Scl binds to primed enhancers in mesoderm to regulate hematopoietic and cardiac fate divergence

Scl/Tal1 confers hemogenic competence and prevents ectopic cardiomyogenesis in embryonic endothelium by unknown mechanisms. We discovered that Scl binds to hematopoietic and cardiac enhancers that become epigenetically primed in multipotent cardiovascular mesoderm, to regulate the divergence of hematopoietic and cardiac lineages. Scl does not act as a pioneer factor but rather exploits a pre‐established epigenetic landscape. As the blood lineage emerges, Scl binding and active epigenetic modifications are sustained in hematopoietic enhancers, whereas cardiac enhancers are decommissioned by removal of active epigenetic marks. Our data suggest that, rather than recruiting corepressors to enhancers, Scl prevents ectopic cardiogenesis by occupying enhancers that cardiac factors, such as Gata4 and Hand1, use for gene activation. Although hematopoietic Gata factors bind with Scl to both activated and repressed genes, they are dispensable for cardiac repression, but necessary for activating genes that enable hematopoietic stem/progenitor cell development. These results suggest that a unique subset of enhancers in lineage‐specific genes that are accessible for regulators of opposing fates during the time of the fate decision provide a platform where the divergence of mutually exclusive fates is orchestrated.     

Tissue- and development-specific distributions of cytoskeletal elements in growing cells of the maize root apex

ABSTRACT

Indirect immunofluorescence performed using sections of actively growing maize root apices fixed and then embedded in low-melting-point Steedman's wax has proved efficient in revealing the arrangements and reorganizations of motility-related cytoskeletal elements which are associated with root cell development and tissue differentiation. This powerful, yet relatively simple, technique shows that specific rearrangements of both microtubular (MT) and actin microfilament (MF) arrays occur in cells as they leave the meristem and traverse the transitional region interpolated between meristem and elongation region. Cytoskeletal and growth analyses have identified the transition zone as critical for both cell and root development; it is in this zone that cell growth is channelled, by the cytoskeleton, into a strictly polarized mode which enables root tips to extend rapidly through the soil in search of water and nutrients. An integrated cytoskeletal network is crucial for both the cytomorphogenesis of individual cells and the overall morphogenesis of the plant body. The latter process can be viewed as a reflection of the tight control which cytoskeletal networks exert not only over cell division planes in the cells within meristematic apices but also over the orientation of cell growth in the meristem and elsewhere. Endoplasmic MTs interconnecting the plasma membrane with the nucleus are suggested to be involved in cell division control; they may also act as a two-way cytoskeletal communication channel for signals passing to and fro between the extracellular environment and the genome. Moreover, the dynamism of endoplasmic MTs exerts direct effects on chromatin structure and the accompanying nuclear architecture and hence can help exert a cellular level of control over cell growth and cell cycle progression. Because the inherent dynamic instability of MTs depends on the concentration of tubulin dimers within the cytoplasm, we propose that when asymmetric cell division occurs, it will result in two daughter cells which differ in the turnover rates of their MTs. This phenomenon could be responsible for different cell fates of daughter plant cells produced by such cell divisions.     

Characterization of Diaphanous-related formin FMNL2 in human tissues

Background  

Diaphanous-related formins govern actin-based processes involved in many cellular functions, such as cell movement and invasion. Possible connections to developmental processes and cellular changes associated with malignant phenotype make them interesting study targets. In spite of this, very little is known of the tissue distribution and cellular location of any mammalian formin. Here we have carried out a comprehensive analysis of the formin family member formin -like 2 (FMNL2) in human tissues.     

Whole Genome Amplification for Sequencing and Applications in Conservation Genetics

Abstract: We describe a method for rapidly amplifying whole genomes via a Phi29 DNA polymerase-mediated strand displacement reaction (SDR). Genomic amplification products derived from the SDR reaction resulted in high quantities of DNA suitable for polymerase chain reaction (PCR) amplification and sequencing of mitochondrial genomes. Control region sequences of DNA derived directly from PCR amplicons of extracted DNA were identical to those derived from PCR amplification of SDR genomic DNA. Effective SDR amplification and subsequent sequencing was successful across tissues sources ranging in age from 1 year to 19 years. Strand replacement reaction genomic amplification offers a means of obtaining large quantities of DNA from small amounts of tissue.     

