Background: Neocentromeres are rare and considered chromosomal aberrations, because a non-centromeric region evolves in an active centromere by mutation. The literature reported several structural anomalies of X chromosome and they influence the female reproductive capacity or are associated to Turner syndrome in the presence of monosomy X cell line. Case presentation: We report a case of chromosome X complex rearrangement found in a prenatal diagnosis. The fetal karyotype showed a mosaicism with a 45,X cell line and a 46 chromosomes second line with a big marker, instead of a sex chromosome. The marker morphology and fluorescence in situ hybridization (FISH) characterization allowed us to identify a tricentric X chromosome constituted by two complete X chromosome fused at the p arms telomere and an active neocentromere in the middle, at the union of the two Xp arms, where usually are the telomeric regions. FISH also showed the presence of a paracentric inversion of both Xp arms. Furthermore, fragility figures were found in 56% of metaphases from peripheral blood lymphocytes culture at birth: a shorter marker chromosome and an apparently acentric fragment frequently lost. Conclusions: At our knowledge, this is the first isochromosome of an entire non-acrocentric chromosome. The neocentromere is constituted by canonical sequences but localized in an unusual position and the original centromeres are inactivated. We speculated that marker chromosome was the result of a double rearrangement: firstly, a paracentric inversion which involved the Xp arm, shifting a part of the centromere at the p end and subsequently a duplication of the entire X chromosome, which gave rise to an isochromosome. It is possible to suppose that the first event could be a result of a non-allelic homologous recombination mediated by inverted low-copy repeats. As expected, our case shows a Turner phenotype with mild facial features and no major skeletal deformity, normal psychomotor development and a spontaneous development of puberty and menarche, although with irregular menses since the last follow-up.
Villa, N., Conconi, D., Gambel Benussi, D., Tornese, G., Crosti, F., Sala, E., et al. (2017). A complete duplication of X chromosome resulting in a tricentric isochromosome originated by centromere repositioning. MOLECULAR CYTOGENETICS, 10(1) [10.1186/s13039-017-0323-7].
|Citazione:||Villa, N., Conconi, D., Gambel Benussi, D., Tornese, G., Crosti, F., Sala, E., et al. (2017). A complete duplication of X chromosome resulting in a tricentric isochromosome originated by centromere repositioning. MOLECULAR CYTOGENETICS, 10(1) [10.1186/s13039-017-0323-7].|
|Tipo:||Articolo in rivista - Articolo scientifico|
|Carattere della pubblicazione:||Scientifica|
|Presenza di un coautore afferente ad Istituzioni straniere:||No|
|Titolo:||A complete duplication of X chromosome resulting in a tricentric isochromosome originated by centromere repositioning|
|Autori:||Villa, N; Conconi, D; Gambel Benussi, D; Tornese, G; Crosti, F; Sala, E; Dalpra', L; Pecile, V|
VILLA, NICOLETTA (Primo)
CONCONI, DONATELLA (Secondo)
DALPRA', LEDA (Penultimo)
|Data di pubblicazione:||2017|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1186/s13039-017-0323-7|
|Appare nelle tipologie:||01 - Articolo su rivista|