Chromosome 2p15-p16.1 microduplication in a boy with congenital anomalies: Is it a distinctive syndrome?

Large Chromosome 2p Duplication-Associated Mechanisms and Clinical Presentations

Chromosome 2p (chr2p) duplication, also known as trisomy 2p, is a rare chromosome abnormality associated with developmental delay, intellectual disability, behavioral problems, and distinctive facial features. Most of the reported cases involving trisomy 2p include additional copy number variants (CNVs) in other regions of the genome and are usually small in size. Little is known about the clinical outcomes of large duplications of chr2p as the sole cytogenetic abnormality. In this study, 193 samples at the Greenwood Genetic Center (GGC) with CNVs involving chr2p were evaluated, out of which 86 had chr2p duplications. Among them, 8 patients were identified with large chr2p duplications ranging in size from 9.3 Mb to 89 Mb, and no deletions or duplications involving other chromosomes were identified in those patients. These duplications were associated with inverted duplication, tandem duplication, and duplication as the result of translocation, with no additional CNVs identified by microarray analysis. Confirmation by conventional cytogenetics was performed in 7 of the 8 patients, and the translocations were confirmed by fluorescence in situ hybridization. Interestingly, 1 patient was found to have mosaic complete trisomy 2p as the result of an unbalanced de novo (X;2) chromosomal translocation. X-inactivation was skewed toward the derivative X chromosome, yet it did not appear to extend into the chromosome 2 material. Various shared clinical manifestations were observed in the individuals in this study, including developmental delay, hemifacial hypoplasia, cleft palate, and short stature, and they also have distinct features such as hypotonia, cerebellar hypogenesis, and corpus callosum agenesis, which might result from a gene dosage effect of the duplication. In conclusion, single-event large chr2p duplications can result from different mechanisms, including inverted or tandem duplications within chromosome 2, or translocations involving chromosome 2 and other chromosomes. Partial or complete trisomy 2p is commonly associated with developmental delay, and additional clinical features may be related to gene dosage effects.

Copy Number Variations in Children with Tourette Syndrome: Systematic Investigation in a Clinical Setting

Tourette syndrome (TS) is a neurodevelopmental disturbance with heterogeneous and not completely known etiology. Clinical and molecular appraisal of affected patients is mandatory for outcome amelioration. The current study aimed to understand the molecular bases underpinning TS in a vast cohort of pediatric patients with TS. Molecular analyses included array-CGH analyses. The primary goal was to define the neurobehavioral phenotype of patients with or without pathogenic copy number variations (CNVs). Moreover, we compared the CNVs with CNVs described in the literature in neuropsychiatric disorders, including TS, to describe an effective clinical and molecular characterization of patients for prognostic purposes and for correctly taking charge. Moreover, this study showed that rare deletions and duplications focusing attention on significant genes for neurodevelopment had a statistically higher occurrence in children with tics and additional comorbidities. In our cohort, we determined an incidence of potentially causative CNVs of about 12%, in line with other literature studies. Clearly, further studies are needed to delineate the genetic background of patients with tic disorders in a superior way to elucidate the complex genetic architecture of these disorders, to describe the outcome, and to identify new possible therapeutic targets.

Cytogenomic epileptology

Molecular cytogenetic and cytogenomic studies have made a contribution to genetics of epilepsy. However, current genomic research of this devastative condition is generally focused on the molecular genetic aspects (i.e. gene hunting, detecting mutations in known epilepsy-associated genes, searching monogenic causes of epilepsy). Nonetheless, chromosomal abnormalities and copy number variants (CNVs) represent an important part of genetic defects causing epilepsy. Moreover, somatic chromosomal mosaicism and genome/chromosome instability seem to be a possible mechanism for a wide spectrum of epileptic conditions. This idea becomes even more attracting taking into account the potential of molecular neurocytogenetic (neurocytogenomic) studies of the epileptic brain. Unfortunately, analyses of chromosome numbers and structure in the affected brain or epileptogenic brain foci are rarely performed. Therefore, one may conclude that cytogenomic area of genomic epileptology is poorly researched. Accordingly, molecular cytogenetic and cytogenomic studies of the clinical cohorts and molecular neurocytogenetic analyses of the epileptic brain appear to be required. Here, we have performed a theoretical analysis to define the targets of the aforementioned studies and to highlight future directions for molecular cytogenetic and cytogenomic research of epileptic disorders in the widest sense. To succeed, we have formed a consortium, which is planned to perform at least a part of suggested research. Taking into account the nature of the communication, "cytogenomic epileptology" has been introduced to cover the research efforts in this field of medical genomics and epileptology. Additionally, initial results of studying cytogenomic variations in the Russian neurodevelopmental cohort are reviewed with special attention to epilepsy. In total, we have concluded that (i) epilepsy-associated cytogenomic variations require more profound research; (ii) ontological analyses of epilepsy genes affected by chromosomal rearrangements and/or CNVs with unraveling pathways implicating epilepsy-associated genes are beneficial for epileptology; (iii) molecular neurocytogenetic (neurocytogenomic) analysis of postoperative samples are warranted in patients suffering from epileptic disorders.

Prenatal diagnosis of familial 2p15 microduplication associated with pulmonary artery stenosis, single umbilical artery and left foot postaxial polydactyly on fetal ultrasound

OBJECTIVE

We present prenatal diagnosis of familial 2p15 microduplication associated with pulmonary artery stenosis, single umbilical artery and left foot postaxial polydactyly on fetal ultrasound.

CASE REPORT

A 34-year-old woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed the karyotype of 46,XX. Prenatal ultrasound examination at 21 weeks of gestation showed pulmonary artery stenosis, single umbilical artery and left foot postaxial polydactyly. Repeat amniocentesis was performed at 22 weeks of gestation and array comparative genomic hybridization (aCGH) analysis on the DNAs extracted from amniocytes revealed the result of arr 2p15 (61, 495, 220-62,885,679) × 3.0 [GRCh37 (hg19)] with a 1.391-Mb 2p15 duplication encompassing seven Online Mendelian Inheritance in Man (OMIM) genes of USP34, XPO1, FAM161A, CCT4, COMMD1, B3GNT2 and TMEM17. aCGH analysis on the DNAs extracted from parental bloods confirmed a familial transmission from a normal carrier mother who had no phenotypic abnormality. A 3270-g female baby was delivered at term with mild pulmonary artery stenosis and left foot postaxial polydactyly. The infant had normal physical and psychomotor development when follow-up at age of one year.

CONCLUSION

Prenatal diagnosis of fetal structural abnormalities should include aCGH analysis in addition to conventional cytogenetic analysis.