Molecular cytogenetic characterization of a duplication of 15q24.2-q26.2 associated with anencephaly and neural tube defect

Novel autopsy and genetic findings in an acardiac twin: case report and literature review

Twin reversed arterial perfusion (TRAP) sequence is a rare complication of monochorionic twinning whereby a donor twin perfuses an acardiac twin via aberrant vascular anastomoses. The resulting paradoxical retrograde blood flow supplying the acardiac twin is oxygen-poor, leading to some of the most severe malformations encountered in humans. Though the first descriptions of acardiac twins date back to at least the 16th century, the pathophysiologic processes which underpin the development of TRAP sequence are still being elucidated. Theories on the pathogenesis of TRAP sequence include deficiencies intrinsic to the embryo and primary abnormalities of the placental vasculature. Autopsy studies continue to provide clues to the underlying pathogenesis of TRAP sequence, and the characterization of the spectrum of manifestations that can be observed in acardiac twins. Herein, we present the clinical, autopsy, and molecular findings in a unique case of TRAP sequence. Novel findings include a primitive cloaca-like structure and chromosomal aberrations involving 6q11.1 and 15q25.1.

A Novel Variant of the CHD2 Gene Associated With Developmental Delay and Myoclonic Epilepsy

Pathogenic variants in CHD2 have been reported to have a wide range of phenotypic variability in neurodevelopmental disorders, such as early-onset epileptic encephalopathy, developmental delay, and behavior problems. So far, there is no clear correlation between genotypes and phenotypes. This study reports a Chinese patient with a novel heterozygous CHD2 mutation (c.4318C>T, pArg1440*). Her main clinical manifestations include developmental delay, myoclonic epilepsy, and hypothyroidism. Then, we reviewed a total of 144 individuals carrying CHD2 variants with epileptic encephalopathy. In terms of clinical manifestations, these patients are usually described with variable epilepsy phenotypes, including idiopathic photosensitive occipital epilepsy, Dravet syndrome, Jeavons syndrome, Lennox–Gastaut syndrome, juvenile myoclonic epilepsy, and non-specific epileptic encephalopathy. Among them, myoclonic seizures and generalized tonic-clonic seizures are the main seizure types in all patients hosting CHD2 single-nucleotide or indel variants (non-CNVs). At the molecular level, there are 102 types of CHD2 non-CNVs in 126 patients, almost one mutational type corresponding to one person, and there is no difference in the incidence ratio of each position. Furthermore, we summarized that a small proportion of patients inherited CHD2 variants, and not all patients with CHD2 variants had seizures. Importantly, the phenotypes, especially seizures control and fever sensitivity, and genotypes had a relative association. These results enriched the database of CHD2-relative neurodevelopmental disorders and provided a theoretical foundation for researching the relationship between genotypes and phenotypes.

Prenatal diagnosis of partial monosomy 8p (8p23.2→pter) and partial trisomy 15q (15q21.2→qter) and incidental detection of a familial chromosome translocation of paternal origin in a pregnancy associated with increased nuchal translucency and an abnormal maternal serum screening result

OBJECTIVE

We present partial monosomy 8p (8p23.2→pter) and partial trisomy 15q (15q21.2→qter) and incidental detection of a familial chromosome translocation of paternal origin in a pregnancy associated with increased nuchal translucency (NT) and an abnormal maternal serum screening result.

CASE REPORT

A 29-year-old primigravid woman underwent chorionic villus sampling (CVS) at 13 weeks of gestation because of an increased NT thickness of 3.2 mm at 12 weeks of gestation and an abnormal maternal serum screening for Down syndrome result with a calculated risk of 1/29. Her husband was 33 years old, and there was no family history of congenital malformations. CVS revealed a derived chromosome 8 or der(8). Cytogenetic analysis of the parents revealed a karyotype of 46,XY,t(8;15)(p21.3;q13) in the father and a karyotype of 46,XX in the mother. The CVS result was 46,XY,der(8)t(8;15)(p21.3;q13)pat. The woman requested for amniocentesis at 16 weeks of gestation. Array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed a result of arr 8p23.3p23.2 (191,530-2,625,470) × 1.0, arr 15q21.2q26.3 (50,903,432-102,338,129) × 3.0 with a 2.434-Mb deletion of 8p23.3-p23.2 including DLGAP2, CLN8 and ARHGEF10, and a 51.435-Mb duplication of 15q21.2-q26.3 including CYP19A1 and IGF1R. Conventional cytogenetic analysis of cultured amniocytes revealed the result of 46,XY,der(8) t(8;15)(p23.2;q21.2)pat in the fetus. The pregnancy was subsequently terminated, and a malformed fetus was delivered with characteristic craniofacial dysmorphism.

