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

Managing constipation in children with ASD - A challenge worth tackling

Autism Spectrum disorder (ASD) is well known to be associated with significantly high rates of gastrointestinal problems, constipation being common among them, imposing a significant burden on child and the family. On account of multiple underlying factors, both diagnosis and subsequent management of constipation in children with ASD are much more challenging as compared to managing constipation in 'neurotypical' children. Associated higher rate of presentation to the hospital emergency and subsequent hospital admission rates add to the burden. Hence, there is a need for recognizing constipation as a problem in children with ASD. This review summarizes optimization of its management by adopting a multidisciplinary holistic approach to achieve good outcomes and enhance the quality of life for the child and the family.

Dysgenesis and Dysfunction of the Pancreas and Pituitary Due to FOXA2 Gene Defects

CONTEXT

Developmental disorders of the pituitary gland leading to congenital hypopituitarism can either be isolated or associated with extrapituitary abnormalities (syndromic hypopituitarism). A large number of syndromic hypopituitarism cases are linked to mutations in transcription factors. The forkhead box A2 (FOXA2) is a transcription factor that plays a key role in the central nervous system, foregut, and pancreatic development.

OBJECTIVE

This work aims to characterize 2 patients with syndromic hypopituitarism due to FOXA2 gene defects.

RESULTS

We report a novel heterozygous nonsense c.616C > T(p.Q206X) variant that leads to a truncated protein that lacks part of the DNA-binding domain of FOXA2, resulting in impaired transcriptional activation of the glucose transporter type 2 (GLUT2)-luciferase reporter. The patient is the sixth patient described in the literature with a FOXA2 mutation, and the first patient exhibiting pancreatic hypoplasia. We also report a second patient with a novel de novo 8.53 Mb deletion of 20p11.2 that encompasses FOXA2, who developed diabetes mellitus that responded to sulfonylurea treatment.

CONCLUSION

Our 2 cases broaden the molecular and clinical spectrum of FOXA2-related disease, reporting the first nonsense mutation and the first case of pancreatic dysgenesis.

Haploinsufficiency of the FOXA2 associated with a complex clinical phenotype

Background

There are few reports describing the proximal deletions of the short arm of chromosome 20, making it difficult to predict the likely consequences of these deletions. Most previously reported cases have described the association of 20p11.2 deletions with Alagille syndrome, while there are others that include phenotypes such as panhypopituitarism, craniofacial dysmorphism, polysplenia, autism, and Hirschsprung disease.

Methods

Molecular karyotyping, cytogenetics, and DNA sequencing were undertaken in a child to study the genetic basis of a complex phenotype consisting of craniofacial dysmorphism, ocular abnormalities, ectopic inguinal testes, polysplenia, growth hormone deficiency, central hypothyroidism, and gastrointestinal system anomalies.

Results

We report the smallest described de novo proximal 20p11.2 deletion, which deletes only the FOXA2 leading to the above complex phenotype.

Conclusions

Haploinsufficiency of the FOXA2 only gene is associated with a multisystem disorder.

Expanding phenotype with severe midline brain anomalies and missense variant supports a causal role for FOXA2 in 20p11.2 deletion syndrome

Rare individuals with 20p11.2 proximal deletions have been previously reported, with a variable phenotype that includes heterotaxy, biliary atresia, midline brain defects associated with panhypopituitarism, intellectual disability, scoliosis, and seizures. Deletions have ranged in size from 277 kb to 11.96 Mb. We describe a newborn with a de novo 2.7 Mb deletion of 20p11.22p11.21 that partially overlaps previously reported deletions and encompasses FOXA2. Her clinical findings further expand the 20p11.2 deletion phenotype to include severe midline cranial and intracranial defects such as aqueductal stenosis with hydrocephalus, mesencephalosynapsis with diencephalic-mesencephalic junction dysplasia, and pyriform aperture stenosis. We also report one individual with a missense variant in FOXA2 who had abnormal glucose homeostasis, panhypopituitarism, and endodermal organ dysfunction. Together, these findings support the critical role of FOXA2 in panhypopituitarism and midline defects.

