The planetary biology of cytochrome P450 aromatases

Background  

Joining a model for the molecular evolution of a protein family to the paleontological and geological records (geobiology), and then to the chemical structures of substrates, products, and protein folds, is emerging as a broad strategy for generating hypotheses concerning function in a post-genomic world. This strategy expands systems biology to a planetary context, necessary for a notion of fitness to underlie (as it must) any discussion of function within a biomolecular system.     

Critical role of the major histocompatibility complex and IL-10 in matrilin-1-induced relapsing polychondritis in mice

Relapsing polychondritis (RP) is an autoimmune disease that affects extra-articular cartilage. Matrilin-1-induced relapsing polychondritis (MIRP) is a model for RP and is useful for studies of the pathogenic mechanisms in this disease. There are indications that the major histocompatibility complex (MHC) class II plays a major role in RP, since DR4⁺ patients are more commonly affected than controls. We have now addressed the role of the MHC region, as well as the non-MHC contribution, using congenic mouse strains. Of the MHC congenic strains, B10.Q (H2 ^q ) was the most susceptible, the B10.P (H2 ^p ) and B10.R (H2 ^r ) strains developed mild disease, while B10 strains carrying the v, b, f, or u H2 haplotypes were resistant. A slight variation of susceptibility of H2 ^q strains (B10.Q> C3H.Q> DBA/1) was observed and the (B10.Q × DBA/1)F₁ was the most susceptible of all strains. Furthermore, macrophages and CD4⁺ T cells were the most prominent cell types in inflammatory infiltrates of the tracheal cartilage. Macrophages are the major source of many cytokines, such as interleukin-10 (IL-10), which is currently being tested as a therapeutic agent in several autoimmune diseases. We therefore investigated B10.Q mice devoid of IL-10 through gene deletion and found that they developed a significantly more severe disease, with an earlier onset, than their heterozygous littermates. In conclusion, MHC genes, as well as non-MHC genes, are important for MIRP induction, and IL-10 plays a major suppressive role in cartilage inflammation of the respiratory tract.     

RNA-binding protein-mediated translational repression of transgene expression in plants

We have demonstrated that RNA-binding proteins from coliphages and yeast can function as translational repressors in plants. RNA sequences called translational operators were inserted at a cap-proximal position in the 5-UTR of mRNAs of two reporter genes, gusor aroA:CP4. Translation of the reporter mRNAs was efficiently repressed when the RNA binding protein that specifically binds to its cognate operator was co-expressed. The efficiency of translational repression by RNA-binding protein positively correlated with the amount of binding protein in transformed plant cells. Detailed studies on coliphage MS2 coat protein-mediated translational repression also suggested that the efficiency of translational repression was position-dependent. A translational operator situated at the cap-proximal position was more efficient in conferring repression than one that was placed cap-distal. Translational repression can be an efficient means for regulation of transgene expression, thereby broadening current approaches for transgene regulation in plants.these authors contributed equally to this workthese authors contributed equally to this work     

Calcium currents in embryonic and neonatal mammalian skeletal muscle

The whole-cell patch-clamp technique was used to study the properties of inward ionic currents found in primary cultures of rat and mouse skeletal myotubes and in freshly dissociated fibers of the flexor digitorum brevis muscle of rats. In each of these cell types, test depolarizations from the holding potential (-80 or -90 mV) elicited three distinct inward currents: a sodium current (INa) and two calcium currents. INa was the dominant inward current: under physiological conditions, the maximum inward INa was estimated to be at least 30-fold larger than either of the calcium currents. The two calcium currents have been termed Ifast and Islow, corresponding to their relative rates of activation. Ifast was activated by test depolarizations to around -40 mV and above, peaked in 10-20 ms, and decayed to baseline in 50-100 ms. Islow was activated by depolarizations to approximately 0 mV and above, peaked in 50-150 ms, and decayed little during a 200-ms test pulse. Ifast was inactivated by brief, moderate depolarizations; for a 1-s change in holding potential, half-inactivation occurred at -55 to -45 mV and complete inactivation occurred at -40 to -30 mV. Similar changes in holding potential had no effect on Islow. Islow was, however, inactivated by brief, strong depolarizations (e.g., 0 mV for 2 s) or maintained, moderate depolarizations (e.g., -40 mV for 60 s). Substitution of barium for calcium had little effect on the magnitude or time course of either Ifast or Islow. The same substitution shifted the activation curve for Islow approximately 10 mV in the hyperpolarizing direction without affecting the activation of Ifast. At low concentrations (50 microM), cadmium preferentially blocked Islow compared with Ifast, while at high concentrations (1 mM), it blocked both Ifast and Islow completely. The dihydropyridine calcium channel antagonist (+)-PN 200-110 (1 microM) caused a nearly complete block of Islow without affecting Ifast. At a holding potential of -80 mV, the half-maximal blocking concentration (K0.5) for the block of Islow by (+)-PN 200-110 was 182 nM. At depolarized holding potentials that inactivated Islow by 35-65%, K0.5 decreased to 5.5 nM.     

