Mosaic trisomy 12 at amniocentesis: Prenatal diagnosis and molecular genetic analysis

Application of various genetic analysis techniques for detecting two rare cases of 9p duplication mosaicism during prenatal diagnosis

BACKGROUND

The identification of genetic mosaicism and the genetic counseling needed following its discovery have been challenging problems in the field of prenatal diagnosis. Herein, we describe the clinical phenotypes and various prenatal diagnostic processes used for two rare cases of 9p duplication mosaicism and review the prior literature in the field to evaluate the merits of different methods for diagnosing mosaic 9p duplication.

METHODS

We recorded ultrasound examinations, reported the screening and diagnosis pathways, and analyzed the mosaic levels of the two cases of 9p duplication using karyotype analysis, chromosomal microarray analysis (CMA), and fluorescence in situ hybridization analysis (FISH).

RESULTS

Case 1 had a normal clinical phenotype for tetrasomy 9p mosaicism, and Case 2 showed multiple malformations caused by both trisomy 9 and trisomy 9p mosaicism. Both cases were initially suspected after non-invasive prenatal screening (NIPT) based on cell-free DNA. The mosaic ratio of 9p duplication found via karyotyping was lower than what was discovered by CMA and FISH, in both cases. Contrary to previous findings, the mosaic level of trisomy 9 found by karyotype analysis was greater than what was found by CMA, in terms of complex mosaicism involving trisomy 9 and trisomy 9p, in Case 2.

CONCLUSION

NIPT can indicate 9p duplication mosaicism during prenatal screening. Different strengths and limitations existed in terms of diagnosing mosaic 9p duplication by karyotype analysis, CMA, and FISH. The combined use of various methods may be capable of more accurately determining break-points and mosaic levels of 9p duplication during prenatal diagnosis.

Pigmentary mosaicism as a recurrent clinical manifestation in three new patients with mosaic trisomy 12 diagnosed postnatally: cases report and literature review

Background

To date, only twenty-one cases diagnosed postnatally with mosaic trisomy 12 have been reported. The most frequent phenotypic manifestations are developmental delay, dysmorphic facial features, congenital heart defects, digital alterations, and pigmentary disorders. In the present report, detailed clinical and genetic profiles of three unrelated new patients with mosaic trisomy 12 are described and compared with previously reported cases.

Case presentation

In the present report, we include the clinical, cytogenetic, and molecular description of three Mexican patients diagnosed postnatally with mosaic trisomy 12. At phenotypic level, the three patients present with developmental delay, dysmorphic facial features, congenital heart defects and skin pigmentary anomalies. Particularly, patient 1 showed unique eye alterations as bilateral distichiasis, triple rows of upper lashes, and digital abnormalities. In patient 2 redundant skin, severe hearing loss, and hypotonia were observed, and patient 3 presented with hypertelorism and telecanthus. Hyperpigmentation with disseminated pigmentary anomalies is a common trait in all of them. The cytogenetic study was carried out under the strict criteria of analysis, screening 50–100 metaphases from three different tissues, showing trisomy 12 mosaicism in at least one of the three different tissues analyzed. With SNParray, the presence of low-level mosaic copy number variants not previously detected by cytogenetics, and uniparental disomy of chromosome 12, was excluded. STR markers allowed to confirm the absence of uniparental disomy as well as to know the parental origin of supernumerary chromosome 12.

Conclusions

The detailed clinical, cytogenetic, and molecular description of these three new patients, contributes with relevant information to delineate more accurately a group of patients that show a heterogeneous phenotype, although sharing the same chromosomal alteration. The possibility of detecting mosaic trisomy 12 is directly associated with the sensitivity of the methodology applied to reveal the low-level chromosomal mosaicism, as well as with the possibility to perform the analysis in a suitable tissue.

