A case of non-mosaic X trisomy (65,XXX) in a Thoroughbred mare confirmed by cytogenetic and molecular analysis

A 9-year-old Thoroughbred mare with normal external genitalia and regular oestrus symptoms was gynecologically examined prior to insemination. This primary examination revealed the presence of a hypoplastic uterus and the lack of normal ovaries, and the mare was therefore subjected to more detailed diagnostics, including endocrinological, genetic, and clinical tests. Diagnostic imaging with the use of ultrasonography and endoscopy confirmed the underdevelopment of internal genitalia. Analysis of circulating sex hormones revealed very low concentrations of progesterone and oestradiol. Finally, cytogenetic analysis showed the presence of non-mosaic X trisomy (65,XXX), an aneuploidy of sex chromosomes that is rarely detected in horses. This finding was also confirmed by molecular methods, including highly sensitive droplet digital PCR (ddPCR) and microsatellite markers genotyping. Our study reveals the need for gynaecological and genetic evaluation of broodmares, even if their phenotype (including developed external genitalia and oestrus symptoms) shows no signs of potential abnormalities.

Prenatal diagnosis of 18p deletion and 8p trisomy syndrome: literature review and report of a novel case

18p deletion syndrome constitutes one of the most frequent autosomal terminal deletion syndromes, affecting one in 50,000 live births. The syndrome has un-specific clinical features which vary significantly between patients and may overlap with other genetic conditions. Its prenatal description is extremely rare as the fetal phenotype is often not present during pregnancy. Trisomy 8p Syndrome is characterized by heterogenous phenotype, with the most frequent components to be cardiac malformation, developmental and intellectual delay. Its prenatal diagnosis is very rare due to the unspecific sonographic features of the affected fetuses. We present a very rare case of a fetus with multiple anomalies diagnosed during the second trimester whose genomic analysis revealed a 18p Deletion and 8p trisomy Syndrome. This is the first case where this combination of DNA mutations has been described prenatally and the second case in general. The presentation of this case, as well as the detailed review of all described cases, aim to expand the existing knowledge regarding this rare condition facilitating its diagnosis in the future.

Therapeutic Management and Outcomes of Hepatoblastoma in a Pediatric Patient with Mosaic Edwards Syndrome

The mosaic form of Edwards syndrome affects 5% of all children with Edwards syndrome. The clinical phenotype is highly variable, ranging from the full spectrum of trisomy 18 to the normal phenotype. The purpose of this publication was to present the therapeutic process in an 18-month-old girl with the mosaic form of Edwards syndrome and hepatoblastoma, against the background of other cases of simultaneous occurrence of this syndrome and hepatoblastoma described so far. It appears that this particular group of patients with hepatoblastoma and Edwards syndrome can have good outcomes, provided they do not have life-threatening cardiac or other severe defects. Due to the prematurity of our patient and the defects associated with Edwards syndrome, the child required constant multidisciplinary care, but Edwards syndrome itself was not a reason to discontinue therapy for a malignant neoplasm of the liver. Regular abdominal ultrasound examination, along with AFP testing, may be helpful in the early detection of liver tumors in children with Edwards syndrome.

Early Chronic Fluoxetine Treatment of Ts65Dn Mice Rescues Synaptic Vesicular Deficits and Prevents Aberrant Proteomic Alterations

Down syndrome (DS) is the most common form of inherited intellectual disability caused by trisomy of chromosome 21, presenting with intellectual impairment, craniofacial abnormalities, cardiac defects, and gastrointestinal disorders. The Ts65Dn mouse model replicates many abnormalities of DS. We hypothesized that investigation of the cerebral cortex of fluoxetine-treated trisomic mice may provide proteomic signatures that identify therapeutic targets for DS. Subcellular fractionation of synaptosomes from cerebral cortices of age- and brain-area-matched samples from fluoxetine-treated vs. water-treated trisomic and euploid male mice were subjected to HPLC-tandem mass spectrometry. Analysis of the data revealed enrichment of trisomic risk genes that participate in regulation of synaptic vesicular traffic, pre-synaptic and post-synaptic development, and mitochondrial energy pathways during early brain development. Proteomic analysis of trisomic synaptic fractions revealed significant downregulation of proteins involved in synaptic vesicular traffic, including vesicular endocytosis (CLTA, CLTB, CLTC), synaptic assembly and maturation (EXOC1, EXOC3, EXOC8), anterograde axonal transport (EXOC1), neurotransmitter transport to PSD (SACM1L), endosomal-lysosomal acidification (ROGDI, DMXL2), and synaptic signaling (NRXN1, HIP1, ITSN1, YWHAG). Additionally, trisomic proteomes revealed upregulation of several trafficking proteins, involved in vesicular exocytosis (Rab5B), synapse elimination (UBE3A), scission of endocytosis (DBN1), transport of ER in dendritic spines (MYO5A), presynaptic activity-dependent bulk endocytosis (FMR1), and NMDA receptor activity (GRIN2A). Chronic fluoxetine treatment of Ts65Dn mice rescued synaptic vesicular abnormalities and prevented abnormal proteomic changes in adult Ts65Dn mice, pointing to therapeutic targets for potential treatment of DS.

The first reported case of double trisomy 10 and 20 in a product of conception

BACKGROUND

Double trisomies are rare findings among products of conception and are often lethal to the developing embryo or fetus.

METHODS

Here we describe a double trisomy case with symptoms of threatened miscarriage at 9 weeks gestation. Ultrasound revealed an anembryonic pregnancy. Pregnancy was terminated by dilation and curettage at gestational age 11 weeks and 6 days. Histologic examination and chromosome microarray were performed on a formalin-fixed product of conception (POC) sample to identify the cause of the anembryonic pregnancy.

RESULTS

Chromosome microarray analysis revealed a female chromosome complement with double trisomies 10 and 20, arr(10,20)x3, consistent with a karyotype of 48,XX,+10,+20.

CONCLUSION

To the best of our knowledge, this is the first reported case of double trisomy 10 and 20 in a POC. Due to nonspecific histopathological findings, chromosomal microarray is a powerful tool in identifying and differentiating chromosomal aneuploidies.

Partial Trisomy 4p Syndrome Diagnosed Prenatally

Introduction: Trisomy 4p is a lethal chromosomal disorder, resulting from segmental or full trisomy of the short arm of chromosome 4. Prenatal diagnosis may allow decisions on whether to continue or terminate the pregnancy. Case report: We diagnosed a fetus with partial trisomy 4p after first-trimester ultrasound detection of increased nuchal translucency, allowing the parents the opportunity to terminate the pregnancy. The partial trisomy 4p was inherited from a balanced translocation carried by the father. Discussion/Conclusion: For this family, the risk of unbalanced chromosomal alterations in subsequent pregnancies is increased due to the father's translocation. Appropriate genetic counseling with future prenatal diagnosis through amniocentesis can be offered to the couple. Trisomy 4p can be associated with increased nuchal thickness in the first trimester.

The role of confined placental mosaicism in fetal growth restriction: A retrospective cohort study

OBJECTIVE

To evaluate which cytogenetic characteristics of confined placental mosaicism (CPM) detected in the first trimester chorionic villi and/or placentas in terms of chromosome aberration, cell lineage involved and trisomy origin will lead to fetal growth restriction and low birthweight.

