Neurodevelopmental profile of a new dysmorphic syndrome associated with submicroscopic partial deletion of 1p36.3

Electroclinical features of epilepsy monosomy 1p36 syndrome and their implications

OBJECTIVIES

Monosomy 1p36 syndrome is a recognized syndrome with multiple congenital anomalies; medical problems of this syndrome include developmental delay, facial dysmorphisms, hearing loss, short stature, brain anomalies, congenital heart defects. Epilepsy can be another feature but there are few data about the types of seizures and long term prognosis. The aim of this work was to analyse the electroclinical phenotype and the long-term outcome in patients with monosomy 1p36 syndrome and epilepsy.

MATERIALS AND METHODS

Data of 22 patients with monosomy 1p36 syndrome and epilepsy were reconstructed by reviewing medical records. For each patient we analysed age at time of diagnosis, first signs of the syndrome, age at seizure onset, seizure type and its frequency, EEG and neuroimaging findings, the response to antiepileptic drugs treatment and clinical outcome up to the last follow-up assessment.

RESULTS

Infantile Spasm (IS) represents the most frequent type at epilepsy onset, which occurs in 36.4% of children, and a half of these were associated with hypsarrhythmic electroencephalogram. All patients with IS had persistence of seizures, unlike other patients with different seizures onset. Children with abnormal brain neuroimaging have a greater chance to develop pharmacoresistant epilepsy.

CONCLUSION

This syndrome represents a significant cause of IS: these patients, who develop IS, can suffer from pharmacoresistent epilepsy, that is more frequent in children with brain abnormalities.

Electroclinical features of epilepsy associated with 1p36 deletion syndrome: A review

1p36 terminal deletion is a recently recognized syndrome with multiple congenital anomalies and intellectual disability. It occurs approximately in 1 out of 5000 to 10,000 live births and is the most common subtelomeric microdeletion observed in human. Medical problems commonly caused by terminal deletions of 1p36 include developmental delay, intellectual disability, seizures, vision problems, hearing loss, short stature, brain anomalies, congenital heart defects, cardiomyopathy, renal anomalies and distinctive facial features. Although the syndrome is considered clinically recognizable, there is significant phenotypic variation among affected individuals. Genotype-phenotype correlation in this syndrome is complicated, because of the similar clinical evidence seen in patients with different deletion sizes. We review 34 scientific articles from 1996 to 2016 that described 315 patients with 1p36 delection syndrome. The aim of this review is to find a correlation between size of the 1p36-deleted segments and the neurological clinical phenotypes with the analysis of electro-clinical patterns associated with chromosomal aberrations, that is a major tool in the identification of epilepsy susceptibility genes. Our finding suggest that developmental delay and early epilepsy are frequent findings in 1p36 deletion syndrome that can contribute to a poor clinical outcome for this reason this syndrome should be searched for in patients presenting with infantile spasms associated with a hypsarrhythmic EEG, particulary if they are combined with dismorphic features, severe hypotonia and developmental delay.

[An updated review of 1p36 deletion (monosomy) syndrome]

The Monosomy 1p36 deletion syndrome is part of the group of diseases known as Rare Diseases. The objective of the present work is to review the characteristics of Monosomy 1p36 deletion syndrome. The monosomy 1p36 deletion syndrome phenotype includes: dysmorphic craniofacial features; large anterior fontanelle, unibrow, deep-set eyes, epicanthus, wide nasal root/bridge, mandible hypoplasia, abnormal location of the pinna, philtrum and pointed chin; neurological alterations: seizures and hydrocephalus (in some cases). Cerebral malformations: ventricular hypertrophy, increased subarachnoid space, morphological alterations of corpus callosum, cortical atrophy, delays in myelinisation, periventricular leukomalacia and periventricular heterotopia. These alterations produce intellectual disability and delays in motor growth, communication skills, language, social and adaptive behaviour. It is Hearing and vision impairments are also observed in subjects with this syndrome, as well as alterations of cardiac, endocrine and urinary systems and alterations at skin and skeletal level.

