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Results for “Gene Expression Regulation, Developmental”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Integrative analysis of the 3D genome and epigenome in mouse embryonic tissues

While a rich set of putative cis-regulatory sequences involved in mouse fetal development have been annotated recently on the basis of chromatin accessibility and histone modification patterns, delineating their role in developmentally regulated gene expression continues to be challenging. To fill this gap, here we mapped chromatin contacts between gene promoters and distal sequences across the genome in seven mouse fetal tissues and across six developmental stages of the forebrain. We identified 248,620 long-range chromatin interactions centered at 14,138 protein-coding genes and characterized their tissue-to-tissue variations and developmental dynamics. Integrative analysis of the interactome with previous epigenome and transcriptome datasets from the same tissues revealed a strong correlation between the chromatin contacts and chromatin state at distal enhancers, as well as gene expression patterns at predicted target genes. We predicted target genes of 15,098 candidate enhancers and used them to annotate target genes of homologous candidate enhancers in the human genome that harbor risk variants of human diseases. We present evidence that schizophrenia and other adult disease risk variants are frequently found in fetal enhancers, providing support for the hypothesis of fetal origins of adult diseases.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Jasmonate Hormone: Regulating Synthesis of Reduced Carbon Compounds in Plants

Our original interest in understanding the role of jasmonate (JA) in regulating the final stages of stamen and pollen development led to our discovery of the JAZ repressors, and the molecular mechanism of JA action is now a second important focus of our research. The specific goals for this grant period are to: 1. Investigate the generation and clearance of the hormone with emphasis on the regulation of the OPR3 enzyme and the hydrolysis of JA-Ile. 2. Use dominant-negative and overexpression constructs to explore the role of the MYC5 transcription factor in initiating and regulating JA responses. 3. Investigate specific JAZ protein interactions that will help us to recognize and understand the extended network of processes, such as sulfur nutrition, that interface with JA signaling. The COI1 F-Box protein is a JA-Ile coreceptor and coi1 mutant plants lack JA responses. We have tested the possibility that sites of JA action can be probed by using tissue-specific promoters to drive expression of a COI1-YFP fusion protein in coi1 mutant plants deficient in stamen and pollen function. When we expressed COI1 behind a filament-specific promoter (from the DAD1 gene), filament elongation was restored but not anther dehiscence or pollen function. Three tapetum specific promoters, all failed to restore any of these three functions but, unexpectedly, a promoter active in the stomium and epidermal cells, restored both pollen function and anther dehiscence. Most importantly, our results demonstrate the power of promoter::COI1-YFP constructs in revealing the primary sites of JA-regulated gene expression that control developmental and other responses in neighboring tissues. We now plan to use this new tool to test current hypotheses about JA action in other organs of the plant. The MYC2, MYC3, and MYC4 proteins are the primary transcription factors initiating defense and root growth responses to JA signaling. However, transgenic plants overexpressing these proteins do not show any substantial reduction in shoot growth, even though they have increased expression of many JA-responsive genes. MYC5 is closely related to MYC2, MYC3, and MYC4 but has not previously been considered a candidate in JA signaling, in part because myc5 mutants exhibit no overt phenotype. However, when we overexpressed the MYC5 protein in wild-type Arabidopsis we got a surprising result. Whereas plants overexpressing MYC2 were similar in size to wild type, as observed previously, MYC5-OE plants were much smaller. This is an exciting discovery because it indicates that growth responses to JA may be controlled by a signaling pathway that is distinct from that pathway (or pathways) controlling secondary-product synthesis and defense.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

The effect of poly(ADP-ribosyl)ation inhibition on the porcine cumulus-oocyte complex during in vitro maturation