METHODS

Cohort study using routinely collected perinatal data and cytogenetic data of non-invasive prenatal testing, the first trimester chorionic villi sampling and postnatal placentas.

RESULTS

215 CPM cases were found. Fetal growth restriction (FGR) and low birthweight below the 10th percentile (BW < p10) were seen in 34.0% and 23.1%, respectively. Excluding cases of trisomy 16, 29.1% showed FGR and 17.9% had a BW < p10. The highest rate of FGR and BW < p10 was found in CPM type 3, but differences with type 1 and 2 were not significant. FGR and BW < p10 were significantly more often observed in cases with meiotic trisomies.

CONCLUSION

There is an association between CPM and FGR and BW < p10. This association is not restricted to trisomy 16, neither to CPM type 3, nor to CPM involving a meiotic trisomy. Pregnancies with all CPM types and origins should be considered to be at increased risk of FGR and low BW < p10. A close prenatal fetal monitoring is indicated in all cases of CPM.

An unusual case of trisomy 8 mosaicism complicated by coexistence of phenylketonuria

Trisomy 8 syndrome, also known as " Warkany syndrome type 2 ", was first reported in 1971. Complete trisomy 8 are mostly aborted spontaneouslyinthe first trimester. Trisomy 8 mosaicism (T8M), predominated in the current cases reported. Itisahighlyheterogeneous Chromosome disorder. We know little about its effects on fertility. In this case, a patient with T8M combined with phenylketonuria was diagnosed. She's mentally retarded. After evaluating the anatomy and function of the reproductive system, the patient conceived through preimplantationgenetictesting-intracytoplasmicsperminjection-embryotransfer (PGT-ICSI-ET) and obtained a healthy fetus, which is the first report. The study focuses on the maintenance of fertility in patients with T8M, the effects of phenylketonuria and genetic counseling.

Cases of trisomy 21 and trisomy 18 among historic and prehistoric individuals discovered from ancient DNA

Aneuploidies, and in particular, trisomies represent the most common genetic aberrations observed in human genetics today. To explore the presence of trisomies in historic and prehistoric populations we screen nearly 10,000 ancient human individuals for the presence of three copies of any of the target autosomes. We find clear genetic evidence for six cases of trisomy 21 (Down syndrome) and one case of trisomy 18 (Edwards syndrome), and all cases are present in infant or perinatal burials. We perform comparative osteological examinations of the skeletal remains and find overlapping skeletal markers, many of which are consistent with these syndromes. Interestingly, three cases of trisomy 21, and the case of trisomy 18 were detected in two contemporaneous sites in early Iron Age Spain (800-400 BCE), potentially suggesting a higher frequency of burials of trisomy carriers in those societies. Notably, the care with which the burials were conducted, and the items found with these individuals indicate that ancient societies likely acknowledged these individuals with trisomy 18 and 21 as members of their communities, from the perspective of burial practice.

Maternal age and the risk of fetal aneuploidy: A nationwide cohort study of more than 500 000 singleton pregnancies in Denmark from 2008 to 2017

INTRODUCTION

In this register-based study of pregnancies in Denmark, we assessed the associations between maternal age and the risk of fetal aneuploidies (trisomy 21, trisomy 18, trisomy 13, triploidy, monosomy X and other sex chromosome aberrations). Additionally, we aimed to disentangle the maternal age-related effect on fetal aneuploidies by cases with translocation trisomies and mosaicisms.

MATERIAL AND METHODS

We followed a nationwide cohort of 542 375 singleton-pregnant women attending first trimester screening in Denmark between 2008 and 2017 until delivery, miscarriage or termination of pregnancy. We used six maternal age categories and retrieved information on genetically confirmed aneuploidies of the fetus and infant from the national cytogenetic register.

RESULTS

We confirmed the known associations between advanced maternal age and higher risk of trisomy 21, 18, 13 and other sex chromosome aberrations, especially in women aged ≥35 years, whereas we found no age-related associations with triploidy or monosomy X. Cases with translocation trisomies and mosaicisms did not influence the overall reported association between maternal age and aneuploidies.

CONCLUSION

This study provides insight into the accurate risk of fetal aneuploidies that pregnant women of advanced ages encounter.

First report on chromosomal abnormalities in Eastern Morocco: Identification of a new case of a de novo partial trisomy 13q using single-nucleotide polymorphism array

BACKGROUND

Chromosomal abnormalities are the main cause of birth defects, intellectual disability, and miscarriages. They contribute to significant human morbidity and infant mortality. Here we report for the first time the chromosomal abnormalities encountered in the population of Eastern Morocco. Furthermore, we describe a new case of a de novo partial trisomy 13q combined with a terminal deletion in an 11-day-old girl.

METHODS

From November 2015 to March 2022, 195 patients from the BRO Biobank who were clinically suspected of having chromosomal abnormalities were referred to the cytogenetics laboratory of the Genetics Unit of the Faculty of Medicine and Pharmacy of Oujda for cytogenetic study. Karyotyping analysis was performed on peripheral blood samples using standard R banding techniques. To identify single-nucleotide polymorphism (SNP) and copy number variants (CNVs), Illumina SNP array was used.

RESULTS

Among 195 studied cases, 32 (16.4 %) had abnormal karyotypes, of which 12 cases had numerical aberrations while 20 cases had structural aberrations. The most common numerical aberrations were Turner syndrome and Down syndrome followed by Edward, Patau, and Klinefelter syndromes. For structural aberrations, translocations were the most common, followed by derivative chromosomes, inversions, deletions, and an addition on chromosome 13 identified in an 11-day-old girl. To further characterize this addition, SNP array was carried out and revealed a 58.8-Mb duplication in region 13q14.3q34 associated with a 1-Mb deletion in region 13q34. Follow-up parental chromosomes analysis showed normal karyotypes for the parents, confirming that this partial trisomy 13q was de novo. Comparison of the phenotype associated with this novel duplication on chromosome 13q with those previously reported confirmed the considerable variability in the phenotype of the patients with partial trisomy 13q.

CONCLUSION

This study provided the first report on chromosomal abnormalities in Eastern Morocco and it enriched the phenotype spectrum of partial trisomy 13q and further confirmed the genotype-phenotype correlations. Furthermore, these findings justify the need to set up microarray comparative genomic hybridization techniques in Morocco for better genetic diagnosis.

Causes of death in individuals with trisomy 18 after the first year of life

Mortality in individuals with trisomy 18 has significantly decreased over the past 20 years, but there is scant literature addressing the prognosis and cause of death in individuals with trisomy 18 and survival past the first year of life (YOL). This study analyzed factors associated with mortality and cause of death in a retrospective cohort of 174 individuals with trisomy 18 and survival past the first YOL, the largest such series to date. Data were collected via retrospective survey of parents of affected individuals. Prenatal diagnosis of trisomy 18; postnatal respiratory distress; maternal age > 35 years; birthweight <2000 g; brain and spinal cord defect(s); atrial and/or ventricular septal defect(s); inability to feed orally without medical assistance; and failure to meet sitting and rolling milestones were associated with mortality in this sample. Cause of death was compared between our cohort of individuals with trisomy 18 and existing literature on those with mortality before the first YOL. Individuals with trisomy 18 with mortality after the first YOL demonstrated a predominance of infectious (n = 10/22) and postoperative (n = 6/22) contributing causes of death, in contrast to the existing literature, which shows a predominance of cardiopulmonary causes of death (e.g., cardiopulmonary arrest, pulmonary hypertension). These findings demonstrate that individuals with trisomy 18 and survival past the first YOL have unique medical needs, but further research is needed to develop clinical guidelines for this growing population.

