Hopkins Syndrome Research Articles

MTT for Children With Both Pitt Hopkins Syndrome and Gastrointestinal Disorders

MTT for Children With Both Pitt Hopkins Syndrome and Gastrointestinal Disorders

Hopkins Syndrome

We report a rare case of a 22-month-old who developed flaccid paralysis of her right arm shortly after she was hospitalized for an asthma exacerbation. There are many etiologies of acute flaccid paralysis; however, because of the uncommon presentation of a focalized finding, establishing the diagnosis of this patient was difficult in the emergency department setting. Associated with asthma exacerbations, Hopkins syndrome is a paralytic illness that resembles poliomyelitis. This case highlights the challenges of evaluating a child with monoparesis and establishing an association with asthma amyotrophy.

The first case of a non‐infertile female patient with Pitt–Hopkins syndrome

The first case of a non‐infertile female patient with Pitt–Hopkins syndrome

Pitt–Hopkins syndrome with electrical stat us epileptic us in slo w-wave sleep: a case report

Pitt–Hoppkins syndrome is rare genetic disorder caused by a molecular variant of TCF4 which is involved in embryologic neuronal differentiation. The syndrome is characterized by specific facial dysmorphism, phychomotor delay, autistic behavior and intellectual disability. Other associated features include ealy-onset myopia, seizures, constipation and hyperventilation-apneic spells. We introduced a clinical case of the patient with molecularly confirmed TCF4 variant and previously undescribed combination with syndrome of the electrical status epilepticus during sleep.

Repurposing Approved Drugs as Inhibitors of Kv7.1 and Nav1.8 to Treat Pitt Hopkins Syndrome.

Pitt Hopkins Syndrome (PTHS) is a rare genetic disorder caused by mutations of a specific gene, transcription factor 4 (TCF4), located on chromosome 18. PTHS results in individuals that have moderate to severe intellectual disability, with most exhibiting psychomotor delay. PTHS also exhibits features of autistic spectrum disorders, which are characterized by the impaired ability to communicate and socialize. PTHS is comorbid with a higher prevalence of epileptic seizures which can be present from birth or which commonly develop in childhood. Attenuated or absent TCF4 expression results in increased translation of peripheral ion channels Kv7.1 and Nav1.8 which triggers an increase in after-hyperpolarization and altered firing properties. We now describe a high throughput screen (HTS) of 1280 approved drugs and machine learning models developed from this data. The ion channels were expressed in either CHO (KV7.1) or HEK293 (Nav1.8) cells and the HTS used either 86Rb+ efflux (KV7.1) or a FLIPR assay (Nav1.8). The HTS delivered 55 inhibitors of Kv7.1 (4.2% hit rate) and 93 inhibitors of Nav1.8 (7.2% hit rate) at a screening concentration of 10μM. These datasets also enabled us to generate and validate Bayesian machine learning models for these ion channels. We also describe a structure activity relationship for several dihydropyridine compounds as inhibitors of Nav1.8. This work could lead to the potential repurposing of nicardipine or other dihydropyridine calcium channel antagonists as potential treatments for PTHS acting via Nav1.8, as there are currently no approved treatments for this rare disorder.

Hopkins syndrome following the first episode of bronchial asthma associated with enterovirus D68: a case report

BackgroundHopkins syndrome (HS) is a rare disorder presenting with acute flaccid paralysis of the limbs following an asthma attack. Neurologists encounter a diagnostic challenge if patients without a history of bronchial asthma develop neurologic features mimicking HS following acute respiratory distress. We report a case of HS occurring after a first episode of bronchial asthma associated with enterovirus D68 infection.Case presentationA 5-year-old girl developed acute respiratory distress. On the fourth hospital day, both her legs became paralyzed except for slight muscle contraction in the right lower limb. Tendon reflexes in the lower limbs were diminished and there was a positive Babinski sign on the right. Sensation was normal in all modalities, and there was no uro-rectal disturbance. Spinal magnetic resonance imaging identified T2-hyperintense lesions with spinal cord edema, mainly involving the bilateral T11 to L1 anterior horns, with left side dominance extending to the left posterior horn. The neurological and neuro-radiological findings of our case were suggestive of HS; however, she had no history of bronchial asthma. An acetylcholine inhalation challenge eventually proved the presence of reversible airway hyper-responsiveness, allowing us to diagnose HS. We identified enterovirus D68 in the patient’s intratracheal aspirates using a sensitive polymerase chain reaction assay. Intravenous immunoglobulin administrations at 2 g/kg2 for 5 consecutive days were repeated every month up to four times. After these treatments, the muscle strength of her right lower limb slightly improved while her left lower leg remained completely paralyzed.ConclusionThis case emphasizes the importance of provocation tests to reveal the presence of airway hyper-responsiveness when a child shows neurological signs mimicking HS following acute respiratory distress. Furthermore, the present case suggests a possible link between HS and acute flaccid paralysis following lower respiratory tract infection by enterovirus D68.

The Psychiatric Risk Gene Transcription Factor 4 (TCF4) Regulates Neurodevelopmental Pathways Associated With Schizophrenia, Autism, and Intellectual Disability.