CONCLUSIONS

Approximately 100 cases have been documented since 1981. This rare disease is the most common subtelomeric-micro-deletion syndrome. In situ hybridization with fluorescence (FISH) and array-comparative genomic hybridization (CGH-array) are at present the two best diagnostic techniques. There is currently no effective medical treatment for this disease.

Delineating the phenotype of 1p36 deletion in adolescents and adults

1p36 deletion is the most common telomeric deletion syndrome, with an incidence of 1/5,000-1/10,000. A variety of clinical complications have been reported including seizures, hypotonia, heart malformations, cardiomyopathy, vision problems, and hearing loss. Approximately 90% are reported to have severe to profound intellectual disability and 75% to have absent expressive language. Little is known about long-term outcomes. The current literature suggests a poor prognosis for most patients. This study attempted to assess medical conditions and function of adolescent and adult patients with 1p36 deletion. A survey was distributed through three support groups to identify patients >12 years of age to assess functional status and medical problems in older patients with 1p36 deletion syndrome. 40 patients were identified between 12 and 46 years old. Among our survey sample, medical complications including seizures, hypotonia, structural heart defects, hearing loss, and vision problems, were similar to previous reports. However, functional skills were better than anticipated, with an overwhelming majority reported to independently sit, walk, and receive the majority of nutrition orally. Forty-four percent were reported to use complex speech abilities. While medical problems in patients with 1p36 deletion were similar to those that have been previously reported, we also demonstrated these same concerns persist into adolescence and adulthood. Additionally, patients were reported to have better functional skills than anticipated. Thus, quality of life and level of function appear to be better than anticipated from previous studies. © 2014 Wiley Periodicals, Inc.

[Subtelomeric rearrangements in cryptogenic mental retardation]

INTRODUCTION

Mental retardation affects 3% of the population, the origin of which cannot be established in 50% of cases. Subtelomeric rearrangements, not detected by routine cytogenetic studies, might explain some cases of unknown cause.

PATIENTS AND METHODS

A study was conducted on 200 subjects with unexplained mental retardations using multiplex ligation dependent probe amplification (MLPA). Abnormal findings were confirmed by fluorescent in situ hybridization (FISH) and/or comparative genomic hybridization technology (CGH-array).

RESULTS

A subtelomeric aberration was identified in 9 patients. Eight were «de novo»; one was inherited from a phenotypically normal parent. There was a statistically significant association with the presence of more than one dysmorphic feature or with intrauterine growth retardation, but not with the severity of retardation or epilepsy.

CONCLUSIONS

Subtelomeric rearrangements explained 4.5% of cases of mental retardation in our series. The presence of more than one dysmorphic feature or intrauterine uterine growth retardation increases the probability of this type of chromosomal aberration.

Etiological heterogeneity in autism spectrum disorders: more than 100 genetic and genomic disorders and still counting

There is increasing evidence that autism spectrum disorders (ASDs) can arise from rare highly penetrant mutations and genomic imbalances. The rare nature of these variants, and the often differing orbits of clinical and research geneticists, can make it difficult to fully appreciate the extent to which we have made progress in understanding the genetic etiology of autism. In fact, there is a persistent view in the autism research community that there are only a modest number of autism loci known. We carried out an exhaustive review of the clinical genetics and research genetics literature in an attempt to collate all genes and recurrent genomic imbalances that have been implicated in the etiology of ASD. We provide data on 103 disease genes and 44 genomic loci reported in subjects with ASD or autistic behavior. These genes and loci have all been causally implicated in intellectual disability, indicating that these two neurodevelopmental disorders share common genetic bases. A genetic overlap between ASD and epilepsy is also apparent in many cases. Taken together, these findings clearly show that autism is not a single clinical entity but a behavioral manifestation of tens or perhaps hundreds of genetic and genomic disorders. Increased recognition of the etiological heterogeneity of ASD will greatly expand the number of target genes for neurobiological investigations and thereby provide additional avenues for the development of pathway-based pharmacotherapy. Finally, the data provide strong support for high-resolution DNA microarrays as well as whole-exome and whole-genome sequencing as critical approaches for identifying the genetic causes of ASDs.

