Mendoza, M. N.Schalnus, S. A.Thomson, B.Bellone, R. R.Juras, R.Raudsepp, T.2021-07-192021-07-192020-11-05Mendoza M, N, Schalnus S, A, Thomson B, Bellone R, R, Juras R, Raudsepp T. Novel Complex Unbalanced Dicentric X-Autosome Rearrangement in a Thoroughbred Mare with a Mild Effect on the Phenotype. Cytogenet Genome Res 2020;160:597-609. doi: 10.1159/000511236https://hdl.handle.net/20.500.12955/1410Complex structural X chromosome abnormalities are rare in humans and animals, and not recurrent. Yet, each case provides a fascinating opportunity to evaluate X chromosome content and functional status in relation to the effect on the phenotype. Here, we report the first equine case of a complex unbalanced X-autosome rearrangement in a healthy but short in stature Thoroughbred mare. Studies of about 200 cells by chromosome banding and FISH revealed an abnormal 2n=63,X,der(X;16) karyotype with a large dicentric derivative chromosome (der). The der was comprised of normal Xp material, a palindromic duplication of Xq12q21, and a translocation of chromosome 16 to the inverted Xq12q21 segment by the centromere, whereas the distal Xq22q29 was deleted from the der. Microsatellite genotyping determined a paternal origin of the der. While there was no option to experimentally investigate the status of X chromosome inactivation (XCI), the observed mild phenotype of this case suggested the following scenario to retain an almost normal genetic balance: active normal X, inactivated X-portion of the der, but without XCI spreading into the translocated chromosome 16. Cases like this present unique resources to acquire information about species-specific features of X regulation and the role of X-linked genes in development, health, and disease.Abstract. Introduction. Material and Methods. Results. Discussion. Conclusions and Future Approaches. References.application/pdfenginfo:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by-nc-nd/4.0/Complex rearrangementDicentricHorseUnbalancedX-autosome translocationinfo:eu-repo/semantics/articlehttps://purl.org/pe-repo/ocde/ford#4.04.02Cytogenet and Genome Researchhttps://doi.org/10.1159/000511236