Genoveva Keyeux

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 γ3 probe allowed us to identify with certainty the Cγ3 gene on Southern genomic blots to describe the first Cγ3 restriction fragment length polymorphism (EZZ γ3 RF) and to show that an IgG3 selective deficiency previously described serologically was not due to a deletion of the C3 gene. Such a probe should be particularly useful for screening libraries from individuals with IgG3 immunodeficiencies or presenting unusual Cγ3 genes and consequently for studying the Cγ gene evolution. Immunoglobulin IgCH gene (Human) Gm allotype Restriction fragment length polymorphism Immunoglobulin G3 deficiency Hinge

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.

New RFLPs of the immunoglobulin switch alpha region in mesangial IgA glomerulonephritis

SummaryNew alleles of the human immunoglobulin switch alpha region are described in patients with mesangial IgA glomerulonephritis.

Distal trisomy 14q

SummaryTwo 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.

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

SummaryMolecular 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 14q32.2 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.