[Genetic testing and analysis of 2 cases of trisomy 11 mosaicism]

Trisomy 11 mosaicism is clinically rare, for which making diagnostic and treatment decisions can be challenging. In this study, we used noninvasive prenatal testing, chromosome karyotype analysis, chromosome microarray analysis, copy number variation sequencing and fluorescence in situ hybridization for detecting trisomy 11 mosaicism in two cases and provided them with genetic counseling. In one of the cases, the fetus with confined placental mosaicism trisomy 11 presented with severe growth restriction and a placental mosaic level of 44%, and pregnancy was terminated at 25+3 weeks of gestation. In the other case with true low-level fetal mosaicism of trisomy 11, the pregnancy continued after exclusion of the possibility of uniparental disomy and structural abnormalities and careful prenatal counseling. The newborn was followed up for more than one year, and no abnormality was found. Noninvasive prenatal testing is capable of detecting chromosomal mosaicism but may cause missed diagnosis of true fetal mosaicism. For cases with positive noninvasive prenatal testing but a normal karyotype of the fetus, care should be taken in prenatal counseling and pregnancy management.

Mosaic Trisomy 12: Prenatal Diagnosis at Amniocentesis and Molecular Genetic Analysis on Fetal Tissues

Background: Mosaic trisomy 12 is a genetic condition with few cases diagnosed prenatally and postnatally. Phenotypic variability is wide ranging from normal patients to severe congenital anomalies. Case report: A 35-year-old woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Prenatal ultrasound was negative. Cultured amniocytes revealed a karyotype of 47,XX,+12/46,XX. Parents opted for termination of pregnancy at 22 weeks. Postmortem revealed dysmorphic face; hands with broad thumbs and incomplete transverse palmar creases; partial anomalous pulmonary venous return, intestinal malrotation, and bicornuate uterus. Histologically, no anomalies were identified. Cytogenetic analyses on fetal tissues detected mosaic trisomy 12 in thymus, lung, brain, kidney, placenta, and cord blood. Discussion/Conclusion: We report a new case of mosaic trisomy 12 with non-lethal morphological findings not previously described. Although prenatal ultrasound may be negative, genetic counseling should consider minor abnormalities and widespread presence of trisomic cell lines in various internal organs.

Prenatal diagnosis of mosaicism for trisomy 12 in a single colony at amniocentesis in a pregnancy with a favorable outcome

OBJECTIVE

We present prenatal diagnosis of mosaicism for trisomy 12 in a single colony at amniocentesis with a favorable outcome.

CASE REPORT

A 36-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+12[1]/46,XY[14]. In 15 colonies of cultured amniocytes, all three cells in one colony had the karyotype of 47,XY,+12, while the rest 14 colonies had the karyotype of 46,XY. The parental karyotypes were normal. Prenatal ultrasound findings were unremarkable. Polymorphic DNA marker analysis using the DNAs extracted from cultured amniocytes and parental bloods excluded uniparental disomy (UPD) 12. At 37 weeks of gestation, a healthy 2,828-g male baby was delivered with no phenotypic abnormality. The cord blood had a karyotype of 46,XY in 40/40 lymphocytes. Postnatal interphase fluorescence in situ hybridization (FISH) analysis on buccal cells and urinary cells revealed normal signals in 72/72 buccal cells, and trisomy 12 signals in 1/47 (2.1%) urinary cells compared with 0% (0/75 cells) of trisomy 12 signals in the normal control.

CONCLUSION

Mosaicism for trisomy 12 in a single colony at amniocentesis without UPD 12 and fetal ultrasound abnormalities can be associated with a favorable outcome.

A rare case of postnatal mosaic trisomy 12 with severe congenital heart disease and literature review

Trisomy 12 is a rare autosomal aneuploidy. All postnatally diagnosed individuals with trisomy 12 have been mosaic for this chromosome abnormality. We herein report an infant girl presented at 2 weeks of age with severe congenital heart defect, tracheobronchomalacia, and dysmorphic features. All of the dysmorphic features of this patient fit into the known phenotype spectrum of mosaic trisomy 12, although this patient uniquely presented with macrocephaly. Tracheo-bronchomalacia has been described once previously but had a significant impact on this patient's clinical course. The patient passed away at 2-month-old due to cardiac and respiratory complications. Chromosomal single nucleotide polymorphism (SNP) microarray analysis on a peripheral blood sample from the patient revealed trisomy 12 in approximately 50% of cells. Concurrent fluorescence in situ hybridization analysis of uncultured blood cells detected a comparable level of trisomy 12 mosaicism. Compared to conventional cytogenetics, SNP microarray examines all nucleated cells without sampling bias, has an increased power to estimate mosaicism level, and can provide a quick assessment of the underlying mechanism. Here we demonstrate the utilization of SNP microarray in the clinical diagnosis of those once considered rare disorders but might have been missed by conventional cytogenetic techniques.