Salivary alpha amylase and salivary cortisol response to fluid consumption in exercising athletes

The objective of the study was to examine salivary biomarker response to fluid consumption in exercising athletes. Exercise induces stress on the body and salivary alpha amylase (sAA) and salivary cortisol are useful biomarkers for activity in the sympathoadrenal medullary system and the hypothalamic pituitary adrenal axis which are involved in the stress response. Fifteen college students were given 150 ml and 500 ml of water on different days and blinded to fluid condition. The exercise protocol was identical for both fluid conditions using absolute exercise intensities ranging from moderate to high. Saliva was collected prior to exercise, post moderate and post high intensities and analyzed by Salimetrics assays. Exercise was significant for sAA with values different between pre-exercise (85 ± 10 U · ml⁻¹) and high intensity (284 ± 30 U · ml⁻¹) as well as between moderate intensity (204 ± 32 U · ml⁻¹) and high intensity. There was no difference in sAA values between fluid conditions at either intensity. Exercise intensity and fluid condition were each significant for cortisol. Cortisol values were different between pre-exercise (0.30 ± 0.03 ug · dL⁻¹) and high intensity (0.45 ± 0.05 ug · dL⁻¹) as well as between moderate intensity (0.33 ± 0.04 ug · dL⁻¹) and high intensity. Moderate exercise intensity cortisol was lower in the 500 ml condition (0.33 ± 0.03 ug · dL⁻¹) compared with the 150 ml condition (0.38 ± 0.03 ug · dL⁻¹). This altered physiological response due to fluid consumption could influence sport performance and should be considered. In addition, future sport and exercise studies should control for fluid consumption.     

Cloning and gene map assignment of the Xiphophorus DNA ligase 1 gene

Fishes represent the stem vertebrate condition and have maintained several gene arrangements common to mammalian genomes throughout the 450 Myr of divergence from a common ancestor. One such syntenic arrangement includes the GPI-PEPD enzyme association on Xiphophorus linkage group IV and human chromosome 19. Previously we assigned the Xiphophorus homologue of the human ERCC2 gene to linkage group U5 in tight association with the CKM locus. CKM is also tightly linked to the ERCC2 locus on human chromosome 19, leading to speculation that human chromosome 19 may have arisen by fusion of two ancestral linkage groups which have been maintained in fishes. To investigate this hypothesis further, we isolated and sequenced Xiphophorus fish genomic regions exhibiting considerable sequence similarity to the human DNA ligase 1 amino acid sequence. Comparison of the fish DNA ligase sequence with those of other species suggests several modes of amino acid conservation in this gene. A 2.2-kb restriction fragment containing part of an X. maculatus DNA ligase 1 exon was used in backcross hybrid mapping with 12 enzyme or RFLP loci. Significant linkage was observed between the nucleoside phosphorylase (NP2) and the DNA ligase (LIG1) loci on Xiphophorus linkage group VI. This assignment suggests that the association of four DNA repair-related genes on human chromosome 19 may be the result of chance chromosomal rearrangements.      

The lactosylceramide binding specificity of Helicobacter pylori

The possible role of glycosphingolipids as adhesion receptors for the human gastric pathogen Helicobacter pylori was examined by use of radiolabeled bacteria, or protein extracts from the bacterial cell surface, in the thin-layer chromatogram binding assay. Of several binding specificities found, the binding to lactosylceramide is described in detail here, the others being reported elsewhere. By autoradiography a preferential binding to lactosylceramide having sphingosine/phytosphingosine and 2-D hydroxy fatty acids was detected, whereas lactosylceramide having sphingosine and nonhydroxy fatty acids was consistently nonbinding. A selective binding of H. pylori to lactosylceramide with phytosphingosine and 2-D hydroxy fatty acid was obtained when the different lactosylceramide species were incorporated into liposomes, but only in the presence of cholesterol, suggesting that this selectivity may be present also in vivo . Importantly, lactosylceramide with sphingosine and hydroxy fatty acids does not bind in this assay. Furthermore, a lactosylceramide-based binding pattern obtained for different trisaccharide glycosphingolipids is consistent with the assumption that this selectivity is due to binding of a conformation of lactosylceramide in which the oxygen of the 2-D fatty acid hydroxyl group forms a hydrogen bond with the Glc hydroxy methyl group, yielding an epitope presentation different from other possible conformers. An alternative conformation that may come into consideration corresponds to the crystal structure found for cerebroside, in which the fatty acid hydroxyl group is free to interact directly with the adhesin. By isolating glycosphingolipids from epithelial cells of human stomach from seven individuals, a binding of H.pylori to the diglycosylceramide region of the non-acid fraction could be demonstrated in one of these cases. Mass spectrometry showed that the binding-active sample contained diglycosylceramides with phytosphingosine and 2-D hydroxy fatty acids with 16-24 carbon atoms in agreement with the results related above.