Relationships among maternal monosomy X mosaicism, maternal trisomy, and discordant sex chromosome aneuploidies

OBJECTIVE

To explore the impact of maternal factors on the false-positive fetal sex chromosome aneuploidies (SCAs) results obtained through noninvasive prenatal screening (NIPS).

METHODS

We retrospectively analyzed pregnant women with high-risk SCAs as revealed using NIPS between January 2017 and December 2022. Clinical data such as results of invasive prenatal diagnoses, copy number variation sequencing (CNV-seq) and pregnancy outcomes were analysed.

RESULTS

Overall, 177 (0.6 %) women with SCA-positive results were collected from 27,941 patients who had undergone NIPS. Among them, 110 (62.2 %) pregnant women chose prenatal diagnosis and 39 (35.5 %) cases were confirmed. For the women with monosomy X false-positive results from the NIPS, 53.1 % (17/32) were found to be maternal mosaicism monosomy X. In cases with 47, XXX false-positive results, 60 % (6/10) of them were maternal 47,XXX (5 cases) or maternal mosaicism 47,XXX (1 case). One (1/6, 16.7 %) case of maternal mosaicism monosomy X was detected in the false positive results of 47, XXY/47, XYY revealed. The incidence rate of maternal sex chromosome abnormalities was positively correlated with the Z-score of ChrX. When the Z-score of ChrX ≥ 15, more than 50 % of pregnant women were found to be maternal sex chromosome abnormalities, and when Z-score ≥ 30, the incidence rate was as high as 100 %.

CONCLUSIONS

Maternal monosomy X mosaicism and trisomy X respectively played an important role in the discordance of 45, X and 47, XXX revealed by NIPS. CNV-seq was recommended for the pregnant women at risk of maternal sex chromosome abnormalities, which could help clinicians to provide more accurate and efficient advice during genetic counseling and to guide appropriate prenatal diagnosis strategy for the next pregnancy.

Combined Z-scores to assess the impact of rare autosomal trisomies that results in non-invasive prenatal screening on pregnancy outcomes

OBJECTIVE

This study aimed to combine Z-scores to evaluate the effects of rare autosomal trisomies (RATs) in non-invasive prenatal screening (NIPS) on pregnancy outcomes at a single center.

METHODS

We retrospectively collected the clinical data of women with high-risk RATs results using NIPS at a single center between January 2017 and December 2021. NIPS-positive results were separated into three groups based on the Z-value of RATs (Group1: 6 ≤ Z < 10; Group2: 10 ≤ Z < 15; Group 3: Z ≥ 15). Pregnancy outcomes of women with RATs were compared with the low-risk NIPS group.

RESULTS

Overall, 83 RATs were identified in 23,321 NIPS results at our center. Prenatal diagnosis was conducted for 55 patients, and no case was confirmed, with a positive predictive value (PPV) of zero. Fifteen of these patients had adverse pregnancy outcomes, including delivered preterm and/or birth weight (9/15, 60.0 %), structural abnormalities (4/15, 26.7 %), miscarriage (1/15, 6.7 %), and intrauterine death (1/15, 6.7 %). There were 8 (8/22, 36.4 %) adverse pregnancy outcomes in Group 3, which was significantly higher than that in the low-risk NIPS group (p < 0.01). No significant difference was observed between the control group and Group 1 and Group 2 (p > 0.01).

CONCLUSIONS

Clinicians should pay more attention to the RATs results when the Z-score is ≥ 15. The data are available for clinicians to guide the prenatal diagnosis of RATs and pregnancy management.

New candidate region for mirror hand movements: two patients with terminal 9p deletion and 20p duplication

The 9p deletion syndrome, which was defined in a detailed way in the previous studies, was characterized by various clinical features such as psychomotor retardation, dysmorphic features and genital anomalies. In contrast to 9p deletion syndrome, 20p duplication was rarely reported in the literature with only a few case reports. Regarding the combination of 9p deletion syndrome and 20p duplication, we found that it was reported in only four patients. In the current study, we aimed to investigate a rare chromosomal rearrangement, partial monosomy 9p and trisomy 20p which was observed in two patients with mirror hand movements. The mirror hand movements was influenced by the combination of genetic and environmental factors. While some cases have been associated with mutations in the DCC, NTN1, RAD51, and DNAL4, there were many cases where the genetic basis of mirror hand movements remained unexplained. There was no alteration detected in genes that were previously known as a cause of mirror hand movement in our patients. This new finding could potentially be attributed to the dosage effect of genes within the 9p deletion or 20p duplication regions or to the genes disrupted within the breakpoint region. Future research focusing on the genes within this genomic locus may hold the potential to uncover novel etiologic reasons for mirror hand movements.

[Prenatal diagnosis and outcome of pregnancy for women with high risks by screening of fetal free DNA from peripheral blood samples]

OBJECTIVE

To analyze the results of prenatal diagnosis and outcome of pregnancy for women with a high risk for fetal aneuploidies.

METHODS

A total of 747 cases of prenatal diagnosis by amniocentesis due to high risks by non-invasive prenatal testing (NIPT) were selected from January 2015 to March 2022 in the Drum Tower Hospital Affiliated to Nanjing University Medical School. The amniotic fluid samples were subjected to chromosomal karyotyping and/or chromosomal microarray analysis. All cases were followed up by searching the birth information or telephone calls, and the results were recorded. 2 test or F test were used for comparing the difference between the groups.

RESULTS

Among the 747 pregnant women with a high risk by NIPT, 387 were true positives, and the overall positive predictive value (PPV) was 51.81%. The PPVs for trisomy 21 (T21), trisomy 18 (T18), trisomy 13 (T13) and sex chromosome aneuploidies (SCA) were 80.24% (199/248), 60% (48/80), 14% (7/50) and 38.97% (106/272), respectively. The PPV for T21 was significantly higher than T18 and T13 (χ2 = 85.216, P < 0.0001). The PPV for other chromosomal aneuploidies and copy number variations (CNVs) were 11.11% (5/45) and 40.74% (22/52), respectively. The PPV for increased X chromosomes was significantly higher than X chromosome decreases (64.29% vs. 22.22%, χ2 = 5.530, P < 0.05). The overall PPV for elder women (≥ 35 years old) was significantly higher than younger women (69.35% vs. 42.39%, χ2 = 49.440, P < 0.0001). For T21 and T18, the PPV of Z ≥ 10 group was significantly higher than that for 3 ≤ Z < 5 group or 5 ≤ Z < 10 group (P < 0.05). Among 52 cases with a high risk for CNVs, the PPV for the ≤ 5 Mb group was significantly higher than the 5 Mb < CNVs < 10 Mb or > 10 Mb groups (60% vs. 30%60% vs. 23.53%, P < 0.05). Among the 387 true positive cases, 322 had opted for induced labor, 53 had delivered with no abnormal growth and development, and 12 were lost during the follow-up.

