Direct evidence for chromosomal inversion during T-cell receptor β-gene rearrangements

127

The genes coding for apolipoproteins (apo) AI, CIII, and AIV, designated APOA1, APOC3, and APOA4, respectively, are closely linked and tandemly organized in the long arm of the human chromosome 11. A DNA rearrangement involving the genes encoding apoAI and apoCIHl in certain patients with premature atherosclerosis has been associated with deficiency of both apoAI and apoCIll in the plasma of these patients. Structural characterization of the genes for apoAI and apoCIII in one of these patients indicates that this rearrangement consists of a DNA inversion containing portions of the 3' ends of the apoAI and apoCHIl genes, including the DNA region between these genes. The breakpoints of this DNA inversion are located within the fourth exon of the apoAI gene and the first intron of the apoCIHi gene. Thus, this DNA inversion results in reciprocal fusion of the apoAI and apoCIll gene transcriptional units. Expression of these gene fusions in cultured mammalian cells results in stable mRNA transcripts with sequences representing fusions of the apoAI and apoCIl mRNAs. These results indicate that absence of transcripts with correct apoAl and apoCIll mRNA sequences causes apoAI and apoCIII deficiency in the plasma of these patients and suggest that these apolipoproteins are involved in cholesterol homeostasis and protection against premature atherosclerosis. (4,5). A less prominent protein constituent of HDL is apolipoprotein CIII (apoCIII), which is actively exchanged between HDL and triglyceride-rich lipoprotein particles and appears to inhibit both the hydrolysis of these particles by the enzyme lipoprotein lipase and the apolipoprotein E (apoE)-mediated uptake of remnants of these particles by the liver (3).The genes coding for apoAl, apoCIII, and another apolipoprotein, apolipoprotein AIV (apoAIV), are closely linked and tandemly organized in the long arm of human chromosome 11 (6) and are designated APOAI, APOC3, and APOA4, respectively. It has been shown recently that the organization of these genes in the rat is remarkably similar to that in humans, and it was proposed that these genes are similarly organized in the genomes of all mammals (7).Previous studies indicated that an inherited DNA rearrangement involving the genes for apoAl and apoCIII but not the gene for apoAIV in certain patients with premature atherosclerosis is associated with deficiency of apoAI, apo-CIII, and HDL in the plasma of these patients (8-10). This report shows that the DNA rearrangement in the genome of one of these patients is due to inversion of a 6.0-kilobase (kb) DNA segment containing portions of the 3' sequences in the genes for apoAI and apoCIII including the DNA region between these genes. Because of the close physical linkage and convergent transcription of these genes in the normal human genome (6), this DNA inversion results in reciprocal fusion of portions of 5' apoAI with 3' apoCIII and 5' apoCIII with 3' apoAl gene transcriptional units. Expression of these gene fusions in cultured mammalian cells results in mRNAs ...

Section: Discussionmentioning

confidence: 99%

DNA inversion within the apolipoproteins AI/CIII/AIV-encoding gene cluster of certain patients with premature atherosclerosis.

Karathanasis

Ferris

Haddad

1987

127

“…As is the case in immunoglobulin heavy-chain variable (VH) genes (8), the genomic organization of the V13 genes may influence the order of V1, gene rearrangement and the acquisition of the TCR p-chain gene repertoire during development. With the exception of V1,14, which is located 3' to, and has an inverted transcriptional orientation relative to, the DP, JP, and constant region (C,3) genes (9), the genomic organization of the 20V1, genes so far identified is largely unknown. The majority of the V13 genes are presumed to lie 5' of, and to have the same transcriptional orientation relative to, the DP, Jo, and C,3 genes.…”

mentioning

confidence: 99%

Tandem linkage and unusual RNA splicing of the T-cell receptor beta-chain variable-region genes.