Poly(ADP-ribosyl)ation (PARylation) plays important roles in DNA repair, apoptosis, transcriptional regulation, and cell death, and occurs via the activity of poly(ADP-ribose) polymerases (PARPs). Previous studies have shown that PARylation affects mouse and porcine pre-implantation development and participates in mechanisms of autophagy. However, there have not yet been reported the role of PARylation during in vitro maturation (IVM) of porcine oocytes. Thus, we investigated the effect of PARylation inhibition on this process; cumulus-oocyte complexes (COCs) were cultured with 3-aminobenzamide (3-ABA, PARP inhibitor) during porcine IVM. Full cumulus expansion was significantly reduced (10.34 ± 1.23 [3-ABA] vs. 48.17 ± 2.03% [control]), but nuclear maturation rates were not changed in the 3-ABA treatment group. Especially, we observed that cumulus cells were little expanded after 22 h in 3-ABA treated COCs. The mRNA expression levels of oocyte maturation- and cumulus expansion-related genes were evaluated at 22 and 44 h. GDF9, BMP15, COX-2, and PTX3 expression were upregulated at 44 h, whereas the levels of HAS2 and TNFAIP6 were downregulated in the 3-ABA treated group. Furthermore, 3-ABA treatment significantly decreased the developmental rate (28.24 ± 1.06 vs. 40.24 ± 3.03%) and total cell number (41.12 ± 2.10 vs. 50.38 ± 2.27), but increased the total apoptotic index (6.44 ± 0.81 vs. 3.08 ± 0.51) in parthenogenetically activated embryos. In conclusion, these results showed that PARylation regulates cumulus expansion through the regulation of gene expression and affects developmental competence and quality in parthenogenetic embryos. - Highlights: • Effect of PARylation inhibition on the porcine cumulus-oocyte complex during IVM. • Inhibition of PARylation reduced cumulus expansion. • PARylation inhibition has a negative effect on developmental competence. • PARylation may play essential roles during IVM of porcine oocytes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Two promoters integrate multiple enhancer inputs to drive wild-type knirps expression in the Drosophila melanogaster embryo

Abstract Proper development depends on precise spatiotemporal gene expression patterns. Most developmental genes are regulated by multiple enhancers and often by multiple core promoters that generate similar transcripts. We hypothesize that multiple promoters may be required either because enhancers prefer a specific promoter or because multiple promoters serve as a redundancy mechanism. To test these hypotheses, we studied the expression of the knirps locus in the early Drosophila melanogaster embryo, which is mediated by multiple enhancers and core promoters. We found that one of these promoters resembles a typical “sharp” developmental promoter, while the other resembles a “broad” promoter usually associated with housekeeping genes. Using synthetic reporter constructs, we found that some, but not all, enhancers in the locus show a preference for one promoter, indicating that promoters provide both redundancy and specificity. By analyzing the reporter dynamics, we identified specific burst properties during the transcription process, namely burst size and frequency, that are most strongly tuned by the combination of promoter and enhancer. Using locus-sized reporters, we discovered that enhancers with no promoter preference in a synthetic setting have a preference in the locus context. Our results suggest that the presence of multiple promoters in a locus is due both to enhancer preference and a need for redundancy and that “broad” promoters with dispersed transcription start sites are common among developmental genes. They also imply that it can be difficult to extrapolate expression measurements from synthetic reporters to the locus context, where other variables shape a gene’s overall expression pattern.

