pubmed.ncbi.nlm.nih.gov

Telomere variation in Xenopus laevis - PubMed

Telomere variation in Xenopus laevis

S Bassham et al. Mol Cell Biol. 1998 Jan.

Abstract

Eukaryotic telomeres are variable at several levels, from the length of the simple sequence telomeric repeat tract in different cell types to the presence or number of telomere-adjacent DNA sequence elements in different strains or individuals. We have investigated the sequence organization of Xenopus laevis telomeres by use of the vertebrate telomeric repeat (TTAGGG)n and blot hybridization analysis. The (TTAGGG)n-hybridizing fragments, which ranged from less than 10 to over 50 kb with frequently cutting enzymes, defined a pattern that was polymorphic between individuals. BAL 31 exonuclease treatment confirmed that these fragments were telomeric. The polymorphic fragments analyzed did not hybridize to 5S RNA sequences, which are telomeric according to in situ hybridization. When telomeric fragments from offspring (whole embryos) were compared to those from the spleens of the parents, the inheritance pattern of some bands was found to be unusual. Furthermore, in one cross, the telomeres of the embryo were shorter than the telomeres of the parents' spleen, and in another, the male's testis telomeres were shorter than those of the male's spleen. Our data are consistent with a model for chromosome behavior that involves a significant amount of DNA rearrangement at telomeres and suggest that length regulation of Xenopus telomeres is different from that observed for Mus spretus and human telomeres.

PubMed Disclaimer

Figures

FIG. 1
FIG. 1

(TTAGGG)n-hybridizing fragments in Xenopus are polymorphic. Spleen DNA samples from different individuals (indicated by roman numerals), suspended in agarose blocks, were digested with the indicated enzymes, separated in 0.4% agarose gels, blotted, and hybridized to a (TTAGGG)n probe. In the rightmost lanes, DNA from liver (L) and spleen (S) tissues of individual IV was digested with MseI-RsaI. The sizes of the marker fragments (lanes λ) are indicated on the left in kilobases.

FIG. 2
FIG. 2

Polymorphic fragments are BAL 31 sensitive. Agarose blocks of spleen DNA from individual VII were treated with Agarase, mixed with lambda DNA, and treated with BAL 31 for the indicated numbers of minutes. Samples were then digested with MseI, run on a 0.4% gel, blotted, and hybridized to a (TTAGGG)n probe. A portion of the BAL 31 reaction mixture was digested with HindIII and hybridized to a lambda probe (data not shown). The sizes of the marker fragments are indicated on the left in kilobases.

FIG. 3
FIG. 3

Hybridization of oocyte-type 5S sequences to Xenopus DNA digests. DNA samples from individual VII were digested with MseI or RsaI, run on a gel, and blotted; the filter was first hybridized to the oocyte 5S spacer probe and then stripped and hybridized to (TTAGGG)n (telo) under appropriate conditions for each. The sizes of the marker fragments are indicated on the left in kilobases.

FIG. 4
FIG. 4

Terminal-fragment variation in parents and offspring. Spleen DNA samples from the father (individual VIII) and the mother (individual IX) and whole-embryo DNA samples from eight offspring of the in vitro fertilization (F1) were all digested with MseI-RsaI and then processed for blot hybridization with a mix of telomere repeat probe and lambda probe, the latter to provide reliable size comparisons on the autoradiogram. The sizes of the marker fragments (lanes λ) are indicated on the left in kilobases. (The 27.5-kb fragment is provided by the 23.1- and 4.4-kb λ fragments that have annealed at the cos sites.)

FIG. 5
FIG. 5

Terminal-fragment variation in offspring and in testis DNA samples. In an experiment with different parents, DNA from samples of spleen (S) or testis (T; two different concentrations) from the father (individual XI) or the spleen (S) of the mother (individual XII) and of whole embryos (numbered 1 to 8) were digested with MseI-RsaI and hybridized to a mix of telomere repeat probe and lambda probe. Results of duplicate experiments with the parent DNA digests are shown; the mother’s DNA sample next to embryo 8 lane was only partially digested, as indicated by staining with ethidium bromide. The right panel shows HaeIII or RsaI digests of spleen and the more concentrated testis DNA sample from individual XI. The sizes of marker fragments (lanes λ) are indicated on the left in kilobases. Arrowheads indicate examples of the bands from the father’s spleen DNA that are clearly different in size from the testis sample DNA bands.

Similar articles

Cited by

References

    1. Ausubel F M, Brent R, Kingston R E, Moore D D, Seidman J G, Smith J A, Struhl K, editors. Current protocols in molecular biology. New York, N.Y: John Wiley and Sons, Inc.; 1994.
    1. Barlow D P. Preparation, restriction, and hybridization analysis of mammalian genomic DNA for pulsed field gel electrophoresis. Methods Mol Biol. 1992;12:107–128. - PubMed
    1. Blackburn E H. Telomeres: no end in sight. Cell. 1994;77:621–623. - PubMed
    1. Broccoli D, Young J W, de Lange T. Telomerase activity in normal and malignant hematopoietic cells. Proc Natl Acad Sci USA. 1995;92:9082–9086. - PMC - PubMed
    1. Broun P, Ganal M W, Tanksley S D. Telomeric arrays display high levels of heritable polymorphism among closely related plant varieties. Proc Natl Acad Sci USA. 1992;89:1354–1357. - PMC - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources