About the origin of the acrocentric part of non-acrocentric satellited chromosomes in humans
Background: Variants in size of the acrocentric short arms (acro-ps) are normally not reported and considered as chromosomal heteromorphisms (CHMs) without any influence on the carrier’s phenotype. However, if acro-ps are translocated to ends of A-chromosomes (i.e. human chromosomes 1-22 and X or Y), those rearrangements are studied in more detail. The aim of the study: Here we characterized 11 healthy carriers of a non-acrocentric satellited chromosomes der(A)t(A;acro)(pter or qter;p1?1.2) to determine the frequency of chromosome 15p and 22p in such rearrangements. Materials and methods: 11 carriers of one (10 cases) or two (1 case) der(A)t(A;acro) were identified during routine cytogenetic analyses. They were originally referred due to infertility or due to a mentally retarded child with otherwise abnormal karyotype. Here derivative chromosomes were studied by fluorescence in situ hybridization applying probes D15Z1 (specific for 15p11.2) and D22Z4 (specific for 22p11.2). As there are no DNA-sequences available for 13p11.2, 14p11.2 and 21p11.2 these regions could not be tested. Results: D15Z1 sequences were identified in 1 out of 12 derivatives der(A)t(A;acro). D22Z1 could not be detected in any of the 11 remainder derivatives. However, only 3 of the 12 der(A)t(A;acro) had acro-ps large enough to potentially comprise sub-band p11.2. Conclusion: In contrast to der(Y)t(Y;acro)(q12;p1?1.2), where in at least 65% of the cases the acro-p part contains D15Z1 sequences, here it could be shown that in der(A)t(A;acro) 15p involvement can be substantiated much less frequently. Also, in none of the two groups D22Z4-sequences were detected in acro-p-parts yet. Besides, breakpoint of acro-p-parts in der(A)t(A;acro) seem to be in ~75% of the cases distal from p11.2.