Reduced telomere length in amniocytes: an early biomarker of abnormal fetal development?

Telomeres protect chromosome ends and control cell division and senescence. During organogenesis, telomeres need to be long enough to ensure the cell proliferation necessary at this stage of development. Previous studies have shown that telomere shortening is associated with growth retardation and congenital malformations. However, these studies were performed in newborns or postnatally, and data on telomere length (TL) during the prenatal period are still very limited. We measured TL using quantitative PCR in amniotic fluid (AF) and chorionic villi (CV) samples from 69 control fetuses with normal ultrasound (52 AF and 17 CV) and 213 fetuses (165 AF and 48 CV) with intrauterine growth retardation (IUGR) or congenital malformations diagnosed by ultrasound. The samples were collected by amniocentesis at the gestational age (GA) of 25.0 ± 5.4 weeks and by CV biopsy at 18.1 ± 6.3 weeks. In neither sample type was TL influenced by GA or fetal sex. In AF, a comparison of abnormal versus normal fetuses showed a significant telomere shortening in cases of IUGR (reduction of 34%, P < 10-6), single (29%, P < 10-6) and multiple (44%, P < 10-6) malformations. Similar TL shortening was also observed in CV from abnormal fetuses but to a lesser extent (25%, P = 0.0002; 18%, P = 0.016; 20%, P = 0.004, respectively). Telomere shortening was more pronounced in cases of multiple congenital anomalies than in fetuses with a single malformation, suggesting a correlation between TL and the severity of fetal phenotype. Thus, TL measurement in fetal samples during pregnancy could provide a novel predictive marker of pathological development.

Antenatal ultrasound features of isolated recurrent copy number variation in 7q11.23 (Williams syndrome and 7q11.23 duplication syndrome).

OBJECTIVE: We aimed to gather fetal cases carrying a 7q11.23 copy number variation (CNV) and collect precise clinical data to broaden knowledge of antenatal features in these syndromes. METHODS: We retrospectively recruited unrelated cases with 7q11.23 deletion, known as Williams-Beuren syndrome (WBS), or 7q11.23 duplication who had prenatal ultrasound findings. We collected laboratory and clinical data, fetal ultrasound, cardiac ultrasound and fetal autopsy reports from 18 prenatal diagnostic centers throughout France. RESULTS: 40 fetuses with WBS were collected and the most common features were intra-uterine growth retardation (IUGR) (70.0%, 28/40), cardiovascular defects (30.0%, 12/40), polyhydramnios (17.5%, 7/40) and protruding tongue (15.0%, 6/40). Fetal autopsy reports were available for 11 cases and were compared with ultrasound prenatal features. Four cases of fetuses with 7q11.23 microduplication were collected and prenatal ultrasound signs were variable and often isolated. CONCLUSION: This work strengthens the fact that 7q11.23 CNVs are associated with a broad spectrum of antenatal presentations. IUGR and cardiovascular defects were the most frequent ultrasound signs. By reporting the biggest series of antenatal WBS, we aim to better delineate distinctive signs in fetuses with 7q11.23 CNVs.

Terminal 6q deletions cause brain malformations, a phenotype mimicking heterozygous DLL1 pathogenic variants: A multicenter retrospective case series.

OBJECTIVE: Terminal 6q deletion is a rare genetic condition associated with a neurodevelopmental disorder characterized by intellectual disability and structural brain anomalies. Interestingly, a similar phenotype is observed in patients harboring pathogenic variants in the DLL1 gene. Our study aimed to further characterize the prenatal phenotype of this syndrome as well as to attempt to establish phenotype-genotype correlations. METHOD: We collected ultrasound findings from 22 fetuses diagnosed with a pure 6qter deletion. We reviewed the literature and compared our 22 cases with 14 fetuses previously reported as well as with patients with heterozygous DLL1 pathogenic variants. RESULTS: Brain structural alterations were observed in all fetuses. The most common findings (>70%) were cerebellar hypoplasia, ventriculomegaly, and corpus callosum abnormalities. Gyration abnormalities were observed in 46% of cases. Occasional findings included cerebral heterotopia, aqueductal stenosis, vertebral malformations, dysmorphic features, and kidney abnormalities. CONCLUSION: This is the first series of fetuses diagnosed with pure terminal 6q deletion. Based on our findings, we emphasize the prenatal sonographic anomalies, which may suggest the syndrome. Furthermore, this study highlights the importance of chromosomal microarray analysis to search for submicroscopic deletions of the 6q27 region involving the DLL1 gene in fetuses with these malformations.