Li, Lily (ORCID:0000000301986521)↗
DOE OSTI2015

Comprehensive identification and analysis of human accelerated regulatory DNA

It has long been hypothesized that changes in gene regulation have played an important role in human evolution, but regulatory DNA has been much more difficult to study compared with protein-coding regions. Recent large-scale studies have created genome-scale catalogs of DNase I hypersensitive sites (DHSs), which demark potentially functional regulatory DNA. To better define regulatory DNA that has been subject to human-specific adaptive evolution, we performed comprehensive evolutionary and population genetics analyses on over 18 million DHSs discovered in 130 cell types. We identified 524 DHSs that are conserved in nonhuman primates but accelerated in the human lineage (haDHS), and estimate that 70% of substitutions in haDHSs are attributable to positive selection. Through extensive computational and experimental analyses, we demonstrate that haDHSs are often active in brain or neuronal cell types; play an important role in regulating the expression of developmentally important genes, including many transcription factors such as SOX6, POU3F2, and HOX genes; and identify striking examples of adaptive regulatory evolution that may have contributed to human-specific phenotypes. More generally, our results reveal new insights into conserved and adaptive regulatory DNA in humans and refine the set of genomic substrates that distinguish humans from their closest living primate relatives.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Developmental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin alters DNA methyltransferase (dnmt) expression in zebrafish (Danio rerio)

DNA methylation is one of the most important epigenetic modifications involved in the regulation of gene expression. The DNA methylation reaction is catalyzed by DNA methyltransferases (DNMTs). Recent studies have demonstrated that toxicants can affect normal development by altering DNA methylation patterns, but the mechanisms of action are poorly understood. Hence, we tested the hypothesis that developmental exposure to TCDD affects dnmt gene expression patterns. Zebrafish embryos were exposed to 5 nM TCDD for 1 h from 4 to 5 h post-fertilization (hpf) and sampled at 12, 24, 48, 72, and 96 hpf to determine dnmt gene expression and DNA methylation patterns. We performed a detailed analysis of zebrafish dnmt gene expression during development and in adult tissues. Our results demonstrate that dnmt3b genes are highly expressed in early stages of development, and dnmt3a genes are more abundant in later stages. TCDD exposure upregulated dnmt1 and dnmt3b2 expression, whereas dnmt3a1, 3b1, and 3b4 are downregulated following exposure. We did not observe any TCDD-induced differences in global methylation or hydroxymethylation levels, but the promoter methylation of aryl hydrocarbon receptor (AHR) target genes was altered. In TCDD-exposed embryos, AHR repressor a (ahrra) and c-fos promoters were differentially methylated. To characterize the TCDD effects on DNMTs, we cloned the dnmt promoters with xenobiotic response elements and conducted AHR transactivation assays using a luciferase reporter system. Our results suggest that ahr2 can regulate dnmt3a1, dnmt3a2, and dnmt3b2 expression. Overall, we demonstrate that developmental exposure to TCDD alters dnmt expression and DNA methylation patterns. - Highlights: • TCDD altered the dnmt expression in a gene and developmental time-specific manner. • TCDD hypermethylated ahrra and hypomethylated c-fos proximal promoter regions. • Functional analysis suggests that ahr2 can regulate dnmt3a1, 3a2, and 3b2 expression. • Dnmt3b genes are expressed early whereas dnmt3a are abundant later in development.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

The transcriptional landscape of basidiosporogenesis in mature Pisolithus microcarpus basidiocarp

Background: Pisolithus microcarpus (Cooke & Massee) G. Cunn is a gasteromycete that produces closed basidiocarps in symbiosis with eucalypts and acacias. The fungus produces a complex basidiocarp composed of peridioles at different developmental stages and an upper layer of basidiospores free of the hyphae and ready for wind dispersal upon the rupture of the basidiocarp pellis. During basidiosporogenesis, a process that takes place inside the basidiocarp peridioles, a conspicuous reserve of fatty acids is present throughout development. While several previous studies have described basidiosporogenesis inside peridioles, very little is known about gene expression changes that may occur during this part of the fungal life cycle. The objective of this work was to analyze gene transcription during peridiole and basidiospore development, while focusing specifically on cell cycle progression and lipid metabolism. Results: Throughout different developmental stages of the peridioles we analyzed, 737 genes were regulated between adjacent compartments (>5 fold, FDR-corrected p-value < 0.05) corresponding to 3.49% of the genes present in the P. microcarpus genome. We identified three clusters among the regulated genes which showed differential expression between the peridiole developmental stages and the basidiospores. During peridiole development, transcripts for proteins involved in cellular processes, signaling, and information storage were detected, notably those for coding transcription factors, DNA polymerase subunits, DNA repair proteins, and genes involved in chromatin structure. For both internal embedded basidiospores (hereto referred to as “Internal spores”, IS) and external free basidiospores (hereto referred to as “Free spores”, FS), upregulated transcripts were found to involve primary metabolism, particularly fatty acid metabolism (FA). High expression of transcripts related to β-oxidation and the glyoxylate shunt indicated that fatty acids served as a major carbon source for basidiosporogenesis. Conclusion: Our results show that basidiocarp formation in P. microcarpus involves a complex array of genes that are regulated throughout peridiole development. We identified waves of transcripts with coordinated regulation and identified transcription factors which may play a role in this regulation. This is the first work to describe gene expression patterns during basidiocarp formation in an ectomycorrhizal gasteromycete fungus and sheds light on genes that may play important roles in the developmental process.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

