Patterns of C-heterochromatin and telomeric DNA in two representative groups of small apes, the genera Hylobates and Symphalangus

Abstract

The course of chromosome evolution in small apes is still not clear, though painting analyses have opened the way for elucidating the puzzle. Even the C-banding pattern of the lar-group of gibbons (the genus Hylobates) is not clarified yet, although our previous studies suggested that lar-group gibbons have a unique C-banding pattern. We therefore made observations to establish C-banded karyotypes of the agile gibbons included in the lar-group. The data were compared with those of siamangs (the genus Symphalangus), which carry distinctive C-bands, to determine the chromosomal patterns in each group. C-banded chromosomes of agile gibbons showed several terminal, interstitial and paracentric bands, whose patterns are specific for each chromosome, whereas the C-bands of siamangs were located only at the terminal and centromeric regions in most chromosomes. Moreover, the C-bands of agile gibbons and siamangs were shown to be G+C-rich and A+T-rich DNA, respectively, by DAPI/C-band sequential staining. Additionally, PRINS labelling with a telomere primer revealed that agile gibbons have telomeric DNA only at chromosome ends where there is no C-band (non-telomeric heterochromatin), whereas the telomeric DNA of siamangs is located in the terminal C-banded regions (telomeric heterochromatin). Although the evolutionary mechanisms in small apes are still unknown, C-banding patterns and distribution of telomeric DNA sequences should provide valuable data to deduce the evolutionary pathways of small apes.

Gorilla genome structural variation reveals evolutionary parallelisms with chimpanzee

“…These duplications appear to have expanded in concert with the satellite sequence creating a higher-order tandem array structure of several hundred copies in each species. Since subterminal heterochromatic blocks have also been reported among the lesser apes (Wijayanto et al 2005), we tested pCht satellite probes on gibbon metaphase chromosomes and observed no hybridization signal above background (data not shown). Combined, these data strongly suggest that the heterochromatic caps have evolved independently in both chimpanzee and gorilla and possibly all ape species.…”

Hypervariability of Nucleolus Organizer Regions in Bengal Slow Lorises, <b><i>Nycticebus bengalensis</i></b> (Primates, Lorisidae)

“…For karyotyping of N. bengalensis , we used DAPI (4',6-diamidino-2-phenylindole, Sigma, St. Louis, Mo., USA) bands, which are very similar to G-bands (due to a common affinity for AT-rich DNA segments) [Sumner, 1990], and are formed through DNA denaturation treatment at pH 12.5 [Wijayanto et al, 2005]. To check the characteristics of the constitutive heterochromatin (Cbands) of the slow loris forms, a slightly modified version of Sumner's [1972] C-banding method was used.…”

Repetitive sequences originating from the centromere constitute large-scale heterochromatin in the telomere region in the siamang, a small ape

“…There is another example in the Hominoidea superfamily: we have previously found that chromosomes of the siamang (Symphalangus syndactylus (SSY)) carry large-scale constitutive heterochromatin at their ends (Wijayanto et al, 2005). This species is a small ape inhabiting the Malay peninsula and Sumatera island in South East Asia.…”