Spatial organization of chromosome territories in the interphase nucleus of trisomy 21 cells.

In the interphase cell nucleus, chromosomes adopt a conserved and non-random arrangement in subnuclear domains called chromosome territories (CTs). Whereas chromosome translocation can affect CT organization in tumor cell nuclei, little is known about how aneuploidies can impact CT organization. Here, we performed 3D-FISH on control and trisomic 21 nuclei to track the patterning of chromosome territories, focusing on the radial distribution of trisomic HSA21 as well as 11 disomic chromosomes. We have established an experimental design based on cultured chorionic villus cells which keep their original mesenchymal features including a characteristic ellipsoid nuclear morphology and a radial CT distribution that correlates with chromosome size. Our study suggests that in trisomy 21 nuclei, the extra HSA21 induces a shift of HSA1 and HSA3 CTs out toward a more peripheral position in nuclear space and a higher compaction of HSA1 and HSA17 CTs. We posit that the presence of a supernumerary chromosome 21 alters chromosome compaction and results in displacement of other chromosome territories from their usual nuclear position.

Risk estimation of uniparental disomy of chromosome 14 or 15 in a fetus with a parent carrying a non-homologous Robertsonian translocation. Should we still perform prenatal diagnosis?

OBJECTIVE: Uniparental disomy (UPD) testing is currently recommended during pregnancy in fetuses carrying a balanced Robertsonian translocation (ROB) involving chromosome 14 or 15, both chromosomes containing imprinted genes. The overall risk that such a fetus presents a UPD has been previously estimated to be around ~0.6-0.8%. However, because UPD are rare events and this estimate has been calculated from a number of studies of limited size, we have reevaluated the risk of UPD in fetuses for whom one of the parents was known to carry a nonhomologous ROB (NHROB). METHOD: We focused our multicentric study on NHROB involving chromosome 14 and/or 15. A total of 1747 UPD testing were performed in fetuses during pregnancy for the presence of UPD(14) and/or UPD(15). RESULT: All fetuses were negative except one with a UPD(14) associated with a maternally inherited rob(13;14). CONCLUSION: Considering these data, the risk of UPD following prenatal diagnosis of an inherited ROB involving chromosome 14 and/or 15 could be estimated to be around 0.06%, far less than the previous estimation. Importantly, the risk of miscarriage following an invasive prenatal sampling is higher than the risk of UPD. Therefore, we do not recommend prenatal testing for UPD for these pregnancies and parents should be reassured.

Sperm meiotic segregation of a balanced interchromosomal reciprocal insertion resulting in recurrent spontaneous miscarriage.

RESEARCH QUESTION: Is sperm fluorescence in-situ hybridization (FISH) useful to evaluate the risk of chromosomally unbalanced gametes in interchromosomal reciprocal insertion (IRI) carriers? How do these imbalances lead to recurrent miscarriages? DESIGN: This study reports a clinical and molecular study of a rare familial balanced IRI resulting in recurrent spontaneous miscarriage. Sperm FISH was performed to estimate the number of unbalanced gametes. RESULTS: A 31-year-old healthy male (proband) and his 28-year-old female partner were referred to the Genetics Department for three spontaneous miscarriages occurring during the first trimester of pregnancy. FISH analysis of the proband with the LSI TRA/D (14q11.2) and DiGeorge N25 (22q11.2) break-apart probes showed the presence of a balanced IRI between 14q11.2 and 22q11.2 chromosomal regions. This IRI was also identified in the proband's father. Sperm FISH with the same probes showed that more than 40% of gametes of the proband were unbalanced for either 14q11.2 or 22q11.2, despite normal sperm parameters. FISH analysis of a product of conception indicated that unbalanced gametes result in a non-viable fetus. CONCLUSIONS: This study shows the value of sperm FISH analysis in improving genetic reproductive advice for IRI carriers. Disruption of critical genes through this rearrangement and their consequent functional impairment could result in recurrent miscarriages. In this case, several genes located in the 14q11.2 region, particularly RNase 3, would be good candidates to explain the lethality of the imbalances.

