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First report on B chromosome content in a reptilian species: the case of Anolis carolinensis


Supernumerary elements of the genome are often called B chromosomes. They usually consist of various autosomal sequences and, because of low selective pressure, are mostly pseudogenized and contain many repeats. There are numerous reports on B chromosomes in mammals, fish, invertebrates, plants, and fungi, but only a few of them have been studied using sequencing techniques. However, reptilian supernumerary chromosomes have been detected only cytogenetically and never sequenced or analyzed at the molecular level. One model squamate species with available genome sequence is Anolis carolinensis. The scope of the present article is to describe the genetic content of A. carolinensis supernumerary chromosomes. In this article, we confirm the presence of B chromosomes in this species by reverse painting and synaptonemal complex analysis. We applied low-pass high-throughput sequencing to analyze flow-sorted B chromosomes. Anole B chromosomes exhibit similar traits to other supernumerary chromosomes from different taxons: they contain two genes related to cell division control (INCENP and SPIRE2), are enriched in specific repeats, and show a high degree of pseudogenization. Therefore, the present study confirms that reptilian B chromosomes resemble supernumerary chromosomes of other taxons.

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The study was funded by the Russian Science Foundation (RSF, 16-14-10009) and by the Russian Foundation for Basic Research (RFBR, 16-04-00087).

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Correspondence to Ilya G. Kichigin.

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The authors declare they have no competing interests.

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This article does not contain any studies with human participants or animals performed by any of the authors.

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Communicated by S. Hohmann.

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Kichigin, I.G., Lisachov, A.P., Giovannotti, M. et al. First report on B chromosome content in a reptilian species: the case of Anolis carolinensis. Mol Genet Genomics 294, 13–21 (2019).

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  • Squamata
  • Supernumerary chromosomes
  • High-throughput sequencing
  • Carolina anole