Obesity and abnormal behaviour associated with interstitial deletion of chromosome 18 (q12.2q21.1)

Prenatal diagnosis and molecular cytogenetic characterization of an interstitial deletion of 18q12.1-q12.3 encompassing DTNA, CELF4 and SETBP1

OBJECTIVE

We present prenatal diagnosis and molecular cytogenetic characterization of an interstitial deletion of 18q12.1-q12.3.

CASE REPORT

A 35-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XX,del(18)(q12.1q12.3). The fetal ultrasound was unremarkable. The woman underwent repeat amniocentesis at 20 weeks of gestation. Array comparative genomic hybridization (aCGH) using uncultured amniocytes revealed a 10.76-Mb interstitial deletion 18q12.1-q12.3 or arr 18q12.1q12.3 (31,944,347-42,704,784) × 1.0 encompassing 19 Online Mendelian Inheritance of in Man (OMIM) genes including DTNA, CELF4 and SETBP1. Metaphase fluorescence in situ hybridization analysis on cultured amniocytes confirmed an 18q proximal interstitial deletion. The parental karyotypes were normal. Polymorphic DNA marker analysis determined a paternal origin of the deletion. The pregnancy was subsequently terminated at 24 weeks of gestation, and a 650-g fetus was delivered with characteristic facial dysmorphism.

CONCLUSION

aCGH analysis and polymorphic DNA marker analysis at amniocentesis are useful for determination of the deleted genes and the parental origin of the de novo deletion, and the acquired information is helpful for genetic counseling.

Features of two cases with 18q deletion syndrome

The 18q Deletion syndrome is seen in 1 out of 10 000 live births. The main features of the syndrome are short stature, hearing loss, hypotonia, mental retardation, endocrine disorders and autoimmunity. Here, we present 2 patients with this syndrome admitted to our clinic who were found to have insulin resistance in addition to mental retardation, short stature, autoimmune thyroiditis and hearing loss. The need to perform a karyogram analysis in cases presenting with these features is emphasized.

Haploinsufficiency of CELF4 at 18q12.2 is associated with developmental and behavioral disorders, seizures, eye manifestations, and obesity

Only 20 patients with deletions of 18q12.2 have been reported in the literature and the associated phenotype includes borderline intellectual disability, behavioral problems, seizures, obesity, and eye manifestations. Here, we report a male patient with a de novo translocation involving chromosomes 12 and 18, with borderline IQ, developmental and behavioral disorders, myopia, obesity, and febrile seizures in childhood. We characterized the rearrangement with Affymetrix SNP 6.0 Array analysis and next-generation mate pair sequencing and found truncation of CELF4 at 18q12.2. This second report of a patient with a neurodevelopmental phenotype and a translocation involving CELF4 supports that CELF4 is responsible for the phenotype associated with deletion of 18q12.2. Our study illustrates the utility of high-resolution genome-wide techniques in identifying neurodevelopmental and neurobehavioral genes, and it adds to the growing evidence, including a transgenic mouse model, that CELF4 is important for human brain development.

Structural Chromosome Abnormalities Associated with Obesity: Report of Four New subjects and Review of Literature

Obesity in humans is a complex polygenic trait with high inter-individual heritability estimated at 40-70%. Candidate gene, DNA linkage and genome-wide association studies (GWAS) have allowed for the identification of a large set of genes and genomic regions associated with obesity. Structural chromosome abnormalities usually result in congenital anomalies, growth retardation and developmental delay. Occasionally, they are associated with hyperphagia and obesity rather than growth delay. We report four new individuals with structural chromosome abnormalities involving 10q22.3-23.2, 16p11.2 and Xq27.1-q28 chromosomal regions with early childhood obesity and developmental delay. We also searched and summarized the literature for structural chromosome abnormalities reported in association with childhood obesity.

Psychiatric syndromes in individuals with chromosome 18 abnormalities

Chromosome 18 abnormalities are associated with a range of physical abnormalities such as short stature and hearing impairments. Psychiatric manifestations have also been observed. This study focuses on the presentations of psychiatric syndromes as they relate to specific chromosomal abnormalities of chromosome 18. Twenty-five subjects (13 with an 18q deletion, 9 with 18p tetrasomy, and 3 with an 18p deletion), were interviewed by psychiatrists (blind to specific chromosomal abnormality) using the DIGS (subjects 18 and older) or KSADS-PL (subjects under 18). A consensus best estimation diagnostic process was employed to determine psychiatric syndromes. Oligonucleotide Array Comparative Genomic Hybridization (Agilent Technologies) was utilized to define specific regions of chromosome 18 that were deleted or duplicated. These data were further analyzed to determine critical regions of the chromosome as they relate to phenotypic manifestations in these subjects. 58.3% of the chromosome 18q- deletion subjects had depressive symptoms, 58.3% had anxiety symptoms, 25% had manic symptoms, and 25% had psychotic symptoms. 66.6% of the chromosome 18p- deletion subjects had anxiety symptoms, and none had depressive, manic, or psychotic symptoms. Fifty percent of the chromosome 18p tetrasomy subjects had anxiety symptoms, 12.5% had psychotic symptoms, and 12.5% had a mood disorder. All three chromosomal disorders were associated with high anxiety rates. Psychotic, manic and depressive disorders were seen mostly in 18q- subjects and this may be helpful in narrowing regions for candidate genes for these psychiatric conditions.

