The probability to initiate X chromosome inactivation is determined by the X to autosomal ratio and x chromosome specific allelic properties.

Background: In female mammalian cells, random X chromosome inactivation (XCI) equalizes the dosage of X-encoded gene products to that in male cells. XCI is a stochastic process, in which each X chromosome has a probability to be inactivated. To obtain more insight in the factors setting up this probability, we studied the role of the X to autosome (X:A) ratio in initiation of XCI, and have used the experimental data in a computer simulation model to study the cellular population dynamics of XCI. Methodology/Principal Findings: To obtain more insight in the role of the X:A ratio in initiation of XCI, we generated triploid mouse ES cells by fusion of haploid round spermatids with diploid female and male ES cells. These fusion experiments resulted in only XXY triploid ES cells. XYY and XXX ES lines were absent, suggesting cell death related either to insufficient X-chromosomal gene dosage (XYY) or to inheritance of an epigenetically modified X chromosome (XXX). Analysis of active (Xa) and inactive (Xi) X chromosomes in the obtained triploid XXY lines indicated that the initiation frequency of XCI is low, resulting in a mixed population of XaXiY and XaXaY cells, in which the XaXiY cells have a small proliferative advantage. This result, and findings on XCI in diploid and tetraploid ES cell lines with different X:A ratios, provides evidence that the X:A ratio determines the probability for a given X chromosome to be inactivated. Furthermore, we found that the kinetics of the XCI process can be simulated using a probability for an X chromosome to be inactivated that is proportional to the X:A ratio. These simulation studies re-emphasize our hypothesis that the probability is a function of the concentration of an X-encoded activator of XCI, and of X chromosome specific allelic properties determining the threshold for this activator. Conclusions: The present findings reveal that the probability for an X chromosome to be inactivated is proportional to the X:A ratio. This finding supports the presence of an X-encoded activator of the XCI process. © 2009 Monkhorst et al

Unorthodoxy in legislation: The Hungarian experience

This paper deals with legal unorthodoxy. The main idea is to study the so-called unorthodox taxes Hungary has adopted in recent years. The study of unorthodox taxes will be preceded by a more general discussion of how law is made under unorthodoxy, and what are the special features of unorthodox legal policy. Unorthodoxy challenges equality before the law and is critical towards mass democracies. It also raises doubts on the operability of the rule of law, relying on personal skills, or loyalty, rather than on impersonal mechanisms arising from checks and balances as developed by the division of political power. Besides, for lack of legal suppositions, legislation suffers from casuistry and regulatory capture

Chromosomal organization at the level of gene complexes

Metazoan genomes primarily consist of non-coding DNA in comparison to coding regions. Non-coding fraction of the genome contains cis-regulatory elements, which ensure that the genetic code is read properly at the right time and space during development. Regulatory elements and their target genes define functional landscapes within the genome, and some developmentally important genes evolve by keeping the genes involved in specification of common organs/tissues in clusters and are termed gene complex. The clustering of genes involved in a common function may help in robust spatio-temporal gene expression. Gene complexes are often found to be evolutionarily conserved, and the classic example is the hox complex. The evolutionary constraints seen among gene complexes provide an ideal model system to understand cis and trans-regulation of gene function. This review will discuss the various characteristics of gene regulatory modules found within gene complexes and how they can be characterized

A Key Commitment Step in Erythropoiesis Is Synchronized with the Cell Cycle Clock through Mutual Inhibition between PU.1 and S-Phase Progression

During red blood cell development, differentiation and cell cycle progression are intimately and uniquely linked through interdependent mechanisms involving the erythroid transcriptional suppressor PU.1 and the cyclin-dependent kinase inhibitor p57KIP2

A Large Fraction of Extragenic RNA Pol II Transcription Sites Overlap Enhancers

A substantial fraction of extragenic Pol II transcription sites coincides with transcriptional enhancers, which may be relevant for functional annotation of mammalian genomes

Gap in publication of comparative information on new medicines

Item does not contain fulltextWHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Randomized active control trials are used by health care professionals and reimbursement authorities for the assessment of the added value of a new medicine. Failing to publish the results of clinical trials limits making an evidence based assessment and conducting systematic reviews. WHAT THIS STUDY ADDS: About one-third of the comparative trials used in the authorization process are published at the moment of market authorization and about four out of five within 2 or 3 years. Most of the rest remain unpublished. Unpublished trials contain information regarding a different therapeutic use or a different comparator of the same medicine and, in some cases, have influenced the risk : benefit assessment of the registration authorities. A standardized public registration of results of the main premarketing trials is advocated to fill the publication gap. AIMS: To determine the time-lag between the EU authorization of new medicines and the publications of the main randomized active control trials (RaCTs) used in the authorization process and to compare unpublished with published RaCTs of the same medicine. METHODS: All RaCTs for new medicines with a new active substance, authorized between 1999 and 2003, were extracted from the European Public Assessment Reports (EPAR). Information about the publication status of RaCTs was obtained from the MEDLINE and EMBASE databases. RESULTS: We identified 116 RaCTs for 42 new medicines; 28% of the RaCTs had been published at the moment of market authorization, 59% after 1 year, 78% after 2 and 83% after 3 years. Most of the rest of the studies remained unpublished after 3 years of follow-up. Unpublished RaCTs differed from published trials of the same medicine especially regarding therapeutic use and/or comparator. In some cases unpublished trials have influenced the risk : benefit asssessment of the registration authorities. CONCLUSIONS: Most of the main RaCTs, relevant for assessing the added value of a new medicine, are published subsequent to market entry; some of these trials remain unpublished. We argue for a standardized public registration of the results of the main premarketing clinical trials as a condition for market authorization