CONCLUSION

The PPVs for common chromosomal aneuploidies are related to the age and Z value of the pregnant women, which were higher in the elder group and higher Z value group. In addition, the PPV is associated with high risk types. The PPV for T21 was higher than T18 and T13, and that for 45,X was lower than 47,XXX, 47,XYY or 47,XXY syndrome. NIPT therefore has relatively high PPVs for the identification of chromosomal CNVs.

[Genetic analysis of the false positive trisomy 7 and false negative trisomy 18 by NIPT-PLUS]

OBJECTIVE

To explore the cause of inconsistency between the results of trisomy 7 by expanded non-invasive prenatal testing (NIPT-PLUS) and trisomy 18 by prenatal diagnosis.

METHODS

A pregnant woman who received genetic counseling at Jiaozuo Maternal and Child Health Care Hospital on July 5, 2020 was selected as the study subject. NIPT-PLUS, systematic ultrasound and interventional prenatal testing were carried out. The middle segment and root of umbilical cord, center and edge of the maternal and fatal surface of the placenta were sampled for the validation by copy number variation sequencing (CNV-seq).

RESULTS

The result of NIPT-PLUS indicated that the fetus has trisomy 7. Systematic ultrasound has shown multiple malformations including atrioventricular septal defect, horseshoe kidney, and rocker-bottom feet. However, QF-PCR, chromosomal karyotyping analysis, and CNV-seq of amniotic fluid samples all showed that the fetus was trisomy 18. Validation using multiple placental samples confirmed that the middle segment of the umbilical cord contains trisomy 18, the center of the placenta contained trisomy 7, and other placental sites were mosaicism for trisomy 7 and trisomy 18. Notably, the ratio of trisomy 18 became lower further away from the umbilical cord.

CONCLUSION

The false positive results of trisomy 7 and false negative trisomy 18 by NIPT-PLUS was probably due to the existence of placental mosaicism. Strict prenatal diagnosis is required needed aneuploidy is detected by NIPT-PLUS to exclude the influence of placental mosaicisms.

Experience of copy number variation sequencing applied in spontaneous abortion

PURPOSE

We evaluated the value of copy number variation sequencing (CNV-seq) and quantitative fluorescence (QF)-PCR for analyzing chromosomal abnormalities (CA) in spontaneous abortion specimens.

METHODS

A total of 650 products of conception (POCs) were collected from spontaneous abortion between April 2018 and May 2020. CNV-seq and QF-PCR were performed to determine the characteristics and frequencies of copy number variants (CNVs) with clinical significance. The clinical features of the patients were recorded.

RESULTS

Clinically significant chromosomal abnormalities were identified in 355 (54.6%) POCs, of which 217 (33.4%) were autosomal trisomies, 42(6.5%) were chromosomal monosomies and 40 (6.2%) were pathogenic CNVs (pCNVs). Chromosomal trisomy occurs mainly on chromosomes 15, 16, 18, 21and 22. Monosomy X was not associated with the maternal or gestational age. The frequency of chromosomal abnormalities in miscarriages from women with a normal live birth history was 55.3%; it was 54.4% from women without a normal live birth history (P > 0.05). There were no significant differences among women without, with 1, and with ≥ 2 previous miscarriages regarding the rate of chromosomal abnormalities (P > 0.05); CNVs were less frequently detected in women with advanced maternal age than in women aged ≤ 29 and 30-34 years (P < 0.05).

CONCLUSION

Chromosomal abnormalities are the most common cause of pregnancy loss, and maternal and gestational ages are strongly associated with fetal autosomal trisomy aberrations. Embryo chromosomal examination is recommended regardless of the gestational age, modes of conception or previous abortion status.

Correlation between telomere shortening in maternal peripheral blood and fetal aneuploidy

BACKGROUND

This study aimed to assess whether maternal telomere length is a more accurate predictor of trisomy 21 than maternal age while also exploring the factors influencing maternal and fetal telomere length.

METHODS

Forty mothers with fetuses carrying extra maternal copies of chromosome 21 were defined as trisomy 21 cases, and 18 mothers with normal karyotype fetuses were defined as controls. Telomere lengths of maternal blood lymphocytes and amniotic fluid cells were determined using real-time polymerase chain reaction. Fetal and maternal telomere lengths were compared between the two groups. Moreover, we analyzed the factors influencing maternal and fetal telomere length in the trisomy 21 pedigree. A logistic regression model was used to analyze the correlation between maternal telomere length and trisomy 21 risk. In addition, receiver operating characteristic (ROC) curve analysis was used to determine the accuracy of using maternal telomere length as an indicator of trisomy 21 risk.

RESULTS

The study revealed that both maternal and fetal telomere lengths were significantly shorter in trisomy 21 cases than in the controls. In the trisomy 21 group, the maternal age, occupation, and nationality showed no significant correlation with their telomere length; fetal telomere length exhibited a positive correlation with maternal telomere length. Furthermore, maternal telomere length shortening is associated with trisomy 21 (OR = 0.311; 95% CI, 0.109-0.885, P < 0.05). The results of ROC curve analysis indicated that a combined assessment of maternal age and maternal telomere length predicted fetal chromosome trisomy more effectively than a single assessment (area under the curve 0.808, 95% CI, 0.674-0.941, P < 0.001).

CONCLUSION

Maternal age combined with maternal telomere length proved to be a superior predictor of trisomy risk. Additionally, maternal telomere length was found to influence fetal telomere length.

Use of the MS-MLPA assay in prenatal diagnosis of Prader-Willi syndrome with mosaic trisomy 15

OBJECTIVE

We present a prenatal diagnosis strategy of using Methylation-Specific Multiplex Ligation-Dependent Probe Amplification (MS-MLPA) for the detection of maternal uniparental disomy 15/trisomy 15 (UPD(15) mat/T15) mosaicism.

CASE REPORT

A 43-year-old woman underwent amniocentesis at 19 weeks of gestation due to a high risk of trisomy 15 (T15) as indicated by non-invasive prenatal testing (NIPT). Cytogenetic analysis revealed a karyotype of 46, XX of cultured amniocytes. Further analysis using copy number variation sequencing (CNV-seq) analysis showed 55 % T15 mosaicism. The second amniocentesis was performed and showed a karyotype of 46, XX and 26 % T15 mosaicism by interphase fluorescence in situ hybridization (FISH). MS-MLPA analysis of uncultured amniocytes showed that the copy number ratio of 15q11-13 ranged from 1.3 to 1.5, and the percentage of methylation was between 70 % and 100 %. MS-MLPA assay of cultured amniocytes showed a copy number ratio of 1 and a methylation percentage of 100 %. Therefore, this fetus was identified to be an UPD(15) mat/T15 mosaicism. The parents decided to terminate the pregnancy.

CONCLUSION

MS-MLPA can be used in combination with karyotype and CNV-seq for prenatal diagnosis of NIPT high-risk T15 to avoid missed diagnosis of UPD(15) mat/T15 mosaicism.

