetically distinct functions (rbp, br, and 2Bc) and a family of four zinc-finger DNA-binding proteins (Z1-Z4). The Z1, Z2, and Z3 protein isoforms are primarily associated with the rbp, br, and 2Bc genetic functions respectively. The Z4 protein isoform also provides some rbp genetic function, however an essential function for the Z4 isoform in metamorphosis has not been identified. To determine the degree of conservation of Z4 function between the tobacco hornworm Manduca sexta and Drosophila we generated transgenic Drosophila expressing the Manduca broad Z4 isoform and used this transgene to rescue rbp mutant lethality during Drosophila metamorphosis. We find that the Manduca Z4 protein has significant biological activity in Drosophila with respect to rescue of rbp-associated lethality. There was also some overlap in effects on cuticle gene expression between the Manduca Z4 and Drosophila Z1 isoforms that was not shared with the Drosophila Z4 isoform. Our findings show that Z4 function has been conserved over the 260-million-year period since the divergence of Diptera and Lepidoptera, and are consistent with the hypothesis that the Drosophila Z4 and Manduca Z4 isoforms have essential roles in metamorphosis.

Research paper thumbnail of A Drosophila Model To Identify Polyamine−Drug Conjugates That Target the Polyamine Transporter in an Intact Epithelium

Journal of Medicinal Chemistry, 2008

Polyamine transport is elevated in many tumor types, suggesting that toxic polyamine-drug conjuga... more Polyamine transport is elevated in many tumor types, suggesting that toxic polyamine-drug conjugates could be targeted to cancer cells via the polyamine transporter (PAT). We have previously reported the use of Chinese hamster ovary (CHO) cells and its PAT-deficient mutant cell line, CHO-MG, to screen anthracene-polyamine conjugates for their PAT-selective targeting ability. We report here a novel Drosophilabased model for screening anthracene-polyamine conjugates in a developing and intact epithelium (Drosophila imaginal discs), wherein cell-cell adhesion properties are maintained. Data from the Drosophila assay are consistent with previous results in CHO cells, indicating that the Drosophila epithelium has a PAT with vertebrate-like characteristics. This assay will be of use to medicinal chemists interested in screening drugs that use PAT for cellular entry, and it offers the possibility of genetic dissection of the polyamine transport process, including identification of a Drosophila PAT.

Research paper thumbnail of Genetic interactions between the RhoA and Stubble-stubbloid loci suggest a role for a type II transmembrane serine protease in intracellular signaling during Drosophila imaginal disc morphogenesis

Genetics, 2003

The Drosophila RhoA (Rho1) GTPase is essential for postembryonic morphogenesis of leg and wing im... more The Drosophila RhoA (Rho1) GTPase is essential for postembryonic morphogenesis of leg and wing imaginal discs. Mutations in RhoA enhance leg and wing defects associated with mutations in zipper, the gene encoding the heavy chain of nonmuscle myosin II. We demonstrate here that mutations affecting the RhoA signaling pathway also interact genetically with mutations in the Stubble-stubbloid (Sb-sbd) locus that encodes an unusual type II transmembrane serine protease required for normal leg and wing morphogenesis. In addition, a leg malformation phenotype associated with overexpression of Sb-sbd in prepupal leg discs is suppressed when RhoA gene dose is reduced, suggesting that RhoA and Sb-sbd act in a common pathway during leg morphogenesis. We also characterized six mutations identified as enhancers of zipper mutant leg defects. Three of these genes encode known members of the RhoA signaling pathway (RhoA, DRhoGEF2, and zipper). The remaining three enhancer of zipper mutations interac...

Research paper thumbnail of Contributors

Research paper thumbnail of The Drosophila Broad-CompZex Encodes a Family of Related Proteins Containing Zinc Fingers

The Broad-Complex (BR-C) is essential for metamorphosis in Drosophila melanogaster. This locus is... more The Broad-Complex (BR-C) is essential for metamorphosis in Drosophila melanogaster. This locus is coextensive with the 2B5 ecdysone-responsive early puff and is necessary for puffing and transcription of many subsequently activated late genes in the developing salivary gland. Mapping of 31 cDNA clones indicates that approximately 100 kb of the genome is devoted to the synthesis of many BR-C RNAs.

