DBA/2J Genetic Background Exacerbates Spontaneous Lethal Seizures but Lessens Amyloid Deposition in a Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a leading cause of dementia in the elderly and is characterized by amyloid plaques, neurofibrillary tangles (NFTs) and neuronal dysfunction. Early onset AD (EOAD) is commonly caused by mutations in amyloid precursor protein (APP) or genes involved in the processing of APP including the presenilins (e.g. PSEN1 or PSEN2). In general, mouse models relevant to EOAD recapitulate amyloidosis, show only limited amounts of NFTs and neuronal cell dysfunction and low but significant levels of seizure susceptibility. To investigate the effect of genetic background on these phenotypes, we generated APP^swe and PSEN1^de9 transgenic mice on the seizure prone inbred strain background, DBA/2J. Previous studies show that the DBA/2J genetic background modifies plaque deposition in the presence of mutant APP but the impact of PSEN1^de9 has not been tested. Our study shows that DBA/2J.APP^swePSEN1^de9 mice are significantly more prone to premature lethality, likely to due to lethal seizures, compared to B6.APP^swePSEN1^de9 mice—70% of DBA/2J.APP^swePSEN1^de9 mice die between 2-3 months of age. Of the DBA/2J.APP^swePSEN1^de9 mice that survived to 6 months of age, plaque deposition was greatly reduced compared to age-matched B6.APP^swePSEN1^de9 mice. The reduction in plaque deposition appears to be independent of microglia numbers, reactive astrocytosis and complement C5 activity.     

Profiling SARS-CoV-2 HLA-I peptidome reveals T cell epitopes from out-of-frame ORFs

1. Download : Download high-res image (225KB)
2. Download : Download full-size image

     

A Molecular Switching Mechanism in Differentiation

Abstract. The selection of polarity in cells of the cambium in higher plants is a regulated process of development which results in horizontally or vertically oriented cells. A set of mathematical equations suggestive of this developmental dichotomy is given a new biologic interpretation. As a result, a molecular scheme capable of acting as a biochemical switch is suggested. The model features two structural protein monomers whose synthesis is controlled autogenously by feedback repression. The implications of this and similar mechanisms to other differentiating systems is discussed.     

Isolation and distribution of myosin isoenzymes in chicken pectoralis muscle

The preparation of rabbit antibodies uniquely specific for the alkali 1 (A1) and alkali 2 (A2) light chains of chicken pectoralis myosin has led to the direct isolation of two homodimeric species of myosin: A1-myosin and A2-myosin, molecules which contain the same light chain on each head. The existence of a heterodimeric species, containing both A1 and A2 light chains, was also inferred. The three types of alkali light chain isoenzymes occur in approximately equal amounts in adult chicken pectoralis muscle.The specificities of the antibodies were determined by modified Farr and solid phase radioimmunoassays, as well as by antibody-affinity chromatography. The determinants in myosin that are recognized by the purified antibodies appear to be confined to the N-terminal sequences of the alkali light chains. As a result of this narrow specificity, these immunological reagents can be used to characterize the distribution of A1 and A2 within the myosin molecule, and to localize the individual light chains within the muscle.By labeling the antibodies with a fluorescent marker we have shown that A1 and A2 are present within each myofibril, as well as within the same fiber (Lowey et al., 1979a). Moreover, by using goat anti-rabbit immunoglobulin to enhance the visualization of the primary antibodies against the light chains, we have demonstrated in the electron microscope that A1 and A2 co-exist along the length of each myofilament. This observation suggests that whatever functional differences may exist among the alkali light chain isoenzymes, they must operate within the constraints of a single filament.     

Developmental progression of myosin gene expression in cultured muscle cells

Myosin heavy chains are encoded by distinct members of a multigene family at different stages of muscle development. Study of the underlying regulatory mechanisms has been hindered because transitions in myosin expression have not been readily attained in tissue culture. Here we show a transition from early (fetal) to late (perinatal/adult) myosins defined by two monoclonal antibodies, F1.652 and N3.36, in the myotubes of mouse C2C12 cells. On day 1 of differentiation, essentially all myosin was early myosin. By day 8, early myosin dropped to 25% of its day 1 value and was replaced by late myosin. The transition occurred without neural contact, connective tissue components, or complex substrates, suggesting that its regulation may be intrinsic to the muscle cell. Our results demonstrate that a developmental progression in myosin gene expression, which occurs rapidly, with high frequency, and under relatively simple conditions, is now amenable to molecular analysis in cultured muscle cells.     

Membrane destabilization assay based on potassium release from liposomes.

Inorganic ions are highly suitable markers for monitoring release of the inner content of liposomes. In the present study, a potassium (K(+)) selective electrode was used to evaluate the rate of K(+) release from large unilamellar vesicles (LUV). The developed method is highly sensitive, reproducible and inexpensive. Since the K(+) ion is smaller than other markers conventionally used, the method described is more sensitive than one of the standard methods that uses ANTS/DPX. In addition, the method allows us to expand the set of molecules used as inner content markers to a lower size range. The experimental protocol we described contains improvements on the method of Breukink et al. (Biochemistry, 36 (1997) 6968). Our developed method was applied to compare the destabilizing activities of two amphipathic peptides of natural origin (Melittin and HIV env seg I, 827-851) and of two artificial peptides (Hels 7:11 and 9:9) synthesized de novo by Kiyota et al. (Biochemistry, 35 (1996) 13196). The tested peptides released 20% of the liposomal K(+) in 1 min at peptide-to-lipid ratio of a few mmol per mol of total lipids (LUV sized to 0.2 micrometer, molar composition is POPC:POPS:Chol 2:2:1).     

Development,validation and reliability of the Chrononutrition Profile - Questionnaire

ABSTRACT

Chrononutrition, or the circadian timing of food intake, has garnered attention as a topic of study due to its associations with health (e.g. weight gain); however, a valid and reliable assessment of chrononutrition in daily life has not yet been developed. This paper details the development and initial reliability and validity testing of the Chrononutrition Profile – Questionnaire (CP-Q). The CP-Q assesses six components of chrononutrition that are likely to influence health (breakfast skipping, largest meal, evening eating, evening latency, night eating, and eating window). This questionnaire is designed to assess general chrononutrition behaviors and preferred timing of food intake. The CP-Q can be used as a sole evaluation of chrononutrition, and can also be utilized in conjunction with existing dietary measures to provide a comprehensive assessment of one’s eating behaviors. This measure offers health-care professionals, researchers, and stakeholders a cost-effective and comprehensive method of evaluating chrononutrition and identifying targets for health improvement.     

Ordering microtubules

How do cells order their cytoplasm? While microtubule organizing centers have long been considered essential to conferring order by virtue of their microtubule nucleating activity, attention has currently refocused on the role that microtubule motors play in organizing microtubules. An intriguing set of recent findings⁽¹⁾ reveals that cell fragments, lacking microtubule organizing centers, rapidly organize microtubules into a radial array during organelle transport driven by the microtubule motor, cytoplasmic dynein. Further, interaction of radial microtubules with the cell surface centers the array, revealing that centering information resides not with centrosomes but with organized microtubules.