Brief cytogenetic report on maternal translocation t(7;9) (p22:p13): two sibs with duplication 9p and one sib with the balanced translocation

Duplication 9p and their implication to phenotype

Background

Trisomy 9p is one of the most common partial trisomies found in newborns. We report the clinical features and cytogenomic findings in five patients with different chromosome rearrangements resulting in complete 9p duplication, three of them involving 9p centromere alterations.

Methods

The rearrangements in the patients were characterized by G-banding, SNP-array and fluorescent in situ hybridization (FISH) with different probes.

Results

Two patients presented de novo dicentric chromosomes: der(9;15)t(9;15)(p11.2;p13) and der(9;21)t(9;21)(p13.1;p13.1). One patient presented two concomitant rearranged chromosomes: a der(12)t(9;12)(q21.13;p13.33) and an psu i(9)(p10) which showed FISH centromeric signal smaller than in the normal chromosome 9. Besides the duplication 9p24.3p13.1, array revealed a 7.3 Mb deletion in 9q13q21.13 in this patient. The break in the psu i(9)(p10) probably occurred in the centromere resulting in a smaller centromere and with part of the 9q translocated to the distal 12p with the deletion 9q occurring during this rearrangement. Two patients, brother and sister, present 9p duplication concomitant to 18p deletion due to an inherited der(18)t(9;18)(p11.2;p11.31)mat.

Conclusions

The patients with trisomy 9p present a well-recognizable phenotype due to facial appearance, although the genotype-phenotype correlation can be difficult due to concomitant partial monosomy of other chromosomes. The chromosome 9 is rich in segmental duplication, especially in pericentromeric region, with high degree of sequence identity to sequences in 15p, 18p and 21p, chromosomes involved in our rearrangements. Thus, we suggest that chromosome 9 is prone to illegitimate recombination, either intrachromosomal or interchromosomal, which predisposes it to rearrangements, frequently involving pericentromeric regions.

Cytogenetic and array-CGH characterization of a complex de novo rearrangement involving duplication and deletion of 9p and clinical findings in a 4-month-old female

Approximately 15 patients with partial trisomy 9p involving de novo duplications have been previously described. Here, we present clinical, cytogenetic, FISH and aCGH findings in a patient with a de novo complex rearrangement in the short arm of chromosome 9 involving an inverted duplication at 9p24→p21.3 and a deletion at 9pter→p24.2. FISH probes generated from BACs selected from the UCSC genome browser were utilized to verify this rearrangement. It is likely that some previously described duplications of 9p may also be products of complex chromosomal aberrations. This report in which FISH and aCGH were used to more comprehensively characterize the genomic rearrangement in a patient with clinical manifestations of 9p duplication syndrome underscores the importance of further characterizing cytogenetically detected rearrangements.

Patient with trisomy 9p and a hypoplastic left heart with a tricentric chromosome 9

We present a patient with a hypoplastic left heart (HLH), dislocations of the hips and knees, and minor dysmorphic features, who had an abnormal karyotype that resulted in trisomy for 9p and a portion of 9q: 46,((, dic(or tri?)(9)(9pter --> 9q34::9q21 --> 9pter).ish(WCP9++).ish(D9Z5X4 +/+++). The derivative chromosome consisted of an additional copy of the proximal q arm and p arm attached to 9qter in an inverted fashion. Fluorescence in situ hybridization (FISH) using a chromosome 9 beta-satellite probe revealed three signals on the abnormal chromosome 9, suggesting the presence of 3 pericentromeric regions on the der(9). The 9q subtelomere was present on both the normal and derivative chromosome 9, suggesting that very little material, if any, is deleted.

Molecular cytogenetic characterization and origin of two de novo duplication 9p cases

We report on two additional cases with duplication of 9p, minor with facial anomalies and developmental delay. Using fluorescence in situ hybridization and single-copy probes, we showed that the first case was a direct duplication, whereas the second case was inverted. The extent of the direct duplication was defined as 9p12 --> p24 by microdissection and microcloning of the aberrant chromosome and subsequent chromosome-specific comparative genomic hybridization. DNA polymorphism analysis with eight microsatellite markers revealed that the origin of the dup(9p) was maternal in the first case, whereas it was paternal in the second.

Case of partial trisomy 9p and partial trisomy 14q resulting from a maternal translocation: overlapping manifestations of characteristic phenotypes

We report on a female infant with partial trisomy 9p (pter-->p13) and partial trisomy 14q (pter-->q22) resulting from a 3:1 segregation of a maternal reciprocal translocation (9;14)(p13;q22). Both trisomy 9p and partial trisomy 14q have been described as recognized phenotypes with characteristic patterns of anomalies. This patient appears to be the first reported with a partial duplication of both 9p and 14q resulting in an overlapping phenotype including minor facial anomalies, cleft palate, and hand-foot anomalies. However, the facial findings were more pronounced than commonly observed in cases with only one or the other duplicated chromosome regions, resulting in a distinctive appearance.

Molecular cytogenetic characterisation of the first familial case of partial 9p duplication (p22p24)

We report on a father and daughter with a partial 9p duplication, dup(9)(p22p24). Their phenotype, albeit mild, is characteristic of partial trisomy 9p. Fluorescence in situ hybridisation (FISH) was used to characterise further and confirm the G banding finding. This is the first reported instance of trisomy 9p occurring in two successive generations. The duplicated segment in these two patients is among the smallest segments reported. Comparison of our two patients and 144 reported patients with trisomy 9p (partial or complete trisomy) suggests that the 9p22 region may be responsible for the observed phenotype in 9p duplication cases.