Chou

Anderson

Louie

et al. 1987

The variable-region (V) genes of the murine MATERIALS AND METHODS Construction and Screening of Genomic and cDNA Libraries. Construction and screening of C57BL/6 and SJL genomic libraries and of a C57BL/6 spleen cDNA library were performed as described (13). The nucleotide sequence of relevant portions of cloned DNA was determined by either the method of Maxam and Gilbert (14) or the chain-termination method of Sanger et al. (15).Hybridization of Genomic DNA Fragments. High molecular weight DNA from C57BL/6 liver and from a cytotoxic T cell clone F3 was digested to completion with EcoRI orPvu II and fractionated in a 0.8% agarose gel. After electrophoresis, the gel was dried, and the DNA inside the gel was denatured and hybridized to radioactive DNA probes by the method of Purrello and Balazs (16). were labeled with [a-32P]

“…fhe RFLP pattern characteristic of the prototypic normal (i.e., undeleted) /-chain haplotype is carried by all the other mouse strains analyzed so far, including those reported in the present investigation. Comparison of allelic V,314 and V1,16 genes from the normal and TCR /-deleted haplotypes (16,32,33), or of V 12 genes from the normal and TCR /3NZW haplotype (7O, 34), reveals distinct but very limited allelic polymorphism among these V.3 genes.…”

mentioning

confidence: 99%

T-cell receptor alpha-chain variable-region haplotypes of normal and autoimmune laboratory mouse strains.

Singer

McEvilly

Balderas

et al. 1988

We used Southern blotting and mRNA analysis to characterize allelic polymorphisms among genes of the T-cell antigen receptor (TCR) a-chain variable-region (V.) locus in a large panel of normal and autoimmune-susceptible or autoimmune-contributing strains of laboratory mice. Four major V. haplotypes were defied on the basis of multiple restriction fragment length polymorphisms for each of nine V.subfamily probes used. Southern blotting also revealed haplotype-specific loss of bands within some Va subfamilles, consistent with the deletion of particular V. genes The antigen-specific receptor on the majority of mature helper and cytotoxic T cells is a disulfide-linked heterodimer composed of polymorphic a and f3 chains that, like immunoglobulins, are encoded by variable (V), diversity (D; p chains only), joining (J), and constant (C) region gene segments (1). As with immunoglobulin genes, T-cell antigen receptor (TCR) a-and p8-chain genes develop a highly diverse, germ-line-encoded repertoire by means of somatic recombination of their polymorphic V-J or V-J-J elements (2-5).. In the mouse, the p-chain locus consists of an estimated 25-30 V genes, arranged in a minimum of 17 one-to three-member subfamilies (6, 7), and two C-region genes, each with a single upstream D element and six J elements (8-11). The murine a-chain locus consists of perhaps 100 V genes, arranged in an estimated 15-20 subfamilies of 1-10 homologous members each (12), and a single C-region gene with more than 50 upstream J elements (13,14). Both Va and V13 gene sequences show a high degree of diversity, displaying 40-70%o nucleotide sequence homology among members of different Va or V1 gene subfamilies (6,7,12,15).In addition to germ-line, junctional, and combinatorial mechanisms for the generation of diversity, allelic polymorphism plays a potentially important role in defining the overall TCR repertoire available to the mouse species.Although such polymorphism appears to be limited among Vat genes (16), information obtained so far for the Va locus suggests a considerable degree of polymorphism, including restriction fragment length polymorphisms (RFLPs) at the Va subfamily level (12) as well as numerous nucleotide substitutions characterizing allelic VY genes (17). Such germ-lineencoded differences in the TCR repertoire may play a role in tolerance, in immune responsiveness, and in genetically determined susceptibility to various types of spontaneous and induced autoimmune diseases (18)(19)(20)(21)(22)(23). We have therefore undertaken a more complete characterization of murine TCR Va (and V,3) haplotypes and the strains carrying them, with particular regard to strains that serve as murine models of systemic and organ-specific autoimmunity.MATERIALS AND METHODS Genomnic Blot Analysis. Genomic DNA was digested to completion with the desired restriction endonuclease, separated in 0.8% agarose gels, and blotted onto nitrocellulose filters according to standard protocols (24). V133, V13S, and V1'J6 probes were obtained from I). Pardoll ...