2010 |
Singh, Amit |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Genetic Control of Axial Patterning in Drosophila Eye
DESCRIPTION (provided by applicant): During organogenesis axial patterning is essential for growth and development. The fruit fly, Drosophila, provides an ideal model for genetic analysis of dorsoventral (DV) patterning and growth of the eye primordium. DV patterning is the first axis formed in eye. Our goal is to identify key genes involved in early eye patterning. In early eye imaginal disc, the DV patterning is established by initiation of expression of a dorsal selector gene, pannier (pnr), which controls the expression of wingless (wg) signaling gene and Iroquois family transcription factors. The dorsal genes antagonize the function of ventral genes including Lobe (L), Serrate (Ser) and fringe (fng). The interaction of these two groups of genes leads to preferential activation of Notch signaling at the DV border to induce growth and differentiation. One of the major questions that need to be addressed is the molecular genetic basis for such regulatory interactions. In the ventral domain, a Notch ligand Serrate (Ser) and a novel protein Lobe (L) play key roles. L is expressed in both dorsal and ventral domains but is only required for ventral eye growth as a component of Notch signaling pathway. L is required for ventral eye development, growth, and survival. To understand the molecular genetic basis of L functions in cell survival, specification and growth, we will use molecular genetics approaches commonly employed in Drosophila model system to analyze (i) the function of L and Homothorax (Hth), a negative regulator of eye development, in the control of eye growth (ii) the L function in retinal cell fate determination and differentiation, and (iii) function of L and Cullin-4, an E3 ubiquitin ligase, in the control of ventral eye cell survival. These studies will help to elucidate the genetic circuitry involved in L mediated Notch pathway regulation of cell survival, growth, and patterning. Most of the genes studied here are highly conserved as they are present in higher mammals including humans, and genetic control of DV patterning is an important event during mammalian eye development. This study will help in revealing mechanisms of genetic interactions involved in early eye development. Thus, our study will also contribute to the understanding of mammalian eye development and etiology of early childhood retinal diseases. PUBLIC HEALTH RELEVANCE: Axial patterning, a fundamental process of organogenesis in multi-cellular organisms, involves transition of a mono-layered epithelium to a three- dimensional organ. A well established model of the Drosophila melanogaster (fruit fly) will be employed to study dorso-ventral (DV) (axial) patterning and growth in the developing eye. DV patterning, the first lineage restriction event occurring in the eye, results in the formation of dorsal and ventral domains of the eye. The border between the dorsal and ventral domains of the eye is the site of Notch (N) signaling pathway which regulates cell proliferation and differentiation of the eye. We will try to understand the genetic mechanism of DV patterning and growth during early eye imaginal disc development in Drosophila. The DV boundary is established by interactions of dorsal selector genes and ventral genes. The dorsal factors include a GATA-family transcription factor Pannier (Pnr), the secreted morphogen Wingless (Wg), and Iroquois (Iro-C) family homeobox proteins. In the ventral domain, a Notch ligand Serrate (Ser) and a novel protein Lobe (L) play key roles. L is expressed in both dorsal and ventral domains but is only required for ventral eye growth as a component of Notch signaling pathway. The Drosophila eye begins from a ventral equivalent state on which dorsal fate is established. One of the important questions is how the initial ventral fate of the eye is established and maintained. Our earlier studies have demonstrated that L is required for ventral eye development, growth, and survival. To understand the molecular genetic basis of L functions in cell survival, specification and growth, we will use molecular genetics approaches commonly employed in Drosophila model system to analyze (i) the function of L and Homothorax (Hth), a negative regulator of eye development, in the control of eye growth (ii) the L function in retinal cell fate determination and differentiation, and (iii) function of L and Cullin-4, an E3 ubiquitin ligase, in the control of ventral eye cell survival. These studies will help to elucidate the genetic circuitry involved in L mediated Notch pathway regulation of cell survival, growth, and patterning. Since the genetic machinery is highly conserved it will be interesting to extrapolate the information to higher vertebrates. These studies will contribute towards understanding the genetic mechanism of early developmental events during organogenesis. The genetic machinery involved in axial patterning is highly conserved across the species. In humans and other vertebrates, DV polarity of the retina directs the retinal axon projections to the brain. These studies will shed light on the role of early developmental events that may affect the retinal axon projection to the brain. It will also help to understand the molecular basis of developmental defects caused by mutations in the human homolog of Drosophila.
