Chromosomal evolution and distribution of telomeric repeats in golden moles (Chrysochloridae, Mammalia)

Abstract

Golden moles (Chrysochloridae) are small, subterranean mammals endemic to sub-Saharan Africa that together with tenrecs constitute one of six orders in Afrotheria. Here we present a comprehensive karyotypic comparison among six species/subspecies of golden moles based on G-banding and chromosome painting. By expanding the species representation to include a further five species recently published in a companion paper, we were able to map the distribution of telomeric repeats in ten species/subspecies that are representative of six of the nine currently recognized genera. We conclude that: (i) the monophyly of Amblysomus is supported by the amplification of heterochromatin in several pericentric regions and one intrachromosomal rearrangement; (ii) A. hottentotus meesteri groups as sister to a clade that contains A. h. hottentotus, A. h. longiceps, A. h. pondoliae and A. robustus, an association that is underpinned by a shared intrachromosomal rearrangement and the detection of telomeric sequences in the centromeres of all chromosomes of the three A. hottentotus subspecies and A. robustus but, importantly, not in those of A. h. meesteri. These findings indicate an absence of gene flow suggesting that A. h. meesteri should be elevated to specific status. We hypothesize that the lack of gene flow may, in part, reflect hybrid dysgenesis resulting from abnormal meiotic segregation as a consequence of differences in the nature of the centromeric specific satellites; (iii) chromosomes 7 and 13 of Chrysochloris asiatica are fused in both Calcochloris obtusirostris and Eremitalpa granti, but that the position of the centromere in the fused chromosome differs in each species. This suggests that rather than being indicative of common ancestry, the fusion is more likely a convergent character which has arisen independently in each lineage. Furthermore our painting data show two centromeric shifts that are probably autapomorphic for C. obtusirostris. Finally, we conclude that (iv) golden moles are characterized by strong karyotypic conservatism but in marked contrast to the constrained rates of change exhibited by most species, A. robustus is unique in that three autapomorphic fissions define its evolutionary history, and hence the more extensive reshuffling of its genome.

Evolution of recombination in eutherian mammals: insights into mechanisms that affect recombination rates and crossover interference

“…The distribution of heterochromatic (hc) regions was consistent with previous cytogenetic studies [19], where chromosomes EED3, EED4, EED5 and EED7 comprised large interstitial hc blocks (see electronic supplementary material, figure S1). We did, however, detect small interstitial hc regions along the short and long arm of several chromosomes (EED1, EED2, EED4 and EED5) that had not previously been reported (see electronic supplementary material, figure S1).…”

“…Amblysomus julianae and A. hottentotus (Afrosoricida, Chrysochloridae) share identical karyotypes (2n ¼ 30 [19]) and these two species did not differ significantly in the mean number of COs per cell (25.9+4.1 for A. julianae and 24.5+4.1 for A. hottentotus). On the other hand, E. edwardii, a macroscelid representative with 2n ¼ 26 [19,20], and thus a lower diploid number than the Amblysomus species, had a higher overall mean number of COs (28.3+3.8). These ranged from 27.2+3.4 (in EED_D) to 30 Owing to the high mean MLH1 scores observed in the tiger (59.4+5.9, figure 1), we investigated whether a similar pattern was reflected by the proteins implicated in the formation and repair of DSBs in the early stages of prophase I. Meiotic recombination is initiated by DSBs generated by the protein Spo11 [24].…”

The Chromosomes of Afrotheria and Their Bearing on Mammalian Genome Evolution

“…All species had 2n = 30, except for Eremitalpa granti (2n = 26), Calcochloris obtusirostris (2n = 28), Amblysomus robustus (2n = 36) and A . septentrionalis (2n = 34) [Bronner, 1995;Gilbert et al, 2006Gilbert et al, , 2008.…”

“…Gilbert et al [2006Gilbert et al [ , 2008 used painting with Chrysochloris asiatica chromosome-specific probes in a comparative analysis of golden mole karyotypes, including 8 species from 7 genera. The results from these experiments were complemented by comparative GTG-banding and FISH with a telomere probe.…”

Karyotypic Evolution of <i>Hapalomys</i> Inferred from Chromosome Painting: A Detailed Characterization Contributing New Insights into the Ancestral Murinae Karyotype

“…Additionally, strongly fluorescent regions were detected in the centromeric regions of HDE 3,10,11,12,13,16,19,and 22. Since these sites do not correlate with breakpoints that were identified using rat chromosome paints (e.g., disruption of RNO 1, RNO 2, RNO 7, RNO 9, RNO 16, and the X-autosome translocation; see above), the signal most likely reflects sequence similarity with the pericentromeric heterochromatin [see also Metcalfe et al, 2004;Gilbert et al, 2008], an observation further substantiated by the detection of arrays of telomeric-like repeats in interstitial telomeric sequences regions [Faravelli et al, 2002;reviewed by Ruiz-Herrera et al, 2008]. Moreover, the strong fluorescent signals detected in H. delacouri track the greater quantity of C-positive material in HDE 3, 10, 11, 12, 13, 16, 19, and 22 [Badenhorst et al, 2009], and cross hybridization with the probe proba- bly reflects increased copy numbers of telomeric-like repeats in these C-positive regions.…”