Molecular evolution of the ZFY and ZNF6 gene families

Members of the ZFY and ZNF6 gene families have been cloned from species representing different taxa and different modes of sex determination. Comparisons of these genes show the ZFY-like and ZNF6 sequences to be strongly conserved across marsupials, birds, and lepidosaurians. Sequence analyzed by neighbor-joining indicated that both gene families are monophyletic with a high bootstrap value. Pairing of sequences from males and females of nonmammalian species showed there to be no significant difference between male and female sequences from a single species, consistent with autosomal locations. The molecular distances between murine Zfy-1, Zfy-2, and other ZFY-like sequences suggested that Zfy genes have undergone a period of rapid evolutionary change not seen in human ZFY.      

Gibbs-Ensemble Molecular Dynamics: A New Method for Simulations Involving Particle Exchange

We discuss a novel simulation method suitable for simulating phenomena involving particle exchange. The method is a molecular dynamics version of the Gibbs-Ensemble Monte Carlo technique, which has been developed some years ago for the direct simulation of phase equilibria in fluid systems. The idea is to have two separate simulation boxes, which can exchange particles or molecules in a thermodynamically consistent fashion. We discuss the general idea of the Gibbs-Ensemble Molecular Dynamics technique and present examples for different simple atomic and molecular fluids. Specifically we will discuss Gibbs-Ensemble Molecular Dynamics simulations of gas-liquid and liquid-solid equilibria in Lennard-Jones systems and in hexane as well as an application of the method to adsorption.     

Effect of drift sampler exposure time and net mesh size on invertebrate drift density in the Njoro River,Kenya

Although invertebrate drift is an important ecological process in lotic ecosystems, very little is known about it in Kenyan rivers. The primary aim of this study was to investigate the effect of driftnet mesh size and exposure duration on drift density in 2017. Drift samples were dominated by Chironomidae, Baetidae, Simuliidae, Caenidae and Culicidae. The 100 µm mesh driftnet had the highest mean invertebrate density, followed by the 250 µm and 500 µm nets. Invertebrate drift densities decreased with increased exposure time. This study demonstrates that sampler mesh size and exposure time should be taken into account when characterising invertebrate drift in streams. Future studies should consider sampling different biotopes and during different seasons.     

Bacterial transposon Tn5: evolutionary inferences

Transposable elements induce spontaneous mutations, promote genome rearrangements, regulate gene expression, and participate in the horizontal spread of genes encoding traits such as antibiotic resistance among bacterial genera too distantly related to undergo homologous recombination. Here we review the bacterial transposon Tn5 and focus on those aspects of its functional organization and transposition which provide insights into how it and other elements may have arisen, proliferated, and evolved.      

The phylogenetic position of Rhopalura ophiocomae (Orthonectida) based on 18S ribosomal DNA sequence analysis

The Orthonectida is a small, poorly known phylum of parasites of marine invertebrates. Their phylogenetic placement is obscure; they have been considered to be multicellular protozoans, primitive animals at a "mesozoan" grade of organization, or secondarily simplified flatworm- like organisms. The best known species in the phylum, Rhopalura ophiocomae, was collected on San Juan Island, Wash. and a complete 18S rDNA sequence was obtained. Using the models of minimum evolution and parsimony, phylogenetic analyses were undertaken and the results lend support to the following hypotheses about orthonectids: (1) orthonectids are more closely aligned with triploblastic metazoan taxa than with the protist or diploblastic metazoan taxa considered in this analysis; (2) orthonectids are not derived members of the phylum Platyhelminthes; and (3) orthonectids and rhombozoans are not each other's closest relatives, thus casting further doubt on the validity of the phylum Mesozoa previously used to encompass both groups.      

Distribution of the molossinus allele of Sry, the testis-determining gene, in wild mice

When the Y chromosome of the laboratory inbred mouse strain C57BL/6 (B6) is replaced by the Y of certain strains of Mus musculus domesticus, testis determination fails and all XY fetuses develop either as hermaphrodites or XY females (XY sex reversal). This suggests the presence of at least two alleles of Sry, the male-determining gene on the Y:M. m. domesticus and B6. The B6 Y chromosome is derived from the Japanese house mouse, M. m. molossinus and therefore carries a molossinus Sry allele. As a first step to determine how the molossinus Sry allele evolved, its distribution pattern was determined in wild mice. The cumulative data of 96 M. musculus samples obtained from 58 geographical locations in Europe, North Africa, and Asia show the molossinus Sry allele is restricted to Japan and the neighboring Asian mainland and confirm that Japanese M. m. molossinus mice were derived in part from a race of M. m. musculus from Korea or Manchuria. Sry polymorphisms, as illustrated by the molossinus Sry allele, can serve as molecular markers for studies on the evolution of wild M. musculus populations and can help determine the role sex determination plays in speciation.