Intron-dependent evolution of chicken glyceraldehyde phosphate dehydrogenase gene

The function of introns in the evolution of genes can be explained in at least two ways: either introns appeared late in evolution and therefore could not have participated in the construction of primordial genes, or RNA splicing and introns existed in the earliest organisms but were lost during the evolution of the modern prokaryotes. The latter alternative allows the possibility of intron participation in the formation of primordial genes before the divergence of modern prokaryotes and eukaryotes. Blake suggested that evidence for intron-facilitated evolution of a gene might be found by comparing the borders of functional protein domains with the placement of introns. We therefore examined glyceraldehyde phosphate dehydrogenase (GAPDH), a glycolytic enzyme, because it is the first protein for which the following data are available: X-ray crystallographic studies demonstrating structurally independent protein 'domains' which were highly conserved during the divergence of prokaryotes and eukaryotes; and a study of genomic organization which mapped introns in the gene. Sequencing of the chicken GAPDH gene revealed 11 introns. We report here that sites of three of the introns (IV, VI and XI) correspond closely with the borders of the NAD-binding, catalytic and helical tail domains of the enzyme, supporting the hypothesis that introns did have a role in the evolution of primitive genes. In addition, other biochemical and structural data were used to construct a model of the intron-mediated assembly of the GAPDH gene that explains the existence of 10 introns.     

Uniparental paternal disomy in a genetic cancer-predisposing syndrome.

The 11p15.5 region of human chromosome 11 seems to contain a locus or loci involved in congenital overgrowth anomalies as well as in the genesis of many tumours associated with the Beckwith-Wiedemann syndrome (BWS). Given the unusual differential parental allele involvement in the different aetiological forms of BWS and the loss of maternal alleles in associated tumours, we have now used 11p15.5 markers to determine the parental origin of chromosome 11 in eight sporadic cases of BWS. Probands in three informative families had uniparental paternal disomy for region 11p15.5. Further, an overall greatly increased frequency of homozygosity for several 11p15.5 markers in 21 sporadic BWS patients suggests that isodisomy probably accounts for an even higher proportion of BWS sporadic cases. This demonstrates that uniparental paternal disomy can be associated with a genetic cancer-predisposing syndrome.     

Immunofluorescent antibody studies of a murine leukemia virus: Comparison of human,bovine and murine systems

Zusammenfassung Antikörper bei genesenden Mäusen nach Infektion mit Leukämie-Viren (S-63) erzeugt, zeigen eine Kreuzreaktion mit den Leukämie-Antigenen aus Rinder- und Menschenserum und Gewebe. Diese Befunde sprechen dafür, dass die Viren-Antigene in den drei Systemen sehr ähnlich sind.

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Aided by grants from the John A. Hartford Foundation Inc. and U.S.P.H. Grant No. CA-03321. Scholar, leukemia Society, Iuc.     

Mouse hemoglobin: Chain composition multiple electrophoretic bands

Résumé L'hémoglobine des souris de type DBA/1J apparaît à l'électrophorèse sous forme de 4 bandes. En les séparant par l'électrophorèse en gel d'urée-amidon, on ne trouve qu'une seule ligne de globine et deux lignes de globine. Les taches se montrant à l'électrophorèse après traitement au bromide cyanogène sur les chaînes peptides suggèrent plusieurs différences entre les 2 séquences d'acides aminés.

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This work was supported in part by National Institutes of Health Grants No. 5TI-HE 5255 and No. 5 RO1 HEO 4706.     

T-cell specificity for H-2 and Ir gene phenotype correlates with the phenotype of thymic antigen-presenting cells

Experiments with chimaeric animals have demonstrated that the H-2 restriction specificity and immune response (Ir) gene phenotype of the T cell is acquired during development in the thymus. The mechanism by which this process occurs is unclear. One level of obligate expression of H-2 and Ir gene products is on the surface of antigen-presenting cells (APCs) which come from bone marrow precursors. We have now examined the turnover of APCs in the thymuses of F1 leads to parent (P) radiation-induced bone marrow chimaeras and found that APCs of donor phenotype appear at about 2 months after reconstitution. If the peripheral T-cell population is depleted after this time, new T cells emerging from the parental thymus (containing F1 APCs) behaving like F1 T cells, suggesting that cells from the bone marrow can influence thymic-directed T-cell differentiation. The thymic APC is an attractive condidate to play such a part in the development of the T-cell repertoire.     

In vitro adherence of sheep red cells to macrophages of normal rats

Résumé Les macrophages péritonéaux de certains rats normaux provoquent in vitro l'adhérence des hématies de mouton, proprieté qui dépend de l'élevage et non de la race ou de l'âge. Un anticorps cytophile (absent chez les rats à macrophages inactifs pour ces hématies) est seulement présent dans les liquides de lavage péritonéaux, tandis que dans les sérums les anticorps (agglutinines complètes ou incomplètes, hémolysines, anticorps cytophiles) sont absents.