The histone methyltransferase SDG8 mediates the epigenetic modification of light and carbon responsive genes in plants

Histone methylation modifies the epigenetic state of target genes to regulate gene expression in the context of developmental and environmental changes. Previously, we used a positive genetic screen to identify an Arabidopsis mutant, cli186 , which was impaired in carbon and light signaling. Here, we report a deletion of the Arabidopsis histone methyltransferase SDG8 in this mutant (renamed sdg8-5), which provides a unique opportunity to study the global function of a specific histone methyltransferase within a multicellular organism.

Biotechnology & Applied Microbiology↗
DOE OSTI2023

Signal Transduction Pathways of Chloroplast Quality Control (Final Report)

Chloroplasts (photosynthetic plastids) of higher plants contain about 3000 proteins of which more than 95% are encoded by nuclear genes. To avoid the accumulation of reactive oxygen species that are the inherent by-product of photosynthesis, gene expression of these spatially separated genomes is regulated by two-way signaling. Thus, while plastid differentiation and development are largely under nuclear control, developmentally arrested or damaged plastids can regulate expression of nuclear genes via retrograde signaling pathways. In previous years of DOE-funded study, we performed a number of genetic screens that implicated the chloroplast-localized tetrapyrrole biosynthesis pathway as the source of both positive and stress-related retrograde signals. Using that work as a foundation, we have recently uncovered a new type of retrograde signal that leads to the selective removal of damaged chloroplasts from the cell. However, the mechanisms of such a chloroplast quality control pathway are not well characterized or understood.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

The integral spliceosomal component CWC15 is required for development in Arabidopsis

Efficient mRNA splicing is a prerequisite for protein biosynthesis and the eukaryotic splicing machinery is evolutionarily conserved among species of various phyla. At its catalytic core resides the activated splicing complex Bact consisting of the three small nuclear ribonucleoprotein complexes (snRNPs) U2, U5 and U6 and the so-called NineTeen complex (NTC) which is important for spliceosomal activation. CWC15 is an integral part of the NTC in humans and it is associated with the NTC in other species. Here we show the ubiquitous expression and developmental importance of the Arabidopsis ortholog of yeast CWC15. CWC15 associates with core components of the Arabidopsis NTC and its loss leads to inefficient splicing. Consistent with the central role of CWC15 in RNA splicing, cwc15 mutants are embryo lethal and additionally display strong defects in the female haploid phase. Interestingly, the haploid male gametophyte or pollen in Arabidopsis, on the other hand, can cope without functional CWC15, suggesting that developing pollen might be more tolerant to CWC15-mediated defects in splicing than either embryo or female gametophyte.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Signal Transduction Pathways of Chloroplast Quality Control

