Prenatal Array-CGH Detection of 3q26.32q26.33 Interstitial Deletion Encompassing the SOX2 Gene: Ultrasound, Pathological, and Cytogenetic Findings

Background: SOX2 disorders are associated with anophthalmia-esophageal-genital syndrome or microphthalmia, syndromic 3 (MCOPS3- # 206900). Case Report: We describe a third fetal case with a de novo 3q26.32q26.33 deletion extending for 4.31 Mb, detected in a 15-week fetus. After legal interruption of pregnancy, at autopsy, the fetus presented bilateral microphthalmia, right cleft lip and palate, bilateral cerebral ventriculomegaly and dilated third ventricle, microcystic left lung, and intestinal malrotation. Histologically, the left lung showed congenital pulmonary airway malformation (CPAM) type 2. Retinal dysplasia was found in both eyes. Discussion/Conclusion: The human SOX2 gene (OMIM #184429) is located on chromosome 3 at position q26.3-27 and encodes a transcription factor involved in the development of the central and peripheral nervous systems, retina, and lung. In our case, the combination of cerebral, retinal, and pulmonary anomalies, not previously described, are consistent with SOX2 haploinsufficiency due to chromosomal deletion.

Essential information on genetic testing methods that each clinician needs to know/understand

Genetic testing is well established in many areas of clinical medicine, is increasingly used in clinical psychiatry and it becomes increasingly important to understand the scope and limitations of the different genetic tests applied. The recommended genetic work-up of patients with neurodevelopmental disorders (such as intellectual disability or autism spectrum disorders) includes conventional karyotyping (low resolution) able to detect chromosomal rearrangement and structural variants (>5Mb, 5 million-bp), testing for fragile X-Syndrome, screening for deletions and duplications down to 20 Kb by Comparative Genomic Hybridisation (CGH), able to detect Copy Number Variation (CNVs; gain or loss of genetic material compared to the reference genome). Sanger sequencing is used for mapping of single base pair genetic variants in single genes but unable to identify deletions or duplications. The more advanced Next Generation Sequencing (NGS) have enabled to detect variants in panels of 10-100 (or more) genes, or in all coding regions using Whole Exome Sequencing (WES; 23.000 genes). Whole Genome Sequencing (WGS) analysis enables also the detection of all size range and types of genetic variation including CNVs, trinucleotide repeats and translocations. All this led to an impressive change in interpreting genomic variants that need to be strictly linked to clinical information before it can be used by clinicians to improve diagnosis or care. Bioinformatic tools to annotate variants, predict their effects and select the genes and genomic regions of interest are needed to guide the clinical work followed with careful evaluation of the prioritized variants based on the clinical knowledge (https://www.cost.eu/actions/CA17130/#tabs|Name:overview).

Prematurity, ventricular septal defect and dysmorphisms are independent predictors of pathogenic copy number variants: a retrospective study on array-CGH results and phenotypical features of 293 children with neurodevelopmental disorders and/or multiple congenital anomalies

BACKGROUND

Since 2010, array-CGH (aCGH) has been the first-tier test in the diagnostic approach of children with neurodevelopmental disorders (NDD) or multiple congenital anomalies (MCA) of unknown origin. Its broad application led to the detection of numerous variants of uncertain clinical significance (VOUS). How to appropriately interpret aCGH results represents a challenge for the clinician.

METHOD

We present a retrospective study on 293 patients with age range 1 month - 29 years (median 7 years) with NDD and/or MCA and/or dysmorphisms, investigated through aCGH between 2005 and 2016. The aim of the study was to analyze clinical and molecular cytogenetic data in order to identify what elements could be useful to interpret unknown or poorly described aberrations. Comparison of phenotype and cytogenetic characteristics through univariate analysis and multivariate logistic regression was performed.

RESULTS

Copy number variations (CNVs) with a frequency < 1% were detected in 225 patients of the total sample, while 68 patients presented only variants with higher frequency (heterozygous deletions or amplification) and were considered to have negative aCGH. Proved pathogenic CNVs were detected in 70 patients (20.6%). Delayed psychomotor development, intellectual disability, intrauterine growth retardation (IUGR), prematurity, congenital heart disease, cerebral malformations and dysmorphisms correlated to reported pathogenic CNVs. Prematurity, ventricular septal defect and dysmorphisms remained significant predictors of pathogenic CNVs in the multivariate logistic model whereas abnormal EEG and limb dysmorphisms were mainly detected in the group with likely pathogenic VOUS. A flow-chart regarding the care for patients with NDD and/or MCA and/or dysmorphisms and the interpretation of aCGH has been made on the basis of the data inferred from this study and literature.