Impact of prenatal diagnosis on the outcome of patients with a transposition of great arteries: A 24-year population-based study.

BACKGROUND: Transposition of great arteries (TGA) defined as the combination of concordant atrioventricular and discordant ventriculo-arterial connections is one of the most common congenital heart defects. Prenatal diagnosis of TGA remains difficult. To determine the impact of antenatal diagnosis we evaluated the sensitivity of antenatal detection and the neonatal mortality of TGA considering two study periods and two major types of TGA. METHODS: A cross-sectional study was performed. Data were collected from a French population-based birth defect registry. From 1988 to 2012, 94 fetuses with TGA were registered. The study period was subdivided into the 1988 to 1999 period and the 2000 to 2012 period. Two types of TGA were considered: isolated TGA (n = 66) and associated TGA (n = 28). A stratified analysis was performed considering the study periods and the types of TGA. RESULTS: Considering the study periods, the sensitivity of prenatal detection of TGA increased significantly (9.8% vs. 51.5%, p = 0.0001). The same trend was found for associated TGA (4.8% vs. 33.3%, p = 0.002) and isolated TGA (21.1% vs. 100%, p < 0.001). A late diagnosis of TGA (7 days after birth) was observed in 13.2% of cases. Neonatal mortality decreased significantly over time for isolated TGA (25.0% vs. 0 p = 0.01). Prenatal diagnosis of both types of TGA did not improve survival. CONCLUSION: We demonstrated that prenatal diagnosis and neonatal mortality of TGA varied greatly according to the malformation type and the study period. This could be explained by an improvement in terms of medical management.

A novel 2q14.1q14.3 deletion involving GLI2 and RNU4ATAC genes associated with partial corpus callosum agenesis and severe intrauterine growth retardation.

BACKGROUND: Microdeletions encompassing chromosome bands 2q14.1q14.3 are rare. To date, eight reports of relatively large deletions of this region (∼20 Mb) but only two small deletions (<6 Mb) have been reported. These deletions can cause a variable phenotype depending on the size and location of the deletion. Cognitive disability, facial dysmorphism, and postnatal growth retardation are the most common phenotypic features. CASE: We report on a novel 5.8 Mb deletion of 2q14.1q14.3 identified by array comparative genomic hybridization in a fetus with severe intrauterine growth retardation and partial agenesis of the corpus callosum. The deletion contained 24 coding genes including STEAP3, GLI2, and RNU4ATAC and was inherited from the mild affected mother. A sibling developmental delay and similar dysmorphic facial features was found to have inherited the same deletion. CONCLUSION: This case emphasizes the variable expressivity of the 2q14 microdeletion and reinforces the hypothesis that agenesis of corpus callosum, microcephaly, developmental delay, and distinctive craniofacial features may be part of the phenotypic spectrum characterizing the affected patients. We suggest that GLI2 is a dosage-sensitive gene that may be responsible for the agenesis of corpus callosum observed in the proband. Birth Defects Research (Part A) 106:793-797, 2016. © 2016 Wiley Periodicals, Inc.

Prenatal Screening of 21 Microdeletion/Microduplication Syndromes and Subtelomeric Imbalances by MLPA in Fetuses with Increased Nuchal Translucency and Normal Karyotype.