Synaptosome-Associated Protein 25 (SNAP25) Gene Association Analysis Revealed Risk Variants for ASD, in Iranian Population

Autism spectrum disorder (ASD) is a common, complex neurological condition, affecting approximately 1% of people worldwide. Monogenic neurodevelopmental disorders which showed autistic behavior patterns have suggested synaptic dysfunction, as a key mechanism in the pathophysiology of ASD. Subsequently, genes involved in synaptic signaling have been investigated with a priority for candidate gene studies. A synaptosomal-associated protein 25 (SNAP25) gene plays a crucial role in the central nervous system, contributing to exocytosis by targeting and fusion of vesicles to the cell membrane. Studies have shown a correlation between aberrant expression of the SNAP25 and a variety of brain diseases. Single nucleotide polymorphisms (SNPs) in this gene are associated with several psychiatric diseases, such as bipolar, schizophrenia, and attention-deficit/hyperactivity disorder. The aim of the present study was to investigate whether polymorphisms (rs3746544 and rs1051312) in the regulatory 3'-untranslated region (3'UTR) of the SNAP25 gene have an association with ASD in unrelated Iranian case (N = 524)-control (N = 472) samples. We observed robust association of the rs3746544 SNP and ASD patients, in both allele and haplotype-based analyses. Our results supported the previous observations and indicated a possible role for SNAP25 polymorphisms as susceptibility genetic factors involved in developing ASD.

A genome-wide association analysis of chromosomal aberrations and Hirschsprung disease

Hirschsprung disease (HSCR) is a neurocristopathy characterized by the absence of intramural ganglion cells along variable lengths of the gastrointestinal tract. Although the RET proto-oncogene is considered to be the main risk factor for HSCR, only about 30% of the HSCR cases can be explained by variations in previously known genes including RET. Recently, copy number variation (CNV) and loss of heterozygosity (LOH) have emerged as new ways to understand human genomic variation. The goal of this present study is to identify new HSCR genetic factors related to CNV in Korean patients. In the genome-wide genotyping, using Illumina's HumanOmni1-Quad BeadChip (1,140,419 markers), of 123 HSCR patients and 432 unaffected subjects (total n = 555), a total of 8,188 CNVs (1 kb ∼ 1 mb) were identified by CNVpartition. As a result, 16 CNV regions and 13 LOH regions were identified as associated with HSCR (minimum P = 0.0005). Two top CNV regions (deletions at chr6:32675155-32680480 and chr22:20733495-21607293) were successfully validated by additional real-time quantitative polymerase chain reaction analysis. In addition, 2 CNV regions (6p21.32 and 22q11.21) and 2 LOH regions (3p22.2 and 14q23.3) were discovered to be unique to the HSCR patients group. Regarding the large-scale chromosomal aberrations (>1 mb), 11 large aberrations in the HSCR patients group were identified, which suggests that they may be a risk factor for HSCR. Although further replication in a larger cohort is needed, our findings may contribute to the understanding of the etiology of HSCR.

Delineation of a region responsible for panhypopituitarism in 20p11.2

We report on the case of a young woman with a de novo 20p11.21p11.23 deletion, discovered by array-CGH. She has behavioral troubles with autistic traits, intellectual disability, panhypopituitarism, severe hypoglycemia, epilepsy, and scoliosis. The majority of the reported 20p deletions are located on the 20p12 region, covering the JAG1 gene responsible for the Alagille syndrome. More proximal deletions are even rarer, with very few cases described in the literature to date. The deletion carried by our patient is, to our knowledge, the smallest described de novo proximal 20p11.2 deletion. It was first discovered by 0.5 Mb BAC array-CGH, further delineated using an oligonucleotide array, and finally confirmed by fluorescence in situ hybridization. The deletion is 4.22 Mb in size, with the exact location on chr20: 19.810.034-24.031.344 (Feb. 2009, GRCh37/hg19). In light of the other reported cases that display genomic and phenotypic overlap with our patient, we discuss the phenotype of our patient, in order to further delineate the 20p proximal deletion phenotype. We propose a minimal critical region responsible for panhypopituitarism with global developmental delay, intellectual disability, scoliosis and facial dysmorphism. Moreover, considering the deleted genes, we highlight the impact of the deletion of this minimal critical region on the Shh signaling pathway.