Prenatal diagnosis of mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis in a pregnancy with a favorable outcome

OBJECTIVE

We present prenatal diagnosis of mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis with a favorable outcome.

CASE REPORT

A 23-year-old woman underwent amniocentesis at 24 weeks of gestation because of congenital bowel dilation in the fetus. Amniocentesis revealed a karyotype of 48,XX,+11,+12[1]/46,XX[24]. In 25 colonies of cultured amniocytes, all five cells in one colony had the karyotype of 48,XX,+11,+12, while the rest 24 colonies had the karyotype of 46,XX. The parental karyotypes were normal. Repeat amniocentesis was performed at 26 weeks of gestation. Interphase fluorescence in situ hybridization (FISH), array comparative genomic hybridization (aCGH) and quantitative fluorescent polymerase chain reaction (QF-PCR) were applied on the uncultured amniocytes, and conventional cytogenetic analysis was applied on cultured amniocytes. Interphase FISH analysis showed no trisomy 11 signal and no trisomy 12 signal in 102 uncultured amniocytes. QF-PCR analysis excluded uniparental disomy (UPD) 11 and UPD 12. aCGH analysis showed no genomic imbalance. The cultured amniocytes at repeat amniocentesis had the karyotype of 46,XX in 13/13 colonies. At term, a healthy 3445-g female baby was delivered with no phenotypic abnormality except imperforate anus and a perianal fistula. The cord blood had a karyotype of 46,XX in 40/40 lymphocytes. Postnatal interphase FISH analysis of buccal cells and urinary cells revealed trisomies 11 and 12 signals in 11/111 (9.9%) buccal cells compared with 3% in normal control, and in 3/103 (2.9%) urinary cells compared with 0.98% in normal control.

CONCLUSION

Mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis without UPD 11 and UPD 12 can be associated with a favorable outcome.

The difference between karyotype analysis and chromosome microarray for mosaicism of aneuploid chromosomes in prenatal diagnosis

OBJECTIVE

To compare karyotype and chromosomal microarray (CMA) analysis of aneuploid chromosome mosaicism in amniocentesis samples.

MATERIALS AND METHODS

A total of 2091 amniocentesis samples from pregnant women were collected from March 1, 2019, to January 31, 2020. Karyotype analysis was performed using G-banding and CMA analysis used the Affymetrix CytoScan 750K SNP microarray.

RESULT

Thirteen cases with aneuploid chromosome mosaicism were detected and compared between the karyotype and CMA methods. Seven of these cases were trisomic mosaicism, and the levels of mosaicism calculated from CMA were higher than those detected from karyotype analysis; noting three cases of trisomy mosaicism were not detected by karyotype analysis. Four cases exhibited monomeric mosaicism, and the levels of mosaicism detected in three of these cases were higher in karyotype compared with CMA analysis; one case had equivalent levels of monomeric mosaicism from both karyotype and CMA analysis. Two other cases from karyotype analysis were a mix of monosomic and trisomic mosaicism, whereas the CMA result was restricted to monosomic mosaicism for these cases.

CONCLUSION

Both karyotype and CMA analysis can be used to detect aneuploid chromosome mosaicism. However, the two methods produced different results. CMA and karyotype analysis have their own advantages in detecting aneuploid mosaicism, and the combination of these methods provides a more rigorous diagnosis.

Four children with postnatally diagnosed mosaic trisomy 12: Clinical features, literature review, and current diagnostic capabilities of genetic testing

Children or adults with mosaic trisomy 12 diagnosed postnatally are extremely rare. Only a small number of patients with this mosaicism have been reported in the literature. The clinical manifestation of mosaic trisomy 12 is variable, ranging from mild developmental delay to severe congenital anomaly and neonatal death. The trisomy 12 cells are not usually able to be detected by phytohemagglutinin stimulated peripheral blood chromosome analysis. The variability of phenotypes and the limited number of patients with this anomaly pose a challenge to predict the clinical outcomes. In this study, we present the phenotypes and laboratory findings in four patients and review the 11 previously reported patients with mosaic trisomy 12 diagnosed postnatally, as well as 11 patients with mosaic trisomy 12 diagnosed prenatally. The findings of this study provide useful information for laboratory diagnosis and clinical management of these patients.