CONCLUSION

Our work contributes to make the investigative process of CNVs more informative and suggests possible directions in aCGH interpretation and phenotype correlation.

Recurrent duplications of 17q12 associated with variable phenotypes

The ability to identify the clinical nature of the recurrent duplication of chromosome 17q12 has been limited by its rarity and the diverse range of phenotypes associated with this genomic change. In order to further define the clinical features of affected patients, detailed clinical information was collected in the largest series to date (30 patients and 2 of their siblings) through a multi-institutional collaborative effort. The majority of patients presented with developmental delays varying from mild to severe. Though dysmorphic features were commonly reported, patients do not have consistent and recognizable features. Cardiac, ophthalmologic, growth, behavioral, and other abnormalities were each present in a subset of patients. The newly associated features potentially resulting from 17q12 duplication include height and weight above the 95th percentile, cataracts, microphthalmia, coloboma, astigmatism, tracheomalacia, cutaneous mosaicism, pectus excavatum, scoliosis, hypermobility, hypospadias, diverticulum of Kommerell, pyloric stenosis, and pseudohypoparathryoidism. The majority of duplications were inherited with some carrier parents reporting learning disabilities or microcephaly. We identified additional, potentially contributory copy number changes in a subset of patients, including one patient each with 16p11.2 deletion and 15q13.3 deletion. Our data further define and expand the clinical spectrum associated with duplications of 17q12 and provide support for the role of genomic modifiers contributing to phenotypic variability.

Revealing the complexity of a monogenic disease: rett syndrome exome sequencing

Rett syndrome (OMIM#312750) is a monogenic disorder that may manifest as a large variety of phenotypes ranging from very severe to mild disease. Since there is a weak correlation between the mutation type in the Xq28 disease-gene MECP2/X-inactivation status and phenotypic variability, we used this disease as a model to unveil the complex nature of a monogenic disorder. Whole exome sequencing was used to analyze the functional portion of the genome of two pairs of sisters with Rett syndrome. Although each pair of sisters had the same MECP2 (OMIM*300005) mutation and balanced X-inactivation, one individual from each pair could not speak or walk, and had a profound intellectual deficit (classical Rett syndrome), while the other individual could speak and walk, and had a moderate intellectual disability (Zappella variant). In addition to the MECP2 mutation, each patient has a group of variants predicted to impair protein function. The classical Rett girls, but not their milder affected sisters, have an enrichment of variants in genes related to oxidative stress, muscle impairment and intellectual disability and/or autism. On the other hand, a subgroup of variants related to modulation of immune system, exclusive to the Zappella Rett patients are driving toward a milder phenotype. We demonstrate that genome analysis has the potential to identify genetic modifiers of Rett syndrome, providing insight into disease pathophysiology. Combinations of mutations that affect speaking, walking and intellectual capabilities may represent targets for new therapeutic approaches. Most importantly, we demonstrated that monogenic diseases may be more complex than previously thought.

[Registry of genetic and malformative diseases in the province of Macerata]

OBJECTIVES

The aim of this epidemiological research is to evaluate the prevalence of genetic diseases and malformative syndromes in paediatric population living in the Macerata county.

MATERIAL AND METHODS

All the data were collected through a careful analysis of a specific questionnaire sent to all the family paediatricians.

RESULTS

23,379 children living in Macerata county, aged 0 to 9 years, were evaluated (93.8% of all this paediatric population). Among those were found N 400 cases of genetic diseases and malformative syndromes: Malformations Tot.N. 255 cases (63.3% of the reported cases); Malformative Syndromes Tot. N. 55 cases (27.8% of the reported cases); Endocrinology and Metabolic Diseases Tot. N. 41 cases (10.3% of the reported cases); Osteochondrodysplasia Tot. N. 22 cases (5.7% of the reported cases); Other Tot. N. 28 cases (7.0% of the reported cases); Male population was found more affected than female: M/F ratio = 1.4. The analysis of the data showed an increasing trend in detecting these pathological conditions, consistent with the increase in geographic altitude (3 areas considered): 0-100 meter = 0.88%; 100-600 m.a.s. = 1.34%; over 600 m.a.s. = 1.88%.

CONCLUSION

The knowledge of the number of children affected by genetic and malformative diseases in the Macerata county is relevant in order to establish a Genetic Service with the aim to better support the medical assistance of these patients and counselling service for the families.