cytidylyl-3--5--guanosine and Severe-Combined-Immunodeficiency

We report three novel adenosine deaminase (ADA) mutations with interesting implications. A Somali child with severe combined immunodeficiency disease (SCID) had reduced ADA mRNA in T cells and was homozygous for the nonsense mutation Q3X. Unexpectedly, her healthy father was a compound ADA heterozygote whose second allele carried a 'partial' mutation, R142Q, due to a G-->A transition of a CpG dinucleotide. A C-->T transition of the same CpG produced a nonsense mutation, R142X, in two homozygous Canadian Mennonite infants with SCID. The severe and healthy phenotypes associated with R142X and R142Q, the high frequency of 'partial' ADA mutations arising from CpGs in healthy individuals of African descent and the presence of CAA (glutamine) at codon 142 in murine ADA, suggest selection for replacement of this CpG hotspot by CpA during ADA evolution. R142X, located within a purine-rich segment at nt 62/116 of exon 5, caused skipping of the exon, possibly by disrupting a splicing enhancer. Absence of exon 5 in T cell ADA mRNA and low ADA activity in T cells and erythrocytes obtained at age 18-22 months from one of the Mennonite children, indicate limited expression of a normal ADA cDNA from retrovirally transduced CD34+ umbilical cord leukocytes infused shortly after birth in an attempt at stem cell gene therapy.

Topics: Adenosine Deaminase; Base Sequence; Biological Evolution; Canada; Child, Preschool; Dinucleoside Phosphates; DNA, Complementary; Enhancer Elements, Genetic; Female; Humans; Infant; Male; Molecular Sequence Data; Mutation; Pedigree; Phenotype; RNA Splicing; Severe Combined Immunodeficiency

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

We evaluated the use of methylation analysis at the DXS255 locus as a method for carrier detection in X-linked severe combined immunodeficiency (XSCID). We also investigated the variations of X inactivation patterns in several haematopoietic cell lineages of XSCID carriers, both within and between XSCID pedigrees.

Topics: B-Lymphocytes; Dinucleoside Phosphates; Dosage Compensation, Genetic; Female; Genetic Carrier Screening; Genetic Linkage; Granulocytes; Hematopoietic System; Humans; Male; Methylation; Severe Combined Immunodeficiency; T-Lymphocytes; X Chromosome