Comprehensive phenotyping of fetuses with trisomy 18: a perinatal center experience

Trisomy 18 is the second most common aneuploidy after trisomy 21. It presents with varying degrees of heterogeneous clinical phenotypes involving multiple organ systems, with a high mortality rate. Clinical assessment of fetal trisomy 18 is always challenging. In this study, we describe the phenotypes of the fetuses with trisomy 18 from a perinatal cohort. We reviewed fetuses with trisomy 18 in referrals for perinatal autopsy over the period of 15 years. A detailed phenotyping of the fetuses with trisomy 18 was executed by perinatal autopsy. Appropriate fetal tissues were obtained to perform genomic testing. We observed trisomy 18 in 16 fetuses (2%) in our cohort of 784 fetal/neonatal losses and a perinatal autopsy was performed on all of them. Abnormal facial profile was the most frequent anomaly (10/16, 62%) followed by anomalies of the extremities (9/16, 56%), and cardiac defects (6/16, 37%). We also observed esophageal atresia, diaphragmatic hernia, and neural tube defect. The study represents one of the largest cohorts of trisomy 18 from a perinatal center from a developing country and highlights the clinical heterogeneity attributed to trisomy 18. We also report a recurrence of trisomy 18 in a family.

[Study of a fetus with confined placental mosaicism for trisomy 2 in conjunct with fetal uniparental disomy and a literature review]

OBJECTIVE

To carry out genetic analysis for a fetus with confined placental mosaicism (CPM) for trisomy 2 (T2) in conjunct with fetal uniparental disomy (UPD).

METHODS

Amniocentesis and chromosomal karyotyping was carried out for a pregnant woman with a high risk for chromosome 2 anomalies indicated by non-invasive prenatal testing (NIPT). Single nucleotide polymorphism array (SNP-array) and trio-whole exome sequencing (Trio-WES) were carried out. Ultrasonography was used to closely monitor the fetal growth. Multifocal sampling of the placenta was performed after delivery for copy number variation sequencing (CNV-seq).

RESULTS

The fetus was found to have a normal chromosomal karyotype. SNP-array has revealed multiple regions with loss of heterozygosity (LOH) on chromosome 2. Trio-WES confirmed the presence of maternal UPD for chromosome 2. Ultrasonography has revealed intrauterine growth restriction and oligohydramnios. Intrauterine fetal demise had occurred at 23+4 weeks of gestation. Pathological examination had failed to find salient visceral abnormality. The placenta was proved to contain complete T2 by CNV-seq.

CONCLUSION

T2 CPM can cause false positive result for NIPT and may be complicated with fetal UPD, leading to adverse obstetric outcomes such as intrauterine growth restriction, oligohydramnios and intrauterine fetal demise.

Prognostic and Pharmacotypic Heterogeneity of Hyperdiploidy in Childhood ALL

PURPOSE

High hyperdiploidy, the largest and favorable subtype of childhood ALL, exhibits significant biological and prognostic heterogeneity. However, factors contributing to the varied treatment response and the optimal definition of hyperdiploidy remain uncertain.

METHODS

We analyzed outcomes of patients treated on two consecutive frontline ALL protocols, using six different definitions of hyperdiploidy: chromosome number 51-67 (Chr51-67); DNA index (DI; DI1.16-1.6); United Kingdom ALL study group low-risk hyperdiploid, either trisomy of chromosomes 17 and 18 or +17 or +18 in the absence of +5 and +20; single trisomy of chromosome 18; double trisomy of chromosomes 4 and 10; and triple trisomy (TT) of chromosomes 4, 10, and 17. Additionally, we characterized ALL ex vivo pharmacotypes across eight main cytotoxic drugs.

RESULTS

Among 1,096 patients analyzed, 915 had B-ALL and 634 had pharmacotyping performed. In univariate analysis, TT emerged as the most favorable criterion for event-free survival (EFS; 10-year EFS, 97.3% v 86.8%; P = .0003) and cumulative incidence of relapse (CIR; 10-year CIR, 1.4% v 8.8%; P = .002) compared with the remaining B-ALL. In multivariable analysis, accounting for patient numbers using the akaike information criterion (AIC), DI1.16-1.6 was the most favorable criterion, exhibiting the best AIC for both EFS (hazard ratio [HR], 0.45; 95% CI, 0.23 to 0.88) and CIR (HR, 0.45; 95% CI, 0.21 to 0.99). Hyperdiploidy and subgroups with favorable prognoses exhibited notable sensitivities to asparaginase and mercaptopurine. Specifically, asparaginase sensitivity was associated with trisomy of chromosomes 16 and 17, whereas mercaptopurine sensitivity was linked to gains of chromosomes 14 and 17.

CONCLUSION

Among different definitions of hyperdiploid ALL, DI is optimal based on independent prognostic impact and also the large proportion of low-risk patients identified. Hyperdiploid ALL exhibited particular sensitivities to asparaginase and mercaptopurine, with chromosome-specific associations.

A novel case of 16q22.3 duplication syndrome in a child with overgrowth: case report and literature review

BACKGROUND

Distal chromosome 16 duplication syndrome (also known as 16q partial trisomy) is a very rare genetic disorder recently described in few clinical reports. 16q trisomy is generally associated with a multisystemic phenotype including intrauterine growth restriction (IUGR), brain and cardiac defects, intellectual disability (ID) and an increased risk of both prenatal and postnatal lethality. Smaller copy number variants (CNV) within the 16q region create partial trisomies, which occur less frequently than full trisomy 16q.

CASE PRESENTATION

We present the clinical case of a 12-years-old male with a 16q22.3q24.1 de novo heterozygous duplication whose phenotype was characterized by ID, facial dysmorphisms, stature and weight overgrowth. To date, only five other cases of this syndrome have been reported in scientific literature, and none of them comprised overgrowth.

CONCLUSIONS

Our case report highlights the great heterogeneity in clinical manifestations and provides new evidence for better defining the phenotypic picture for smaller 16q distal CNVs, suggesting unusual features.

Cell-free DNA-based prenatal screening via rolling circle amplification: Identifying and resolving analytic issues

OBJECTIVE

A rolling circle amplification (RCA) based commercial methodology using cell-free (cf)DNA to screen for common trisomies became available in 2018. Relevant publications documented high detection but with a higher than expected 1% false positive rate. Preliminary evidence suggested assay variability was an issue. A multi-center collaboration was created to explore this further and examine whether subsequent manufacturer changes were effective.

METHODS

Three academic (four devices) and two commercial (two devices) laboratories provided run date, chromosome 21, 18, and 13 run-specific standard deviations, number of samples run, and reagent lot identifications. Temporal trends and between-site/device consistency were explored. Proportions of run standard deviations exceeding pre-specified caps of 0.4%, 0.4% and 0.6% were computed.

RESULTS

Overall, 661 RCA runs between April 2019 and July 30, 2022 tested 39,756 samples. In the first 24, subsequent 9, and final 7 months, proportions of capped chromosome 21 runs dropped from 39% to 22% to 6.0%; for chromosome 18, rates were 76%, 36%, and 4.0%. Few chromosome 13 runs were capped using the original 0.60%, but capping at 0.50%, rates were 28%, 16%, and 7.6%. Final rates occurred after reformulated reagents and imaging software modifications were fully implemented across all devices. Revised detection and false positive rates are estimated at 98.4% and 0.3%, respectively. After repeat testing, failure rates may be as low as 0.3%.

CONCLUSION

Current RCA-based screening performance estimates are equivalent to those reported for other methods, but with a lower test failure rate after repeat testing.