Fetuses with increased nuchal translucency thickness (NT) are at increased risk for chromosomal abnormalities. In case of a normal karyotype, a minority of them may present with structural abnormalities or genetic syndromes, which may be related to submicroscopic chromosomal imbalances. The objective of this study was to evaluate whether MLPA screening of 21 syndromic and subtelomeric regions could improve the detection rate of small chromosomal aberrations in fetuses with increased NT and a normal karyotype. A total of 106 prenatal samples from fetuses with NT ≥ 99th centile and normal R- and G-banding were analyzed by MLPA for subtelomeric imbalances (SALSA P036 and P070) and 21 syndromic regions (SALSA P245). One sample showed a benign CNV (dup(8)pter, FBXO25 gene), and 1 patient was found to have a loss of 18 qter and a gain of 5 pter as a result of an unbalanced translocation. The incidence of cryptic pathogenic variants was <1% or 2.7% when only fetuses with other ultrasound abnormalities were taken into account. Submicroscopic imbalances in fetuses with increased NT may be individually rare, and genome-wide screening seems more likely to improve the diagnostic yield in these fetuses.

Congenital diaphragmatic hernia may be associated with 17q12 microdeletion syndrome.

Microdeletions of 17q12 encompassing TCF2 are associated with maturity-onset of diabetes of the young type 5, cystic renal disease, pancreatic atrophy, Mullerian aplasia in females and variable cognitive impairment. We report on a patient with a de novo 17q12 microdeletion, 1.8 Mb in size, associated with congenital diaphragmatic hernia (CDH). The 5-year-old male patient presented multicystic renal dysplasia kidneys, minor facial dysmorphic features and skeletal anomalies, but neither developmental delay nor behavioral abnormalities. CDH has been previously associated with the 17q12 microdeletion syndrome only in one prenatal case. The present study reinforces the hypothesis that CDH is part of the phenotype for 17q12 microdeletion and that 17q12 encompasses candidate(s) gene(s) involved in diaphragm development. We suggest that PIGW, a gene involved in an early step of GPI biosynthesis, could be a strong candidate gene for CDH.

Prenatal diagnosis of the VACTERL association using routine ultrasound examination.

BACKGROUND: The prognosis and early neonatal management of the VACTERL association depend mainly on the severity of malformations ascertained prenatally. METHODS: Here we reviewed the spectrum of clinical features observed in cases of VACTERL association ascertained prenatally through ultrasound examination but examined at birth and compared them with cases ascertained postnatally. RESULTS: From 1995 to 2011, a total of 19 cases of VACTERL association were observed in our center; 10 were ascertained prenatally and confirmed after birth whereas 9 were ascertained only after birth. The types and frequencies of malformations observed prenatally were as follows: renal malformations (45%), tracheoesophageal fistula (44%), cardiac malformations (20%), vertebral (13%), and limb (11%) defects. Anal atresia was never detected using routine prenatal ultrasound examination. CONCLUSION: Further studies of fetuses with the VACTERL association are necessary to better delineate the malformations spectrum observed prenatally to improve the early recognition of the VACTERL association.

De novo 2q36.1q36.3 interstitial deletion involving the PAX3 and EPHA4 genes in a fetus with spina bifida and cleft palate.

BACKGROUND: Interstitial 2q36 deletion is a rare event. Only two previously published cases of 2q36 deletions were characterized using array-CGH. This is the first case diagnosed prenatally. METHODS: We report on the prenatal diagnosis of a 2q36.1q36.3 interstitial deletion in a fetus with facial dysmorphism, spina bifida, and cleft palate. RESULTS: Array-CGH analysis revealed a 5.6 Mb interstitial deletion of the long arm of chromosome 2q36.1q36.3, including the PAX3 and EPHA4 genes. CONCLUSION: The present study reinforces the hypothesis that PAX3 haploinsufficiency may be associated with neural tube defects in humans and suggests that the EPHA4 gene might be implicated during palate development. This report also illustrates the added value of array-CGH to detect cryptic chromosomal imbalances in malformed fetuses and to improve genetic counseling prenatally.

A new case of 8q22.1 microdeletion restricts the critical region for Nablus mask-like facial syndrome.

