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Loss of Sip1 leads to migration defects and retention of ectodermal markers during lens development

ABSTRACT: We report the application of RNA-sequencing technology for the high-throughput profiling of mammalian lens gene expression at embryonic day 15.5. The lens has a particularly biased transcriptome, with the top 50 genes encoding approximately 90% of the protein content. Using RNA-Seq, we have shown that there are over 7,700 genes being expressed in the lens at embryonic day 15.5. As expected, the crystallins and many structural genes were amoung the most highly expressed; however, numerous genes expressed at lower transcript abundance were also identified. This study provides a framework for the application of RNA-Seq technology towards characterization of the mammalian lens transcriptome during development. Using high-throughput RNA-sequencing, gene expression in the mammalian lens was compared between an inbred C56Bl/6 strain and a mix background strain at E15.5. This analysis identifies almost 2,000 genes being differentially expressed between the inbred and mixed background lenses, ranging from 6.5 fold upregulated to 5.2 fold downregulated in the mixed background compared to the inbred strain. This list does not include unknown/predicted genes or pseudogenes which are known to change between strains. Further, it appears that approximately 98% of these genes are altered at levels less than 2.5 fold. This study therefore provides a fold change threshold cutoff (2.5 fold) to use in the analysis of differentially expressed lens genes at E15.5 using RNA-Seq technology as it takes into account genetic variation due to background strain differences. SIP1 encodes a DNA-binding transcription factor that regulates multiple developmental processes as highlighted by the pleiotropic defects observed in Mowat-Wilson Syndrome, which results from mutations in this gene. Further, in adults, dysregulated SIP1 expression has been implicated in both cancer and fibrotic diseases where it functionally links TGFb signaling to the loss of epithelial preferred gene expression. In the ocular lens, an epithelial tissue important for vision, Sip1 is co-expressed with epithelial markers such as E-cadherin, and is required for the complete separation of the lens vesicle from the head ectoderm during early ocular morphogenesis. However, the function of Sip1 after early lens morphogenesis is still unknown. Here, we conditionally deleted Sip1 from the developing mouse lens shortly after lens vesicle closure, leading to defects in coordinated fiber cell tip migration, defective suture formation and cataract. Interestingly, RNA-Sequencing analysis on Sip1 knockout lenses identified 190 differentially expressed genes, all of which are distinct from previously described Sip1 target genes involved in EMT/cancer. Furthermore, 34% of the upregulated genes in the Sip1 knockout lenses are normally downregulated as the lens transitions from the lens vesicle to early lens, while 49% of the genes downregulated in the Sip1 knockout lenses are normally upregulated during early lens development. Overall, these data imply that Sip1 plays a major role in reprogramming the lens vesicle away from a surface ectoderm cell fate towards that necessary for the development of a transparent lens and demonstrate that Sip1 regulates distinctly different sets of genes in different cellular contexts.

