ABSTRACT
The murine Xce locus, first identified by Bruce Cattanach, influences the primary choice of the X chromosome to be inactivated. Methylation of a GC-rich region (DXPas34) that includes multiple 34 bp repeats and lies some 15 kb 3' to Xist has been shown to vary with Xce haplotype. The degree of methylation on the active X chromosome at this locus represents one of the few molecular correlates of Xce action currently available. Data relating to the specificity and other characteristics of this association are presented.
Subject(s)
Dosage Compensation, Genetic , RNA, Untranslated , X Chromosome/genetics , Animals , Cell Line , Cloning, Molecular , DNA Methylation , Female , Male , Mice , Mice, Inbred Strains , Microsatellite Repeats/genetics , Polymerase Chain Reaction , RNA, Long Noncoding , Sequence Analysis, DNA , Transcription Factors/geneticsABSTRACT
The initiation of X-chromosome inactivation in female mammals is controlled by a key locus, the X-inactivation centre (Xic). The Xist gene, which maps to the candidate region for Xic and is expressed exclusively from the inactive X chromosome, is thought to be an essential component of the Xic. To test whether sequences spanning several hundred kilobases and including Xist from the Xic region are capable of initiating inactivation, we have created a series of transgenic mice using a 460 kb yeast artificial chromosome (YAC). Analysis in these mice of the expression of Xist, of a LacZ reporter gene and of two genes in the region that are normally silent on the inactive X chromosome, suggests that essential sequences for Xist expression and X-inactivation may be absent in these transgenic animals.
Subject(s)
Chromosomes, Artificial, Yeast , Dosage Compensation, Genetic , RNA, Untranslated , Transcription Factors/genetics , Animals , Base Sequence , DNA Primers , Female , Gene Dosage , Gene Expression Regulation, Developmental , Homeodomain Proteins/genetics , Humans , Lac Operon , Male , Mice , Mice, Inbred C3H , Mice, Transgenic , Molecular Sequence Data , Nerve Tissue Proteins/genetics , RNA, Long Noncoding , TransgenesABSTRACT
During early mammalian embryogenesis, one of the two X chromosomes in somatic cells of the female becomes inactivated through a process that is thought to depend on a unique initiator region, the X-chromosome inactivation center (Xic). The recently characterized Xist sequence (X-inactive-specific transcript) is thought to be a possible candidate for Xic. In mice a further genetic element, the X chromosome-controlling element (Xce), is also known to influence the choice of which of the two X chromosomes is inactivated. We report that a region of the mouse X chromosome lying 15 kb distal to Xist contains several sites that show hypermethylation specifically associated with the active X chromosome. Analysis of this region in various Xce strains has revealed a correlation between the strength of the Xce allele carried and the methylation status of this region. We propose that such a region could be involved in the initial stages of the inactivation process and in particular in the choice of which of the two X chromosomes present in a female cell will be inactivated.
Subject(s)
DNA Restriction-Modification Enzymes/metabolism , Dosage Compensation, Genetic , RNA, Untranslated , Regulatory Sequences, Nucleic Acid/genetics , Transcription Factors/genetics , X Chromosome/genetics , Animals , DNA/metabolism , Deoxyribonuclease HpaII , Deoxyribonucleases, Type II Site-Specific/metabolism , Female , Genetic Variation , Haplotypes , Male , Methylation , Mice , Mice, Inbred Strains , Phosphoglycerate Kinase/genetics , RNA, Long Noncoding , Restriction Mapping , Sex Differentiation/genetics , Species SpecificityABSTRACT
The inhibitory glycine receptor is a ligand-gated ion channel protein that occurs in different developmentally regulated isoforms in the mammalian central nervous system. Here, we have analyzed genomic clones covering the coding regions of the murine glycine receptor alpha 1 and alpha 2 subunit genes. Both genes contain eight intronic regions with precisely conserved boundaries. The same structure was also found for seven exons of a third homologous gene, alpha 4, identified during screening. The predicted alpha 4 polypeptide displays very high homology to the alpha 2 subunit. Like the alpha 2 gene, the alpha 4 gene maps to the mouse X chromosome. Our data indicate that the genomic organization of glycine receptor alpha subunit genes is conserved during evolution.
Subject(s)
Chromosome Mapping , DNA/chemistry , Genetic Variation , Ion Channels/genetics , Mice, Inbred C57BL/genetics , Receptors, Glycine/genetics , X Chromosome , Amino Acid Sequence , Animals , Base Sequence , Biological Evolution , Chickens/genetics , Cloning, Molecular , Conserved Sequence , DNA/metabolism , DNA, Complementary , Drosophila melanogaster/genetics , Exons , Genomic Library , Hominidae/genetics , Humans , Macromolecular Substances , Mice , Molecular Sequence Data , Polymerase Chain Reaction/methods , Restriction Mapping , Sequence Homology, Amino Acid , Transcription, GeneticABSTRACT
The Xist sequence has been proposed as a potential candidate for the X-inactivation center based both on its localization within the candidate region for the X-inactivation center in man and mouse and on its unique pattern of expression from the inactive X chromosome. We have cloned 550 kb of DNA surrounding the mouse Xist sequence in contiguously overlapping YAC clones and have developed a long-range restriction map that spans almost 1 Mb of this region and includes this YAC contig. The detailed restriction map we have established provides a framework for the identification of expressed sequences other than Xist that may equally exhibit unusual expression characteristics associated with X inactivation. The presence of possible structural or methylation differences within this region between the active and inactive X chromosomes has been investigated through comparative analysis of male and female genomic DNA, and we report here the identification of certain CpG-containing restriction sites around Xist that have an interesting differential methylation status on the inactive and active X chromosomes.
Subject(s)
Dosage Compensation, Genetic , X Chromosome , Animals , Chromosomes, Fungal , DNA , Dinucleoside Phosphates/metabolism , Female , Gene Deletion , Gene Rearrangement , Genomic Library , Humans , Hybrid Cells , Male , Methylation , Mice , Restriction MappingABSTRACT
The effects of the dihydrofolate reductase inhibitors proguanil and chlorproguanil, their active metabolites cycloguanil and chlorcycloguanil, and pyrimethamine, against the hepatic stages of Plasmodium yoelii yoellii were investigated in cultured BALB/c mouse hepatocytes. Proguanil was inactive at concentrations of 10(-8) M, whereas the other compounds were fully active at this and lower concentrations. Chlorcycloguanil was the most active compound and almost completely inhibited schizont development in concentrations as low as 10(-12) M.