Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of mouse to identify strain-specific variation and the onset of gap junction mutation-induced cataractsc

ABSTRACT: Disruption of the mouse gene encoding the gap junction subunit alpha3 connexin 46 (Cx46) results in the formation of lens cataracts. The timing of the onset of this lens opacity is affected by the genetic background, i.e. the mouse strain. To elucidate the mechanism by which cataracts form in the 129Sv/Jae strain earlier than in the C57BL/6J strain, global gene expression was quantitated in the lenses of these strains. Lens cDNAs were analyzed by hybridization to DNA microarrays and with real time-PCR. Theories are proposed based on the observed higher level of expression of the stress-response genes in the C57BL/6J strain and variations in the expression levels of genes involved in protein synthesis, metabolism, catabolism and cell proliferation. How these variations in gene expression might affect the response of lens fiber cells to the increased calcium, caused by lack of alpha3Cx46, is considered. The possibility that the proteins coded by the strain-variable genes might influence the cataract-associated proteolysis of gamma-crystallin is also addressed. Experiment Overall Design: To determine differences in transcript expression between the lenses of two mouse wild type strains (129 SvJae and C57BL/6J), as well as between alpha3Cx46 KO and wild-type mice. The former comparison may lead to identification of potential candidate(s) genes that prevent (or promote) cataract formation, whereas the latter comparison may provide insights into the mechanism by which cataract formation occurs in the alpha3Cx46 KO mice. Total 8 samples were used ( two separate samples for each of the following 4 types of mice: 129SvJae wild type, 129SvJae alpha3Cx46 KO, C57BL/6J wild type and C57BL/6J alpha3Cx46 KO)

ORGANISM(S): Mus musculus

SUBMITTER: Nalin Kumar

PROVIDER: E-GEOD-5645 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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:Although majority of the genes linked to pediatric cataract exhibit lens fiber cell-enriched expression, our understanding of gene regulation in these cells is limited to function of just eight transcription factors and largely in the context of crystallins. Here, we identify small Maf transcription factors MafG and MafK as regulators of several non-crystallin human cataract genes in fiber cells and establish their significance to cataract. We applied a bioinformatics tool for cataract gene discovery iSyTE to identify MafG and its co-regulators in the lens, and generated various null-allelic combinations of MafG:MafK mouse mutants for phenotypic and molecular analysis. By age 4-months, MafG-/-:MafK+/- mutants exhibit lens defects that progressively develop into cataract. High-resolution phenotypic characterization of MafG-/-:MafK+/- lens reveals severe defects in fiber cells, while microarrays-based expression profiling identifies 97 differentially regulated genes (DRGs). Integrative analysis of MafG-/-:MafK+/- lens-DRGs with 1) binding-motifs and genomic targets of small Mafs and their regulatory partners, 2) iSyTE lens-expression data, and 3) interactions between DRGs in the String database, unravels a detailed small Maf regulatory network in the lens, several nodes of which are linked to human cataract. This analysis prioritizes 36 highly promising candidates from the original 97 DRGs. Significantly, 8/36 (22%) DRGs are associated with cataracts in human (GSTO1, MGST1, SC4MOL, UCHL1) or mouse (Aldh3a1, Crygf, Hspb1, Pcbd1), suggesting a multifactorial etiology that includes elevation of oxidative stress. These data identify MafG and MafK as new cataract-associated candidates and define their function in regulating largely non-crystallin genes linked to mouse and human cataract. Microarray comparision of lenses from mixed background (129Sv/J, C57BL/6J, and ICR) control (MafG+/-:MafK+/-; no-cataract) and compound (MafG-/-:MafK+/-; cataract) mouse mutants

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Transcription profiling of mouse to identify strain-specific variation and the onset of gap junction mutation-induced cataractsc

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