ORGANISM(S): Mus musculus

PROVIDER: GSE49949 | GEO | 2014/06/01

SECONDARY ACCESSION(S): PRJNA215449

REPOSITORIES: GEO

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Project description:We report the application of RNA-sequencing technology for the high-throughput profiling of mammalian lens gene expression at embryonic day 15.5. The lens has a particularly biased transcriptome, with the top 50 genes encoding approximately 90% of the protein content. Using RNA-Seq, we have shown that there are over 7,700 genes being expressed in the lens at embryonic day 15.5. As expected, the crystallins and many structural genes were amoung the most highly expressed; however, numerous genes expressed at lower transcript abundance were also identified. This study provides a framework for the application of RNA-Seq technology towards characterization of the mammalian lens transcriptome during development. Using high-throughput RNA-sequencing, gene expression in the mammalian lens was compared between an inbred C56Bl/6<har> strain and a mix background strain at E15.5. This analysis identifies almost 2,000 genes being differentially expressed between the inbred and mixed background lenses, ranging from 6.5 fold upregulated to 5.2 fold downregulated in the mixed background compared to the inbred strain. This list does not include unknown/predicted genes or pseudogenes which are known to change between strains. Further, it appears that approximately 98% of these genes are altered at levels less than 2.5 fold. This study therefore provides a fold change threshold cutoff (2.5 fold) to use in the analysis of differentially expressed lens genes at E15.5 using RNA-Seq technology as it takes into account genetic variation due to background strain differences. SIP1 encodes a DNA-binding transcription factor that regulates multiple developmental processes as highlighted by the pleiotropic defects observed in Mowat-Wilson Syndrome, which results from mutations in this gene. Further, in adults, dysregulated SIP1 expression has been implicated in both cancer and fibrotic diseases where it functionally links TGFb signaling to the loss of epithelial preferred gene expression. In the ocular lens, an epithelial tissue important for vision, Sip1 is co-expressed with epithelial markers such as E-cadherin, and is required for the complete separation of the lens vesicle from the head ectoderm during early ocular morphogenesis. However, the function of Sip1 after early lens morphogenesis is still unknown. Here, we conditionally deleted Sip1 from the developing mouse lens shortly after lens vesicle closure, leading to defects in coordinated fiber cell tip migration, defective suture formation and cataract. Interestingly, RNA-Sequencing analysis on Sip1 knockout lenses identified 190 differentially expressed genes, all of which are distinct from previously described Sip1 target genes involved in EMT/cancer. Furthermore, 34% of the upregulated genes in the Sip1 knockout lenses are normally downregulated as the lens transitions from the lens vesicle to early lens, while 49% of the genes downregulated in the Sip1 knockout lenses are normally upregulated during early lens development. Overall, these data imply that Sip1 plays a major role in reprogramming the lens vesicle away from a surface ectoderm cell fate towards that necessary for the development of a transparent lens and demonstrate that Sip1 regulates distinctly different sets of genes in different cellular contexts. RNA-Seq of inbred background wild type lenses at E15.5 RNA-Seq comparison of mixed background wild type controls and inbred wild type (C57Bl/6<har>) lenses at E15.5 RNA-Seq comparison of mixed background wild type controls and Sip1 conditional knockout lenses at E15.5

Project description:Overview: We report here that gene expression in E13.5 wild type (WT) mouse lenses differs from the lenses of mice that conditionally lack the Prox1 transcription factor in the lens of their eyes (Prox1 cKO) as assayed by high throughput RNA sequencing (RNAseq). The methodology outlined herein is similar to a previous RNAseq experiment from our lab (Manthey et al., 2014a)(Geo ascension: GSE 49949), and the filtering and processing criteria for this experiment was published as well.(Manthey et al., 2014b). The mammalian lens is notable for its biased gene expression, where 90% of the observed protein is expressed by just 50 genes. RNAseq was employed to sequence past these highly expressed lens structural genes and report the relative abundance of both high and low expression genes. In this study we demonstrated that 642 genes were differentially expressed in the lenses of Prox1 cKOs as compared to WT lenses. These data were analyzed using the DAVID biostatical analysis package and we found that the expression of lens specific proteins, as well as cytoskeletal genes and genes that regulated the cytoskeleton were expressed at lower levels in Prox1 cKOs. This analysis showed that the expression of genes encoding extracellular matrix components and their regulators, as well as cell adhesion increased in Prox1 cKO lenses when compared to WTs. Description of Filtering Criteria: Our initial analysis identified 5,492 genes that were differentially expressed in Prox1 cKO lenses as compared to WTs as computed by Pair-wise qCML method exact tests with a Benjamini Hochberg false discovery rate correction greater than the threshold of P < 0.05. As we described previously, there is significant variation in gene expression between inbred C57Bl/6 <har> and mice with a mixed background below a threshold of 2.5 fold. For this reason we filtered out all genes whose differential expression was less than 2.5 fold. We also wanted to filter out genes that were expressed at such low levels that they were unlikely to impact cellular function. We restricted our list to those genes that were expressed at greater than 2 Reads per Kilobase per million reads (RPKM) in either WT or Prox1 cKO samples, a value which corresponds to approximately 1 mRNA molecule per cell. The application of these filtering criteria resulted in narrowing our list to 642 genes that were likely to impact the Prox1 cKO lens phenotype. Manthey, A. L., Lachke, S. A., FitzGerald, P. G., Mason, R. W., Scheiblin, D. A., McDonald, J. H. and Duncan, M. K. (2014a) 'Loss of Sip1 leads to migration defects and retention of ectodermal markers during lens development', Mech Dev 131: 86-110. Manthey, A. L., Terrell, A. M., Lachke, S. A., Polson, S. W. and Duncan, M. K. (2014b) 'Development of novel filtering criteria to analyze RNA-sequencing data obtained from the murine ocular lens during embryogenesis', Genom Data 2: 369-374.