Epilepsy and chromosomal abnormalities

Background

Many chromosomal abnormalities are associated with Central Nervous System (CNS) malformations and other neurological alterations, among which seizures and epilepsy. Some of these show a peculiar epileptic and EEG pattern. We describe some epileptic syndromes frequently reported in chromosomal disorders.

Methods

Detailed clinical assessment, electrophysiological studies, survey of the literature.

Results

In some of these congenital syndromes the clinical presentation and EEG anomalies seems to be quite typical, in others the manifestations appear aspecific and no strictly linked with the chromosomal imbalance. The onset of seizures is often during the neonatal period of the infancy.

Conclusions

A better characterization of the electro clinical patterns associated with specific chromosomal aberrations could give us a valuable key in the identification of epilepsy susceptibility of some chromosomal loci, using the new advances in molecular cytogenetics techniques - such as fluorescent in situ hybridization (FISH), subtelomeric analysis and CGH (comparative genomic hybridization) microarray. However further studies are needed to understand the mechanism of epilepsy associated with chromosomal abnormalities.

Molecular characterization of a monosomy 1p36 presenting as an Aicardi syndrome phenocopy

Monosomy 1p36 is the most frequent terminal deletion known in Humans. Typical craniofacial features, developmental delay/mental retardation, seizures and sensorineural defects characterize 1p36 deletion syndrome. Aicardi syndrome (AIS) is a rare genetic disorder characterized by chorioretinal lacunae, corpus callosum agenesis and infantile spasms responsible for mental retardation. By screening DNA from diagnosed AIS patients with oligonucleotide array-based comparative genomic hybridization (aCGH), we report a 1p36 monosomy in this study. There were no other deletions or duplications. Regarding clinical criteria, the patient did not have the typical facial appearance commonly described for 1p36 monosomy patients. We showed that this 1p36 monosomy corresponded to combined interstitial and terminal de novo deletions of the chromosome 1 leading to an 11.73 Mb deletion confirmed with qPCR. By microsatellite markers and FISH analyses, we have concluded that this deletion occurred on maternal chromosome 1 during oogenesis. We did find some clinical features shared by the 1p36 monosomy and AIS: infantile spasms, corpus callosum dysgenesis, ophthalmological abnormalities, and skeletal malformations. To date, no relationship between these two phenotypes has been established. We conclude that the monosomy 1p36 should be considered in the differential diagnosis of AIS.

Consistent chromosome abnormalities identify novel polymicrogyria loci in 1p36.3, 2p16.1-p23.1, 4q21.21-q22.1, 6q26-q27, and 21q2

Polymicrogyria is a malformation of cortical development characterized by loss of the normal gyral pattern, which is replaced by many small and infolded gyri separated by shallow, partly fused sulci, and loss of middle cortical layers. The pathogenesis is unknown, yet emerging data supports the existence of several loci in the human genome. We report on the clinical and brain imaging features, and results of cytogenetic and molecular genetic studies in 29 patients with polymicrogyria associated with structural chromosome rearrangements. Our data map new polymicrogyria loci in chromosomes 1p36.3, 2p16.1-p23, 4q21.21-q22.1, 6q26-q27, and 21q21.3-q22.1, and possible loci in 1q44 and 18p as well. Most and possibly all of these loci demonstrate incomplete penetrance and variable expressivity. We anticipate that these data will serve as the basis for ongoing efforts to identify the causal genes located in these regions.

Further delineation of deletion 1p36 syndrome in 60 patients: a recognizable phenotype and common cause of developmental delay and mental retardation

OBJECTIVES

Deletion 1p36 syndrome is a recently delineated disorder, considered to be the most common subtelomeric microdeletion syndrome (1 in 5000 newborns). 1p36.3 deletions account for 0.5% to 1.2% of idiopathic mental retardation; thus, knowledge about the condition is important for pediatricians caring for such patients. Despite 100 reported cases, little is known about its natural history. Our aim was to delineate the natural history of deletion 1p36 and develop complete and accurate information with which to answer families' questions in the clinical setting.

PATIENTS AND METHODS

We evaluated 60 patients with the 1p36 deletion syndrome (41 female, 19 male). All underwent physical and neurologic assessments, and most received a psychological evaluation. Standard cytogenetics, fluorescence in situ hybridization of the subtelomeric regions, or array comparative genomic hybridization were used for diagnosis.