Chloroplasts (photosynthetic organelles) of higher plants contain about 3000 proteins, but fewer than 5% of these proteins are encoded by genes in the chloroplast. The rest are encoded by genes in the nucleus, which is a separate organelle within the plant cell. To avoid the accumulation of dangerous reactive oxygen species that are the inherent by-product of photosynthesis, gene expression of these spatially separated genomes is regulated by two-way signaling. Thus, while plastid differentiation and development are largely controlled by the nucleus and the proteins encoded within, developmentally arrested or damaged plastids can regulate expression of nuclear genes via retrograde signaling pathways. During the early years of this DOE-funded study, we performed a number of genetic screens to identify genes and protein involved in these signals. Based on the genes that we identified, we found that chloroplast gene expression and the chlorophyll (the major light-harvesting pigment that gives plant tissue its characteristic green color) biosynthetic pathway can act as the source of both positive and stress-related retrograde signals. We also found a new protein called GUN1, that plays a crucial role in retrograde signaling. Although the exact molecular mechanism of GUN1 remains a mystery, our work showed that it likely acts in the chloroplast to coordinate chloroplast gene expression with nuclear gene expression and to ensure that seedlings can quickly green after germination. Using that work as a foundation, we have recently uncovered a new type of retrograde signal that leads to the selective removal of damaged chloroplasts from the cell. We have only begun the characterization of this pathway, but our initial studies have suggested that this may be an extremely important mechanism that allows plants to adapt to stressful conditions. Together this will aid in the understanding of the developmental control of photosynthesis, the chloroplast assembly/disassembly pathways, and how plants adapt to stressful conditions. Ultimately, we hope this work will allow us to begin to engineer these crucial pathways into agriculturally important or bioenergy rich crops. This will be crucial to our quest for an abundant food supply and cheap, dependable sources of energy.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

An extensible vector toolkit and parts library for advanced engineering of plant genomes

Abstract Plant biotechnology is rife with new advances in transformation and genome engineering techniques. A common requirement for delivery and coordinated expression in plant cells, however, places the design and assembly of transformation constructs at a crucial juncture as desired reagent suites grow more complex. Modular cloning principles have simplified some aspects of vector design, yet many important components remain unavailable or poorly adapted for rapid implementation in biotechnology research. Here, we describe a universal Golden Gate cloning toolkit for vector construction. The toolkit chassis is compatible with the widely accepted Phytobrick standard for genetic parts, and supports assembly of arbitrarily complex T‐DNAs through improved capacity, positional flexibility, and extensibility in comparison to extant kits. We also provision a substantial library of newly adapted Phytobricks, including regulatory elements for monocot and dicot gene expression, and coding sequences for genes of interest such as reporters, developmental regulators, and site‐specific recombinases. Finally, we use a series of dual‐luciferase assays to measure contributions to expression from promoters, terminators, and from cross‐cassette interactions attributable to enhancer elements in certain promoters. Taken together, these publicly available cloning resources can greatly accelerate the testing and deployment of new tools for plant engineering.

42 ENGINEERING↗
DOE OSTI2019

Interrogating the Grainyhead-like 2 ($Grhl2$) genomic locus identifies an enhancer element that regulates palatogenesis in mouse

The highly-conserved Grainyhead-like (Grhl) transcription factors are critical regulators of embryogenesis that regulate cellular survival, proliferation, migration and epithelial integrity, especially during the formation of the craniofacial skeleton. Family member Grhl2 is expressed throughout epithelial tissues during development, and loss of Grhl2 function leads to significant defects in neurulation, abdominal wall closure, formation of the face and fusion of the maxilla/palate. Whereas numerous downstream target genes of Grhl2 have been identified, very little is known about how this crucial developmental transcription factor itself is regulated. Using in silico and in utero expression analyses and functional deletion in mice, we have identified a novel 2.4 kb enhancer element (mm1286) that drives reporter gene expression in a pattern that strongly recapitulates endogenous Grhl2 in the craniofacial primordia, modulates Grhl2expression in these tissues, and augments Grhl2-mediated closure of the secondary palate. Deletion of this genomic element, in the context of inactivation of one allele of Grhl (through generation of double heterozygous Grhl2 +/- ;mm1286 +/- mice), results in a significant predisposition to palatal clefting at birth. Moreover, we found that a highly conserved 325 bp region of mm1286 is both necessary and sufficient for mediating the craniofacial-specific enhancer activity of this region, and that an extremely well-conserved 12-bp sequence within this element (CTGTCAAACAGGT) substantially determines full enhancer function. Together, these data provide valuable new insights into the upstream genomic regulatory landscape responsible for transcriptional control of Grhl2 during palatal closure.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Downregulation of Nedd4L predicts poor prognosis, promotes tumor growth and inhibits MAPK/ERK signal pathway in hepatocellular carcinoma

