Slipped-strand mispairing in a plastid gene: rpoC2 in grasses (Poaceae)

An exception to the generally conservative nature of plastid gene evolution is the gene coding for the beta" subunit of RNA polymerase, rpoC2. Previous work by others has shown that maize and rice have an insertion in the coding region of rpoC2, relative to spinach and tobacco. To assess the distribution of this extra coding sequence, we surveyed a broad phylogenetic sample comprising 55 species from 17 angiosperm families by using Southern hybridization. The extra coding sequence is restricted to the grasses (Poaceae). DNA sequence analysis of 11 species from all five subfamilies within the grass family demonstrates that the extra sequence in the coding region of rpoC2 is a repetitive array that exhibits more than a twofold increase in nucleotide substitution, as well as a large number of insertion/deletion events, relative to the adjacent flanking sequences. The structure of the array suggests that slipped-strand mispairing causes the repeated motifs and adds to the mechanisms through which the coding sequence of plastid genes are known to evolve. Phylogenetic analyses based on the sequence data from grass species support several relationships previously suggested by morphological work, but they are ambiguous about broad relationships within the family.      

The effects of tin (Sn) additions on the growth of spinach plants

An increase in bioavailable tin in the environment could result in bioaccumulation thereof in agricultural crops, and therefore, have adverse health consequences on humans that eat these crops. The aims of the current study were thus to assess the uptake of Sn by spinach plants, and the subsequent effects this will have on the uptake of Na, Zn, K, Ca, and Mg as well as the growth of spinach plants. Spinach plants were grown in sand culture and received tin at concentrations of 0.02, 0.2, 2 and 20 mg/L along with a nutrient solution. The uptake of tin at detectible concentrations only occurred at the highest concentrations (2 and 20 mg/L), and it was mostly retained in the roots of the plants. Tin additions also resulted in no visual toxicity symptoms, and might be beneficial to biomass production. Further field trials are needed to ensure that these experimental results remain true under field conditions.     

Haploinsufficient Bmp4 ocular phenotypes include anterior segment dysgenesis with elevated intraocular pressure

Background  

Glaucoma is a common disease but its molecular etiology is poorly understood. It involves retinal ganglion cell death and optic nerve damage that is often associated with elevated intraocular pressure. Identifying genes that modify glaucoma associated phenotypes is likely to provide insights to mechanisms of glaucoma. We previously reported glaucoma in DBA/2J mice caused by recessive alleles at two loci, isa and ipd, that cause iris stromal atrophy and iris pigment dispersion, respectively. A approach for identifying modifier genes is to study the effects of specific mutations in different mouse strains. When the phenotypic effect of a mutation is modified upon its introduction into a new strain, crosses between the parental strains can be used to identify modifier genes. The purpose of this study was to determine if the effects of the DBA/2J derived isa and ipd loci are modified in strain AKXD-28/Ty.     

The T705I mutation of the low density lipoprotein receptor gene (FH Paris-9) does not cause familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disease caused by mutations in the low-density lipoprotein receptor gene. Among the more than 200 mutations so far identified, the T705I substitution in exon 15, designated FH-Paris 9, has been previously described as an FH-causing mutation. During the course of denaturing gradient gel electrophoretic screening of exon 15 we have identified the T705I single-base substitution not only in an FH family but also in a control, normocholesterolemic population. Therefore, we conclude that FH-Paris 9 is a missense mutation not associated with FH. Received: 5 March 1996 / Revised: 28 July 1996     

A rapid micromethod for apolipoprotein E phenotyping directly in serum

A new method for the apolipoprotein E phenotyping has been developed. The method is based on isoelectric focusing of either delipidated or guanidine-HC1-treated serum or plasma in a horizontal slab gel system followed by immunoblotting using either polyclonal or monoclonal anti-apolipoprotein E antibodies as first antibody. Apolipoprotein E phenotyping with this method in 200 serum samples that had been stored at -20 degrees C for more than one year gave exactly the same results as obtained with the conventional method based on isoelectric focusing of delipidated very low density lipoproteins isolated from fresh serum followed by protein staining. Compared with the conventional method, the present method is less laborious because ultracentrifugation to isolate VLDL is not needed; it is suitable for large scale screening purposes; it needs only a few microliters of serum or plasma, and can easily be performed with samples with low concentrations of apolipoprotein E.     

Functional analogy between lipoprotein(a) and plasminogen in the binding to the kringle 4 binding protein, tetranectin

Apolipoprotein(a), apo(a), contains 37 repeats structurally homologous to kringle 4 structures of the fibrinolysis zymogen plasminogen. The aim of the study was to explore the functional analogy between apolipoprotein(a) and plasminogen in the binding to the kringle-4-binding plasma protein, tetranectin. With a modified crossed immunoelectrophoresis technique, reversible binding between lipoprotein(a) and tetranectin could be demonstrated with an apparent Kd of 0.013 muMol/l. Lys- and Glu-plasminogen showed an apparent Kd of 0.5 muMol/l. Binding of lipoprotein(a) to fibrin and to fibrin-bound tetranectin was found to be negligible. The absence of fibrin binding of lipoprotein(a) excludes a potential mechanism of coexistence of fibrin and lipid deposits in arterial diseases and does not provide for a link between lipoprotein and the clotting system. Plasminogen and lipoprotein(a) show functional analogy in their binding to tetranectin, but tetranectin primarily targets at lipoprotein(a).     

Characterisation of the LDL receptor in Epstein-Barr virus transformed lymphocytes

Non-dividing human lymphocytes were transformed upon infection with the Epstein-Barr virus (EBV) into lymphoblasts which are capable of continuous growth in culture. We studied the properties of the LDL receptor in EBV-transformed human lymphocytes (EBV-L) by binding experiments and by ligand blotting. EBV-L show a high affinity binding of LDL in the same order of magnitude as found with fibroblasts; EBV-L obtained from a homozygous familial hypercholesterolemic (FH) patient fail to express LDL receptor activity. Similar to that of fibroblasts, the LDL receptor activity in EBV-L is Ca2(+)-dependent and is down-regulated by the presence of an exogenous source of cholesterol in the medium. The LDL receptor protein of EBV-L has an apparent molecular weight of 130,000. Since our results show that EBV-L display a LDL receptor protein similar to the LDL receptor present in fibroblasts, we conclude that in comparison with other cell types the EBV-L offer a suitable model system to investigate LDL receptor protein abnormalities in FH patients.