Significant improvement in survival outcomes of trisomy 18 with neonatal intensive care compared to non-intensive care: a single-center study

Background

Trisomy 18 syndrome, also known as Edwards syndrome, is a chromosomal trisomy. The syndrome has historically been considered lethal owing to its poor prognosis, and palliative care was primarily indicated for trisomy 18 neonates. Although there have been several reports on the improvement of survival outcomes in infants with trisomy 18 syndrome through neonatal intensive care, few studies have compared the impact of neonatal intensive care on survival outcomes with that of non-intensive care. Therefore, we compared the survival-related outcomes of neonates with trisomy 18 between intensive and non-intensive care.

Methods

Seventeen infants of trisomy 18 admitted to our center between 2007 and 2019 were retrospectively studied. We divided the patients into a non-intensive group (n = 5) and an intensive group (n = 12) and evaluated their perinatal background and survival-related outcomes of the two groups.

Results

The 1- and 3-year survival rates were both 33% in the intensive group, which was significantly higher than that in the non-intensive group (p < 0.001). Half of the infants in the intensive care group were discharged alive, whereas in the non-intensive care group, all died during hospitalization (p = 0.049).

Conclusions

Neonatal intensive care for neonates with 18 trisomy significantly improved not only survival rates but also survival-discharge rates. Our findings would be helpful in providing 18 trisomy neonates with standard neonatal intensive care when discussing medical care with their parents.

Chromosome analysis of foetal tissue from 1903 spontaneous abortion patients in 5 regions of China: a retrospective multicentre study

BACKGROUND

Abnormal foetal tissue chromosome karyotypes are one of the important pathogenic factors for spontaneous abortion (SA). To investigate the age and abnormal foetal karyotypes of 1903 couples who experienced SA.

METHODS

A retrospective multicentre study collected age and foetal tissue karyotypes CNV-seq data of 1903 SA couples from 6 hospitals in 5 regions from January 2017 to March 2022. The distribution and correlation of abnormal foetal tissue karyotypes were evaluated by using regions and age.

RESULTS

In our study, 1140 couples (60.5% of the total) had abnormal foetal tissue chromosome karyotypes in all regions. We found that there were differences in the number of abnormal foetal tissue chromosome karyotypes, of which the incidence of trisomy was higher. At the same time, the populations situated in the eastern region had a more triploid (15.5%) distribution, trisomy (58.1%) in the southern region, mosaicism (14.8%) and microduplication (31.7%) in the southwestern region, microdeletion (16.7%) in the northern region. There are variances across areas, and it is more common in the north. The incidence risk of prenatal chromosomal abnormalities varied according to age group.

CONCLUSION

The findings of this study suggest that the karyotypes of patients with abnormal foetal tissue chromosome abortion in different regions were different. Meanwhile, patients ≥ 35 years old had a higher risk of abnormal foetal tissue chromosome abortion.

Complete trisomy 9 detected by noninvasive prenatal testing and confirmed by amniocentesis

Complete chromosome 9 trisomy (T9) is a rare and fatal chromosomal disorder. We performed non-invasive prenatal testing (NIPT) in a patient with threatened abortion symptoms and found that the fetal was at risk for complete chromosome 9 trisomy. This shows that NIPT has certain accuracy in detecting trisomy of chromosome 9, which provide options for prenatal diagnosis of rare chromosomal abnormalities.

Occurrence of mosaic trisomy 22 and pericentric inversion of chromosome 9 in a patient with a good prognosis

Complete trisomy 22 is a rare chromosomal condition that is incompatible with life. However, mosaic trisomy 22 usually has prolonged survival compatibility and may present a good prognosis depending on the tissues affected. Herein, we described a male patient with the occurrence of mosaic trisomy 22 associated with the inversion of chromosome 9, with karyotype 47, XY, inv (9) (p11q13), + 22 [5] / 46, XY, inv(9) (p11q13) [45] and arr 22q11.1 ~ q13.33(16,417008-51,219,009)x2 ~ 3. It is not possible to infer, in general, the clinical characteristics associated with mosaic trisomy 22. However, the patient presented common clinical features observed in reported cases (in parentheses the percentage observed comparing all reported cases): facial dysmorphia (100%), delay in motor development/growth (82%), cardiac abnormalities (73%), ear abnormalities (55%) and facial and/or body asymmetry (55%), in addition to hypotonia, skin spots, hypoplastic nails. Given the survival and quality of life associated with multidisciplinary treatment, it can be concluded that the patient has a good prognosis. Conclusively, we're presenting the occurrence of mosaic trisomy 22 and chromosome 9 inversion in the patient with favorable prognosis. Thus, this study proposed a guide which should be inserted in databases of rare genetic conditions to help genetic counselors define mosaic trisomy 22 diagnosis.

Trisomies Reorganize Human 3D Genome

Trisomy is the presence of one extra copy of an entire chromosome or its part in a cell nucleus. In humans, autosomal trisomies are associated with severe developmental abnormalities leading to embryonic lethality, miscarriage or pronounced deviations of various organs and systems at birth. Trisomies are characterized by alterations in gene expression level, not exclusively on the trisomic chromosome, but throughout the genome. Here, we applied the high-throughput chromosome conformation capture technique (Hi-C) to study chromatin 3D structure in human chorion cells carrying either additional chromosome 13 (Patau syndrome) or chromosome 16 and in cultured fibroblasts with extra chromosome 18 (Edwards syndrome). The presence of extra chromosomes results in systematic changes of contact frequencies between small and large chromosomes. Analyzing the behavior of individual chromosomes, we found that a limited number of chromosomes change their contact patterns stochastically in trisomic cells and that it could be associated with lamina-associated domains (LAD) and gene content. For trisomy 13 and 18, but not for trisomy 16, the proportion of compacted loci on a chromosome is correlated with LAD content. We also found that regions of the genome that become more compact in trisomic cells are enriched in housekeeping genes, indicating a possible decrease in chromatin accessibility and transcription level of these genes. These results provide a framework for understanding the mechanisms of pan-genome transcription dysregulation in trisomies in the context of chromatin spatial organization.

Trisomy 22: First and Second Trimester Cytogenetic Analysis and Phenotypic Presentation in a Series of Seven Cases

INTRODUCTION

Trisomy 22 is a chromosomal disorder rarely encountered prenatally. Even fewer live births are observed and generally correspond to confined placental mosaic trisomy 22, or even more uncommonly, to true fetal mosaic trisomy 22.

CASE PRESENTATION

We examine and describe a series of seven cases of trisomy 22 encountered prenatally in terms of their cytogenetic and phenotypic presentations and discuss their interrelationships along with case management and outcomes. We aimed to identify aspects of prenatal data suggestive of fetal trisomy 22 and to determine whether a prognosis can be established from these factors.

CONCLUSION

Our conclusion is that prenatal data elements can provide key elements of information to guide multidisciplinary care and support for the couple and the neonate.