Highlights: • Nedd4L is down-regulated in HCC tissues. • Downregulation of Nedd4L predicts poor prognosis of HCC. • Nedd4L inhibits the proliferation of HCC in vitro and in vivo. • Nedd4L phosphorylates ERK1/2 and regulates genes related with apoptosis. Accumulating evidence indicates that the neural precursor cell–expressed, developmentally downregulated 4–like (Nedd4L) related with some tumor progression pathways and was found abnormally expressed in several kinds of solid cancers. However, the role and mechanism of Nedd4L in HCC remain unknown. This study was to assess the role of Nedd4L in HCC tumorigenesis and prognosis. The real-time quantitative RT-PCR and immunohistochemistry results revealed that Nedd4L was downregulated in HCC tissues compared to corresponding peri-noncancerous tissue, and HCC patients with low expression of Nedd4L exhibited poor prognosis assessed by Kaplan-Meier and Cox regression analysis in 78 HCC patients. Furthermore, knockdown of Nedd4L could significantly promote proliferation of HCC cells by CCK-8 and colony formation assays in vitro; whereas ectopic expression of Nedd4L resulted in attenuating proliferation in vitro and tumor growth in vivc determined by nude mice xenografts model. Mechanically, Nedd4L could phosphorylate ERK1/2 and regulate genes related with apoptosis. Collectively, Nedd4L plays a tumor suppressive role in HCC, possibly through triggering MAPK/ERK-mediated apoptosis, and Nedd4L downregulation may be a potential prognostic biomarker as well as a therapeutic target for HCC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2026

From chromatin to crop: epigenetic innovations in bioenergy systems

Energy crops encompass a diverse array of plant species cultivated primarily as a source of biomass for energy generation and biofuel production. As such, they play a pivotal role in the transition to sustainable energy systems. However, their productivity is often limited by environmental stresses, nutrient availability, and the need for optimized yield. While traditional breeding and genetic engineering have driven improvements, challenges such as narrow genetic diversity, long development cycles, trait instability, and unexpected gene interactions remain. Epigenetics offers a largely untapped opportunity to overcome these constraints by regulating gene expression through mechanisms that are dynamic, finely tuned, and responsive to environmental and developmental cues. Epigenetic modifications including DNA methylation, histone post-translational changes, and small non-coding RNAs influence nearly all aspects of plant development and physiology, including traits central to bioenergy crops. While these mechanisms are well characterized in model species such as Arabidopsis thaliana, they remain underexplored in many purpose-grown energy crops. This review summarizes the current state of knowledge of epigenetic regulation in bioenergy species, explores how these mechanisms can be leveraged to enhance crop resilience and productivity, and identifies gaps in our understanding. By characterizing epigenetic mechanisms and harnessing epigenetic variation, we can expand the toolkit for developing resilient, high-yielding bioenergy crops to meet future environmental and energy demands.

