Five Novel Locations of Neocentromeres in Human: 18q22.1, Xq27.1 27.2, Acro p13, Acro p12, and Heterochromatin of Unknown Origin

Since the first report in 1993, an ectopic centromere, i.e. neocentromere formation, has been reported in more than 100 small supernumerary marker chromosomes (sSMC), in 7 instances of centromere repositioning, and in about a dozen cases with more complex chromosomal rearrangements. Here we report 2 new cases with centromere repositioning and 3 neocentric sSMC consisting exclusively of heterochromatic material. Yet, no centromere formation was reported for the regions 18q22.1 and Xq27.1-27.2 as it was observed in the 2 cases with centromere repositioning here; in both cases, cytogenetically an inversion was suggested. Two of the 3 neocentric sSMC were derived from a short arm of an acrocentric chromosome. The remainder neocentric sSMC case was previously reported and was stainable only by material derived from itself. Human neocentromeres have been known since 1993 [Voullaire et al., 1993]. Since then, 107 neocentric small supernumerary marker chromosomes (sSMC) [Liehr 2011], 7 carriers of centromere repositioning, and 13 cases with other rearrangements including neocentromere formation have been reported [reviewed in Liehr et al., 2010]. Here we describe 2 more cases with centromere repositioning and 3 neocentric sSMC, the latter exclusively derived from heterochromatic material