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During meiotic prophase I, tightly regulated processes take place, from pairing and synapsis of homologous chromosomes to recombination, which are essential for the generation of genetically variable haploid gametes. These processes have canonical meiotic features conserved across different phylogenetic groups. However, the dynamics of meiotic prophase I in non-mammalian vertebrates are poorly known. Here, we compare four species from Sauropsida to understand the regulation of meiotic prophase I in reptiles: the Australian central bearded dragon ( Pogona vitticeps ), two geckos ( Paroedura picta and Coleonyx variegatus ) and the painted turtle ( Chrysemys picta ). We first performed a histological characterization of the spermatogenesis process in both the bearded dragon and the painted turtle. We then analyzed prophase I dynamics, including chromosome pairing, synapsis and the formation of double strand breaks (DSBs). We show that meiosis progression is highly conserved in reptiles with telomeres clustering forming the bouquet , which we propose promotes homologous pairing and synapsis, along with facilitating the early pairing of micro-chromosomes during prophase I (i.e., early zygotene). Moreover, we detected low levels of meiotic DSB formation in all taxa. Our results provide new insights into reptile meiosis.
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This content will become publicly available on August 1, 2026
Non-homologous sequence interactions during meiosis: meiotic challenges and evolutionary opportunities
A hallmark of meiosis is pairing of homologous chromosomes, an event that ensures proper segregation into the gametes. Homology pairing is crucial to the formation of normal gametes, the maintenance of genomic integrity, and avoidance of aneuploidy. However, chromosomes are not completely homologous. Here we discuss two notable exceptions to homology: the mammalian sex chromosomes and centromeres. In themselves, these exceptions illustrate meiotic adaptations that both ensure correct chromosome segregation and present evolutionary opportunities. More broadly, such examples of non-homology provide a window for viewing normal mechanisms of meiotic pairing and chromosome modifications. Current analyses of mammalian meiotic chromosome dynamics suggest that the basis for the initial recognition of homology early in meiosis may be based in epigenetic chromatin modifications. Chromatin units may both form pairing sites and provide the modifications that allow non-homologous sequences to be tolerated. Despite recent research progress, we have yet to understand why some non-homologies are tolerated, while others lead to aneuploidy. Understanding how genomes evolve strategies to subvert the usual rules of meiosis will benefit from studies focused on the identification and characterization of meiosis in species with recently acquired non-homology. Looking forward, we are now armed with technologies and tools suited to precisely measure the extent of nonhomology across mammalian chromosomes and to probe the molecular and biophysical steps required for the initiation of homologous chromosome recognition and pairing. These goals are important for elucidating an essential mechanism of meiosis and ultimately for advancing the clinical diagnosis of gametic and embryo aneuploidy.
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- Award ID(s):
- 1942620
- PAR ID:
- 10600858
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Current Opinion in Genetics & Development
- Volume:
- 93
- Issue:
- C
- ISSN:
- 0959-437X
- Page Range / eLocation ID:
- 102365
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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