CONCLUSION

Maternal serum screening and NT screening may incidentally detect familial unbalanced reciprocal translocations, and aCGH analysis is useful for a precise determination of the breakpoints of the translocation and the involvement of the related genes under such a circumstance.

Prenatal diagnosis of a pure 15q distal trisomy derived from a maternal pericentric inversion: A case report

Distal trisomy or duplication of 15q is a very rare chromosomal disorder; most of the previously reported cases were derived from unbalanced translocations involving chromosome 15 and another chromosome, whereas other mechanisms (e.g. duplication) have rarely been reported. We herein report a very rare prenatal case of a partial 15q trisomy, a 42.64-Mb duplication of 15q22.2-q26.3, arising from a maternal pericentric inversion of chromosome 15 (p11q22) that was not the result of an unbalanced translocation or duplication, and was not associated with concomitant partial monosomy. Fetal ultrasound revealed isolated thickened nuchal translucency at 12 weeks and multiple abnormalities in the second trimester, including early growth restriction, unilateral ventriculomegaly, narrow cavum septi pellucidi with hypoplasia of the corpus callosum, unilateral postaxial polydactyly, clenched hands and clubfoot with clawing of the toes, and a particular general dysplastic and hypotrophic aspect of the heart. The distinctive aspects of the present case may help to refine the phenotype associated with distal duplication 15q. To the best of our knowledge, this is the first report of a prenatal diagnosis with a 15q22.2-q26.3 duplication that did not result from an unbalanced translocation and did not have a concomitant monosomic component.

Guideline No. 410: Prevention, Screening, Diagnosis, and Pregnancy Management for Fetal Neural Tube Defects

OBJECTIVE

This revised guideline is intended to provide an update on the genetic aspects, prevention, screening, diagnosis, and management of fetal neural tube defects.

TARGET POPULATION

Women who are pregnant or may become pregnant. Neural tube defect screening should be offered to all pregnant women.

OPTIONS

For prevention: a folate-rich diet, and folic acid and vitamin B₁₂ supplementation, with dosage depending on risk level. For screening: second-trimester anatomical sonography; first-trimester sonographic screening; maternal serum alpha fetoprotein; prenatal magnetic resonance imaging. For genetic testing: diagnostic amniocentesis with chromosomal microarray and amniotic fluid alpha fetoprotein and acetylcholinesterase; fetal exome sequencing. For pregnancy management: prenatal surgical repair; postnatal surgical repair; pregnancy termination with autopsy. For subsequent pregnancies: prevention and screening options and counselling.

OUTCOMES

The research on and implementation of fetal surgery for prenatally diagnosed myelomeningocele has added a significant treatment option to the previous options (postnatal repair or pregnancy termination), but this new option carries an increased risk of maternal morbidity. Significant improvements in health and quality of life, both for the mother and the infant, have been shown to result from the prevention, screening, diagnosis, and treatment of fetal neural tube defects.

BENEFITS, HARMS, AND COSTS

The benefits for patient autonomy and decision-making are provided in the guideline. Harms include an unexpected fetal diagnosis and the subsequent management decisions. Harm can also result if the patient declines routine sonographic scans or if counselling and access to care for neural tube defects are delayed. Cost analysis (personal, family, health care) is not within the scope of this clinical practice guideline.

EVIDENCE

A directed and focused literature review was conducted using the search terms spina bifida, neural tube defect, myelomeningocele, prenatal diagnosis, fetal surgery, neural tube defect prevention, neural tube defect screening, neural tube defect diagnosis, and neural tube defect management in order to update and revise this guideline. A peer review process was used for content validation and clarity, with appropriate ethical considerations.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations).

