Amphibian and Avian Karyotype Evolution: Insights from Lampbrush Chromosome Studies

Abstract

Amphibian and bird karyotypes typically have a complex organization, which makes them difficult for standard cytogenetic analysis. That is, amphibian chromosomes are generally large, enriched with repetitive elements, and characterized by the absence of informative banding patterns. The majority of avian karyotypes comprise a small number of relatively large macrochromosomes and numerous tiny morphologically undistinguishable microchromosomes. A good progress in investigation of amphibian and avian chromosome evolution became possible with the usage of giant lampbrush chromosomes typical for growing oocytes. Due to the giant size, peculiarities of organization and enrichment with cytological markers, lampbrush chromosomes can serve as an opportune model for comprehensive high-resolution cytogenetic and cytological investigations. Here, we review the main findings on chromosome evolution in amphibians and birds that were obtained using lampbrush chromosomes. In particular, we discuss the data on evolutionary chromosomal rearrangements, accumulation of polymorphisms, evolution of sex chromosomes as well as chromosomal changes during clonal reproduction of interspecies hybrids.

Comparative cytogenetics of the ground frogs Eupsophus emiliopugini Formas, 1989 and E. vertebralis Grandison, 1961 (Alsodidae) with comments on their inter- and intraspecific chromosome differentiation

“…C-banding has been largely used in amphibians to compare karyotypes and to distinguish species with the same diploid number (Bogart 1970, Cuevas and Formas 2003, Nogueira et al 2015, Sangpakdee et al 2017, Targueta et al 2018. Moreover, homogeneous C-banding patterns among related species has been associated with low genetic differentiation (Pellegrino et al 1997, Lourenço et al 1998, Bruschi et al 2012) and enrichment of repetitive elements, characteristic of amphibian chromosomes (Schmid et al 1978, Bruschi et al 2012, Zlotina et al 2017. Therefore, the absence of interspecific variations in heterochromatin banding reported in this study (Fig.…”

Comparative Distribution of Repetitive Sequences in the Karyotypes of Xenopus tropicalis and Xenopus laevis (Anura, Pipidae)

“…Chromosome morphology: Metacentric (M) (1 > q/p > 1.17); Submetacentric (S) (1.2 > q/p > 2.8); Acrocentric (A) (2.3 > q/p > 5.7); Telocentric (T). 1 Alternative possibilities for the positive signal identified by GISH with chromosomes and probe from X. laevis: the proposed signal in XLA3S could be in XLA4L instead. ; according to chromosome morphology could be on XLA4L instead).…”

“…Amphibian genomes show the greatest size variability among vertebrates, generally due to their high content of repetitive DNA and transposons [ 1 , 2 , 3 ], and due to polyploidization events [ 4 ]. The way in which changes in ploidy can affect repetitive DNA is of particular interest since polyploidization can trigger transposon activity and cause genome expansion and instability [ 5 ].…”

Assignment of the somatic A/B compartments to chromatin domains in giant transcriptionally active lampbrush chromosomes

“…Lampbrush chromosomes are a convenient object for chromatin mapping and have been studied in detail in a number of model organisms [40][41][42]. However, the correspondence between the chromomere-loop complexes of meiotic lampbrush chromosomes and chromatin compartment identity in the interphase nucleus has not been investigated.…”