RESULTS

Fourteen cases were detected by standard cytogenetics, and 46 were detected by fluorescence in situ hybridization of the subtelomeric regions or array comparative genomic hybridization. Occipitofrontal circumference was at < or = 2nd centile in 95%, and height and weight ranged between the < 3rd and 90th centiles. All patients had straight eyebrows, deep-set eyes, midface hypoplasia, broad nasal root/bridge, long philtrum, and pointed chin. Other features included microbrachycephaly (65%), epicanthus (50%), large, late-closing anterior fontanel (77%), and posteriorly rotated, low-set, abnormal ears (40%). Brachy/camptodactyly and short feet were prominent. Seventy-one percent exhibited heart defects, including 23% with a "noncompaction cardiomyopathy." Fifty-two percent had eye/visual abnormalities, and 64% had visual inattentiveness. Twenty-eight percent had sensorineural deafness, 41% had skeletal anomalies, 25% had abnormal genitalia, and 22% had renal abnormalities. Eighty-eight percent had central nervous system anomalies, and 44% had seizures. All patients demonstrated developmental delay with poor/absent speech; 95% had hypotonia. Twenty-six percent were able to walk alone, and 47% had a behavior disorder. Constant developmental progress was observed in all cases over time. Noncompaction cardiomyopathy and most seizures were controlled by pharmacotherapy.

CONCLUSIONS

These 60 patients with deletion 1p36 represent the largest clinical series to date and provide new information on several aspects of this disorder, which is characterized by neurodevelopmental disability and a recognizable pattern of malformation.

Idiopathic learning disability and genome imbalance

Learning disability (LD) is a very common, lifelong and disabling condition, affecting about 3% of the population. Despite this, it is only over the past 10-15 years that major progress has been made towards understanding the origins of LD. In particular, genetics driven advances in technology have led to the unequivocal demonstration of the importance of genome imbalance in the aetiology of idiopathic LD (ILD). In this review we provide an overview of these advances, discussing technologies such as multi-telomere FISH and array CGH that have already emerged as well as new approaches that show diagnostic potential for the future. The advances to date have highlighted new considerations such as copy number polymorphisms (CNPs) that can complicate the interpretation of genome imbalance and its relevance to ILD. More importantly though, they have provided a remarkable approximately 15-20% improvement in diagnostic capability as well as facilitating genotype/phenotype correlations and providing new avenues for the identification and understanding of genes involved in neurocognitive function.

Prader-Willi-like phenotype: investigation of 1p36 deletion in 41 patients with delayed psychomotor development, hypotonia, obesity and/or hyperphagia, learning disabilities and behavioral problems

Monosomy 1p36 is one of the most commonly observed mental retardation (MR) syndromes that results in a clinically recognizable phenotype including delayed psychomotor development and/or MR, hypotonia, epilepsy, hearing loss, growth delay, microcephaly, deep-set eyes, flat nasal bridge and pointed chin. Besides, a Prader-Willi syndrome (PWS)-like phenotype has been described in patients with 1p36 monosomy. Forty-one patients presenting hypotonia, developmental delay, obesity and/or hyperphagia and behavioral problems who tested negative for PWS were investigated by FISH and/or microsatellite markers. Twenty-six were analyzed with a 1p-specific subtelomeric probe, and one terminal deletion was identified. Thirty patients (15 of which also studied by FISH) were investigated by microsatellite markers, and no interstitial 1p36 deletion was found. Our patient presenting the 1p36 deletion did not have the striking features of this monosomy, but her clinical and behavioral features were quite similar to those observed in patients with PWS, except for the presence of normal sucking at birth. The extent of the deletion could be limited to the most terminal 2.5 Mb of 1p36, within the chromosomal region 1p36.33-1p36.32, that is smaller than usually seen in monosomy 1p36 patients. Therefore, chromosome 1p36.33 deletion should be investigated in patients with hypotonia, developmental delay, obesity and/or hyperphagia and behavioral problems who test negative for PWS.