INTENDED AUDIENCE

Maternity care professionals who provide any part of pre-conception, antenatal, delivery, and neonatal care. This guideline is also appropriate for patient education. RECOMMENDATIONS (GRADE RATINGS IN PARENTHESES).

Directive clinique no 410 : Anomalies du tube neural : Prévention, dépistage, diagnostic et prise en charge de la grossesse

OBJECTIF

La présente directive clinique révisée vise à fournir une mise à jour sur les aspects génétiques, la prévention, le dépistage, le diagnostic et la prise en charge des anomalies du tube neural.

POPULATION CIBLE

Les femmes enceintes ou qui pourraient le devenir. Il convient d'offrir le dépistage des anomalies du tube neural à toutes les femmes enceintes.

OPTIONS

Pour la prévention : un régime alimentaire riche en acide folique et des suppléments d'acide folique et de vitamine B₁₂ selon une posologie d'après le niveau de risque. Pour le dépistage : l'échographie obstétricale du deuxième trimestre, le dépistage échographique du premier trimestre, le dosage de l'alphafœtoprotéine sérique maternelle et l'imagerie par résonance magnétique prénatale. Pour les tests génétiques : l'amniocentèse diagnostique avec analyse chromosomique sur micropuce et le dosage de l'alphafœtoprotéine et de l'acétylcholinestérase dans le liquide amniotique et le séquençage de l'exome fœtal. Pour la prise en charge de la grossesse : la réparation chirurgicale prénatale, la réparation chirurgicale postnatale et l'interruption de grossesse avec autopsie. Pour les grossesses subséquentes : les options de prévention et de dépistage et les conseils. RéSULTATS: La recherche et la mise en œuvre du traitement chirurgical fœtal en cas de diagnostic prénatal de myéloméningocèle ont ajouté une option thérapeutique fœtale importante aux options précédentes (réparation postnatale ou interruption de grossesse), mais cette nouvelle option comporte un risque accru de morbidité maternelle. La prévention, le dépistage, le diagnostic et le traitement des anomalies du tube neural se révèlent entraîner des améliorations importantes à la mère et au nourrisson en matière de santé et de qualité de vie. BéNéFICES, RISQUES ET COûTS: Le type et l'ampleur des bénéfices, risques et coûts attendus pour les patientes grâce à la mise en œuvre de la présente directive clinique par un établissement de soins de santé intègrent un canal maternel préconception et prénatal adéquat comprenant l'accès des patientes aux soins, les conseils, les analyses et examens, l'imagerie, le diagnostic et l'interprétation. Les bénéfices relatifs à l'autonomie de la patiente et au processus décisionnel sont énoncés dans la présente directive clinique. Les risques comprennent un diagnostic fœtal inattendu et les décisions de prise en charge subséquentes. Le fait que la patiente refuse les échographies habituelles et le retard du conseil ou d'accès aux soins en cas d'anomalie du tube neural comportent également des risques. L'analyse des coûts (personnels, familiaux, santé publique) ne fait pas partie de la portée de la présente directive clinique. DONNéES PROBANTES: Afin de mettre à jour et réviser la présente directive, une revue de la littérature ciblée et dirigée a été effectuée à l'aide des termes de recherche suivants : spina bifida, neural tube defect, myelomeningocele, prenatal diagnosis, fetal surgery, neural tube defect prevention, neural tube defect screening, neural tube defect diagnosis et neural tube defect management. Un processus d'examen par les pairs a été utilisé pour la validation et la clarté du contenu, avec des considérations appropriées d'ordre éthique. MéTHODES DE VALIDATION: Les auteurs ont évalué la qualité des données probantes et la force des recommandations en utilisant l'approche d'évaluation, de développement et d'évaluation (GRADE). Consulter l'annexe A en ligne (le tableau A1 pour les définitions et le tableau A2 pour les interprétations des recommandations fortes et faibles). PROFESSIONNELS CONCERNéS: Professionnels des soins de maternité qui offrent des soins préconception, prénataux, obstétricaux ou néonataux. La présente directive clinique convient également aux fins d'éducation des patientes. RECOMMANDATIONS (CLASSEMENT GRADE ENTRE PARENTHèSES).

