Cytotypes of Kirk’s Dik-Dik (<i>Madoqua kirkii</i>,Bovidae) Show Multiple Tandem Fusions

Abstract

Madoqua kirkii, a miniature African antelope, is noted for extensive chromosomal variation that has been categorized in four distinct cytotypes (A–D). In this investigation, we analyzed the A cytotype (2n = 46, FN = 48) using a suite of molecular cytogenetic approaches that entailed (i) whole chromosome and subchromosomal painting by fluorescence in situ hybridization (FISH), (ii) the study of Madoqua centromeric-specific DNA derived from pooled DNA obtained from the centromeric regions of the acrocentric chromosomes, and (iii) DNA from the telomere:centromere junctions of tandemly fused chromosomes. DNA from these sources was used to probe for the persistence of interstitial satellite DNA and residual centromeric sequences in the tandem and centric fusion junctions by PCR and FISH. The analyses show centromeric sequences at two of the six tandem fusion junctions. These data, and those of hybrid specimens (A × B cytotypes) in conjunction with published information permitted an interpretation of the probable sequence of chromosomal rearrangements among the M. kirkii cytotypes. We discuss the findings in the context of chromosomal evolution in these antelopes, and the implications that these hold for ex-situ breeding programs of the species.

Comparative Molecular Cytogenetics in Cetartiodactyla

“…Bovidae ancestral karyotype was very similar to the present karyotype of the Bovinae subfamily with Bovinae chromosomes 9 and 14, as well as an X chromosome of Bovinae type [Iannuzzi et al, 2009]. Chromosomal evolution in Bovidae is largely attributable to Robertsonian fusions, although the increasing number of cytogenetic reports reveal that tandem fusions also impact karyotype shaping in this family [Rubes et al, 2008;Ropiquet et al, 2010;Cernohorska et al, 2011] by reducing the ancestral diploid number (2n = 60) in derived karyotypes. Recorded chromosome numbers vary from 2n = 30 in gazelles to 2n = 60 in a range of species within the tribes Aepycerotini, Hippotragini, Oreotragini, Cephalophini and Bovini.…”

Integrative lineage delimitation in rodents of the Ctenomys Corrientes group

“…Tandem fusions are known to have powerful negative heterotic effects (King 1995). In mammals, hetero zygotes' sterility for tandem fusions was found in controlled breeding experiments in rodents of the genera Otomys Couvier, 1824 (Pillay and Willan Meester 1992, Pillay et al 1995, Taylor 2000 and Taterillus Thomas, 1910(Dobigny et al 2005 as well as in the antelope Madoqua kirkii Günther, 1880 (Ryder et al 1989, Cernohorska et al 2011). Since they are heterotically deleterious, once occurred, tandem fusions have an all or nothing fate: they reach homozygosis and promote instantaneous reproductive isolation from the non-rearranged stock, or they are lost (Dobigny et al 2005).…”

Molecular Insights into X;BTA5 Chromosome Rearrangements in the Tribe Antilopini (Bovidae)

“…A previous report by D 'Aiuto et al [1997] described the distribution of sat I and sat II organized in 2 separate domains in the centromeric region in sheep (Ovis aries). More recently, Cernohorska et al [2011] revealed 2 different hybridization patterns with centromeric clones in Kirk's dik-dik ( Madoqua kirkii, Neotragini). Two satellite DNA families organized in 2 separate domains located in centromeric regions are well-known in the mouse genome as well [Kipling et al, 1991].…”

“…Copyright © 2012 S. Karger AG, Basel One of the most controversial mammalian taxa from a classification point of view is that of the family Bovidae being subdivided into 2 distinct clades -Bovinae (Bovini, Boselaphini and Tragelaphini) and Antilopinae (Aepycerotini, Alcelaphini, Antilopini, Caprini, Cephalophini, Hippotragini, Neotragini, Oreotragini and Reduncini). The most recent classification recognizes 9 genera within Antilopini: Ammodorcas, Antidorcas, Antilope, Eudorcas, Gazella, Litocranius, Nanger, Procapra and Saiga [Robinson and Ropiquet, 2011].Chromosomal evolution in Bovidae is largely attributable to Robertsonian fusions, although the increasing number of cytogenetic reports reveals that tandem fusions also impact karyotype shaping in this family [Rubes et al, 2008;Ropiquet et al, 2010;Cernohorska et al, 2011] by reducing the ancestral diploid number (2n = 60) in derived karyotypes. Many Robertsonian chromosomal fusions are homoplasic, or are often lineage-specific (autapomorphic), and thus phylogenetically uninformative [Robinson and…”