Project description:The vertebrate retina uses diverse neuronal cell types arrayed into complex neural circuits to extract, process and relay information from the visual scene to the higher order processing centers of the brain. Amacrine cells, a diverse class of inhibitory interneurons, are thought to mediate the majority of the processing of the visual signal that occurs within the retina. Despite morphological characterization, the number of known molecular markers of amacrine cell types is still much smaller than the 26 morphological types that have been identified. Furthermore, it is not known how this diversity arises during development. Here, we have combined in vivo genetic labeling and single cell genome-wide expression profiling to: 1) Identify specific molecular types of amacrine cells; 2) Demonstrate the molecular diversity of the amacrine cell class. It is difficult to identify new markers of amacrine cells, due to the fact that they only comprise a small percentage of the total cells in the retina. Additionally, given that there are at least 26 distinct types of amacrine cells, population based approaches fail to achieve the precision necessary to discover markers of each type. To facilitate the identification of new markers for different amacrine cell classes and to more fully characterize the molecular signatures of these classes, we isolated single amacrine cells. To accomplish this goal, we introduced genetic reporters (pNdrg4::GFP or pSynapsin::GFP) into the developing retina (P0) by either in vivo or ex vivo electroporation. These reporters were observed to label morphologically distinct sets of amacrine cells at the different timepoints harvested in this study. Electroporated retinas were then dissociated at different time points and single retinal amacrine cells were isolated by virtue of their GFP expression and placed in tubes containing lysis buffer. Then, their mRNAs were reverse transcribed, and the resulting cDNAs were PCR amplified for 35 cycles. Labeled cDNA samples were hybridized to Affymetrix 430 2.0 microarrays and the data was normalized using MAS5.0 software.
Project description:It is widely believed that the molecular and cellular features of a tumor reflect its cell-of-origin and can thus provide clues about treatment targets. The retinoblastoma cell-of-origin has been debated for over a century. Here we report that human and mouse retinoblastomas have molecular, cellular, and neurochemical features of multiple cell classes, principally amacrine/horizontal interneurons, retinal progenitor cells, and photoreceptors. Importantly, single-cell gene expression array analysis showed that these multiple cell type–specific developmental programs are coexpressed in individual retinoblastoma cells, which creates a progenitor/neuronal hybrid cell. Importantly, neurotransmitter receptors, transporters, and biosynthetic enzymes are expressed in human retinoblastoma, and targeted disruption of these pathways reduces retinoblastoma growth in vivo and in vitro. Our finding that retinoblastoma tumor cells express multiple neuronal differentiation programs that are normally incompatible in development suggests that the pathways that control retinal development and establish distinct cell types are perturbed during tumorigenesis. Therefore, the cell-of-origin for retinoblastoma cannot be inferred from the features of the tumor cells themselves. However, we now have a detailed understanding of the neuronal pathways that are deregulated in retinoblastoma and targeting the catecholamine and indolamine receptors or downstream components could provide useful therapeutic approaches in future studies. This example highlights the importance of comprehensive molecular, cellular and physiological characterization of human cancers with single cell resolution as we incorporate molecular targeted therapy into treatment regimens. 20 single cells isolated from primary pediatric retinoblastoma tumors were assayed to asses the within tumor consistency of expression signals
Project description:It is widely believed that the molecular and cellular features of a tumor reflect its cell-of-origin and can thus provide clues about treatment targets. The retinoblastoma cell-of-origin has been debated for over a century. Here we report that human and mouse retinoblastomas have molecular, cellular, and neurochemical features of multiple cell classes, principally amacrine/horizontal interneurons, retinal progenitor cells, and photoreceptors. Importantly, single-cell gene expression array analysis showed that these multiple cell type–specific developmental programs are coexpressed in individual retinoblastoma cells, which creates a progenitor/neuronal hybrid cell. Importantly, neurotransmitter receptors, transporters, and biosynthetic enzymes are expressed in human retinoblastoma, and targeted disruption of these pathways reduces retinoblastoma growth in vivo and in vitro. Our finding that retinoblastoma tumor cells express multiple neuronal differentiation programs that are normally incompatible in development suggests that the pathways that control retinal development and establish distinct cell types are perturbed during tumorigenesis. Therefore, the cell-of-origin for retinoblastoma cannot be inferred from the features of the tumor cells themselves. However, we now have a detailed understanding of the neuronal pathways that are deregulated in retinoblastoma and targeting the catecholamine and indolamine receptors or downstream components could provide useful therapeutic approaches in future studies. This example highlights the importance of comprehensive molecular, cellular and physiological characterization of human cancers with single cell resolution as we incorporate molecular targeted therapy into treatment regimens. 55 primary pediatric retinoblastoma tumors were collected and assayed and compared to with 3 passaged xenografts and 4 RB cell lines
Project description:Loss of the Atrx chromatin remodeling protein causes dysfunction and death of post-mitotic retinal interneurons in mice. Embryonic conditional deletion of Atrx from multipotent retinal progenitor cells results in the selective loss of the retinal inhibitory interneurons, namely amacrine and horizontal cells. The cell death occurs postnatally after the development of these cell types, peaking at postntal day 17 in the mouse retina. Identification of molecular factors and pathways that mediate the health and survival of these neurons may suggest novel therapeutic strategies for neuroprotection in ATR-X syndrome and other neurodegenerative diseases. We performed gene expression profiling of wildtype and Atrx conditional knockout mouse retina tissues to identify putative targets of Atrx and molecular pathways that underlie the neurodegenerative phenotype.