The significance of trisomy 7 mosaicism in noninvasive prenatal screening

Background

This study was an evaluation of the role of noninvasive prenatal testing (NIPT) in the detection of trisomy 7 in prenatal diagnosis.

Method

A total of 35 consecutive cases underwent screening for trisomies by cell-free DNA testing between April 2015 and November 2017 due to suspicious NIPT results; these cases represented 0.11% of patients (35/31,250) with similar frequencies of abnormal results among the laboratories performing the tests. NIPT was offered to further screen for common fetal chromosomal abnormalities. Karyotype analysis, chromosomal microarray analysis (CMA), and next-generation sequencing (NGS) were used to detect 20, 14, and 25 patients, respectively, who accepted confirmatory diagnostic testing.

Results

High-risk results by NIPT were recorded for trisomy 7 alone in 29 women: dual aneuploidy in 4 patients and multiple aneuploidy in 2 patients. Karyotype analysis of amniotic fluid cells was normal in all 20 pregnancies, suggesting a probability of confined placental mosaicism. Further CMA data were obtained in 14 of the cases mentioned above, and 2 fetuses were detected with positive results with copy number variation. The NGS results suggested that all these samples were placental chimerisms of chromosome 7, except for one sample that was found to be an additional chimerism of chromosome 2, which was also consistent with the NIPT result.

Conclusion

Our results may be useful for the counseling of pregnant women in the detection of trisomy 7 by NIPT.

Mosaic Trisomy 12 Associated with Overgrowth Detected in Fibroblast Cell Lines

Mosaic trisomy 12 is a rare anomaly, and only 9 cases of live births with this condition have been reported in the literature. The clinical phenotype is variable, including neuropsychomotor developmental delay, congenital heart disease, microcephaly, cutaneous spots, facial asymmetry, prominent ears, hypotonia, retinopathy, and sensorineural hearing loss. A 2-year-old female presented with neuropsychomotor developmental delay, prominent forehead, dolichocephaly, patchy skin pigmentation, and unexpected overgrowth at birth. Cytogenetic analysis of her peripheral blood showed normal results, suggesting the presence of a chromosomal alteration in other tissues. Further studies using G-banding and FISH performed on fibroblasts from both hyper- and hypopigmented regions identified a 47,XX,+12/46,XX karyotype. To the best of our knowledge, no patients with mosaic trisomy 12 associated with overgrowth have been reported to date. Congenital overgrowth and neonatal overgrowth have been frequently linked to Pallister-Killian syndrome (PKS; OMIM 601803). This case suggests the possibility of an association of genes present in the 12p region with fetal overgrowth, considering that chromosomal duplications could lead to an increase in the production of aberrant transcripts and disturbing gene dosage effects. This case highlights the importance of cytogenetic analysis in different tissues to provide relevant information to the specific genotype/phenotype correlation.

Long-term effects of chromatin remodeling and DNA damage in stem cells induced by environmental and dietary agents

The presence of histones acts as a barrier to protein access; thus chromatin remodeling must occur for essential processes such as transcription and replication. In conjunction with histone modifications, DNA methylation plays critical roles in gene silencing through chromatin remodeling. Chromatin remodeling is also interconnected with the DNA damage response, maintenance of stem cell properties, and cell differentiation programs. Chromatin modifications have increasingly been shown to produce long-lasting alterations in chromatin structure and transcription. Recent studies have shown environmental exposures in utero have the potential to alter normal developmental signaling networks, physiologic responses, and disease susceptibility later in life during a process known as developmental reprogramming. In this review we discuss the long-term impact of exposure to environmental compounds, the chromatin modifications that they induce, and the differentiation and developmental programs of multiple stem and progenitor cell types altered by exposure. The main focus is to highlight agents present in the human lifestyle that have the potential to promote epigenetic changes that impact developmental programs of specific cell types, may promote tumorigenesis through altering epigenetic marks, and may be transgenerational, for example, those able to be transmitted through multiple cell divisions.