Physical mapping of the globin gene deletion in (δβ)° - thalassaemia

counts for all of the Ayproduction in heterozygotes, indicating that persistent production of y chains occurs cis to the 6j3-thalassemia gene. The molecular heterogeneity of these conditions is demonstrated by restriction enzyme mapping of DNA; Sicilian and Calabrian patients show a deletion starting from the 6-globin intron and extending several kilobases 3' to the f3-globin gene; in Spanish patients the deletion starts -2-3 kilobases 5' to the 6-globin gene and extends well beyond the ,8-globin gene. Comparison of these deletions with previously described ones in Negro and in a new Southern Italian case of hereditary persistence of fetal hemoglobin suggests that the deletion of a region centered at a cluster of repetitive sequences "3.5 kilobases 5' to the 6-globin gene may be critical for the persistent expression of high levels of y-globin in hereditary persistence of fetal hemoglobin compared to 6(3-thalassemia. The concept that the deletion or mutation of specific areas (rather than nonspecific changes brought about by large deletions in the globin cluster) is important in determining the persistent expression of y-globin genes is supported by the finding of a nondeletion type of 8(3-thalassemia in Sardinians.

supporting

confidence: 73%

Molecular comparison of delta beta-thalassemia and hereditary persistence of fetal hemoglobin DNAs: evidence of a regulatory area?

Ottolenghi¹,

Giglioni²,

Taramelli³

et al. 1982

“…In one form of 65(-thalassemia, the deletion has been mapped to extend from the middle of the B-globin gene to approximately 1.0 kb 3' to the f3-globin gene (33). Several restriction endonuclease sites that we have mapped match those found in the region 3' to the 5bf-thalassemia deletion.…”

Section: Resultsmentioning

confidence: 82%

Cloning and characterization of DNA sequences surrounding the human gamma-, delta-, and beta-globin genes.

Kaufman¹,

Kretschmer²,

Adams³

et al. 1980

The human -, 6-, and globin genes are located within a 30-kilobase (kb) region of DNA, of which only 20% represents the globin genes. We have attempted to define the nature of flanking and intergenic sequences by isolating recombinants containing the human e-, both y-, or the 3' end of the "globin gene from a bacteriophage library of cloned human DNA. Comparison of these recombinants and a recombinant containing the 6-and h-globin genes (HfG1) has provided the following results. The -lobin gene is located 14 kb 5' to the G7 gene. DNA sequence homology between the region containing the two G7 genes and the a an ene region is limited to only a few hundred nucleotides which include the globin coding sequences. Repetitive DNA sequences have been found in the region 3' to the globin gene. Sequences located adjacent to the -globin gene are repeated in the globin gene region. A repetitive DNA sequence more than 3.2 kb long is repeated frequently in the human genome but is not repeated in the globin gene region in the clones examined.Human hemoglobins are selectively produced in a characteristic and orderly fashion during different stages of development (1-4). During early embryogenesis, expression of the rand E genes leads to production of Hb Gower I (ref2) (5). As the primary site of erythropoiesis switches from the yolk sac to the fetal liver, production of A-and e-globins dramatically decreases.These are replaced by a-and -y-globin chain production (6). Hb Gower II (a2e2) is temporarily produced while fetal he-

“…In the human /3-globin locus, it has been argued, on the basis of the different extents of gene deletions in individual cases of f3-thalassemia and hereditary persistence of fetal hemoglobin, that the switch from the synthesis of fetal yto adult ,&globin chains requires DNA sequences between the two gene sets which would act in cis (46)(47)(48). That is, the developmental regulation of the locus requires the genes to be tandemly arranged, in the order of their temporal expresson; embryonic-*fetal-*adult /3-globin.…”

Section: Discussionmentioning

confidence: 99%

alpha-Fetoprotein and albumin genes are in tandem in the mouse genome.

Ingram¹,

Scott²,

Tilghman³

1981

116

The murine a-fetoprotein (AFP) and serum albumin genes most probably arose in evolution as the consequence ofa duplication ofa common ancestral gene. They have both been previously mapped to chromosome 5 in the mouse. We now have evidence that these genes are closely linked. By using a unique copy DNA probe derived from previously cloned AFP 5' flanking DNA, a recombinant DNA phage has been isolated, from a bacteriophage DNA library, that contains sequences flanking the 5' end of the AFP gene and the 3' end of the albumin gene. Restriction endonuclease mapping and DNA sequence determination of the recombinant phage and comparison to total genomic DNA confirmed that the genes are in tandem, 13.5 kilobase pairs apart, with the albumin gene to the 5' side of the AFP gene. Thus, they are transcribed from the same strand of DNA.a-Fetoprotein (AFP), which is synthesized by the embryonic liver and yolk sac, is the major serum protein of the developing mammalian fetus (1, 2). In rodents, its rate of synthesis by fetal liver begins to decline just prior to birth, at a time when the rate of synthesis of serum albumin, the major adult serum protein, is increasing (3,4). This reciprocal expression ofAFP and albumin, coupled to a number offunctional and structural properties which they share (5, 6), led to the proposal that they were the products of a pair of duplicated genes. Two strong lines of evidence support this hypothesis. First, the complete mouse AFP amino acid sequence, deduced from direct determination of the nucleotide sequences of AFP cDNA and AFP chimeric cDNA plasmids (7), shows an overall 32% conservation of primary sequence with several mammalian albumins. Similar results have been obtained from more limited sequence comparisons ofthe human (6) and rat (8,9) proteins. Second, structural analysis of the mouse AFP and albumin genes, by using cloned segments of genomic DNA, revealed that both genes were organized identically into 15 coding segments interrupted by 14 intervening sequences (10, 11). The corresponding coding segments in each gene were the same size, although no nucleotide cross-hybridization was detected between them.More recently we have found that the two genes are present on chromosome 5 in the mouse (12). By using a series of hamster-mouse somatic cell hybrids in which the mouse chromosomes had differentially segregated, the presence of murine albumin and AFP DNA sequences was detected by hybridization and correlated to the presence of mouse chromosome 5 in the cell lines. In the present report, the close linkage ofthe AFP and albumin genes is demonstrated by the isolation and characterization of a recombinant genomic DNA clone whose sequences span the distance between them. MATERIALS AND METHODSIdentification of Unique Copy DNA Flanking the AFP and Albumin Genes. DNA from AAFP14 (11) was cleaved with several restriction enzymes (New England BioLabs) in both single and double digestions. The fragments were electrophoresed through 1.5% agarose gels and transferred from the agarose gels...