Subtelomeric chromosome aberrations: still a lot to learn

Subtelomeric chromosome aberrations: still a lot to learn.Cryptic subtelomeric chromosome aberrations are a significant cause of mental retardation (MR). More than 4000 patients have been investigated, and the mean overall prevalence of subtelomeric rearrangements has been found to be 5.2%. In order to contribute to knowledge on the clinical presentation of subtelomeric rearrangements, we retrospectively studied patients with unexplained MR who had been evaluated for subtelomeric abnormalities by different fluorescence in situ hybridization (FISH) techniques. Hundred and two patients had an unexplained combination of MR with dysmorphism, congenital anomalies, and/or a positive family history and were investigated by total subtelomeric (TS) FISH (89/102), or by total painting (TP) in an obligate carrier in the case of familial MR (13/102). In 59 additional patients, a sequence-specific FISH was performed on clinical indication. In the 102 patients studied by TS or TP, six pathogenic aberrations (5.9%) were found in addition to one polymorphism. In total, eight clinically significant subtelomeric aberrations were found in the 161 index patients; four of these eight aberrations were familial. We report on the clinical presentation of all patients with an aberration and review the relevant literature. Factors complicating the interpretation of subtelomeric rearrangements are discussed, such as the occurrence of variants, clinical variability, and limited knowledge of the phenotype.

Del 1p36 syndrome: a newly emerging clinical entity

Monosomy 1p36 is a recently delineated contiguous gene syndrome, which is now considered to be the most common subtelomeric microdeletion syndrome. From the recent literature it appears as if 1p36 deletions account for 0.5-1.2% of idiopathic mental retardation. The deletions can be detected by high resolution cytogenetic studies in a minority of patients, and fluorescence in situ hybridisation (FISH) is required in most. The deletions' parent of origin seems still unclear, although in one large series it was shown to be maternal. 1p36 deletion syndrome is characterized by distinct craniofacial features, associated with developmental delay/mental retardation, hypotonia, muscle hypotrophy, seizures, brain abnormalities, and heart defects. To help child neurologists and other professionals in the recognition of this emerging and common chromosomal syndrome, we have reviewed published articles on patients with this deletion.

Girl with monosomy 1p36 and Angelman syndrome due to unbalanced der(1) transmission of a maternal translocation t(1;15)(p36.3;q13.1)

We report on a girl with monosomy 1p36.3 and Angelman syndrome due to an unbalanced transmission of a maternal balanced chromosomal translocation. She manifested monosomy 1p36 and Angelman syndrome including generalized hypopigmentation, ataxic movements, intractable seizures with characteristic electroencephalographic (EEG) abnormality compatible with Angelman syndrome, and other minor anomalies, large anterior fontanelle, severe psychomotor retardation, and seizures due to monosomy 1p36. Her karyotype was 45, XX, der(1) t(1;15)(p36.31;q13.1),-15, derived from maternal translocation. Molecular analysis determined a breakpoint of 1p between D1S243 and D1S468, which suggested that most genes contributing to the common phenotype are in the distal region.

Partial duplication 4q and deletion 1p36 in monozygotic twins with discordant phenotypes

We report on monozygotic (MZ) twins with a de novo chromosome abnormality consisting of a partial duplication of chromosome 4 (q25-qter) and deletion of chromosome 1p36. These infants had dysmorphic facial features and other clinical manifestations similar to those described with the previously delineated duplication 4q and deletion 1p36 phenotypes and two other reported cases of combined partial duplication 4q and deletion 1p36. However, the twins were discordant for a number of congenital anomalies. The discordant phenotypes described in these genetically identical infants demonstrate that nongenetic factors may play a significant role in the phenotypic differences in patients with recognized chromosome duplication and deletion syndromes, which are usually attributed to the individual genotypic differences in the duplicated and/or deleted chromosome segments.

