No abstract

The nuclear lamina, an intermediate filament meshwork lining the inner nuclear membrane, is formed by the nuclear lamins (lamins A, C, B1, and B2). Defects or deficiencies in individual nuclear lamin proteins have been reported to elicit nuclear blebs (protrusions or outpouchings of the nuclear envelope) and increase susceptibility for nuclear membrane ruptures. It is unclear, however, how a complete absence of nuclear lamins would affect nuclear envelope morphology and nuclear membrane integrity (i.e., whether nuclear membrane blebs or protrusions would occur and, if not, whether cells would be susceptible to nuclear membrane ruptures). To address these issues, we generated mouse embryonic fibroblasts (MEFs) lacking all nuclear lamins. The nuclear lamin-deficient MEFs had irregular nuclear shapes but no nuclear blebs or protrusions. Despite a virtual absence of nuclear blebs, MEFs lacking nuclear lamins had frequent, prolonged, and occasionally nonhealing nuclear membrane ruptures. By transmission electron microscopy, the inner nuclear membrane in nuclear lamin-deficient MEFs have a "wavy" appearance, and there were discrete discontinuities in the inner and outer nuclear membranes. Nuclear membrane ruptures were accompanied by a large increase in DNA damage, as judged by γ-H2AX foci. Mechanical stress increased both nuclear membrane ruptures and DNA damage, whereas minimizing transmission of cytoskeletal forces to the nucleus had the opposite effects.

Metal in the middle: A metallo base pair incorporating 6‐pyridylpurine (Purp) was synthesized and characterized. PurP binds nickel(II) preferentially over other divalent ions and yields a base pair that is more stable than natural Watson–Crick pairs with high mismatch selectivity. Computational studies support a dimensional resemblance between PurP⋅Ni2+⋅PurP (see structure) and natural base pairs.

Hutchinson-Gilford progeria syndrome is a progeroid disorder of children caused by de novo mutations in LMNA that lead to the synthesis of an internally truncated form of prelamin A (commonly called progerin). The production of progerin causes multiple disease phenotypes, including an unusual vascular phenotype characterized by the loss of smooth muscle cells in the arterial media and fibrosis of the adventitia. In this report, we show that progerin expression, combined with mechanical stress, promotes smooth muscle cell death. Disrupting the LInker of Nucleoskeleton and Cytoskeleton (LINC) complex in smooth muscle cells ameliorates the toxic effects of progerin on smooth muscle cells and limits the accompanying adventitial fibrosis.

A novel detection strategy for DNA sequencing applications that utilizes a frequency-based electrochemical method is reported. Sinusoidal voltammetry is used to selectively identify four unique redox molecules that are covalently attached to the 5'-end of a 20-base sequencing primer. The tags used in this work are ferrocene derivatives with different substituents attached to the ferrocene ring, where the electron-donating or -withdrawing character of the substituent alters the half-wave potential of the modified ferrocene. Therefore, each tag has a unique SV frequency spectrum that can be easily identified in the frequency domain. In this work, the discrimination of one tag versus all others is accomplished through a "phase-nulling" technique. The signal for each tag is selectively eliminated while the other three responses remain virtually unchanged. This analysis scheme allows for the selective identification of each tagged oligonucleotide eluting in sieving polymer capillary gel electrophoresis with a separation efficiency of 2 x 10(6) theoretical plates per meter. This separation efficiency is sufficient to perform "low-resolution" DNA sequencing; the conditions used in this work have not yet been optimized for high-resolution sequencing applications.