Recurrent interstitial deletions of proximal 18q: a new syndrome involving expressive speech delay

Most deletions of the long arm of chromosome 18 involve some part of the most distal 30 Mb. We have identified five individuals with cytogenetically diagnosed interstitial deletions that are all proximal to this commonly deleted region. The extent of their deletions was characterized using molecular and molecular cytogenetic techniques. Each participant was assessed under the comprehensive clinical evaluation protocol of the Chromosome 18 Clinical Research Center. Three of the five individuals were found to have apparently identical interstitial deletions between positions of 37.5 and 42.5 Mb (18q12.3-->18q21.1). One individual's deletion was much larger and extended from a more proximal breakpoint position of 23 Mb (18q11.2) to a more distal breakpoint at 43 Mb (18q21.1). The fifth individual had a proximal breakpoint identical to the other three, but a distal breakpoint at 43.5 Mb (18q21.1). The clinical findings were of interest because the three individuals with the smaller deletions lacked major anomalies. All five individuals were developmentally delayed; however, the discrepancy between their expressive and receptive language abilities was striking, with expressive language being much more severely affected. This leads us to hypothesize that there are genes in this region of chromosome 18 that are specific to the neural and motor planning domains necessary for speech. Additionally, this may represent a previously underappreciated syndrome since these children do not have the typical clinical abnormalities that would lead to a chromosome analysis.

Cytogenetic abnormalities and fragile-X syndrome in Autism Spectrum Disorder

BACKGROUND

Autism is a behavioral disorder with impaired social interaction, communication, and repetitive and stereotypic behaviors. About 5-10 % of individuals with autism have 'secondary' autism in which an environmental agent, chromosome abnormality, or single gene disorder can be identified. Ninety percent have idiopathic autism and a major gene has not yet been identified. We have assessed the incidence of chromosome abnormalities and Fragile X syndrome in a population of autistic patients referred to our laboratory.

METHODS

Data was analyzed from 433 patients with autistic traits tested using chromosome analysis and/or fluorescence in situ hybridization (FISH) and/or molecular testing for fragile X syndrome by Southern and PCR methods.

RESULTS

The median age was 4 years. Sex ratio was 4.5 males to 1 female [354:79]. A chromosome (cs) abnormality was found in 14/421 [3.33 %] cases. The aberrations were: 4/14 [28%] supernumerary markers; 4/14 [28%] deletions; 1/14 [7%] duplication; 3/14 [21%] inversions; 2/14 [14%] translocations. FISH was performed on 23 cases for reasons other than to characterize a previously identified cytogenetic abnormality. All 23 cases were negative. Fragile-X testing by Southern blots and PCR analysis found 7/316 [2.2 %] with an abnormal result. The mutations detected were: a full mutation (fM) and abnormal methylation in 3 [43 %], mosaic mutations with partial methylation of variable clinical significance in 3 [43%] and a permutation carrier [14%]. The frequency of chromosome and fragile-X abnormalities appears to be within the range in reported surveys (cs 4.8-1.7%, FRAX 2-4%). Limitations of our retrospective study include paucity of behavioral diagnostic information, and a specific clinical criterion for testing.

CONCLUSIONS

Twenty-eight percent of chromosome abnormalities detected in our study were subtle; therefore a high resolution cytogenetic study with a scrutiny of 15q11.2q13, 2q37 and Xp23.3 region should be standard practice when the indication is autism. The higher incidence of mosaic fragile-X mutations with partial methylation compared to FRAXA positive population [50% vs 15-40%] suggests that faint bands and variations in the Southern band pattern may occur in autistic patients.

Del(18)(q12.2q21.1) caused by a paternal sister chromatid rearrangement in a developmentally delayed girl

Monosomy of 18q12.3 has been reported in only 16 cases, in one as a mosaic with a normal cell line. Abnormal behaviour, developmental delay, normal measurements, and minor facial anomalies including ptosis, bilateral epicanthus, strabismus, short and slightly down-slanting palpebral fissures, and full cheeks are characteristic manifestations. We report on a 26-month-old girl with del(18)(q12.2q21.1) and typical phenotype. Microsatellite mediated haplotype analysis showed approximately 12 Mb deletion and demonstrated that the deletion was most likely formed during paternal meiosis by a rearrangement between the grandpaternal sister chromatids.

