Partial duplication of the short arm of chromosome 9 (p13 leads to p22) in a child with typical 9p trisomy phenotype

A rare familial rearrangement of chromosomes 9 and 15 associated with intellectual disability: a clinical and molecular study

Background

There are many reports on rearrangements occurring separately in the regions of chromosomes 9p and 15q affected in the case under study. 15q duplication syndrome is caused by the presence of at least one extra maternally derived copy of the Prader–Willi/Angelman critical region. Trisomy 9p is the fourth most frequent chromosome anomaly with a clinically recognizable syndrome often accompanied by intellectual disability. Here we report a new case of a patient with maternally derived unique complex sSMC resulting in partial trisomy of both chromosomes 9 and 15 associated with intellectual disability.

Case presentation

We characterise a supernumerary derivative chromosome 15: 47,XY,+der(15)t(9;15)(p21.2;q13.2), likely resulting from 3:1 malsegregation during maternal gametogenesis. Chromosomal analysis showed that a phenotypically normal mother is a carrier of balanced translocation t(9;15)(p21.1;q13.2). Her 7-year-old son showed signs of intellectual disability and a number of physical abnormalities including bilateral cryptorchidism and congenital megaureter. The child’s magnetic resonance imaging showed changes in brain volume and in structural and functional connectivity revealing phenotypic changes caused by the presence of the extra chromosome material, whereas the mother’s brain MRI was normal. Sequence analyses of the microdissected der(15) chromosome detected two breakpoint regions: HSA9:25,928,021-26,157,441 (9p21.2 band) and HSA15:30,552,104-30,765,905 (15q13.2 band). The breakpoint region on chromosome HSA9 is poor in genetic features with several areas of high homology with the breakpoint region on chromosome 15. The breakpoint region on HSA15 is located in the area of a large segmental duplication.

Conclusions

We discuss the case of these phenotypic and brain MRI features in light of reported signatures for 9p partial trisomy and 15 duplication syndromes and analyze how the genomic characteristics of the found breakpoint regions have contributed to the origin of the derivative chromosome. We recommend MRI for all patients with a developmental delay, especially in cases with identified rearrangements, to accumulate more information on brain phenotypes related to chromosomal syndromes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13039-021-00565-y.

Pure 9p duplication syndrome with aplasia of the middle phalanges of the fifth fingers

9p duplication syndrome is a common congenital anomaly syndrome with specific facial features, mental and developmental retardations, and characteristic fingers. Pure 9p duplication without other chromosomal structural variations is very rare. It has recently been reported that cases with partial 9p duplication including SMARCA2 have phenotypes overlapping with Coffin-Siris syndrome (CSS). Herein, we present a family with pure 9p duplication syndrome in which phenotypes partially characteristic of CSS were identified. In one of two siblings, X-ray examination revealed hypoplasia of the distal phalanges of the fifth fingers, aplasia of the middle phalanges of the fifth fingers, and aplasia of the distal phalanges of the second to fifth toes. In pure 9p duplication together with our one affected case, 9 out of 14 cases (64.3%), excluding cases whose clinical data were unavailable, presented the absence or hypoplasia of the middle phalanges of fingers or toes. Interestingly, there are no reports on CSS with aplasia or hypoplasia of the middle phalanx. Therefore, this family might suggest that the aplasia or hypoplasia of the middle phalanges of the fifth fingers or toes is a distinct finding that can distinguish between pure 9p duplication and CSS.

De Novo Duplication of Chromosome 9p in a Female Infant: Phenotype and Genotype Correlation

Trisomy 9p syndrome is the fourth most frequent chromosome aberration seen in infants. Duplication of the critical region 9p22p24 leads to mental retardation, psychomotor delay, and craniofacial and digital anomalies. We report a 2-year-old Ecuadorian girl with Trisomy 9p syndrome. Although her phenotype shares characteristics of Noonan syndrome, Giemsa trypsin banding technique shows there is an extra chromosomal segment on chromosome 14, and array analysis shows that it belongs to a duplication of 38 Mb of 9p13.1p24.3. Fluorescence in situ hybridization analysis detected three signals from 9p chromosome. The duplication is de novo, being another unique case of the few reported in the literature.