Project description:During development of the central nervous system (CNS), cycling uncommitted progenitor cells give rise to a variety of distinct neuronal and glial cell types. As these different cell types are born, they progress from newly specified cells to fully differentiated neurons and glia. In order to define the developmental processes of individual cell types, single cell expression profiling was carried out on developing ganglion and amacrine cells of the murine retina. Individual cells from multiple developmental stages were isolated and profiled on Affymetrix oligonucleotide arrays. These experiments have yielded an expanded view of the processes underway in developing retinal ganglion and amacrine cells, as well as several hundred new marker genes for these cell types. In addition, this study has allowed for the definition of some of the molecular heterogeneity both between developing ganglion and amacrine cells and among subclasses of each cell type. Experiment Overall Design: Single retinal cells were isolated in tubes containing lysis buffer, their mRNAs were reverse transcribed, and the resulting cDNAs were PCR amplified for 35 cycles. Labeled cDNA samples were hybridized to Affymetrix 430 2.0 microarrays and the data was normalized using MAS5.0 software. Cells were identified post hoc as either developing retinal ganglion cells, amacrine cells or rod photoreceptor cells.
Project description:In mammals, retinal damage is followed by Müller glia cell activation and proliferation. While retinal gliosis persists in adult mammals after an insult or disease, some vertebrates, including zebrafish, have the capacity to regenerate. We believe we are the first group to show that gliosis is a fibrotic-like process in mammals’ eyes caused by differential activation of canonical and non-canonical TGFβ signaling pathways.
Project description:Previous lineage analyses have shown that retinal progenitor cells (RPCs) are multipotent throughout development, and expression profiling studies have shown a great deal of molecular heterogeneity among RPCs. To determine if the molecular heterogeneity predicts that an RPC will produce particular types of progeny, clonal lineage analysis was used to investigate the progeny of a subset of RPCs, those that express the basic helix-loop-helix (bHLH) transcription factor, Olig2. In contrast to the large and complex set of clones generated by viral marking of random embryonic RPCs, the embryonic Olig2+ RPCs underwent terminal divisions, producing small clones with primarily two of the five cell types being made by the pool of RPCs at that time. The embryonically produced cell types made by Olig2+ RPCs were cone photoreceptors and horizontal cell (HC) interneurons. Moreover, the embryonic Olig2+ RPC did not make the later Olig2+ RPC. The later, postnatal Olig2+ RPCs also made terminal divisions, which were biased towards production of rod photoreceptors and amacrine cell (AC) interneurons. These data indicate that the multipotent progenitor pool is made up of distinctive types of RPCs, which have biases towards producing subsets of retinal neurons in a terminal division, with the types of neurons produced varying over time. This strategy is similar to that of the developing Drosophila melanogaster ventral nerve cord, with the Olig2+ cells behaving as ganglion mother cells. Single retinal cells were isolated in tubes containing lysis buffer, their mRNAs were reverse transcribed, and the resulting cDNAs were PCR amplified for 35 cycles. Labeled cDNA samples were hybridized to Affymetrix 430 2.0 microarrays and the data was normalized using MAS5.0 software. These cells were examined for the expression of Olig2 or other bHLH factors.