[A clinical and genetic analysis of a child with supernumerary marker chromosome 15-caused mental retardation, intractable epilepsy, and central precocious puberty]

Supernumerary marker chromosome 15 is a rare chromosome abnormality. This paper reports the clinical diagnosis and treatment, as well as genetic defects, of a child with supernumerary marker chromosome 15. The patient was a 9.5-year-old girl who had mental and motor retardation since infancy, breast development at the age of 7 years, and seizures at the age of 8.5 years. Seizures occurred with various features and could not be controlled by a variety of antiepileptic drugs. No abnormalities were found by brain magnetic resonance imaging. Electroencephalogram showed frequent epileptiform discharges. G-banding karyotype analysis, fluorescence in situ hybridization, methylation-specific multiplex ligation-dependent probe amplification, and array comparative genomic hybridization identified a de novo 15q duplication in the patient. The maternal copy number increased in the 15q11-13 region. The form of genome rearrangement was 47,XX,+inv dup(15)(pter to q13:q13 to pter). The increased copy number in the 15q11-13 region is closely related to mental retardation, intractable epilepsy, and central precocious puberty. High-resolution karyotype analysis is recommended for children with unexplained mental retardation and epilepsy.

Transcriptome profiling of white adipose tissue in a mouse model for 15q duplication syndrome

Obesity is not only associated with unhealthy lifestyles, but also linked to genetic predisposition. Previously, we generated an autism mouse model (patDp/+) that carries a 6.3 Mb paternal duplication homologous to the human 15q11–q13 locus. Chromosomal abnormalities in this region are known to cause autism spectrum disorder, Prader–Willi syndrome, and Angelman syndrome in humans. We found that, in addition to autistic-like behaviors, patDp/+ mice display late-onset obesity and hypersensitivity to a high-fat diet. These phenotypes are likely to be the results of genetic perturbations since the energy expenditures and food intakes of patDp/+ mice do not significantly differ from those of wild-type mice. Intriguingly, we found that an enlargement of adipose cells precedes the onset of obesity in patDp/+ mice. To understand the underlying molecular networks responsible for this pre-obese phenotype, we performed transcriptome profiling of white adipose tissue from patDp/+ and wild-type mice using microarray. We identified 230 genes as differentially expressed genes. Sfrp5 — a gene whose expression is positively correlated with adipocyte size, was found to be up-regulated, and Fndc5, a potent inducer of brown adipogenesis was identified to be the top down-regulated gene. Subsequent pathway analysis highlighted a set of 35 molecules involved in energy production, lipid metabolism, and small molecule biochemistry as the top candidate biological network responsible for the pre-obese phenotype of patDp/+. The microarray data were deposited in NCBI Gene Expression Omnibus database with accession number GSE58191. Ultimately, our dataset provides novel insights into the molecular mechanism of obesity and demonstrated that patDp/+ is a valuable mouse model for obesity research.

Partial tetrasomy of the proximal long arm of chromosome 15 in two patients: the significance of the gene dosage in terms of phenotype

Background

Large amounts of low copy number repeats in the 15q11.2q13.3 chromosomal region increase the possibility of misalignments and unequal crossover during meiosis in this region, leading to deletions, duplications, triplications and supernumerary chromosomes. Most of the reported cases with epilepsy, autism and Prader-Willi/Angelman syndrome are in association with rearrangements of the proximal long arm of chromosome 15.

Results

Here we report the first two unrelated Hungarian patients with the same epileptic and dysmorphic features, who were investigated by array comparative genomic hybridization (array CGH). By G-banded karyotype followed by FISH and array CGH we could detect partial tetrasomy of the 15q11.2q13.3 chromosomal region, supporting proximal 15q duplication syndrome. Findings of the array CGH gave fully explanation of the phenotypic features of these patients, including epileptic seizures, delayed development, hyperactivity and craniofacial dysmorphic signs. Besides the described features of isodicentric (15) (idic(15)) syndrome Patient 1. suffered from bigeminic extrasystoles and had postnatal growth retardation, which had been published only in a few articles.

Conclusions

Dosage effect of some genes in the concerned genomic region is known, but several genes have no evidence to have dosage dependence. Our results expanded the previous literature data. We assume dosage dependence in the case of CHRNA7 and OTUD7A, which might be involved in growth regulation. On the other hand increased dosage of the KLF13 gene seems to have no direct causal relationship with heart morphology. The genomic environment of the affected genes may be responsible for the observed phenotype.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-015-0137-4) contains supplementary material, which is available to authorized users.

Gastrointestinal problems in 15q duplication syndrome

Chromosome 15q duplication syndrome (Dup15q syndrome) is a neurodevelopmental disorder involving copy number gains of the maternal chromosome 15q11.2-q13 region, characterized by intellectual disability, developmental delay, autism spectrum disorder (ASD), and epilepsy. Gastrointestinal (GI) problems in Dup15q syndrome have been reported only rarely, mostly focused on neonatal feeding difficulties. A retrospective review of the medical records of 46 patients with Dup15q syndrome was conducted to assess GI issues and their treatments in this population. GI symptoms were present in 76.7% of subjects with an isodicentric duplication and 87.5% with an interstitial duplication. There was no clear association between GI issues and ASD, with symptoms occurring in 78.9% of all subjects and 78.2% of ASD subjects. The most commonly reported symptoms were gastroesophageal reflux (56.7%) and constipation (60%), with 30% of subjects reporting both. The most common treatments were polyethylene glycol for constipation and proton pump inhibitors for reflux. Behaviors such as irritability and aggressiveness improved with treatment of GI symptoms in several subjects. The results indicate that GI symptoms are common in Dup15q syndrome and may have an atypical presentation. Diagnosis may be difficult, especially in individuals who are nonverbal or minimally verbal, so increased awareness is critical for early diagnosis and treatment.

Chromosome 15q11-q13 copy number gain detected by array-CGH in two cases with a maternal methylation pattern

Background

The 15q11-q13 region contains many low copy repeats and is well known for its genomic instability. Several syndromes are associated with genomic imbalance or copy-number-neutral uniparental disomy. We report on two patients: Patient 1 is a boy with developmental delay and autism; and Patient 2 is a girl with developmental delay, hypotonia and dysmorphism. We performed analyses to delineate their dosage in the 15q region, determine whether the patients’ dosage correlates with phenotypic severity, and whether genes in the amplified regions are significantly associated with identified functional networks.

Results

For the proximal region of 15q, molecular cytogenetic analysis with Agilent oligonucleotide array showed a copy number of 3 for Patient 1 and a copy number of 4 for Patient 2. Fluorescent in situ hybridization analysis of Patient 2 showed two different populations of cells with different marker chromosomes. Methylation analysis of the amplified region showed that the extra copies of small nuclear ribonucleoprotein polypeptide N gene were of maternal origin. Phenotypic severity did not correlate with the size and dosage of 15q, or whether the amplification is interstitial or in the form of a supernumerary marker. Pathway analysis showed that in Patient 2, the main functional networks that are affected by the genes from the duplicated/triplicated regions are developmental disorder, neurological disease and hereditary disease.

Conclusions

The 15q11-q13 gains that were found in both patients could explain their phenotypic presentations. This report expands the cohort of patients for which 15q11-q13 duplications are molecularly characterized.