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G Keyeux

Publications and source records attributed to G Keyeux.

11 recordsLinked to original sources
PubMed1990

Distal trisomy 14q. I. Clinical and cytogenetical studies.

Two cases of de novo duplication of the distal part of the long arm of chromosome 14 are reported. In one case, the partial trisomy of 14q is due to translocation of a segment (14q24 to 14qter) at the end of the satellite stalk of chromosome 14. The clinical picture is very severe. In the second case, a tandem duplication in 14 (q23----q32) is present with only minor malformations and mild mental retardation.

Chromosome Banding↗
PubMed1990

Distal trisomy 14q. II. Molecular study of the 14q32 locus in two cases of chromosome 14 rearrangements with partial duplication.

Two cases of chromosome 14 rearrangements with partial duplication which occurred de novo were analyzed by Southern blot analysis using IGH, D14S1 and PI probes. In the first case, with a 46,XX,14p+ karyotype, our study confirms that the additional material on chromosome 14p+ results from a duplication of the 14q region containing the IGH, D14S1 and PI loci. In the second case, our study reveals only one 14q32 locus per chromosome 14 indicating that the extra material does not contain the 14q32 region. Our results demonstrate that molecular probes of the 14q32 region are valuable tools for the characterisation of chromosome 14 abnormalities appearing de novo.

Blotting, Southern↗
PubMed1990

Molecular analysis of the IGHA and MHC class III region genes in one family with IgA and C4 deficiencies.

We report molecular studies in 2 IgA-deficient persons. One of them had an unusual association with an acute lymphoblastic leukaemia; his sister was also IgA deficient and shared an HLA haplotype and a complotype known to be associated to IgA deficiencies. The 2 IgA-deficient siblings also had low C4 serum levels due to C4A*Q0 allele. We showed that both defects were transmitted independently in the family. Molecular analysis revealed no major structural defects of the IGHA coding and switch regions, whereas a broad C4A-21-OHA deletion was responsible for the C4A*Q0 phenotype. These results confirm previous data showing that IgA deficiencies seem to be, in most cases, a regulatory defect rather than a structural defect of the coding IGHA region itself. These data were further supported by another molecular study in a patient with a recurrent Landry-Guillain-Barre syndrome who showed total absence of serum IgA and sIgA+B cells with no major structural defect of the IGHA region.

Adolescent↗
PubMed1990

Association between acute lymphoblastic leukemia and partial IgA deficiency in a young man--a family study.

We report on an unusual association between partial IgA deficiency and acute lymphoblastic leukemia in a young man. We also report results of the family study of immunoglobulin levels, sIgA B cells, in vitro IgA synthesis and molecular analysis of the structural C alpha genes. The IgA deficiency was present at diagnosis of leukemia prior to any therapy. The indirect arguments for a preexisting IgA deficiency are the absence of improvement of the IgA level during complete remission and especially the finding of a similar partial IgA deficiency in a sister who shared the same HLA haplotype, had a low percentage of sIgA B cells and decreased in vitro IgA production. The mother, who had a normal IgA serum level also had decreased in vitro IgA synthesis. No major structural C alpha gene defect was found. The relationship between acute lymphoblastic leukemia and IgA deficiency remains to be elucidated.

Adolescent↗
PubMed1989

Molecular characterization of a ring chromosome 14 showing that the PI locus is centromeric to the D14S1 and IGH loci.

Molecular characterization of a ring chromosome 14 was carried out in a patient with the 46,XX,r(14) karyotype. The breakpoints shown by chromosome banding were within bands p11 and q32. Using molecular probes for the immunoglobulin heavy chain (IGH), D14S1 and PI loci located at 14q32, we showed that the IGH and D14S1 loci, located at 14q32.3 and 14q32.2 respectively, were deleted on the ring chromosome 14, but that the PI locus was not. Therefore, the chromosomal break lies between PI and D14S1. These results show that the order of these chromosome 14 markers is cen-PI-D14S1-IGH, in keeping with multipoint linkage data. Further molecular characterization of ring 14 chromosomes should lead to a detailed understanding of the molecular events and clinical consequences of the gene deletion associated with such chromosomal aberrations.

Blotting, Southern↗
PubMed1989

A multigene deletion in the human IGH constant region locus involves highly homologous hot spots of recombination.

A simultaneous absence of the IgG1, IgG2, IgG4, and IgA1 immunoglobulins (Ig) was unambiguously demonstrated in six healthy individuals of two different families (family HASS and family TOU). These individuals were shown to be homozygous for a large deletion in the immunoglobulin heavy chain constant region locus. This deletion, which encompasses the G1-EP1-A1-GP-G2-G4 genes, allowed us to predict an order for the IgCH genes and to localize GP between A1 and G2. In this paper, we study the deletion-recombination point in the IGH locus of individual EZZ from the TOU family. We show that the distance between the G3 and the E genes on the EZZ recombinant chromosome is 24.7 kb and that the multigene deletion in the IgCH locus involves two highly homologous regions (hsg3 and hsg4) which are hot spots of recombination, outside of the switch sequences.

Base Sequence↗
PubMed1986

A gamma 3 hinge region probe: first specific human immunoglobulin subclass probe.

We report the first specific human immunoglobulin subclass probe which was obtained by subcloning the gamma 3 hinge region. This specific gamma 3 probe allowed us to identify with certainty the C gamma 3 gene on Southern genomic blots, to describe the first C gamma 3 restriction fragment length polymorphism (EZZ gamma 3 RF) and to show that an IgG3 selective deficiency, previously described serologically, was not due to a deletion of the C gamma 3 gene. Such a probe should be particularly useful for screening libraries from individuals with IgG3 immunodeficiencies or presenting unusual C gamma 3 genes and, consequently, for studying the C gamma gene evolution.

Amino Acid Sequence↗
PubMedDate not supplied

Complement polymorphism in Colombia.

The polymorphism of complement component C3, BF and C4 was studied in an urban population of Bogota, Colombia and for C3 and BF, genetic heterogeneity was further examined among the five villages of the Colombian Andes. For both C3 and BF systems there is considerable variation of allele frequencies among the five villages and overall there is significant heterogeneity among the six population groups studied.

Alleles↗