Microdeletions of 8q21.3-8q22.1 have been identified in all patients with Nablus mask-like facial syndrome (NMLFS). A recent report of a patient without this specific phenotype presented a 1.6 Mb deletion in this region that partially overlapped with previously reported 8q21.3 microdeletions, thus restricting critical region for this syndrome. We report on another case of an 8q21.3 deletion revealed by array comparative genome hybridization (aCGH) in a 4-year-old child with global developmental delay, autism, microcephaly, but without Nablus phenotype. The size of the interstitial deletion was estimated to span 5.2 Mb. By combining the data from previous reports on 8q21.3-8q22.1 deletions and our case, we were able to narrow the critical region of Nablus syndrome to 0.5 Mb. The deleted region includes FAM92A1, which seems to be a potential candidate gene in NMLFS.

Prenatal ultrasound findings observed in the Wolf-Hirschhorn syndrome: data from the registry of congenital malformations in Auvergne.

BACKGROUND: Wolf-Hirschhorn syndrome (WHS) is associated with facial dysmorphism including high forehead, high nasal bridge, hypertelorism and severe mental retardation. WHS results from a 4p16.3 deletion. Only a small number of reports have been made on the prenatal ultrasound findings observed in WHS. CASES: Here we report our experience on 10 cases of WHS ascertained prenatally between 1983 and 2009 through the CEMC-Auvergne registry of congenital malformations. CONCLUSION: The assumption that a "Greek warrior helmet" facies is pathognomonic of WHS could lead to misdiagnosis. Other clinical findings such as severe and early onset intrauterine growth retardation, facial dysmorphism (high forehead, high nasal bridge, low-set ears, micrognathia, hypertelorism), atrial or ventricular septal defect, and renal dysplasia should help obstetricians to suspect the diagnosis of WHS prenatally.

Optical Genome Mapping in Routine Cytogenetic Diagnosis of Acute Leukemia.

Cytogenetic aberrations are found in 65% of adults and 75% of children with acute leukemia. Specific aberrations are used as markers for the prognostic stratification of patients. The current standard cytogenetic procedure for acute leukemias is karyotyping in combination with FISH and RT-PCR. Optical genome mapping (OGM) is a new technology providing a precise identification of chromosomal abnormalities in a single approach. In our prospective study, the results obtained using OGM and standard techniques were compared in 29 cases of acute myeloid (AML) or lymphoblastic leukemia (ALL). OGM detected 73% (53/73) of abnormalities identified by standard methods. In AML cases, two single clones and three subclones were missed by OGM, but the assignment of patients to cytogenetic risk groups was concordant in all patients. OGM identified additional abnormalities in six cases, including one cryptic structural variant of clinical interest and two subclones. In B-ALL cases, OGM correctly detected all relevant aberrations and revealed additional potentially targetable alterations. In T-ALL cases, OGM characterized a complex karyotype in one case and identified additional abnormalities in two others. In conclusion, OGM is an attractive alternative to current multiple cytogenetic testing in acute leukemia that simplifies the procedure and reduces costs.

Feasibility of Optical Genome Mapping from Placental and Umbilical Cord Sampled after Spontaneous or Therapeutic Pregnancy Termination.

Optical genome mapping (OGM) is an alternative to classical cytogenetic techniques to improve the detection rate of clinically significant genomic abnormalities. The isolation of high-molecular-weight (HMW) DNA is critical for a successful OGM analysis. HMW DNA quality depends on tissue type, sample size, and storage conditions. We assessed the feasibility of OGM analysis of DNA from nine umbilical cord (UC) and six chorionic villus (CV) samples collected after the spontaneous or therapeutic termination of pregnancy. We analyzed quality control metrics provided by the Saphyr system (Bionano Genomics) and assessed the length of extracted DNA molecules using pulsed-field capillary electrophoresis. OMG data were successfully analyzed for all six CV samples. Five of the UC samples did not meet the Saphyr quality criteria, mainly due to poor DNA quality. In this regard, we found that DNA quality assessment with pulsed-field capillary electrophoresis can predict a successful OGM analysis. OGM data were fully concordant with the results of standard cytogenetic methods. Moreover, OGM detected an average of 14 additional structural variants involving OMIM genes per sample. On the basis of our results, we established the optimal conditions for sample storage and preparation required for a successful OGM analysis. We recommend checking DNA quality before analysis with pulsed-field capillary electrophoresis if the storage conditions were not ideal or if the quality of the sample is poor. OGM can therefore be performed on fetal tissue harvested after the termination of pregnancy, which opens up the perspective for improved diagnostic yield.

