Background —Functional mitral regurgitation (FMR) occurs with a structurally normal valve as a complication of systolic left ventricular dysfunction (LVD). Determinants of degree of FMR are poorly defined; thus, mechanistic therapeutic approaches to FMR are hindered. Methods and Results —In a prospective study of 21 control subjects and 128 patients with LVD (defined as ejection fraction <50%, mean 31±9%) in sinus rhythm, we quantified simultaneously by echocardiography the effective regurgitant orifice (ERO) of FMR by using 2 methods: mitral deformation (valve and annulus) and left ventricular (LV) global (volumes, stress, function, and sphericity) and local (papillary muscle displacements and regional wall motion index) remodeling. A wide range of ERO (15±14 mm 2 , 0 to 87 mm 2 ) was observed, unrelated to ejection fraction ( P =0.32). The major determinant of ERO was mitral deformation, ie, systolic valvular tenting and annular contraction in univariate ( r =0.74 and r =−0.61, respectively; both P <0.0001) and multivariate (both P <0.0001) analyses, independent of global LV remodeling. Systolic valvular tenting was strongly determined by local LV alterations, particularly apical ( r =0.75) and posterior ( r =0.70) displacement of papillary muscle, with confirmation in multivariate analysis (both P <0.0001), independent of LV volumes, function, and sphericity. Conclusions —The presence and degree of FMR complicating LVD are unrelated to the severity of LVD. Local LV remodeling (apical and posterior displacement of papillary muscles) leads to excess valvular tenting independent of global LV remodeling. In turn, excess tenting and loss of systolic annular contraction are associated with larger EROs. These determinants of FMR warrant consideration for specific approaches to the treatment of FMR complicating LVD.
Methionine aminopeptidase 2 is required for HSC initiation and proliferation
AbstractIn a chemical screening, we tested the antiangiogenic effects of fumagillin derivatives and identified fumagillin as an inhibitor of definitive hematopoiesis in zebrafish embryos. Fumagillin is known to target methionine aminopeptidase II (MetAP2), an enzyme whose function in hematopoiesis is unknown. We investigated the role of MetAP2 in hematopoiesis by using zebrafish embryo and human umbilical cord blood models. Zebrafish metap2 was expressed ubiquitously during early embryogenesis and later in the somitic region, the caudal hematopoietic tissue, and pronephric duct. metap2 was inhibited by morpholino and fumagillin treatment, resulting in increased mpo expression at 18 hours postfertilization and reduced c-myb expression along the ventral wall of dorsal aorta at 36 hours postfertilization. It also disrupted intersegmental vessels in Tg(fli1:gfp) embryos without affecting development of major axial vasculatures. Inhibition of MetAP2 in CB CD34+ cells by fumagillin had no effect on overall clonogenic activity but significantly reduced their engraftment into immunodeficient nonobese diabetes/severe combined immunodeficiency mice. metap2 knock-down in zebrafish and inhibition by fumagillin in zebrafish and human CB CD34+ cells inhibited Calmodulin Kinase II activity and induced ERK phosphorylation. This study demonstrated a hithertoundescribed role of MetAP2 in definitive hematopoiesis and a possible link to noncanonical Wnt and ERK signaling.
The tau (MAPT) locus exists as two distinct clades, H1 and H2. The H1 clade has a normal linkage disequilibrium structure and is the only haplotype found in all populations except those derived from Caucasians. The H2 haplotype is the minor haplotype in Caucasian populations and is not found in other populations. It shows no recombination over a region of 2 Mb with the more common H1 haplotype. The distribution of the haplotype and analysis of the slippage of dinucleotide repeat markers within the haplotype suggest that it entered Homo sapiens populations between approx. 10000 and 30000 years ago. However, sequence comparison of the H2 haplotype with the H1 haplotype and with the chimp sequence suggests that the common founder of the H1 and H2 haplotypes was far earlier than this. We suggest that the H2 haplotype is derived from Homo neanderthalensis and entered H. sapiens populations during the co-existence of these species in Europe from approx. 45000 to 18000 years ago and that the H2 haplotype has been under selection pressure since that time, possibly because of the role of this H1 haplotype in neurodegenerative disease.