Comparative analysis of estrogen receptor gene polymorphisms in apes

Polymorphic microsatellite repeats in the promoter region of estrogen receptor alpha gene (ESR alpha and the intron 6 region of estrogen receptor beta gene (ESR beta) have been reported in human populations. To examine the evolutional state of both repeats, we surveyed the corresponding regions in DNA sequences from the following great apes and gibbons: 56 chimpanzees, 3 bonobos, 16 gorillas, 20 orangutans and 60 gibbons (four species: 17 of Hylobates agilis, 11 of H. lar, 15 of H. muelleri, and 17 of H. syndactylus). In the corresponding region of the TA repeat of human ESRa, chimpanzees and bonobos had two motifs in the repeat tract, (TA)(7-9) and (CA)(4-6). Gorillas had the (TA)(9-10) repeat tracts and orangutans had monomorphic (TA)(7) repeats. Although all great apes maintained the TA expansion, all gibbon sequences contained (TA)(2), implying that the CA dinucleotide expansion arose in the ancestor of chimpanzees and bonobos. The nucleotide sequences of ESR beta showed a very complex repeat pattern in apes. The human sequences had a non-variable preceding sequence at (CA),, (GA)(2)(TA)(8)(CA)(4)(TA). In apes that region included {(TA)(n)(CA)(n)}(n). Gibbon sequences included (TATG)(n) and (TATC)(n) and no regular construction was observed. A deletion event in the reverse primer site seems to have occurred in the orangutan lineage. In addition, a great diversity of allele length was detected in each gibbon species.