Partial trisomy 9 (9pter->9q22.1) and partial monosomy 14 (14pter- >14q11.2) due to paternal translocation t(9;14)(q22.1;q11.2) in a case of Dysmorphic features

Trisomy 9 including mosaic and partial trisomy is less frequently seen chromosomal abnormality in live born children. The pure or partial trisomy 9 frequently been reported in prenatal diagnosis and product of conception. However few studies reported partial trisomy 9 in live born children. In addition data on genotype and phenotype correlation of partial trisomy is not well understood except few case reports. Here we report a case of partial trisomy 9 and monosomy 14 with a 46,XY,der(9)t(9;14)(q22.1;q11.2)pat,-14 karyotype in a 5-year old dysmorphic child. The proband was confirmed as trisomic for 9pter->9q22.1 and monosomic for 14pter->q11.2 due to paternal t(9;14)(q22.1;q11.2) balanced translocation using a combination of conventional and molecular cytogenetic (fluorescence in situ hybridization, array-comparative genomic hybridization) techniques. The clinical features similar to pure trisomy 9 is due to duplication of the large region of chromosome 9. However, the present report of partial trisomy 9 and monosomy 14 is a novel case report and showing comparatively longer survival which have not been previously reported in the literature. The parent of the proband was counseled for the future pregnancies.

A de novo marker chromosome derived from 9p in a patient with 9p partial duplication syndrome and autism features: genotype-phenotype correlation

Background

Previous studies focusing on candidate genes and chromosomal regions identified several copy number variations (CNVs) associated with increased risk of autism or autism spectrum disorders (ASD).

Case Presentation

We describe a 17-year-old girl with autism, severe mental retardation, epilepsy, and partial 9p duplication syndrome features in whom GTG-banded chromosome analysis revealed a female karyotype with a marker chromosome in 69% of analyzed metaphases. Array CGH analysis showed that the marker chromosome originated from 9p24.3 to 9p13.1 with a gain of 38.9 Mb. This mosaic 9p duplication was detected only in the proband and not in the parents, her four unaffected siblings, or 258 ethnic controls. Apart from the marker chromosome, no other copy number variations (CNVs) were detected in the patient or her family. Detailed analysis of the duplicated region revealed: i) an area extending from 9p22.3 to 9p22.2 that was previously identified as a critical region for the 9p duplication syndrome; ii) a region extending from 9p22.1 to 9p13.1 that was previously reported to be duplicated in a normal individual; and iii) a potential ASD locus extending from 9p24.3 to 9p23. The ASD candidate locus contained 34 genes that may contribute to the autistic features in this patient.

Conclusion

We identified a potential ASD locus (9p24.3 to 9p23) that may encompass gene(s) contributing to autism or ASD.

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.

Molecular characterisation of a mosaicism with a complex chromosome rearrangement: evidence for coincident chromosome healing by telomere capture and neo-telomere formation

BACKGROUND

Broken chromosomes must acquire new telomeric "caps" to be structurally stable. Chromosome healing can be mediated either by telomerase through neo-telomere synthesis or by telomere capture.

AIM

To unravel the mechanism(s) generating complex chromosomal mosaicisms and healing broken chromosomes.

METHODS

G banding, array comparative genomic hybridization (aCGH), fluorescence in-situ hybridisation (FISH) and short tandem repeat analysis (STR) was performed on a girl presenting with mental retardation, facial dysmorphism, urogenital malformations and limb anomalies carrying a complex chromosomal mosaicism.