Early symptoms of autism spectrum disorder (ASD) in 1-8 year old children with sex chromosome trisomies (XXX, XXY, XYY), and the predictive value of joint attention

The objective of the present study is to investigate the impact of Sex Chromosome Trisomy (SCT; XXX, XXY, XYY) on the early appearance of Autism Spectrum Disorder (ASD) symptoms, and the predictive value of Joint Attention for symptoms of ASD. SCTs are specific genetic conditions that may serve as naturalistic 'at risk' models of neurodevelopment, as they are associated with increased risk for neurobehavioral vulnerabilities. A group of 82 children with SCT (aged 1-8 years) was included at baseline of this longitudinal study. Joint Attention was measured at baseline with structured behavior observations according to the Early Social Communication Scales. ASD symptoms were assessed with the Modified Checklist for Autism in Toddlers questionnaire and Autism Diagnostic Interview-Revised in a 1-year follow-up. Recruitment and assessment took place in the Netherlands and in the United States. The results demonstrate that ASD symptoms were substantially higher in children with SCT compared to the general population, with 22% of our cohort at clinical risk for ASD, especially in the domain of social interaction and communication. Second, a predictive value of Joint Attention was found for ASD symptoms at 1-year follow-up. In this cohort, no differences were found between karyotype-subtypes. In conclusion, from a very early age, SCT can be associated with an increased risk for vulnerabilities in adaptive social functioning. These findings show a neurodevelopmental impact of the extra X or Y chromosome on social adaptive development associated with risk for ASD already from early childhood onward. These findings advocate for close monitoring and early (preventive) support, aimed to optimize social development of young children with SCT.

Wilms Tumor in Child With Trisomy 18 and Horseshoe Kidney

Trisomy 18 is associated with several congenital malformations, including horseshoe kidney. It can be full, partial, or mosaic, and mosaicism is often associated with lesser severity and longer life expectancy, placing patients at greater risk of developing neoplasms or malignancies. One common tumor among children with Trisomy 18 is Wilms tumor, which is also associated with renal congenital abnormalities such as horseshoe kidney. We present a case describing the occurrence of these three characteristics: development of Wilms tumor in a patient with Trisomy 18 and a horseshoe kidney and discuss treatment with regards to these conditions.

Low-level mosaic trisomy 21 at amniocentesis in a pregnancy associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome

OBJECTIVE

We present low-level mosaic trisomy 21 at amniocentesis in a pregnancy with a favorable fetal outcome.

CASE REPORT

A 34-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+21 [7]/46,XY [33]. At 23 weeks of gestation, repeat amniocentesis revealed a karyotype of 47,XY,+21 [4]/46,XY [22], and cord blood sampling revealed the karyotype of 47,XY,+21 [5]/46,XY [35]. The parental karyotypes were normal. Quantitative fluorescent polymerase chain reaction (QF-PCR) analysis on uncultured amniocytes and parental bloods excluded UPD 21, array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr 21q11.2q22.3 × 2.3, consistent with 30% mosaicism for trisomy 21. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 43.8% (35/80 cells) mosaicism for trisomy 21. The woman was advised to continue the pregnancy, and a phenotypically normal 3,340-g male baby was delivered at 39 weeks of gestation. The cord blood had a karyotypes of 46,XY (40/40 cells). QF-PCR on placenta showed mosaic trisomy 21. When follow-up at age three months, the neonate was normal in phenotype and development. FISH analysis on buccal mucosal cells showed 9% (10/101 cells) mosaicism for trisomy 21, compared with 0% (0/100 cells) in the normal control.

CONCLUSION

Low-level mosaic trisomy 21 at amniocentesis can be associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome.

Investigating brain alterations in the Dp1Tyb mouse model of Down syndrome

Down syndrome (DS) is one of the most common birth defects and the most prevalent genetic form of intellectual disability. DS arises from trisomy of chromosome 21, but its molecular and pathological consequences are not fully understood. In this study, we compared Dp1Tyb mice, a DS model, against their wild-type (WT) littermates of both sexes to investigate the impact of DS-related genetic abnormalities on the brain phenotype. We performed in vivo whole brain magnetic resonance imaging (MRI) and hippocampal 1H magnetic resonance spectroscopy (MRS) on the animals at 3 months of age. Subsequently, ex vivo MRI scans and histological analyses were conducted post-mortem. Our findings unveiled the following neuroanatomical and biochemical alterations in the Dp1Tyb brains: a smaller surface area and a rounder shape compared to WT brains, with DS males also presenting smaller global brain volume compared with the counterpart WT. Regional volumetric analysis revealed significant changes in 26 out of 72 examined brain regions, including the medial prefrontal cortex and dorsal hippocampus. These alterations were consistently observed in both in vivo and ex vivo imaging data. Additionally, high-resolution ex vivo imaging enabled us to investigate cerebellar layers and hippocampal sub-regions, revealing selective areas of decrease and remodelling in these structures. An analysis of hippocampal metabolites revealed an elevation in glutamine and the glutamine/glutamate ratio in the Dp1Tyb mice compared to controls, suggesting a possible imbalance in the excitation/inhibition ratio. This was accompanied by the decreased levels of taurine. Histological analysis revealed fewer neurons in the hippocampal CA3 and DG layers, along with an increase in astrocytes and microglia. These findings recapitulate multiple neuroanatomical and biochemical features associated with DS, enriching our understanding of the potential connection between chromosome 21 trisomy and the resultant phenotype.

IGH cytogenetic abnormalities can be detected in multiple myeloma by imaging flow cytometry

AIMS

Cytogenetic abnormalities involving the IGH gene are seen in up to 55% of patients with multiple myeloma. Current testing is performed manually by fluorescence in situ hybridisation (FISH) on purified plasma cells. We aimed to assess whether an automated imaging flow cytometric method that uses immunophenotypic cell identification, and does not require cell isolation, can identify IGH abnormalities.

METHODS

Aspirated bone marrow from 10 patients with multiple myeloma were studied. Plasma cells were identified by CD38 and CD138 coexpression and assessed with FISH probes for numerical or structural abnormalities of IGH. Thousands of cells were acquired on an imaging flow cytometer and numerical data and digital images were analysed.

RESULTS

Up to 30 000 cells were acquired and IGH chromosomal abnormalities were detected in 5 of the 10 marrow samples. FISH signal patterns seen included fused IGH signals for IGH/FGFR3 and IGH/MYEOV, indicating t(4;14) and t(11;14), respectively. In addition, three IGH signals were identified, indicating trisomy 14 or translocation with an alternate chromosome. The lowest limit of detection of an IGH abnormality was in 0.05% of all cells.

CONCLUSIONS

This automated high-throughput immuno-flowFISH method was able to identify translocations and trisomy involving the IGH gene in plasma cells in multiple myeloma. Thousands of cells were analysed and without prior cell isolation. The inclusion of positive plasma cell identification based on immunophenotype led to a lowest detection level of 0.05% marrow cells. This imaging flow cytometric FISH method offers the prospect of increased precision of detection of critical genetic lesions involving IGH and other chromosomal defects in multiple myeloma.