Long-term survival in a patient with del(18)(q12.2q21.1)

The 18q- syndrome is relatively common among cytogenetic abnormalities occurring in approximately 1 in 40,000 live births. However, interstitial deletions involving 18q12.2 to q21.1 are much less common. Only 15 cases have been reported in the literature. A phenotypic pattern is emerging of mild dysmorphic features, mental retardation, behavior abnormalities, and the lack of serious malformations. We present a 67-year-old woman with minor dysmorphic features, moderate mental retardation, hyperphagia, and del(18)(q12.2q21.1). This patient is presented for the natural history of this deletion syndrome as well as the behavioral phenotype.

Chromosomal disorders and autism

Many cases of autism appear to be caused by several abnormal genes acting in concert. The literature on chromosomal aberrations in autism is reviewed, with a view to finding potential gene markers for the neuropsychiatric disorder. Most of the chromosomes have been implicated in the genesis of autism. However, aberrations on the long arm of Chromosome 15 and numerical and structural abnormalities of the sex chromosomes have been most frequently reported. These chromosomes appear to hold particular promise in the search for candidate genes.

Intersitial deletion of 20p: new candidate region for Hirschsprung disease and autism?

We describe a patient with Hirschsprung disease and autism. High-resolution karyotyping indicated that the patient has an interstitial deletion of 20p11.22-p11.23. Microsatellite analysis showed a deletion involving a 5-6 cM region from the maternally derived chromosome 20. The deleted region is proximal to, and does not overlap, the recently characterized Alagille syndrome region. This region of 20p has not yet been implicated in Hirschsprung disease or autism. However, this region contains several genes that could plausibly contribute to any phenotype that includes abnormal neural development.

Clinical review: Medical differential diagnosis and treatment of the autistic syndrome

Autism, like mental retardation, is not a definitive diagnosis. This paper discusses the medical differential diagnosis to consider when patients present with autistic symptoms. Summarizing the medical literature, the known infectious, metabolic, chromosomal and structural lesions are reviewed. Autism also can be associated with sensory handicaps, such as blindness and deafiness. When the autistic syndrome is associated with a second syndrome, this produces a "double syndrome" in the patient. A thorough medical evaluation of all individuals with autism is suggested.

Abnormalities of chromosome 18 in a girl with mental retardation and autistic disorder

Structural autosome defects have rarely been described in autism. In this report, the authors describe the association of autism and mental retardation in a girl with mosaicism for a duplication of the long arm of chromosome 18 and a deletion of the short arm of chromosome 18.

Recognizable behavioral and somatic phenotype in patients with proximal interstitial 18q deletion: report on a new affected child and follow-up on the original reported familial cases

We describe a moderately retarded boy with a chromosome 18 deletion involving the regions q11.2q12.2. His phenotype is similar to that of other reported cases of proximal interstitial deletions involving 18q. We also provide follow-up information on the first 4 cases of proximal interstitial deletion of 18q from a family with a complex chromosome rearrangement originally reported in 1974.

Monosomy 18q12.1----21.1: a recognizable aneuploidy syndrome? Report of a patient and review of the literature

This report of a patient with an interstitial deletion 18q and review of previously described cases suggest a clinically recognizable syndrome. The phenotype appears to result from a microdeletion of part of 18q12.2 or q12.3, or a deletion of parts of both bands.

Interstitial deletion of chromosome 18[del(18)(q11.2q12.2 or q12.2q21.1]

A 27-month old boy with mild developmental delay, growth delay, strabismus, midface hypoplasia, relative telecanthus, downslanting palpebral fissures, epicanthal folds, dental hypoplasia, and cardiac defects was found to have an interstitial deletion of chromosome 18 involving band q12.1 or q12.3

Interstitial deletion of the long arm of chromosome 18, del(18)(q12.2q21.1): a report of three cases of an autosomal deletion with a mild phenotype

We describe three unrelated patients with apparently identical interstitial deletions of the segment (18) (q12.2q21.1). They were a short and markedly mentally retarded 5 year old girl, a macrocephalic and obese 2 1/2 year old boy with moderate mental retardation, and a macrocephalic, severely mentally retarded 5 year old boy. Findings common to all five liveborn patients so far identified as carrying this deletion include a pattern of minor dysmorphic features (prominent forehead, ptosis of the upper eyelids, full periorbital tissue, epicanthic folds, strabismus), muscular hypotonia, seizures, behavioural disorders, and lack of major malformations.