Familial whole-arm translocations (1;19), (9;13), and (12;21): a review of 101 constitutional exchanges

Abstract

We report here on 3 familial whole-arm translocations (WATs), namely the 8th instance of t(1;19)(p10;q10) and 2 novel exchanges: t(9;13)(p10;q10) and t(12;21)(p10;q10). The exchanges (1;19) and (12;21) were ascertained through a balanced carrier, whereas the t(9;13) was first diagnosed in a boy with a trisomy 9p syndrome and der(9p13p). Results of FISH analyses with the appropriate ?-satellite probes were as follows. Family 1, t(1;19): the D1Z5 probe gave a strong signal on both the normal chromosome 1 and the der(1q19p) as well as a weak signal on the der(1p19q). Family 2, t(9;13): the centromere-9 alphoid and D13Z1/D21Z1 probes under standard stringency gave no signal on the der(9p13p) in both the proband and a carrier brother, whereas the der(9q13q) was labelled only with the centromere-9 alphoid repeat in the latter; yet, this probe under low stringency revealed a residual amount of alphoid DNA on the der(9p13p) in the carrier. Family 3, t(12;21): the D12Z3 probe gave a signal on the normal chromosome 12 and the der(12p21q), whereas the D13Z1/D21Z1 repeat labelled the der(12q21p), the normal chromosome 21, and both chromosomes 13. Out of 101 WATs compiled here, 73 are distinct exchanges, including 32 instances between chromosomes with common alphoid repeats. Moreover, 7/9 of recurrent WATs involved chromosomes from the same alphoid family. Thus constitutional WATs appear to recur more frequently than other reciprocal exchanges, often involve chromosomes with common alphoid repeats, and can mostly be accounted for the great homology in alphoid DNA that favours mispairing and illegitimate nonhomologous recombination.

Clinical and molecular delineation of duplication 9p24.3q21.11 in a patient with psychotic behavior

“…The marker's mitotic stability indicates that the broken end is capped with a functional telomere be it a neotelomere or captured from 9q or another chromosome. Although we did not analyze the chromosomes of the patient's parents and therefore cannot exclude a parental translocation (e.g., Teraoka et al, 2001; family 2 in Vázquez-Cárdenas et al, 2007), the family history rather supports a de novo origin as it has been documented for other extra 9p chromosomes (patient 4 in Temtamy et al, 2007;Abu-Amero et al, 2010). The region shares a duplicated segment with the 9p duplication syndrome critical region (9p22.3-9p22.2) (Abu-Amero et al, 2010), which partially explains her dysmorphic features.…”

Cytogenetic and molecular analyses of de novo translocation dic(9;13)(p11.2;p12) in an infertile male

“…We speculate that in this case, a mitotic instability could be an additional co-founding factor leading to spermatogenetic arrest. Earlier described cases of t(9;13)(p11;p12) were familial and therefore did not result in azoospermia [12,14]. …”

“…This type of rearrangement belongs to the class of whole-arm translocations, which result from the centromeric fusion of two chromosomes [12]. In this type of translocation, one possibility is that both breakpoints are located juxta-centromeric and both derivative chromosomes contain their own centromere sequences.…”

“…Another mechanism is when one breakpoint occurs within the centromere and the other is located juxta-centromeric; one derivative chromosome therefore has a hybrid centromere and the other one has a reduced but conserved original centromere [13]. Whole arm translocations occur most frequently between chromosomes with similar alphoid domains [12]. However, carriers of a (9;13)(p11;p12) translocation have been described only a few times, and all of these cases were familial [12,14].…”

“…Whole arm translocations occur most frequently between chromosomes with similar alphoid domains [12]. However, carriers of a (9;13)(p11;p12) translocation have been described only a few times, and all of these cases were familial [12,14]. In contrast to the previously described cases, the patient described herein with dic(9;13)(p11.2;p12) has an increased number of immature germ cells but no mature sperm cells in his ejaculate.…”