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by claude@2026-07, 2026-07-04
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This paper investigated how centromere sequence differences might drive the unusual segregation and programmed elimination of the germline-restricted chromosome (GRC) in songbirds, using cytogenetic and genomic approaches in two closely related species (common nightingale and thrush nightingale). The authors identified a 436-bp satellite repeat in the centromeric regions of all regular chromosomes, found it to be highly similar across the two species, and used meiotic spread hybridization to show the repeat appears missing on the GRC. The key finding is that a change in centromeric sequence is consistent with misattachment and lagging of the GRC during division, which could contribute to its elimination. The limitation is that the study does not determine the exact mechanism of GRC elimination beyond associating it with centromeric sequence loss. The paper does not explicitly discuss endometriosis or adenomyosis; it was included in the corpus via a keyword match in the upstream search index.
Abstract
Centromeres are an important part of chromosomes which direct chromosome segregation during cell division. Their modifications can therefore explain the unusual mitotic and meiotic behaviour of certain chromosomes, such as the germline-restricted chromosome (GRC) of songbirds. This chromosome is eliminated from somatic cells during early embryogenesis and later also from male germ cells during spermatogenesis. Although the mechanism of elimination is not yet known, it is possible that it involves a modification of the centromeric sequence on the GRC, resulting in problems with the attachment of this chromosome to the mitotic or meiotic spindle and its lagging during anaphase, which eventually leads to its elimination from the nucleus. However, the repetitive nature and rapid evolution of centromeres make their identification and comparative analysis across species and chromosomes challenging. Here, we used a combination of cytogenetic and genomic approaches to identify the centromeric sequence of two closely related songbird species, the common nightingale ( Luscinia megarhynchos ) and the thrush nightingale ( L. luscinia ). We found a 436-bp satellite repeat present in the centromeric regions of all regular chromosomes, making it a strong candidate for the centromeric repeat. This centromeric repeat was highly similar between the two nightingale species. Interestingly, hybridization of the probe to this satellite repeat on meiotic spreads suggested that this repeat is missing on the GRC. Our results indicate that the change of the centromeric sequence may underlie the unusual inheritance and programmed DNA elimination of the GRC in songbirds.
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Abstract
Centromeres are an important part of chromosomes which direct chromosome segregation during cell division. Their modifications can therefore explain the unusual mitotic and meiotic behaviour of certain chromosomes, such as the germline-restricted chromosome (GRC) of songbirds. This chromosome is eliminated from somatic cells during early embryogenesis and later also from male germ cells during spermatogenesis. Although the mechanism of elimination is not yet known, it is possible that it involves a modification of the centromeric sequence on the GRC, resulting in problems with the attachment of this chromosome to the mitotic or meiotic spindle and its lagging during anaphase, which eventually leads to its elimination from the nucleus. However, the repetitive nature and rapid evolution of centromeres make their identification and comparative analysis across species and chromosomes challenging. Here, we used a combination of cytogenetic and genomic approaches to identify the centromeric sequence of two closely related songbird species, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia). We found a 436-bp satellite repeat present in the centromeric regions of all regular chromosomes, making it a strong candidate for the centromeric repeat. This centromeric repeat was highly similar between the two nightingale species. Interestingly, hybridization of the probe to this satellite repeat on meiotic spreads suggested that this repeat is missing on the GRC. Our results indicate that the change of the centromeric sequence may underlie the unusual inheritance and programmed DNA elimination of the GRC in songbirds.
Competing Interest Statement
The authors have declared no competing interest.
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