The human gamma-aminobutyric acid A receptor delta (GABRD) gene: molecular characterisation and tissue-specific expression

Terminal deletions of 1p36 result in a specific and common syndrome characterised by the following: growth delay, distinctive facial anomalies, hearing and visual deficits, heart defects, body asymmetry, moderate to severe psychomotor retardation, epilepsy, and self-abusive behaviour. The human gamma-aminobutyric acid A receptor delta-subunit gene (GABRD) encodes for one of at least 15 ligand-gated chloride channels for gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian brain. Recently we have mapped this gene by radiation hybrid mapping to the critical region of gene loss of the 1p36 deletion syndrome within 1p36.33. The complete complementary DNA (cDNA) sequence of GABRD was generated using assembled sequence of cDNA fragments already available, and 5'-rapid amplification of cDNA ends products. Fine physical mapping of the GABRD gene within this genomic interval was performed by screening bacterial artificial chromosome contigs spanning the critical region of the 1p36 deletion syndrome. The GABRD gene maps immediately proximal to the PRKCZ gene that is located between marker D1S243 and cosmid D1Z2--a region thought to be critical for cognition and speech development. The GABRD gene is expressed most abundantly in brain and has three alternative exons (1A-C) with alternative start codons at the 5'-end. Genomic localisation, function, and expression would suggest that the GABRD gene represents a good candidate for the neurodevelopmental and neuropsychiatric anomalies seen in the 1p36 deletion syndrome.

Chromosomal abnormalities and epilepsy: a review for clinicians and gene hunters

PURPOSE

We analyzed databases on chromosomal anomalies and epilepsy to identify chromosomal regions where abnormalities are associated with clinically recognizable epilepsy syndromes. The expectation was that these regions could then be offered as targets in the search for epilepsy genes.

METHODS

The cytogenetic program of the Oxford Medical Database, and the PubMed database were used to identify chromosomal aberrations associated with seizures and/or EEG abnormalities. The literature on selected small anomalies thus identified was reviewed from a clinical and electroencephalographic viewpoint, to classify the seizures and syndromes according to the current International League Against Epilepsy (ILAE) classification.

RESULTS

There were 400 different chromosomal imbalances described with seizures or EEG abnormalities. Eight chromosomal disorders had a high association with epilepsy. These comprised: the Wolf-Hirschhorn (4p-) syndrome, Miller-Dieker syndrome (del 17p13.3), Angelman syndrome (del 15q11-q13), the inversion duplication 15 syndrome, terminal deletions of chromosome 1q and 1p, and ring chromosomes 14 and 20. Many other segments had a weaker association with seizures. The poor quality of description of the epileptology in many reports thwarted an attempt to make precise karyotype-phenotype correlations.

CONCLUSIONS

We identified certain chromosomal regions where aberrations had an evident association with seizures, and these regions may be useful targets for gene hunters. New correlations with specific epilepsy syndromes were not revealed. Clinicians should continue to search for small chromosomal abnormalities associated with specific epilepsy syndromes that could provide important clues for finding epilepsy genes, and the epileptology should be rigorously characterized.

The gene for a new brain specific RhoA exchange factor maps to the highly unstable chromosomal region 1p36.2-1p36.3

Guanine nucleotide exchange factors from the Dbl family are proto-oncogenic proteins that activate small GTPases of the Rho family. Here we report the characterization of GEF720, a novel Dbl-like protein related to p115Rho-GEF. GEF720 activated RhoA both in our recently developed Yeast Exchange Assay and in biochemical in vitro exchange assays. GEF720 induced RhoA dependent assembly of actin stress fibers in REF52 fibroblastic cells. In NIH3T3 cells this Dbl-like protein elicited formation of transformation foci with a morphology similar to RhoA-V14 induced foci. In the PC12 neuron-like cell line, expression of GEF720, whose mRNA is brain specific, inhibited NGF-induced neurite outgrowth. Finally, GEF720 gene is located on human chromosome 1 on band 1p36, between Tumor Protein 73 and Tumor Necrosis Factor Receptor 12, two genes rearranged in many neuroblastoma cell lines. Together, these results show that this new Dbl related protein, GEF720, is an exchange factor that can directly activate RhoA in vivo and is potentially involved in the control of neuronal cell differentiation. GEF720 is also a new candidate gene involved in the progression of neuroblastoma and developmental abnormalities associated with rearrangements in the 1p36 chromosomal region.