Closing in on Mechanisms of Open Neural Tube Defects

Neural tube defects (NTDs) represent a failure of the neural plate to complete the developmental transition to a neural tube. NTDs are the most common birth anomaly of the CNS. Following mandatory folic acid fortification of dietary grains, a dramatic reduction in the incidence of NTDs was observed in areas where the policy was implemented, yet the genetic drivers of NTDs in humans, and the mechanisms by which folic acid prevents disease, remain disputed. Here, we discuss current understanding of human NTD genetics, recent advances regarding potential mechanisms by which folic acid might modify risk through effects on the epigenome and transcriptome, and new approaches to study refined phenotypes for a greater appreciation of the developmental and genetic causes of NTDs.

CHD2-related epilepsy: novel mutations and new phenotypes

The aim of this report was to refine the genotypes and phenotypes of chromodomain helicase DNA-binding protein 2 (CHD2)-related epilepsy. Seventeen patients with CHD2 mutations were enrolled. CHD2 mutations were identified by application of next-generation sequencing of epilepsy or whole exome sequencing. Sixteen mutations were identified, among which 15 have not yet been reported. Thirteen mutations were de novo. Age at seizure onset ranged from 3 months to 10 years 5 months. Seizures observed were generalized tonic-clonic, myoclonic, atonic, atypical absence, focal, and myoclonic-atonic. Epileptic spasms occurred in two patients. Developmental disability was present in 14 patients. Autism features were observed in seven patients. Video electroencephalogram was abnormal in 15 patients. Five patients were diagnosed with non-specific epileptic encephalopathy, two with epilepsy with myoclonic-atonic seizures, two with Lennox-Gastaut syndrome, two with febrile seizures plus, and one with West syndrome. Seizures were controlled in nine patients. Q1392TfsX17 may be a hot-spot mutation of CHD2. West syndrome was observed as a new phenotype of CHD2 mutation. The severity of the phenotypes of CHD2 mutations ranged from mild febrile seizures to severe epileptic encephalopathy. WHAT THIS PAPER ADDS: Q1392TfsX17 maybe the hot-spot mutation of CHD2. West syndrome could be a new phenotype of CHD2 mutation.

Prenatal diagnosis of a de novo tetrasomy 15q24.3-25.3: Case report and literature review

BACKGROUND

Terminal duplication on chromosome 15q is a rare chromosomal variation. Affected individuals show similar features such as growth dysplasia or the development of frontal bossing, body deformities, facial abnormalities, and genitourinary or cardiovascular disorders. However, it is not yet clear whether such 15q repeats lead to identifiable patterns of clinical abnormalities. Therefore, the purpose of this study was to analyze the prenatal diagnostic results and clinical manifestations of a fetus with 15q duplication and to summarize the literature.

METHODS

The case was a fetus at 28 weeks of gestation. The risk of Down syndrome from second-trimester screening was 1/140. Prenatal ultrasound and amniocentesis were performed, and chromosomal microarray analysis (CMA) was used for genetic analysis.

RESULTS

The fetus had abnormal clinical features, including intracardiac echogenic focus in the left ventricle, an aberrant right subclavian artery, and growth delay. The fetal chromosomal karyotype was 46,XX,15q?,12q?,21pstk+, and CMA revealed a 10.163 Mb duplication at 15q24.3-q25.3. The couple chose to terminate the pregnancy after careful consideration.

CONCLUSIONS

The combination and rational application of cytogenetics technology and molecular genetics technology such as CMA will open up the field of clinical application and provide useful genetic counseling for parents of fetuses carrying such chromosomal duplications.

Prenatal diagnosis and molecular cytogenetic characterization of a de novo duplication of 15q24.3-q26.1

Reported cases of distal 15q interstitial duplications are uncommon and do not result in a recognizable pattern of abnormalities. Some studies report prenatal overgrowth, while others describe growth retardation. We present molecular cytogenetic characterization of a 14 Mb interstitial duplication, encompassing 81 Online Mendelian Inheritance in Man (OMIM) genes, in a fetus with single umbilical artery and short limbs. We propose that growth restriction, previously described and present in our patient, may be due to duplication of a gene or genes contained in the 15q24 region.