Subtelomeric deletion of 12p: Description of a third case and review

Variable Phenotypes of Epilepsy, Intellectual Disability, and Schizophrenia Caused by 12p13.33-p13.32 Terminal Microdeletion in a Korean Family: A Case Report and Literature Review

A simultaneous analysis of nucleotide changes and copy number variations (CNVs) based on exome sequencing data was demonstrated as a potential new first-tier diagnosis strategy for rare neuropsychiatric disorders. In this report, using depth-of-coverage analysis from exome sequencing data, we described variable phenotypes of epilepsy, intellectual disability (ID), and schizophrenia caused by 12p13.33–p13.32 terminal microdeletion in a Korean family. We hypothesized that CACNA1C and KDM5A genes of the six candidate genes located in this region were the best candidates for explaining epilepsy, ID, and schizophrenia and may be responsible for clinical features reported in cases with monosomy of the 12p13.33 subtelomeric region. On the background of microdeletion syndrome, which was described in clinical cases with mild, moderate, and severe neurodevelopmental manifestations as well as impairments, the clinician may determine whether the patient will end up with a more severe or milder end-phenotype, which in turn determines disease prognosis. In our case, the 12p13.33–p13.32 terminal microdeletion may explain the variable expressivity in the same family. However, further comprehensive studies with larger cohorts focusing on careful phenotyping across the lifespan are required to clearly elucidate the possible contribution of genetic modifiers and the environmental influence on the expressivity of 12p13.33 microdeletion and associated characteristics.

12p deletion spectrum syndrome: a new case report reinforces the evidence regarding the potential relationship to autism spectrum disorder and related developmental impairments

BACKGROUND

Autism Spectrum Disorders (ASD) now encompass a broad heterogeneous group of people who present in the early developmental years with a wide range of social and communication deficits, which are typically also associated with complex repetitive behaviors and circumscribed interests. The target goal is to heighten readers' perception into the trend to personalize the distinct autistic and related developmental conditions encompassing the 12p region.

CASE PRESENTATION

This is a case-report of a 4-year-old male who presented the core signs of ASD, which were thought to be related to a rare 12p13.2 deletion.  We further reviewed the literature in order to outline the related developmental conditions in the 12p region. Aside from this patient reported here, we found an additional number of 43 cases described in the medical literature since 1974, that have been related to deletions in the 12p region. However, to the best of our knowledge, none of the previous had been specifically linked to the 12p13.2 band.

CONCLUSIONS

The 12p deletion spectrum is rarely described as part of the selective genotypes thought to be related to ASD. Even inside of a small piece of the puzzle, there might be ample variation in the behavioral and clinical phenotypes of children and adults presenting with this particular genetic profile. In that regard, the particular 12p13.2 distal deletion presentation is one of the possible genotypes encompassed by the "12p deletion spectrum syndrome", that might be potentially connected to the diagnosis of ASD and related developmental disorders.

Concurrent Loss of Heterozygosity and Mosaic Deletion of 12p13.32pter

Deletions in the short arm of chromosome 12 are the rarest subtelomeric imbalances. Less than 20 patients have been reported to date, and their microdeletions were identified either by FISH or array-CGH without SNP data. Here, we report a patient with a 12p13.32pter mosaic deletion detected by chromosome microarray analysis with loss of heterozygosity (LOH) of the deleted segment in addition to the adjacent distal segment. LOH is indicative of a complex rearrangement, suggestive of mitotic microhomology-mediated break-induced replication.

Interstitial 12p deletion involving more than 40 genes in a patient with postnatal microcephaly, psychomotor delay, optic nerve atrophy, and facial dysmorphism

Interstitial deletions of chromosome 12p are rare, and the phenotype spectrum is therefore still unknown. The thirteen patients reported so far suffer from developmental delay, optic nerve hypoplasia, micropenis, hypoplastic hair and skin, oligodontia, brachydactyly, and arterial hypertension. We report a de novo 12p12.2-p11.22 deletion of 9.2 Mb detected by array CGH analysis in a boy with global developmental delay, muscular hypotonia, postnatal microcephaly, facial dysmorphism including small ears, epicanthus, broad nasal bridge and hypoplastic nostrils. In addition, the patient had optic nerve atrophy, inverted nipples, micropenis, and a hemangioma. The deleted region encompasses more than 40 reference genes. We compare phenotype and deletion extent of our index patient to that of previous reports and thereby contribute to the understanding of interstitial 12p deletion phenotypes. Knowledge of the pattern of this deletion phenotype will help clinicians to diagnose this abnormality in their patients and to counsel the parents accordingly. Further descriptions may be able to contribute to the clarification.

Effect of copy number variants on outcomes for infants with single ventricle heart defects

BACKGROUND

Human genomes harbor copy number variants (CNVs), which are regions of DNA gains or losses. Although pathogenic CNVs are associated with congenital heart disease (CHD), their effect on clinical outcomes is unknown. This study sought to determine whether pathogenic CNVs among infants with single ventricle physiology were associated with inferior neurocognitive and somatic growth outcomes.

METHODS AND RESULTS

Genomic DNAs from 223 subjects of 2 National Heart, Lung, and Blood Institute-sponsored randomized clinical trials in infants with single ventricle CHD and 270 controls from The Cancer Genome Atlas project were analyzed for rare CNVs>300 kb using array comparative genomic hybridization. Neurocognitive and growth outcomes at 14 months from the CHD trials were compared among subjects with and without pathogenic CNVs. Putatively pathogenic CNVs, comprising 25 duplications and 6 deletions, had a prevalence of 13.9%, significantly greater than the 4.4% rate of such CNVs among controls. CNVs associated with genomic disorders were found in 13 cases but not in controls. Several CNVs likely to be causative of single ventricle CHD were observed, including aberrations altering the dosage of GATA4, MYH11, and GJA5. Subjects with pathogenic CNVs had worse linear growth, and those with CNVs associated with known genomic disorders had the poorest neurocognitive and growth outcomes. A minority of children with pathogenic CNVs were noted to be dysmorphic on clinical genetics examination.

CONCLUSIONS

Pathogenic CNVs seem to contribute to the cause of single ventricle forms of CHD in ≥10% of cases and are clinically subtle but adversely affect outcomes in children harboring them.

12p13.33 microdeletion including ELKS/ERC1, a new locus associated with childhood apraxia of speech

Speech sound disorders are heterogeneous conditions, and sporadic and familial cases have been described. However, monogenic inheritance explains only a small proportion of such disorders, in particular in cases with childhood apraxia of speech (CAS). Deletions of <5 Mb involving the 12p13.33 locus is one of the least commonly deleted subtelomeric regions. Only four patients have been reported with such a deletion diagnosed with fluorescence in situ hybridisation telomere analysis or array CGH. To further delineate this rare microdeletional syndrome, a French collaboration together with a search in the Decipher database allowed us to gather nine new patients with a 12p13.33 subtelomeric or interstitial rearrangement identified by array CGH. Speech delay was found in all patients, which could be defined as CAS when patients had been evaluated by a speech therapist (5/9 patients). Intellectual deficiency was found in 5/9 patients only, and often associated with psychiatric manifestations of various severity. Two such deletions were inherited from an apparently healthy parent, but reevaluation revealed abnormal speech production at least in childhood, suggesting variable expressivity. The ELKS/ERC1 gene, which encodes for a synaptic factor, is found in the smallest region of overlap. These results reinforce the hypothesis that deletions of the 12p13.33 locus may be responsible for variable phenotypes including CAS associated with neurobehavioural troubles and that the presence of CAS justifies a genetic work-up.