20p11 deletion in a female child with panhypopituitarism, cleft lip and palate, dysmorphic facial features, global developmental delay and seizure disorder

Deletions of 20p are rare with the majority of reported cases involving individuals with 20p12 deletions associated with Alagille syndrome. We report on a child with a de novo mosaic 20p11 deletion who presents with panhypopituitarism; hypoplastic pituitary gland and ectopic posterior pituitary gland on MRI of the brain; cleft lip and palate; kyphosis with anterior beaking of L1 and L2 vertebral bodies; pulmonic stenosis; dysmorphic facial features including flat nasal bridge, hypoplastic premaxilla, hypotelorism, preauricular pit, and cupped ears; seizure disorder; variable muscle tone; and global developmental delay. Array comparative genomic hybridization revealed this deletion to be approximately 5.4 Mb in size, containing 35 genes. Previously, an infant with 20p11.22 deletion who had panhypopituitarism, craniofacial, and genital abnormalities was reported, but the precise parameters of that deletion are unavailable. Several other reported cases of 20p11 deletions also have phenotypic overlap with our case. The similarities in clinical features of these patients suggest that the genes at 20p11 have a critical role in development of midline brain structures.

Parent-of-origin effects in autism identified through genome-wide linkage analysis of 16,000 SNPs

BACKGROUND

Autism is a common heritable neurodevelopmental disorder with complex etiology. Several genome-wide linkage and association scans have been carried out to identify regions harboring genes related to autism or autism spectrum disorders, with mixed results. Given the overlap in autism features with genetic abnormalities known to be associated with imprinting, one possible reason for lack of consistency would be the influence of parent-of-origin effects that may mask the ability to detect linkage and association.

METHODS AND FINDINGS

We have performed a genome-wide linkage scan that accounts for potential parent-of-origin effects using 16,311 SNPs among families from the Autism Genetic Resource Exchange (AGRE) and the National Institute of Mental Health (NIMH) autism repository. We report parametric (GH, Genehunter) and allele-sharing linkage (Aspex) results using a broad spectrum disorder case definition. Paternal-origin genome-wide statistically significant linkage was observed on chromosomes 4 (LOD(GH) = 3.79, empirical p<0.005 and LOD(Aspex) = 2.96, p = 0.008), 15 (LOD(GH) = 3.09, empirical p<0.005 and LOD(Aspex) = 3.62, empirical p = 0.003) and 20 (LOD(GH) = 3.36, empirical p<0.005 and LOD(Aspex) = 3.38, empirical p = 0.006).

CONCLUSIONS

These regions may harbor imprinted sites associated with the development of autism and offer fruitful domains for molecular investigation into the role of epigenetic mechanisms in autism.

A tale of two deletions: a report of two novel 20p13 --> pter deletions

We report on two patients with 1.7 and 1.2 Mb terminal 20p deletions, which have apparently not been reported previously. Both individuals exhibit certain similar features including large fontanelles, ear abnormalities, and seizures. However, even though the deletions are of similar size, there were many disparate features between the two. The deletions in each patient encompass at least 28 genes that may provide useful candidates for ear development and cranial ossification.

SNP array mapping of chromosome 20p deletions: genotypes, phenotypes, and copy number variation

The use of array technology to define chromosome deletions and duplications is bringing us closer to establishing a genotype/phenotype map of genomic copy number alterations. We studied 21 patients and five relatives with deletions of the short arm of chromosome 20 using the Illumina HumanHap550 SNP array to: 1) more accurately determine the deletion sizes; 2) identify and compare breakpoints; 3) establish genotype/phenotype correlations; and 4) investigate the use of the HumanHap550 platform for analysis of chromosome deletions. Deletions ranged from 95 kb to 14.62 Mb, and all of the breakpoints were unique. Eleven patients had deletions between 95 kb and 4 Mb and these individuals had normal development, with no anomalies outside of those associated with Alagille syndrome (AGS). The proximal and distal boundaries of these 11 deletions constitute a 5.4-Mb region, and we propose that haploinsufficiency for only 1 of the 12 genes in this region causes phenotypic abnormalities. This defines the JAG1-associated critical region, in which deletions do not confer findings other than those associated with AGS. The other 10 patients had deletions between 3.28 Mb and 14.62 Mb, which extended outside the critical region, and, notably, all of these patients had developmental delay. This group had other findings such as autism, scoliosis, and bifid uvula. We identified 47 additional polymorphic genome-wide copy number variants (>20 SNPs), with 0 to 5 variants called per patient. Deletions of the short arm of chromosome 20 are associated with relatively mild and limited clinical anomalies. The use of SNP arrays provides accurate high-resolution definition of genomic abnormalities.