The first case report of distal 16p12.1p11.2 trisomy and proximal 16p11.2 tetrasomy inherited from both parents

Recurrent copy number variants in the chromosomal region 16p11.2 are among the most frequent genetic causes of neurodevelopmental disorders. The increasing prevalence of brain structural anomalies is also associated with 16p11.2 deletions and duplications. We report on a four-year-old boy with microcephaly, trigonocephaly, and dysmorphic features. The patient also exhibited motor delay and autism spectrum disorder. Microarray analysis showed a single-copy gain of a 1.187 kb segment in the 16p12.1p11.2 region and a two-copy gain of a 525 kb segment in the 16p11.2 region. Parental analysis revealed a 1.7 Mb duplication at the 16p12.1p11.2 (BP1-BP5 region) in the father and a 525 kb duplication in the 16p11.2 region (BP4-BP5) in the mother. The patient inherited the entire abnormality from each parent and, as a result, presented with partial trisomy of the 16p12.1p11.2 region and partial tetrasomy of the 16p11.2 region. The MLPA P343 Autism-1 Probemix was used to verify the copy number gains in the 16p11.2 region detected by chromosomal microarray analysis. Double duplications are very rare chromosomal rearrangements. The phenotype for distal 16p12.1p11.2 trisomy (BP1-BP3) and proximal 16p11.2 (BP4-BP5) tetrasomy is unknown. To our knowledge, this is the first patient described in the literature who inherited 16p11.2 duplications from both parents.

Double Trisomy 16 and 22 Clinically Mimic Partial Hydatidiform Mole in a Case of Subsequent Pregnancy Loss

A case of double trisomy 16 and 22 in the second pregnancy loss is presented. DNA analyses (short tandem repeats genotyping) of miscarriage specimen was indicated because of ultrasound suspicion of partial hydatidiform mole. After the partial hydatidiform mole exclusion, further DNA analyses focused on the most common aneuploidies causing pregnancy loss, detected double trisomy 16 and 22 in the product of conception. The couple was referred to clinical genetic consultation and normal parental karyotypes were proved. For further explanatory purposes, archived material from the first pregnancy loss was analyzed and trisomy of chromosome 18 was detected. By comparison of allelic profiles of the mother, father, and both losses, the maternal origin of all aneuploidies was proven what can be attributed to frequent meiosis errors, probably due to advanced maternal age (44 years at the first loss and 45 years at the second loss). In conclusion, aneuploidies can mimic partial hydatidiform mole. Genetic analysis is helpful on the one hand to rule out partial hydatidiform mole and on the other hand to identify aneuploidies and in this way to determine the cause of miscarriage.

Identification of Fetuses at Increased Risk of Trisomies in the First Trimester Using Axial Planes

INTRODUCTION

The measurement of nuchal translucency (NT) is crucial for assessing risk of aneuploidies in the first trimester. We investigate the ability of NT assessed by a transverse view of the fetal head to detect fetuses at increased risk of common aneuploidies at 11-13 weeks of gestation.

METHODS

We enrolled a nonconsecutive series of women who attended our outpatient clinic from January 2020 to April 2021 for aneuploidy screening by means of a first trimester combined test. All women were examined by operators certified by the Fetal Medicine Foundation. In each patient, NT measurements were obtained both from the median sagittal view and transverse view. We calculated the risk of aneuploidy using NT measurements obtained both with sagittal and axial scans, and then we compared the results.

RESULTS

A total of 1,023 women were enrolled. An excellent correlation was found between sagittal and transverse NT measurements. The sensitivity and specificity of the axial scan to identify fetuses that were deemed at risk of trisomy 21 using standard sagittal scans were 40/40 = 100.0% (95% confidence interval [CI]: 91.2-100.0) and 977/983 = 99.4% (95% CI: 98.7-99.7), respectively. The sensitivity and specificity of the axial scan to identify fetuses at risk of trisomy 13 or 18 were 16/16 = 100.0% (95% CI: 80.6-100.0) and 1,005/1,007 = 99.8% (95% CI: 99.3-99.9).

CONCLUSIONS

When the sonogram, a part of combined test screening, is performed by an expert sonologist, axial views can reliably identify fetuses at increased risk of trisomies without an increase in false negative results.

Assessing the value of second-trimester nasal bone hypoplasia in predicting chromosomal abnormalities: a retrospective chromosomal microarray analysis of 351 fetuses

PURPOSE

To evaluate the value of fetal nasal bone hypoplasia and other prenatal risk factors in predicting chromosomal abnormalities.

METHODS

In this retrospective cohort study, we collected data on singleton pregnancies diagnosed with fetal nasal bone hypoplasia during second-trimester ultrasound. Fetal karyotyping and chromosomal microarray analysis (CMA) were performed, and pregnancy outcomes were assessed. The association between fetal nasal bone hypoplasia and chromosomal abnormalities was evaluated according to whether other prenatal risk factors were observed.

RESULTS

Our final analysis included 351 pregnancies, of which 62 (17.7%) fetuses had chromosomal abnormalities, including 36 cases of trisomy-21, six cases of trisomy-18, one case each of trisomy-13, and 47, XYY syndrome, and 18 cases of copy number variations (CNVs). Among the 243 cases of isolated nasal bone hypoplasia, 28 (11.5%) cases of chromosomal aberrations were identified. The incidence was significantly higher if other soft markers or structural abnormalities were simultaneously detected. Pregnancy was terminated in 43 aneuploid fetuses and nine fetuses detected with CNVs. The parents of the fetuses diagnosed with 47, XYY syndrome and the other nine CNVs chose to continue the pregnancy, and no abnormalities were detected in the newborns. Furthermore, we found that other prenatal risk factors should be considered in evaluating the likelihood of chromosomal abnormalities in fetuses with nasal bone hypoplasia.

CONCLUSIONS

Nasal bone hypoplasia is a highly specific soft marker that is associated with multiple chromosomal abnormalities. The risk of chromosomal abnormalities increases when combined with structural abnormalities or increased nuchal translucency (NT). Chromosomal microarray analysis is a powerful prenatal test for chromosomal abnormalities, which may be warranted in fetuses with nasal bone hypoplasia.

Single-nucleus RNA sequencing reveals cell type-specific transcriptome alterations of Down syndrome hippocampus using the Dp16 mouse model

BACKGROUND

Down syndrome (DS), the most frequently occurring human chromosomal disorder, is caused by trisomy 21. The exact molecular effects of trisomy on certain cell populations in the brain remain poorly understood.

OBJECTIVE

The purpose of this study was to investigate the effects of trisomy on the transcriptomes of various types of neurons and nonneuronal cells in the hippocampus.

METHODS

A total of 8993 nuclei from the WT and 6445 nuclei from the Dp16 hippocampus were analyzed by single-nucleus RNA sequencing (snRNA-seq). Cell clustering was achieved by the Seurat program.

RESULTS

Hippocampal cells were grouped into multiple neuronal and nonneuronal populations. Only a limited number of trisomic genes were upregulated (q < 0.001) over 1.25-fold in a specific type of hippocampal cell. Specifically, deregulation of genes associated with synaptic signaling and organization was observed in multiple cell populations, including excitatory neurons, oligodendrocytes, and microglia. This observation suggests the potential importance of synapse deficits in DS. Interestingly, GO annotation of the upregulated genes suggested potential activation of the immune system by hippocampal excitatory neurons. Fewer trisomic genes were altered in nonneuronal cells than in neurons. Notably, microglial transcriptome analysis revealed significantly (q < 0.001) increased expression of C1qb and C1qc, which suggested potential involvement of complement-mediated synapse loss mediated by microglia in DS.

CONCLUSION

The trisomy-related hippocampal deficits should be driven by a small amount, not all, of the trisomic genes in a specific type of cell. Our work may help to narrow down both the molecular and cellular targets for future gene therapies in DS.