Research paper thumbnail of Relationships between Protein Isoforms and Genetic Functions Demonstrate Functional Redundancy at theBroad-ComplexduringDrosophilaMetamorphosis

Developmental Biology, 1997

reproductive, adult form. At the onset of metamorphosis ecdysone induces a set of early genes whi... more reproductive, adult form. At the onset of metamorphosis ecdysone induces a set of early genes which coordinate tissuespecific responses to hormone. The Broad-Complex (BR-C) early gene, which acts as a global regulator of tissue-specific responses to ecdysone, encodes a family of zinc-finger DNA binding proteins known as Z1, Z2, Z3, and Z4. Genetically the BR-C encodes three complementing functions, br, rbp, and 2Bc, and a class of npr1 alleles that fail to complement any of the other genetic functions. The effects of BR-C mutations on metamorphic development are highly pleiotropic, yet little is known about the roles of individual BR-C proteins in directing the required responses to ecdysone. Because the BR-C is a vital regulator of metamorphosis it is essential to establish the relationships between BR-C genetic functions and protein products. We present here the first general and definitive study of these relationships. Using heat-inducible transgenes we have rescued lethality associated with each of the complementing genetic functions and have restored transcriptional activity of tissue-specific BR-C / -dependent target genes. Our data lead us to conclude that br / function is only provided by the Z2 isoform. We find that Z1 transgenes provide full rbp / function, while Z4 provides partial function. Likewise, while Z3 provides full 2Bc / function, Z2 also provides partial function. These results indicate possible functional redundancy or regulatory dependence (via autoregulation) associated with the rbp / and 2Bc / functions. The establishment of these relationships between BR-C genetic functions and protein isoforms is an important step toward understanding the roles of BR-C proteins in directing metamorphic responses to ecdysone. ᭧ 1997 Academic Press 2 To whom correspondence should be addressed. Fax

Research paper thumbnail of TheDrosophila Broad-ComplexEarly Gene Directly Regulates Late Gene Transcription during the Ecdysone-Induced Puffing Cascade

Developmental Biology, 1996

The ensemble of tissue-specific changes that drivesDrosophilametamorphosis is initiated by the st... more The ensemble of tissue-specific changes that drivesDrosophilametamorphosis is initiated by the steroid hormone ecdysone and proceeds through a transcriptional cascade comprised of primary response transcriptional regulators and secondary response structural genes. TheBroad-Complex(BR-C) primary response early gene is composed of several distinct genetic functions and encodes a family of related transcription factor isoforms. Our objective in this study was to determine

Research paper thumbnail of A Switch inBroad-ComplexZinc-Finger Isoform Expression Is Regulated Posttranscriptionally during the Metamorphosis ofDrosophilaImaginal Discs

Developmental Biology, 1996

The Broad-Complex (BR-C) is a key member of the 20-hydroxyecdysone regulatory hierarchy that coor... more The Broad-Complex (BR-C) is a key member of the 20-hydroxyecdysone regulatory hierarchy that coordinates changes in gene expression during Drosophila metamorphosis. The family of transcription factors encoded by the BR-C share a common amino-terminal domain which is fused by alternative splicing to one of four pairs of C2H2 zinc-finger domains (Z1, Z2, Z3, and Z4). In this study, we examine the temporal expression of transcripts encoding each BR-C zinc-finger isoform-including the newly discovered fourth zinc-finger domain-during the metamorphosis of imaginal discs which form the integumental structures of the adult head and thorax. We find that all BR-C zinc-finger RNA isoforms are induced as a primary response to 20-hydroxyecdysone. However, induced BR-C RNA isoforms exhibit two divergent expression profiles. The Z2, Z3, and Z4 RNA isoforms accumulate to high levels at the beginning of the ecdysone response and abruptly disappear after several hours. In contrast, the Z1 RNA isoform continues to accumulate while the others decline, resulting in a switch in relative isoform levels. Using probes specific to different regions of the BR-C, we show that the switch in BR-C RNA isoform expression appears to be posttranscriptionally regulated, presumably by ecdysone-responsive factors. We propose that this switch results from a change in splice acceptor site choice. Finally, we present a model describing how this temporal switch in isoform expression could mediate changes in BR-C function, from transcriptional activation to repression and vice versa, that are critical for coordinate downstream target gene expression.

Research paper thumbnail of Dynamic Expression of Broad-Complex Isoforms Mediates Temporal Control of an Ecdysteroid Target Gene at the Onset of Drosophila Metamorphosis

Developmental Biology, 2000

Metamorphosis in Drosophila melanogaster is orchestrated by the steroid hormone ecdysone, which t... more Metamorphosis in Drosophila melanogaster is orchestrated by the steroid hormone ecdysone, which triggers a cascade of primary-response transcriptional regulators and secondary effector genes during the third larval instar and prepupal periods of development. The early ecdysone-response Broad-Complex (BR-C) gene, a key regulator of this cascade, is defined by three complementing functions (rbp, br, and 2Bc) and encodes several distinct zinc-finger-containing isoforms (Z1 to Z4). Using isoform-specific polyclonal antibodies we observe in the fat body a switch in BR-C isoform expression from the Z2 to the other three isoforms during the third instar. We show that the 2Bc ؉ function that corresponds presumably to the Z3 isoform is required for the larval fat body-specific expression of a transgenic construct (AE) in which the lacZ gene is under the control of the ecdysone-regulated enhancer and minimal promoter of the fat body protein 1 (Fbp1) gene. Using hs(BR-C) transgenes, we demonstrate that overexpression of Z1, Z3, or Z4, but not Z2, is able to rescue AE activity with faithful tissue specificity in a BR-C null (npr1) genetic context, demonstrating a partial functional redundancy between Z1, Z3, and Z4 isoforms. We also show that continuous overexpression of Z2 during the third instar represses AE, while conversely, expression of Z3 earlier than its normal onset induces precocious expression of the construct. This finding establishes a tight correlation between the dynamic pattern of expression of the BR-C isoforms and their individual repressive or inductive roles in AE regulation. Altogether our results demonstrate that the balance between BR-C protein isoforms in the fat body mediates, in part, the precise timing of the ecdysone activation of the AE construct but does not modulate its tissue specificity.

Research paper thumbnail of Evolution of the Drosophila broad locus: the Manduca sexta broad Z4 isoform has biological activity in Drosophila

Development Genes and Evolution, 2003

The Drosophila melanogaster broad locus is essential for normal metamorphic development. Broad en... more The Drosophila melanogaster broad locus is essential for normal metamorphic development. Broad encodes three genetically distinct functions (rbp, br, and 2Bc) and a family of four zinc-finger DNA-binding proteins (Z1-Z4). The Z1, Z2, and Z3 protein isoforms are primarily associated with the rbp, br, and 2Bc genetic functions respectively. The Z4 protein isoform also provides some rbp genetic function, however an essential function for the Z4 isoform in metamorphosis has not been identified. To determine the degree of conservation of Z4 function between the tobacco hornworm Manduca sexta and Drosophila we generated transgenic Drosophila expressing the Manduca broad Z4 isoform and used this transgene to rescue rbp mutant lethality during Drosophila metamorphosis. We find that the Manduca Z4 protein has significant biological activity in Drosophila with respect to rescue of rbp-associated lethality. There was also some overlap in effects on cuticle gene expression between the Manduca Z4 and Drosophila Z1 isoforms that was not shared with the Drosophila Z4 isoform. Our findings show that Z4 function has been conserved over the 260-million-year period since the divergence of Diptera and Lepidoptera, and are consistent with the hypothesis that the Drosophila Z4 and Manduca Z4 isoforms have essential roles in metamorphosis.

Research paper thumbnail of A Drosophila Model To Identify Polyamine−Drug Conjugates That Target the Polyamine Transporter in an Intact Epithelium

Journal of Medicinal Chemistry, 2008

Polyamine transport is elevated in many tumor types, suggesting that toxic polyamine-drug conjuga... more Polyamine transport is elevated in many tumor types, suggesting that toxic polyamine-drug conjugates could be targeted to cancer cells via the polyamine transporter (PAT). We have previously reported the use of Chinese hamster ovary (CHO) cells and its PAT-deficient mutant cell line, CHO-MG, to screen anthracene-polyamine conjugates for their PAT-selective targeting ability. We report here a novel Drosophilabased model for screening anthracene-polyamine conjugates in a developing and intact epithelium (Drosophila imaginal discs), wherein cell-cell adhesion properties are maintained. Data from the Drosophila assay are consistent with previous results in CHO cells, indicating that the Drosophila epithelium has a PAT with vertebrate-like characteristics. This assay will be of use to medicinal chemists interested in screening drugs that use PAT for cellular entry, and it offers the possibility of genetic dissection of the polyamine transport process, including identification of a Drosophila PAT.