Prokineticin-1 (Prok-1) works coordinately with glial cell line-derived neurotrophic factor (GDNF) to mediate proliferation and differentiation of enteric neural crest cells

Enteric neural crest cells (NCC) are multipotent progenitors which give rise to neurons and glia of the enteric nervous system (ENS) during fetal development. Glial cell line-derived neurotrophic factor (GDNF)/RET receptor tyrosine kinase (Ret) signaling is indispensable for their survival, migration and differentiation. Using microarray analysis and isolated NCCs, we found that 45 genes were differentially expressed after GDNF treatment (16 h), 29 of them were up-regulated including 8 previously undescribed genes. Prokineticin receptor 1 (PK-R1), a receptor for Prokineticins (Prok), was identified in our screen and shown to be consistently up-regulated by GDNF in enteric NCCs. Further, PK-R1 was persistently expressed at a lower level in the enteric ganglions of the c-Ret deficient mice when compared to that of the wild-type littermates. Subsequent functional analysis showed that GDNF potentiated the proliferative and differentiation effects of Prok-1 by up-regulating PK-R1 expression in enteric NCCs. In addition, expression analysis and gene knock-down experiments indicated that Prok-1 and GDNF signalings shared some common downstream targets. More importantly, Prok-1 could induce both proliferation and expression of differentiation markers of c-Ret deficient NCCs, suggesting that Prok-1 may also provide a complementary pathway to GDNF signaling. Taken together, these findings provide evidence that Prok-1 crosstalks with GDNF/Ret signaling and probably provides an additional layer of signaling refinement to maintain proliferation and differentiation of enteric NCCs.

Prevalence of gastrointestinal disorders in adult clients with pervasive developmental disorders

BACKGROUND

In clients with pervasive developmental disorders (PDD), some authors have noticed the presence of gastrointestinal disorders and behavioural disorders. An augmented prevalence of different histological anomalies has also been reported. The aim of our study is to highlight the prevalence of gastrointestinal disorders in this adult with PDD sample and to demonstrate the importance of accurate evaluation of gastrointestinal disorders in clients with PDD.

METHODS

The present comparative study involved 118 clients. Our research was motivated by the clinical observation that behavioural disorders sometimes disappeared with administration of anti-gastric acid or anti-ulcerous medications. It focused on two samples of clients with intellectual disability - those with associated PDD and those without. The presence of gastrointestinal disorders was assessed retrospectively on the basis of hospital records.

RESULTS

The prevalence of gastrointestinal disorders reported in clinical files was 48.8% in clients with PDD, as compared with 8.0% in non-PDD clients (P < 0.00001).

CONCLUSION

Gastrointestinal disorders, and especially gastro-oesophageal reflux, if neglected, may contribute to behavioural disorders in PDD clients. Moreover, gastrointestinal disorders may be considered as a feature of PDD. We highlight the fact that somatic disorders may coexist in persons with PDD.

A deletion of proximal 20p inherited from a normal mosaic carrier mother in a newborn with panhypopituitarism and craniofacial dysmorphism

We describe a newborn male with a constitutional deletion of proximal chromosome 20p involving band p11.2. The phenotype included panhypopituitarism, craniofacial dysmorphism, a small phallus with a semi bifid scrotum, and bilateral widely separated first and second toes. The deletion was inherited from his mother, a mosaic carrier of the same deletion in peripheral lymphocytes. The only other similar case with a deletion of 20p11.22-p11.23 exhibited a phenotype that also included abnormal neural development (autism, craniofacial dysmorphism, and Hirschsprung disease). Our patient expands the spectrum of neurodevelopmental abnormalities associated with haploinsufficiency of band 20p11.2, and is the second deletion of 20p inherited from a normal mosaic carrier mother.

Mosaic paternal uniparental (iso)disomy for chromosome 20 associated with multiple anomalies

Uniparental disomy for a number of human chromosomes is associated with clinical abnormalities. We report a child with a complex chromosomal rearrangement involving chromosome 20 (45,XY,psu dic (20;20)(p13;p13)) and paternal uniparental isodisomy for chromosome 20 in peripheral blood and bone marrow. This patient had multiple congenital abnormalities including microtia/anotia, micrencephaly, congenital heart disease, neuronal subependymal heterotopias, and colonic agangliosis. Molecular studies on DNA from peripheral blood demonstrated paternal uniparental inheritance of chromosome 20. However, fibroblasts demonstrated a mosaic karyotype, with one cell line having 45 chromosomes, including the pseudodicentric chromosome 20 (75% of cells), and a second cell line having 46 chromosomes, including the pseudodicentric chromosome 20, and a normal chromosome 20 (trisomy 20) (25% of cells). FISH experiments using a sub-telomeric probe that maps approximately 120 kb from the 20p telomere, showed that both copies of these sequences were present on the rearranged chromosome, consistent with deletion of a very small interval. This leads us to suggest that in addition to trisomy 20 mosaicism, paternal uniparental disomy for chromosome 20 could contribute to his clinical phenotype.

