Comprehensive cytogenetic analysis of the aardwolf ( Proteles cristatus ) and comparative chromosome painting with the domestic cat ( Felis catus )

Aardwolf (Proteles cristatus) is one of the four extant hyenas. Up to now, chromosome analysis of the aardwolf is limited to the knowledge that this insectivorous hyena shares the same 2n = 40 diploid chromosome number with the three bone-crushing hyena species. Here we present a detailed conventional banding and molecular cytogenetic characterization of the aardwolf karyotype. A chromosome-by-chromosome comparison with the spotted hyena (Crocuta crocuta) shows extensive conservation of chromosome size, morphology, and banding patters between the two hyenas. Karyotype conservation in hyenas is further supported by cat-aardwolf Zoo-FISH revealing almost identical patterns with previously available cat-spotted hyena Zoo-FISH, as well as extensive conserved synteny between cats and hyenas. Notably, hyena Chr12 and cat E1 share conserved synteny and carry the single nucleolus organizer region in both groups of species. Telomere-FISH in aardwolf and cat revealed only canonical telomeres and no interstitial sites, thus consistent with the overall karyotype conservation. However, there are also differences between aardwolf and spotted hyena Chr15, Chr16, and Chr19 due to heterochromatic additions in the aardwolf. Of these, the metacentric aardwolf Chr16 serves as a genomic feature that distinguishes this species from the spotted hyena in which the homeologous chromosome is acrocentric. In conclusion, improved cytogenetic and molecular characterization of the aardwolf karyotype expands the comparative knowledge about mammalian karyotypes and chromosome evolution, supports karyotypic conservation in feliform carnivores, and facilitates the construction of a high-quality chromosome-level annotated genome assemblies for the aardwolf and other hyenas.