RESULTS & DISCUSSION

The karyotype showed a de novo chromosome rearrangement with two cell lines: one cell line with a deletion 9pter and one cell line carrying an inverted duplication 9p and a non-reciprocal translocation 5pter fragment. aCGH, FISH and STR analysis enabled the deduction of the most likely sequence of events generating this complex mosaic. During embryogenesis, a double-strand break occurred on the paternal chromosome 9. Following mitotic separation of both broken sister chromatids, one acquired a telomere vianeo-telomere formation, while the other generated a dicentric chromosome which underwent breakage during anaphase, giving rise to the del inv dup(9) that was subsequently healed by chromosome 5 telomere capture.

CONCLUSION

Broken chromosomes can coincidently be rescued by both telomere capture and neo-telomere synthesis.

20-Mb duplication of chromosome 9p in a girl with minimal physical findings and normal IQ: narrowing of the 9p duplication critical region to 6 Mb

We studied the case of a girl with a partial 9p duplication, dup(9)(p22.1 --> p13.1). Molecular cytogenetics studies defined the chromosome 9 rearrangement as a direct duplication of 20 Mb from D9S1213 to D9S52. Microsatellite analysis demonstrated the presence of a double dosage of the paternal alleles and demonstrated that the duplication occurred between sister chromatids. The patient's phenotype was almost normal, with a few minor anomalies (dolichocephaly, crowded teeth, high arched palate) and normal IQ. The breakpoint's location in this patient and previously reported cases suggest that the critical region for the 9p duplication syndrome lies within a 6-Mb portion of chromosome 9p22 between markers D9S267 and D9S1213.

Complex chromosome re-arrangement 45,X,t(Y;9) in a girl with sex reversal and mental retardation

A girl with mental retardation and multiple minor anomalies was found to have a complex chromosome 9p re-arrangement comprising a deleted, translocated Y chromosome, a deletion of the sex reversal gene region (DMRT1) at 9p, together with an inverted duplication of the more proximal part of 9p. The karyotype was 45,X,der(Y;9)(Ypter-->Yq12::9p21.1-->9p22.2::9p22.2-->9qter) de novo. The karyotypic male, phenotypic female had a dysgerminoma of the left dysplastic ovary. The patient had typical 'trisomy 9p' syndrome, and we propose that the critical region for this phenotype is located between 9p22.1 and 9p22.2.

Characterization of partial trisomy 9p due to insertional translocation by chromosomal (micro)FISH

We describe a family with an insertion 12;9 translocation occurring in a balanced form in a mother and two sons, but in an unbalanced form in the proband, resulting in trisomy of chromosome region 9p22-->9p24. The proband manifests typical features of trisomy 9p; the clinical signs were mental and growth retardation, microcephaly, epicanthus, low-set ears, micrognathia, clinodactyly and hypoplastic phalanges of the fifth fingers, hypoplasia or absence of toenails, and extremely small genitals. The GTG-banded findings were confirmed using (micro)FISH. Intriguingly, the mother and the two carrier sons exhibited major learning difficulties that were not present in the non-carrier sister of the mother: this may be due to a gene disruption or induction of abnormal expression. Dysmorphic features were not present in the three carriers. We compare our clinical and cytogenetic findings with other cases of partial trisomy 9p reported in the literature.

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.

De novo inverted duplication 9p21pter involving telomeric repeated sequences

We report on clinical and cytogenetic findings in a boy with partial 9p duplication, dup(9)(p21pter). Clinical manifestations included facial and hand anomalies and mental retardation. Fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH) were used to characterize further and confirm the conventional banding data. Investigation by FISH using whole chromosome 9 paint probe showed that the additional material was derived from chromosome 9. Using CGH, a region of gain was found in the chromosome segment 9p21pter. YACs and telomeric probes confirmed the duplicated region. Using the all-human telomeric sequences probe, intrachromosomal telomeric signal was noted on the short arm of the abnormal chromosome 9. Mechanism of formation of the duplication, including intrachromosomal telomeric sequences, is discussed.

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.