Molecular genetics of autism spectrum disorders

Autistic disorder belongs to a broad spectrum of pervasive developmental disorders. Autism is a clinically and genetically heterogeneous condition. It is characterized by impairment in a broad range of social interactions, communication, and repetitive patterns of behavior and interest. Although the exact etiology of the condition is not known, family and twin studies strongly support genetic factors in autism. Genome-wide scans suggest several susceptibility loci that may contain one or more predisposing genes. However, no such genes have been identified so far that predispose patients to autism. The condition is over 90% heritable, but the mode of inheritance is not clear. Moreover, it does not seem to be a single gene disorder. There is no cure for autism. Individualized structured education, family support services, and antipsychotic drugs are recommended. These may alleviate some behavioral problems. The identification of autism genes, an understanding of the neurobiology of the condition, and additional clinical studies may help to develop pharmacological interventions in the future.

Autistic disorder and chromosomal mosaicism 46,XY[123]/46,XY,del(20)(pter --> p12.2)[10]

We report on a 3-year-old boy with a moderate to severe mental retardation, autistic behavior patterns, and myoclonic epilepsy of early childhood. The cytogenetic analysis of blood lymphocytes revealed a deletion of chromosome 20pter --> p12.2 occurring as mosaicism in 8% of the analyzed metaphases: 46,XY[123]/46,XY,del(20)(pter --> p12.2)[10]. The deletion was confirmed by the recently developed multicolor banding approach and additionally by region specific fluorescence in situ hybridization (FISH) probes. To the best of our knowledge, this is the first report on a patient with autistic behavior with terminal 20p deletion mosaicism reported up to present.

Presence of large deletions in kindreds with autism

Autism is caused, in part, by inheritance of multiple interacting susceptibility alleles. To identify these inherited factors, linkage analysis of multiplex families is being performed on a sample of 105 families with two or more affected sibs. Segregation patterns of short tandem repeat polymorphic markers from four chromosomes revealed null alleles at four marker sites in 12 families that were the result of deletions ranging in size from 5 to >260 kb. In one family, a deletion at marker D7S630 was complex, with two segments deleted (37 kb and 18 kb) and two retained (2,836 bp and 38 bp). Three families had deletions at D7S517, with each family having a different deletion (96 kb, 183 kb, and >69 kb). Another three families had deletions at D8S264, again with each family having a different deletion, ranging in size from <5.9 kb to >260 kb. At a fourth marker, D8S272, a 192-kb deletion was found in five families. Unrelated subjects and additional families without autism were screened for deletions at these four sites. Families screened included 40 families from Centre d'Etude du Polymorphisme Humaine and 28 families affected with learning disabilities. Unrelated samples were 299 elderly control subjects, 121 younger control subjects, and 248 subjects with Alzheimer disease. The deletion allele at D8S272 was found in all populations screened. For the other three sites, no additional deletions were identified in any of the groups without autism. Thus, these deletions appear to be specific to autism kindreds and are potential autism-susceptibility alleles. An alternative hypothesis is that autism-susceptibility alleles elsewhere cause the deletions detected here, possibly by inducing errors during meiosis.

Molecular and cytogenetic characterisation of a small interstitial de novo 20p13-->p12.3 deletion in a patient with severe growth deficit

We report on a small de novo interstitial deletion of the short arm of chromosome 20, 46,XY,del(20)(p12.3p13), in a young boy with hypotonia, moderate development delay, mild facial dysmorphism and severe growth failure. This patient did not show major features of Alagille-Watson Syndrome (AWS) which are common in more proximal 20p deletions. Standard and high resolution chromosome banding analysis revealed an apparent terminal deletion. Nevertheless, using chromosomal fluorescent in situ hybridization (FISH) and molecular analysis with polymorphic markers, we demonstrated that the abnormal chromosome resulted from a de novo interstitial deletion of paternal origin spanning from D20S842 to D20S900 and covering approximately 6 Mb. These findings indicate that a karyotype can lead to insufficient characterization of an apparently terminal deletion, and that one or a few genes in 20p13-->p12.3 bands are important for normal growth.