Optical genome mapping for prenatal diagnosis: A prospective study.

PURPOSE: Cytogenetic analysis provides important information for prenatal decision-making and genetic counseling. Optical genome mapping (OGM) has demonstrated its performances in retrospective studies. In our prospective study, we assessed the quality of DNA obtained from cultures of amniotic fluid (AF) and chorionic villi (CV) and evaluated the ability of OGM to detect all clinically relevant aberrations identified by standard methods. METHODS: A total of 37 prenatal samples from pregnancies with a fetal anomaly on ultrasound were analyzed prospectively by OGM between January 1, 2021 and June 31, 2022. OGM results were interpreted blindly and compared to the results obtained by standard techniques. RESULTS: OGM results were interpretable in 92% of samples. We observed 100% concordance between OGM and karyotype and/or chromosomal microarray results. In addition, OGM identified a median of 30 small (<100 kb) structural variations per case with the involvement of 12 OMIM genes, of which 3 were OMIM morbid genes. CONCLUSION: This prospective study showed OGM performed well in detecting genomic alterations in cell cultures from prenatal samples. The place of OGM in relation to CMA or exome sequencing remains to be defined in order to optimize the prenatal diagnostic procedure.

Further refining the critical region of 10q26 microdeletion syndrome: A possible involvement of INSYN2 and NPS in the cognitive phenotype.

BACKGROUND: The 10q26 subtelomeric microdeletion syndrome is a rare and clinically heterogeneous disorder. The precise relationships between the causative genes and the phenotype are unclear. CASE PRESENTATION: We report two new cases of 860 kb deletion of 10q26.2 identified by array CGH in a fetus with intrauterine growth retardation and his mother. The deleted region encompassed only four coding genes, DOCK1, INSYN2, NPS and FOX12. The proband had dysmorphic facies characterized by a high forehead, malformed ears, a prominent nose, and retrognathia. He had bilateral club feet, clinodactily and mild psychomotor retardation. His mother had a short stature, microcephaly, a long face with a high forehead and bitemporal narrowing, arched and sparse eyebrows, strabismus, prominent nose and chin, a thin upper lip and large protruding ears, and mild intellectual disability. CONCLUSIONS: This study presents the smallest 10q26.2 deletion so far identified, which further refines the minimal critical region associated with the 10q26 microdeletion syndrome. It focuses on three genes potentially responsible for the phenotype: DOCK1, which is the major candidate gene, and INSYN2 and NPS, which could be involved in cognitive functions.

Prenatal detection of cryptic rearrangements by multiplex ligation probe amplification in fetuses with ultrasound abnormalities.

PURPOSE: Congenital malformations are a major cause of morbidity and mortality in newborn infants, and genomic imbalances are a significant component of their etiology. The aim of this study was to evaluate the ability of prenatal multiplex ligation probe amplification screening to detect cryptic chromosomal imbalances in fetuses with ultrasound abnormalities of unknown etiology. METHODS: Multiplex ligation probe amplification was performed with three separate sets of probes: two for subtelomeric regions and one for mental retardation syndrome loci. Sixty-one fetuses with significant ultrasound anomalies and normal karyotype at a minimum of 400-band resolution were tested between January 2007 and January 2009. RESULTS: We identified four unbalanced rearrangements: one del 18pter/amp 5pter, one del 9pter, one 15q11q13 microdeletion, and one 22q11 microdeletion with atypical presentation. After genetic counseling, two of the pregnancies were terminated. CONCLUSION: Multiplex ligation probe amplification analysis was able to identify clinically significant rearrangements in 6.5% of fetuses with prenatally identified sonographic abnormalities. This prospective study highlights that multiplex ligation probe amplification screening of fetuses with ultrasound abnormalities in the prenatal period is technically feasible and relevant for diagnosis and prognosis.