Molecular and cytogenetic characterization of 9p- abnormalities

We report on 2 girls with terminal deletion of the short arm of chromosome 9 with concurrent duplication unrecognizable by routine chromosome studies. The phenotype of the patients was not specifically suggestive of the 9p-syndrome in the absence of trigonocephaly and long philtrum as cardinal manifestations. In addition to psychomotor retardation, their manifestations were mild and include upward slant of palpebral fissures and dolichomesophalangy which are characteristic of del(9p). Chromosome abnormalities were de novo in both cases. The two rearranged chromosomes 9 exhibit similar G-banding patterns and suggested the possible duplication of distal 7p. Fluorescence in situ hybridization (FISH) with a chromosome-7 specific library probe indeed identified that one derivative chromosome 9 was the result of a translocation between chromosomes 7 and 9 [der(9)t(7;9)(p15.3;p24] but failed to detect a signal on the other derivative 9. In the second case, the concurrent abnormality was an inverted duplication of proximal 9p and deletion of distal 9p [inv dup(9)(p13-->p22::p22-->qter)] confirmed by FISH using a chromosome 9 specific library probe. FISH clearly identified the origin of these 2 abnormal chromosomes 9 and provided crucial information for clinical evaluation. We emphasize the importance of utilizing updated cytogenetic and molecular techniques in the precise delineation of subtle or complex abnormalities where there are no useful phenotypic clues.

Syndrome of developmental retardation, facial and skeletal anomalies, and hyperphosphatasia in two sisters: nosology and genetics of the Coffin-Siris syndrome

We report on 2 sisters, 3 and 6 years old, with a possible new syndrome consisting of developmental retardation, facial and skeletal anomalies, and hyperphosphatasia. This disorder closely resembles the Coffin-Siris syndrome (McKusick number 135900). We describe the difficulties in achieving a diagnosis. A major diagnostic clue was the radiological recognition of hypoplasia/aplasia of the terminal phalanx of the 5th finger. Minor facial anomalies and mental retardation alone had not led to the proper diagnosis. Still, several diagnostic possibilities remain. For unknown reasons both children have an increased level of serum alkaline phosphatase activity.

De novo tandem duplication 9p (p12----p24) with normal GALT activity in red cells

A 3 month old boy with a tandem duplication 9p (p12----p24) is reported. Both clinical and dermatoglyphic features were consistent with those of the trisomy 9p syndrome. However, the red cell galactose-1-P uridyl transferase (GALT) activity was normal despite the presence of the duplicated segment 9p13.

The origin of inverted tandem duplications, and phenotypic effects of tandem duplication of the X chromosome long arm

Tandem repeats of chromosome material can arise as inverted or as direct duplications. Such duplications of the X chromosome are instructive regarding X-linked genetic determinants of phenotype. We describe a 40-year-old woman with a direct duplication Xq13.3 to Xq27.2, short stature, gonadal dysgenesis, and secondary amenorrhea. Comparison of her phenotype with that of two other women with a direct duplication of part of Xq confirms the existence of statural determinants within the region X13 to Xq21, determinants of ovarian function within X22 to X27, and the X inactivation center within or proximal to band Xq13.3. In humans, direct duplications are more frequent than inverted, but both forms are rare. The mean age of parents is normal in subjects with direct duplications, but is advanced in subjects with inverted duplications. An inverted duplication can arise from a three-break rearrangement that includes a U-type exchange; a similar origin (two breaks and a U-type exchange) and a parental age association can be postulated for dicentric inverted duplications including dicentric isochromosome X.

Duplication of the short arm of chromosome 9. Analysis of five cases

Five females with duplication of the short arm of one chromosome 9 are reported, one tetrasomic and four trisomic for 9p. The tetrasomy is due to an isochromosome 9p while the trisomies are due in one case to an intrachromosomal duplication present in lymphocytes but not in fibroblasts, two are secondary to translocations with chromosomes 22 and 13 respectively, and one is a mosaic with a cell line with an additional deleted chromosome 9 present in lymphocytes and fibroblasts. This analysis indicates that duplications 9p may result in impairment of ovarian function. The phenotypic differences between trisomy and tetrasomy 9p are discussed.