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- Matsubara, K., et al.
(author)
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No Interstitial Telomeres on Autosomes but Remarkable Amplification of Telomeric Repeats on the W Sex Chromosome in the Sand Lizard (Lacerta agilis)
- 2015
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In: Journal of Heredity. - : Oxford University Press (OUP). - 0022-1503 .- 1465-7333. ; 106:6, s. 753-757
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Journal article (peer-reviewed)abstract
- Telomeres are repeat ( TTAGGG) (n) sequences that form terminal ends of chromosomes and have several functions, such as protecting the coding DNA from erosion at mitosis. Due to chromosomal rearrangements through evolutionary history ( e.g., inversions and fusions), telomeric sequences are also found between the centromere and the terminal ends ( i.e., at interstitial telomeric sites, ITSs). ITS telomere sequences have been implicated in heritable disease caused by genomic instability of ITS polymorphic variants, both with respect to copy number and sequence. In the sand lizard ( Lacerta agilis), we have shown that telomere length is predictive of lifetime fitness in females but not males. To assess whether this sex specific fitness effect could be traced to ITSs differences, we mapped ( TTAGGG) n sequences using fluorescence in situ hybridization in fibroblast cells cultured from 4 specimens of known sex. No ITSs could be found on autosomes in either sex. However, females have heterogametic sex chromosomes in sand lizards ( ZW, 2n = 38) and the female W chromosome showed degeneration and remarkable ( TTAGGG) n amplification, which was absent in the Z chromosomes. This work warrants further research on sex chromosome content, in particular of the degenerate W chromosome, and links to female fitness in sand lizards.
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| 2. |
- Srikulnath, K., et al.
(author)
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Identification of the linkage group of the Z sex chromosomes of the sand lizard (Lacerta agilis, Lacertidae) and elucidation of karyotype evolution in lacertid lizards
- 2014
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In: Chromosoma. - : Springer Science and Business Media LLC. - 0009-5915 .- 1432-0886. ; 123:6, s. 563-575
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Journal article (peer-reviewed)abstract
- The sand lizard (Lacerta agilis, Lacertidae) has a chromosome number of 2n = 38, with 17 pairs of acrocentric chromosomes, one pair of microchromosomes, a large acrocentric Z chromosome, and a micro-W chromosome. To investigate the process of karyotype evolution in L. agilis, we performed chromosome banding and fluorescent in situ hybridization for gene mapping and constructed a cytogenetic map with 86 functional genes. Chromosome banding revealed that the Z chromosome is the fifth largest chromosome. The cytogenetic map revealed homology of the L. agilis Z chromosome with chicken chromosomes 6 and 9. Comparison of the L. agilis cytogenetic map with those of four Toxicofera species with many microchromosomes (Elaphe quadrivirgata, Varanus salvator macromaculatus, Leiolepis reevesii rubritaeniata, and Anolis carolinensis) showed highly conserved linkage homology of L. agilis chromosomes (LAG) 1, 2, 3, 4, 5(Z), 7, 8, 9, and 10 with macrochromosomes and/or macrochromosome segments of the four Toxicofera species. Most of the genes located on the microchromosomes of Toxicofera were localized to LAG6, small acrocentric chromosomes (LAG11-18), and a microchromosome (LAG19) in L. agilis. These results suggest that the L. agilis karyotype resulted from frequent fusions of microchromosomes, which occurred in the ancestral karyotype of Toxicofera and led to the disappearance of microchromosomes and the appearance of many small macrochromosomes.
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