Epigenetic reprogramming in the mammalian embryo: struggle of the clones

During preimplantation development in mammals, distinct epigenetic marks on oocyte and sperm DNA are remodeled to an embryonic pattern. A recent study examining global methylation of repetitive elements in various mammals showed that the reprogramming that occurs during normal preimplantation development is aberrant in cloned embryos.     

Evolution by leaps: gene duplication in bacteria

Background  

Sequence related families of genes and proteins are common in bacterial genomes. In Escherichia coli they constitute over half of the genome. The presence of families and superfamilies of proteins suggest a history of gene duplication and divergence during evolution. Genome encoded protein families, their size and functional composition, reflect metabolic potentials of the organisms they are found in. Comparing protein families of different organisms give insight into functional differences and similarities.     

A radioimmunoassay specific for [Gln]LH-RH: Application in the confirmation of the structure of chicken hypothalamic luteinizing hormone-releasing hormone

In the first report on the chemical structure of a nonmammalian LH-RH, chicken hypothalamic LH-RH was demonstrated to be [Gln⁸]LH-RH [2–4]. However, these studies and subsequent reports [7,8] did not totally exclude the possibility of a reverse sequence of the two amino acids Leu-Gln. In view of the recently described structure of salmon brain LH-RH as [Trp⁷,Leu⁸]LH-RH [9], we undertook to confirm our earlier conclusion that chicken LH-RH is [Gln⁸]LH-RH and not [Gln⁷,Leu⁸]LH-RH. The immunologic, chromatographic and biological properties of natural chicken hypothalamic LH-RH were compared with those of the two synthetic peptides, [Gln⁸]LH-RH and [Gln⁷,Leu⁸]LH-RH. A radioimmunoassay highly specific for [Gln⁸]LH-RH was developed. Natural chicken LH-RH cross-reacted fully with the antiserum which requires the COOH-terminal Gln⁸ to Gly¹⁰-NH₂ for binding, while [Gln⁷,Leu⁸]LH-RH showed less than 0.1% cross-reaction. On a high resolution reverse phase high performance liquid chromatography system, natural chicken LH-RH co-eluted with [Gln⁸]LH-RH and was well separated from [Gln⁷,Leu⁸]LH-RH. In a chicken anterior pituitary cell bioassay, natural chicken LH-RH and [Gln⁸]LH-RH were equipotent in stimulating luteinizing hormone release, while the relative potency of [Gln⁷,Leu⁸]LH-RH was 4.4%. These data, in particular the use of a specific [Gln⁸]LH-RH antiserum, provide conclusive evidence that chicken LH-RH is [Gln⁸]LH-RH.     

Sequence of the phosphothreonyl regulatory site peptide from inactive maize leaf pyruvate, orthophosphate dikinase

The regulatory site peptide sequence of phosphorylated inactive pyruvate, orthophosphate dikinase from maize leaf tissue was determined by automated Edman degradation analysis of 32P-labeled peptides purified by reversed-phase high performance liquid chromatography. The overlapping phosphopeptides were products of a digestion of the [beta-32P]ADP-inactivated dikinase with either trypsin or Pronase E. The sequence is Thr-Glu-Arg-Gly-Gly-Met-Thr(P)-Ser-His-Ala-Ala-Val-Val-Ala-Arg. The phosphothreonine residue, which appeared as either an anomalous proline or an unidentifiable phenylthiohydantoin derivative during sequencing, was verified by two-dimensional phosphoamino acid analysis of the phosphopeptides and by resequencing the tryptic peptide after dephosphorylation with exogenous alkaline phosphatase. This sequence, starting at position 4, is completely homologous to the previously published sequence of the tryptic dodecapeptide harboring the catalytically essential (phospho)histidyl residue in the active-site domain of the dikinase from the nonphotosynthetic bacterium, Bacteroides symbiosus (Goss, N.H., Evans, C.T., and Wood, H.G. (1980) Biochemistry 19, 5805-5809). These comparative results indicate that the regulatory phosphothreonine causing complete inactivation of maize leaf dikinase is separated from the critical active-site (phospho)histidine by just one intervening residue in the primary sequence.     

Levels of Soluble Apolipoprotein E/Amyloid-β (Aβ) Complex Are Reduced and Oligomeric Aβ Increased with APOE4 and Alzheimer Disease in a Transgenic Mouse Model and Human Samples

Human apolipoprotein E (apoE) isoforms may differentially modulate amyloid-β (Aβ) levels. Evidence suggests physical interactions between apoE and Aβ are partially responsible for these functional effects. However, the apoE/Aβ complex is not a single static structure; rather, it is defined by detection methods. Thus, literature results are inconsistent and difficult to interpret. An ELISA was developed to measure soluble apoE/Aβ in a single, quantitative method and was used to address the hypothesis that reduced levels of soluble apoE/Aβ and an increase in soluble Aβ, specifically oligomeric Aβ (oAβ), are associated with APOE4 and AD. Previously, soluble Aβ42 and oAβ levels were greater with APOE4 compared with APOE2/APOE3 in hippocampal homogenates from EFAD transgenic mice (expressing five familial AD mutations and human apoE isoforms). In this study, soluble apoE/Aβ levels were lower in E4FAD mice compared with E2FAD and E3FAD mice, thus providing evidence that apoE/Aβ levels isoform-specifically modulate soluble oAβ clearance. Similar results were observed in soluble preparations of human cortical synaptosomes; apoE/Aβ levels were lower in AD patients compared with controls and lower with APOE4 in the AD cohort. In human CSF, apoE/Aβ levels were also lower in AD patients and with APOE4 in the AD cohort. Importantly, although total Aβ42 levels decreased in AD patients compared with controls, oAβ levels increased and were greater with APOE4 in the AD cohort. Overall, apoE isoform-specific formation of soluble apoE/Aβ modulates oAβ levels, suggesting a basis for APOE4-induced AD risk and a mechanistic approach to AD biomarkers.