Altering chromatin methylation patterns and the transcriptional network involved in regulation of hematopoietic stem cell fate
JOURNAL OF CELLULAR PHYSIOLOGY
Authors: Shokouhian, Mohammad; Bagheri, Marziye; Poopak, Behzad; Chegeni, Rouzbeh; Davari, Nader; Saki, Najmaldin
Abstract
Hematopoietic stem cells (HSCs) are quiescent cells with self-renewal capacity and potential multilineage development. Various molecular regulatory mechanisms such as epigenetic modifications and transcription factor (TF) networks play crucial roles in establishing a balance between self-renewal and differentiation of HSCs. Histone/DNA methylations are important epigenetic modifications involved in transcriptional regulation of specific lineage HSCs via controlling chromatin structure and accessibility of DNA. Also, TFs contribute to either facilitation or inhibition of gene expression through binding to enhancer or promoter regions of DNA. As a result, epigenetic factors and TFs regulate the activation or repression of HSCs genes, playing a central role in normal hematopoiesis. Given the importance of histone/DNA methylation and TFs in gene expression regulation, their aberrations, including changes in HSCs-related methylation of histone/DNA and TFs (e.g., CCAAT-enhancer-binding protein alpha, phosphatase and tensin homolog deleted on the chromosome 10, Runt-related transcription factor 1, signal transducers and activators of transcription, and RAS family proteins) could disrupt HSCs fate. Herewith, we summarize how dysregulations in the expression of genes related to self-renewal, proliferation, and differentiation of HSCs caused by changes in epigenetic modifications and transcriptional networks lead to clonal expansion and leukemic transformation.
Improving reference equations for cardiorespiratory fitness using multiplicative allometric rather than additive linear models: Data from the Fitness Registry and the Importance of Exercise National Database Registry
PROGRESS IN CARDIOVASCULAR DISEASES
Authors: Nevill, Alan M.; Myers, Jonathan; Kaminsky, Leonard A.; Arena, Ross
Abstract
New improved reference equations for cardiorespiratory fitness have recently been published, using Data from the Fitness Registry and the Importance of Exercise National Database (FRIEND Registry). The new linear equation for VO2max (ml.kg(-1).min(-1)) was additive, derived using multiple-linear regression. An alternative multiplicative allometric model has also been published recently, thought to improve further the quality of fit. The purpose of the current study was to compare the accuracy and quality/goodness-of-fit of the linear, additive model with the multiplicative allometric model using the FRIEND database. The results identified that the allometric model out performs the linear model based on all model-comparison criteria. The allometric model demonstrates; 1) greater explained variance (R-2 = 0.645; R = 0.803) vs. (R-2 = 0.62; R = 0.79), 2) residuals that were more normally distributed, 3) residuals that yielded less evidence of curvature, 4) superior goodness-of-fit statistics i.e., greater maximum log-likelihood (MLL) and smaller Akaike Information Criterion (AK) statistics, 5) less systematic bias together with smaller unexplained standard error of estimates. The Bland and Altman plots also confirmed little or no evidence of curvature with the allometric model, but systematic curvature (lack-of-fit) in the linear model. The multiplicative allometric model to predict VO2max was; VO2max (ml.kg(-1).min(-1)) = M-0.854 . H-1.44 . exp. (0.424-0.346 . (sex) -0.011.age), where M = body mass and H = height (R-2 = 0.645; R = 0.803) and sex is entered as a[0,1] indicator variable (male = 0 and female = 1). Another new insight obtained from the allometric model (providing construct validity) is that the height-to-body-mass ratio is similar to inverse body mass index or the lean body mass index, both associated with leanness when predicting VO2max. In conclusion adopting allometric models will provide more accurate predictions of VO2max (ml.kg(-1).min(-1)) using more plausible, biologically sound and interpretable models. (C) 2019 Elsevier Inc. All rights reserved.