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Chromosome Research

, Volume 21, Issue 8, pp 805–819 | Cite as

Karyotype evolution in monitor lizards: cross-species chromosome mapping of cDNA reveals highly conserved synteny and gene order in the Toxicofera clade

  • Kornsorn Srikulnath
  • Yoshinobu Uno
  • Chizuko Nishida
  • Yoichi Matsuda
Article

Abstract

The water monitor lizard (Varanus salvator macromaculatus (VSA), Platynota) has a chromosome number of 2n = 40: its karyotype consists of 16 macrochromosomes and 24 microchromosomes. To delineate the process of karyotype evolution in V. salvator macromaculatus, we constructed a cytogenetic map with 86 functional genes and compared it with those of the butterfly lizard (Leiolepis reevesii rubritaeniata (LRE); 2n = 36) and Japanese four-striped rat snake (Elaphe quadrivirgata (EQU); 2n = 36), members of the Toxicofera clade. The syntenies and gene orders of macrochromosomes were highly conserved between these species except for several chromosomal rearrangements: eight pairs of VSA macrochromosomes and/or chromosome arms exhibited homology with six pairs of LRE macrochromosomes and eight pairs of EQU macrochromosomes. Furthermore, the genes mapped to microchromosomes of three species were all located on chicken microchromosomes or chromosome 4p. No reciprocal translocations were found in the species, and their karyotypic differences were caused by: low frequencies of interchromosomal rearrangements, such as tandem fusions, or centric fissions/fusions between macrochromosomes and between macro- and microchromosomes; and intrachromosomal rearrangements, such as paracentric inversions or centromere repositioning. The chromosomal rearrangements that occurred in macrochromosomes of the Varanus lineage were also identified through comparative cytogenetic mapping of V. salvator macromaculatus and V. exanthematicus. Morphologic differences in chromosomes 6–8 between the two species could have resulted from pericentric inversion or centromere repositioning.

Keywords

Monitor lizard Toxicofera Squamata Synteny and gene order Karyotype evolution Cytogenetic map 

Abbreviations

BLAST

Basic Local Alignment Search Tool

cDNA

Complementary DNA

EQU

Elaphe quadrivirgata

FISH

Fluorescence in situ hybridization

GGA

Gallus gallus

LRE

Leiolepis reevesii rubritaeniata

MYA

Million years ago

rRNA

Ribosomal RNA

VSA

Varanus salvator macromaculatus

Notes

Acknowledgments

This work was financially supported by Grants-in-Aid for Scientific Research on Innovative Areas (no. 23113004) and Scientific Research (B) (no. 22370081) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

Supplementary material

10577_2013_9398_MOESM1_ESM.xls (20 kb)
Supplementary Table 1 Species and their accession numbers of the mitochondrial ND2 gene fragments used for molecular identification of V. exanthematicus(XLS 20 kb)
10577_2013_9398_MOESM2_ESM.xls (40 kb)
Supplementary Table 2 The cDNA fragments of L. reevesii rubritaeniata (LRE), G. hokouensis (GHO), L. agilis (LAG), and E. quadrivirgata (EQU) homologues of chicken genes, and nucleotide sequence identities between chicken and these squamate reptile cDNA fragments(XLS 39.5 kb)

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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.Laboratory of Animal Genetics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural SciencesNagoya UniversityNagoyaJapan
  2. 2.Laboratory of Animal Cytogenetics and Comparative Genomics, Department of Genetics, Faculty of ScienceKasetsart UniversityBangkokThailand
  3. 3.Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University (CASTNAR, NRU-KU, Thailand)Kasetsart UniversityBangkokThailand
  4. 4.Department of Natural History Sciences, Faculty of ScienceHokkaido UniversitySapporoJapan

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