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1 |
2017 |
Singh, Amit |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Genetic Basis of Patterning and Growth in Drosophila Eye
In multi-cellular organisms, axial patterning is required for transition of a mono-layered epithelium of an organ primordium to a three-dimensional organ by delineation of antero-posterior (AP), dorso-ventral (DV), and proximo-distal (PD) axis. We employ Drosophila melanogaster (fruit fly) eye model to study the highly conserved fundamental process of (axial) DV patterning and growth. During eye development, DV patterning precedes AP and PD axis patterning, and forms dorsal and ventral compartments. The border between the dorsal and the ventral domains of eye, termed equator, is the site for upregulation of the Notch (N) signaling, which regulates cell proliferation and differentiation. Discerning the mechanism of axes determination (DV) is crucial for our understanding of organogenesis as the problems with DV delineation results in developmental/ birth defects in flies to humans. Our long term goal is to understand the genetic basis of DV patterning which is established by interactions of the dorsal selector genes and the ventral genes. The Drosophila eye begins from a ventral equivalent state on which the dorsal fate is established by onset of expression of GATA-family transcription factor Pannier (Pnr), the secreted morphogen Wingless (Wg), and Iroquois (Iro-C) family proteins. In the dorsal eye, pnr is not the sole regulator of Wg expression. It strongly suggests that there may be other dorsal eye genes that are yet to be identified. To understand the molecular genetic basis of DV patterning, we will analyze the (1) Determine the role of new dorsal eye gene dve during eye development, (2) Investigate genetic hierarchy of dorsal eye patterning genes, and (3) Whether DV patterning and Hippo signaling may co-regulate Wg during DV patterning.. Given that the genetic machinery is conserved, we will also test the role of SATB1, a human ortholog of dve in the eye, which is known to be involved in growth regulation, cancer and metastasis. These studies will help discern (a) a new role of dve in axial patterning and complex process of retinal differentiation, (b) role of dve in delineating eye versus head boundary and (c) genes involved in growth and cancer do have function in patterning and differentiation, (d) How do independent pathways interact to regulate growth and patterning in the developing eye?. These studies will have significant bearings on understanding the (i) molecular basis of developmental defects caused by mutations in the human homolog of Drosophila dve, and (ii) genetic mechanism of early developmental events during organogenesis in higher vertebrates too. In humans and other vertebrates, DV polarity of the retina regulate the retinal axon projections to the brain. These studies will shed light on the role of early developmental events on the retinal axon projection to the brain during normal development and disease. The knowledge generated from these studies is expected to elucidate fundamental mechanisms in patterning and growth of normal visual function and within the context of retinal disease and birth defects in the eye.
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1 |
2021 |
Kango-Singh, Madhuri (co-PI) [⬀] Singh, Amit |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Genetic Basis of Dorso-Ventral Patterning in the Drosophila Eye
In multi-cellular organisms, axial patterning is required for transition of a mono-layered epithelium of an organ primordium to a three-dimensional organ by delineation of antero-posterior (AP), dorso-ventral (DV), and proximo-distal (PD) axis. We use Drosophila melanogaster (fruit fly) eye model to study the highly conserved fundamental process of (axial) DV patterning and growth. During eye development, DV patterning precedes AP and PD axis patterning, and forms dorsal and ventral compartments. Discerning the mechanism of axes determination (DV) is crucial for our understanding of organogenesis as the problems with DV delineation results in developmental/ birth defects in flies to humans. Our long term goal is to understand the genetic basis of DV patterning which is established by interactions of the dorsal selector genes and the ventral genes. The Drosophila eye begins from a ventral equivalent state on which the dorsal fate is established by onset of expression of GATA-family transcription factor Pannier (Pnr), the secreted morphogen Wingless (Wg), and Iroquois (Iro-C) family proteins. In the dorsal eye, pnr is not the sole regulator of Wg expression. It strongly suggests that there may be other dorsal eye genes that are yet to be identified. We have identified a new dorsal eye selector defective proventriculus (dve), a transcription factor, which acts upstream of wg. To understand the molecular genetic basis of DV patterning, we will analyze the (1) Investigate wg regulation in the dorsal eye. (2) How Wg gradient from dorsal eye is interpreted for eye versus head fate? (3) Test if Hippo signaling co- regulate Wg signaling with DV patterning genes in the eye. Given that the genetic machinery is conserved, we will also test the role of SATB1, a human ortholog of dve in the eye. Our study will have significant bearing on (i) developmental mechanisms of lineage restriction and patterning that follow DV patterning during organogenesis, (ii) role of growth regulatory gene in patterning and (iii) the understanding of etiology of early childhood retinal diseases. (iv) How do independent pathways interact to regulate growth and patterning in the developing eye? The proposed studies will generate insights into (1) how dorsal eye genes interact to determine eye versus head fate by regulating Wg signaling, (2) How two independent pathways like Hippo signaling and DV patterning coregulate Wg signaling to promote growth and patterning in the developing eye? (3) SATB1 is mainly known to regulate growth and our studies in eye will provide insight into growth regulation and patterning function of SATB1. These studies will have significant bearings on understanding the genetic mechanism of early developmental events during organogenesis in higher vertebrates. The knowledge generated from these studies is expected to elucidate fundamental mechanisms in patterning and growth of normal visual function and within the context of retinal disease and birth defects in the eye.
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