A notable feature of Ly-5, among immunogenetic systems that identify glycoproteins of the cell surface and define the surface phenotype of cells according to their lineage, is that the Ly-5 locus specifies a range of molecular isoforms that distinguish cells of different stages and branches of hematopoietic development. The composition of the Ly-5 locus is of much interest in regard to how these isoforms are constructed and differentially regulated according to cell lineage. We describe here a cDNA clone, pLy-5-68, that identifies Ly-5. The Ly-5 specificity of the pLy-5-68 clone was first indicated by a restriction fragment length polymorphism (RFLP), which in Southern blotting distinguishes genomic DNA of C57BL/6 (B6) mice (Ly-5a) from that of B6-Ly_5b congeneic mice whose genome is the same as B6 except for the segment of chromosome 1 that bears Ly_5b. For the following reasons it is unlikely that pLy-5-68 represents a gene linked to Ly-5 that was carried over with Ly_5b during serial backcrossing to make the B6&Ly_5b congeneic strain. In all mouse strains The Ly-S locus of the mouse (1, 2) specifies a set of different glycoprotein isoforms, each of which is expressed on the surface of cells of a particular lineage within the hematopoietic compartment of development (3). Of five NaDod-S04/PAGE bands derived from Ly-5 precipitated from cells of different hematopoietic lineages by Ly-5 antiserum or monoclonal antibody (3-5), two have been studied biochemically in some detail. These represent a 200-kDa isoform expressed by T cells and a 220-kDa isoform expressed by B cells. The size of the respective protein components of these two isoforms, which appear to be highly related to one another in two-dimensional peptide mapping, is 160 kDa and 190 kDa, and the Ly-5 locus, on chromosome 1 (unpublished data), is the site of the protein structural gene or genes for at least these two isoforms (6). The cDNA probe described here should help to elucidate the genetic basis of Ly-5 isoform diversity. MATERIALS AND METHODSPreparation of Sublibraries Based on cDNA Insert Size. A T-cell cDNA library, consisting of 3.8 x 105 independent transformants, was constructed by using the pcD vector of Okayama and Berg (7) and poly(A)+ mRNA of the Con-Astimulated (22 hr) inducer T-cell clone C1.Lyl-T1 (8). Plasmid DNA was prepared by the alkaline lysis procedure (9) followed by equilibrium sedimentation in CsCl. Twelve micrograms ofplasmid DNA was digested with 12 units of Sal I or Cla I endonuclease and electrophoresed in adjacent wells in a 1.3% agarose gel. DNA fragments whose sizes spanned the range 2-23 kilobases (kb) were electrophoresed in adjacent tracks. After staining with ethidium bromide, the gel was sliced into eight sections corresponding to cDNA insert sizes of 0-0.5, 0.5-1.2, 1.2-2, 2-3, 3-4, 4-5, 5-9, and 9-20 kb. DNA was extracted from each slice by the sodium iodide/glass powder method (10), recyclized with T4 DNA ligase, and used to transform Escherichia coli, strain MC1061. The individual transformed cultures...
Immunoglobulin variable (V) gene regions typify extensive multigenic families in terms of overall size, chromosomal arrangement and presence of large numbers of apparent pseudogenes. A unique mechanism of somatic reorganization involving recombination of VH, D and JH or VL and JL segments accompanies the differentiation of lymphoid cells and together with somatic mutation and other types of recombination accounts for V-region diversity. Although these processes have been well characterized in higher mammals, little is known concerning their origin and diversification during phylogenetic time. Previously, we described the blot-hybridization characteristics of murine VHIII probes with restriction enzyme-digested genomic DNA isolated from several phylogenetically critical species, including Caiman crocodylus, a modern representative of an ancient reptilian subclass. Here we have used a murine probe, S107V, to select homologous clones from a library of Caiman genomic DNA constructed in a lambda bacteriophage. The complete nucleotide sequence of a Caiman gene homologous to the murine VH gene and its adjacent 5' and 3' region is described. Comparison of the sequence with mammalian prototypes shows evidence of considerable organizational and structural homology extending outside the presumed VH-coding region and including elements believed to be involved in somatic recombination. Inferences about the evolution of this multigenic family can now be extended to the level of phylogenetic class.
Appropriately selected phylogenetic models are capable of providing insight into genetic mechanisms which may have become obscured during the passage of evolutionary time. In higher vertebrates a complex multigenic family encodes immunoglobulin-variable regions. The mechanisms involved in the expansion of the gene family and the stable maintenance of large numbers of individual genes presently are not understood. By defining the nature of antibody diversity in lower vertebrate species, it may be possible to approach such issues at a more fundamental level. Analyses of the immunoglobulins in Heterodontus francisci (horned shark), a representative phylogenetically primitive elasmobranch, indicate that this species may represent a useful developmental model.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.