cytidylyl-3--5--guanosine and Agammaglobulinemia

X-linked agammaglobulinemia (XLA) is an immunodeficiency caused by mutations in the gene coding for Bruton's agammaglobulinemia tyrosine kinase (BTK). A database (BTKbase) of BTK mutations has been compiled and the recent update lists 368 entries from 318 unrelated families showing 228 unique molecular events. In addition to mutations the database lists also some polymorphisms and site-directed mutations. Each patient is given a unique patient identity number (PIN). Information is provided regarding the phenotype including symptoms. Mutations in all the five domains of BTK have been noticed to cause the disease, the most common event being missense mutations. The mutations appear almost uniformly throughout the molecule and frequently affect CpG sites forming arginine residues. These hot spots have generally pyrimidines 5'and purines 3'to the mutated cytosine. A decreased frequency of missense mutations was found in the TH, SH3 and the upper lobe of the kinase domain. The putative structural implications of all the missense mutations are given in the database showing 228 unique molecular events, including a novel missense mutation causing an R28C substitution as previously seen in the Xid mouse.

Topics: Agammaglobulinaemia Tyrosine Kinase; Agammaglobulinemia; Databases, Factual; Dinucleoside Phosphates; Exons; Genetic Linkage; Humans; Mutation; Protein Structure, Secondary; Protein-Tyrosine Kinases; X Chromosome

CpG dinucleotides are efficiently methylated in vertebrate genomes except in the CpG islands having a high C+G content. Methylated CpGs are the single most mutated dinucleotide. Sequences surrounding disease causing CpG mutation sites were analyzed from locus-specific mutation databases. Both tetra- and heptanucleotide analyses indicated clear overall sequence preference for having pyrimidines 5' and purines 3' to the mutated 5-methylcytosine. The most mutated tetranucleotides are TCGA and TCGG, the former being also a frequent restriction and modification site. The results will help in elucidating the still controversial mutation mechanism of CpG doublets.

Topics: Agammaglobulinaemia Tyrosine Kinase; Agammaglobulinemia; Base Sequence; Dinucleoside Phosphates; DNA Methylation; Factor VIII; Genes, p53; Genetic Linkage; Hemophilia A; Molecular Sequence Data; Mutation; Oligodeoxyribonucleotides; Phenylalanine Hydroxylase; Phenylketonurias; Point Mutation; Protein-Tyrosine Kinases; X Chromosome

We developed an X chromosome inactivation PCR assay, based on differential methylation of the 5' CpG island of the monoamine oxidase A gene (MAOA), close to a highly polymorphic region just downstream of the first exon. The assay provides a method to determine the carrier status of females from pedigrees with X-linked immunodeficiency diseases (XLID).

Topics: Agammaglobulinemia; Chromosome Mapping; Dinucleoside Phosphates; Dosage Compensation, Genetic; Exons; Female; Genetic Carrier Screening; Genetic Linkage; Humans; Immunologic Deficiency Syndromes; Male; Methylation; Monoamine Oxidase; Polymerase Chain Reaction; Severe Combined Immunodeficiency; Wiskott-Aldrich Syndrome; X Chromosome

The differential methylation of a CpG island 2.5 kb distant from a hypervariable region at the DXS255 locus provides the basis for a Southern blotting X chromosome inactivation analysis system. The technique enables carrier detection in about 90% of females at risk from pedigrees with Wiskott-Aldrich syndrome, X-linked severe combined immunodeficiency or X-linked agammaglobulinemia.

Topics: Agammaglobulinemia; Chromosome Mapping; Dinucleoside Phosphates; Dosage Compensation, Genetic; Female; Genetic Carrier Screening; Genetic Linkage; Humans; Immunologic Deficiency Syndromes; Male; Methylation; Repetitive Sequences, Nucleic Acid; Severe Combined Immunodeficiency; Wiskott-Aldrich Syndrome; X Chromosome

The X-linked agammaglobulinaemia (XLA) gene locus has previously been mapped to Xq22. Genetic linkage analysis has shown tight linkage between the disease and the DXS178 locus and that DXS3 and DXS94 are the closet proximal and distal flanking markers, respectively, separated by a genetic distance of 10-12 cM. We attempted to construct a physical map of Xq22 using pulsed field gel electrophoresis (PFGE) and rare-cutting restriction enzymes in order to obtain a finite physical value for the distance between DXS3 and DXS94. However, these attempts were hampered by the large number of rare-cutting restriction enzyme sites around the DXS178 locus, indicative of the presence of CpG rich regions of DNA. We were able to construct a physical map of the sites close to DXS178 that suggests the presence of at least three, and perhaps as many as five, CpG islands. These are arranged on either side of DXS178, extending over about 550kb of genomic DNA. Each of these regions must be considered as being associated with a potential "candidate" gene sequence for the XLA gene and we have initiated a chromosome walk from DXS178 to the nearest of these islands.

Topics: Agammaglobulinemia; Cells, Cultured; Chromosome Mapping; Chromosome Walking; Cosmids; Dinucleoside Phosphates; Electrophoresis, Gel, Pulsed-Field; Female; Genetic Linkage; Humans; Restriction Mapping; X Chromosome