Project description:β1-integrin is the major β-integrin subunit expressed in both lens epithelial and fiber cells. Our previous research indicated that β1-integrin is essential for the maintenance of lens epithelial integrity and survival in late embryonic lens development (Simirskii et al, 2009). Lack of β1-integrin in the lens will lead to severe micropthalmia and lack of lens in adult mice. In order to study the mechanisms involved, high throughput RNA sequencing (RNAseq) was performed to determine the genes that are differentially expressed between E15.5 wild type (WT) lenses and lenses that lack β1-integrin expression due to the action of MLR10 CRE (β1-cKO). The methodology used here is similar to the other RNAseq experiments that were previously performed in our lab (Manthey et al., 2014a and Audette et al, 2015) (Geo accession: GSE 49949 and GSE69940) . Meanwhile, the filtering criteria and processing procedures were also published (Manthey et al., 2014b). Compared to WT, 120 genes were found to be differentially expressed in β1-cKO lenses. Moreover, bioinformatics tools (DAVID (the database for Annotation, Visulization and Integrated Discovery), and PANTHER (Protein Analysis through Evolutionary Relationship) classification system) as well as manual literature searching was applied for further data analysis. It showed that genes involved in EMT and stress-responses were differentially expressed in β1-cKO compared to that of WT. Description of filtering criteria: To identify the differentially expressed genes, pair-wise qCML method exact tests with a Benjamini Hochberg false discovery rate correction greater than the threshold of P<0.05 was applied, which identified 5120 genes. As previously described (Manthey et al., 2014b), most of the genes differentially expressed between inbred C57Bl/6 <har> and mice with a mixed background were below a threshold of 2.5 fold change. Therefore, all differentially expressed genes with a less than 2.5 fold change were filtered out. Further, genes whose expression level were not high enough to be biologically significant were also filtered out, based on the RPMK (Reads per Kilobase per million reads) value. Any gene in the final list has RPKM greater that 2 in either WT or β1-cKO samples, a value that corresponds to approximately 1 mRNA molecule per cell. By applying a combination of these filtering criteria, 120 differentially expressed genes were found, which could potentially elucidate the molecular connections between conditional deletion of β1-intergrin from the lens and the observed phenotypic abnormalities. Manthey, A. L., Lachke, S. A., FitzGerald, P. G., Mason, R. W., Scheiblin, D. A., McDonald, J. H. and Duncan, M. K. (2014a) 'Loss of Sip1 leads to migration defects and retention of ectodermal markers during lens development', Mech Dev 131: 86-110. Manthey, A. L., Terrell, A. M., Lachke, S. A., Polson, S. W. and Duncan, M. K. (2014b) 'Development of novel filtering criteria to analyze RNA-sequencing data obtained from the murine ocular lens during embryogenesis', Genom Data 2: 369-374.

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Loss of Sip1 leads to migration defects and retention of ectodermal markers during lens development

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