09 BIOMASS FUELS↗
DOE OSTI2024

Mechanically induced localisation of SECONDARY WALL INTERACTING bZIP is associated with thigmomorphogenic and secondary cell wall gene expression

Plant growth requires the integration of internal and external cues, perceived and transduced into a developmental programme of cell division, elongation and wall thickening. Mechanical forces contribute to this regulation, and thigmomorphogenesis typically includes reducing stem height, increasing stem diameter, and a canonical transcriptomic response. We present data on a bZIP transcription factor involved in this process in grasses. Brachypodium distachyon SECONDARY WALL INTERACTING bZIP (SWIZ) protein translocated into the nucleus following mechanostimulation. Classical touch-responsive genes were upregulated in B. distachyon roots following touch, including significant induction of the glycoside hydrolase 17 family, which may be unique to grass thigmomorphogenesis. SWIZ protein binding to an E-box variant in exons and introns was associated with immediate activation followed by repression of gene expression. SWIZ overexpression resulted in plants with reduced stem and root elongation. These data further define plant touch-responsive transcriptomics and physiology, offering insights into grass mechanotranduction dynamics.

Coomey, Joshua↗
DOE OSTI2018

Evolution and expression of core SWI / SNF genes in red algae

Red algae are the oldest identifiable multicellular eukaryotes, with a fossil record dating back more than a billion years. During that time two major rhodophyte lineages, bangiophytes and florideophytes, have evolved varied levels of morphological complexity. These two groups are distinguished, in part, by different patterns of multicellular development, with florideophytes exhibiting a far greater diversity of morphologies. Interestingly, during their long evolutionary history, there is no record of a rhodophyte achieving the kinds of cellular and tissue‐specific differentiation present in other multicellular algal lineages. To date, the genetic underpinnings of unique aspects of red algal development are largely unexplored; however, they must reflect the complements and patterns of expression of key regulatory genes. Here we report comparative evolutionary and gene expression analyses of core subunits of the SWI / SNF chromatin‐remodeling complex, which is implicated in cell differentiation and developmental regulation in more well studied multicellular groups. Our results suggest that a single, canonical SWI / SNF complex was present in the rhodophyte ancestor, with gene duplications and evolutionary diversification of SWI / SNF subunits accompanying the evolution of multicellularity in the common ancestor of bangiophytes and florideophytes. Differences in how SWI / SNF chromatin remodeling evolved subsequently, in particular gene losses and more rapid divergence of SWI 3 and SNF 5 in bangiophytes, could help to explain why they exhibit a more limited range of morphological complexity than their florideophyte cousins.

Stiller, John W.↗
DOE OSTI2017

Retinal expression and localization of Mef2c support its important role in photoreceptor gene expression

Photoreceptor-specific gene expression is controlled by a hierarchical network of transcription factors, including the master regulators cone-rod homeobox (Crx) and neural retina leucine zipper (Nrl). Myocyte-enhancer factor 2c (Mef2c) is an ubiquitously expressed transcription factor with important functions in the cardiovascular system. Here, we performed a detailed analysis of Mef2c expression, localization and function in the retina to further elucidate its potential role for photoreceptor gene regulation. We showed that murine retinal Mef2c mRNA expression was high at birth and peaked at late postnatal developmental stages. Using immunohistochemistry and Western blot, Mef2c protein was detected in the outer nuclear layer of adult mouse and human retinas and localized to the nucleus of 661W photoreceptor-like cells. Mef2c knock-down in 661W cells reduced the expression of arrestin 3 (Arr3) and medium-wave-sensitive cone opsin (Opn1mw) but increased transcript levels of mitogen-activated protein kinase 15 (Mapk15) and phosphodiesterase 6h (Pde6h). In conclusion, Mef2c is highly expressed in the retina where it modulates photoreceptor-specific gene expression. - Highlights: • Mef2c is highly expressed in the mouse and human retina. • Mef2c localizes to mouse and human photoreceptor nuclei in situ. • Mef2c is present in the nucleus of 661W photoreceptor-like cells. • Mef2c knock-down in 661W cells impairs photoreceptor gene expression.

60 APPLIED LIFE SCIENCES↗