BackgroundCommon genetic variants in and around the gene encoding transcription factor 4 (TCF4) are associated with an increased risk of schizophrenia. Conversely, rare damaging TCF4 mutations cause Pitt–Hopkins syndrome and have also been found in individuals with intellectual disability (ID) and autism spectrum disorder (ASD).MethodsChromatin immunoprecipitation and next generation sequencing were used to identify the genomic targets of TCF4. These data were integrated with expression, epigenetic and disease gene sets using a range of computational tools.ResultsWe identify 10604 TCF4 binding sites in the genome that were assigned to 5437 genes. De novo motif enrichment found that most TCF4 binding sites contained at least one E-box (5′-CAtcTG). Approximately 77% of TCF4 binding sites overlapped with the H3K27ac histone modification for active enhancers. Enrichment analysis on the set of TCF4 targets identified numerous, highly significant functional clusters for pathways including nervous system development, ion transport and signal transduction, and co-expression modules for genes associated with synaptic function and brain development. Importantly, we found that genes harboring de novo mutations in schizophrenia (P = 5.3 × 10−7), ASD (P = 2.5 × 10−4), and ID (P = 7.6 × 10−3) were also enriched among TCF4 targets. TCF4 binding sites were also found at other schizophrenia risk loci including the nicotinic acetylcholine receptor cluster, CHRNA5/CHRNA3/CHRNB4 and SETD1A.ConclusionsThese data demonstrate that TCF4 binding sites are found in a large number of neuronal genes that include many genetic risk factors for common neurodevelopmental disorders.

Acute flaccid paralysis after asthma attack: A probable Hopkins syndrome case

Acute flaccid paralysis after asthma attack: A probable Hopkins syndrome case

The Intellectual Disability and Schizophrenia Associated Transcription Factor TCF4 Is Regulated by Neuronal Activity and Protein Kinase A.

Transcription factor 4 (TCF4 also known as ITF2 or E2-2) is a basic helix-loop-helix (bHLH) protein associated with Pitt-Hopkins syndrome, intellectual disability, and schizophrenia (SCZ). Here, we show that TCF4-dependent transcription in cortical neurons cultured from embryonic rats of both sexes is induced by neuronal activity via soluble adenylyl cyclase and protein kinase A (PKA) signaling. PKA phosphorylates TCF4 directly and a PKA phosphorylation site in TCF4 is necessary for its transcriptional activity in cultured neurons and in the developing brain in vivo We also demonstrate that Gadd45g (growth arrest and DNA damage inducible gamma) is a direct target of neuronal-activity-induced, TCF4-dependent transcriptional regulation and that TCF4 missense variations identified in SCZ patients alter the transcriptional activity of TCF4 in neurons. This study identifies a new role for TCF4 as a neuronal-activity-regulated transcription factor, offering a novel perspective on the association of TCF4 with cognitive disorders.SIGNIFICANCE STATEMENT The importance of the basic helix-loop-helix transcription factor transcription factor 4 (TCF4) in the nervous system is underlined by its association with common and rare cognitive disorders. In the current study, we show that TCF4-controlled transcription in primary cortical neurons is induced by neuronal activity and protein kinase A. Our results support the hypotheses that dysregulation of neuronal-activity-dependent signaling plays a significant part in the etiology of neuropsychiatric and neurodevelopmental disorders.

Molecular Mechanisms of Transcription Factor 4 in Pitt Hopkins Syndrome.

Pitt Hopkins syndrome (PTHS) is a rare neurodevelopmental disorder that results from mutations of the clinically pleiotropic Transcription Factor 4 (TCF4) gene. Mutations in the genomic locus of TCF4 on chromosome 18 have been linked to multiple disorders including 18q syndrome, schizophrenia, Fuch's corneal dystrophy, and sclerosing cholangitis. For PTHS, TCF4 mutation or deletion leads to the production of a dominant negative TCF4 protein and/or haploinsufficiency that results in abnormal brain development. The biology of TCF4 has been studied for several years in regards to its role in immune cell differentiation, although its role in neurodevelopment and the mechanisms resulting in the severe symptoms of PTHS are not well studied. Here, we summarize the current understanding of PTHS and recent findings that have begun to describe the biological implications of TCF4 deficiency during brain development and into adulthood. In particular, we focus on recent work that has looked at the role of TCF4 biology within the context of PTHS and highlight the potential for identification of therapeutic targets for PTHS. PTHS research continues to uncover mutations in TCF4 that underlie the genetic cause of this rare disease, and emerging evidence for molecular mechanisms that TCF4 regulates in brain development and neuronal function is contributing to a more complete picture of how pathology arises from this genetic basis, with important implications for the potential of future clinical care.

Neurodevelopmental models of transcription factor 4 deficiency converge on a common ion channel as a potential therapeutic target for Pitt Hopkins syndrome.

ABSTRACTThe clinically pleiotropic gene, Transcription Factor 4 (TCF4), is a broadly expressed basic helix-loop-helix (bHLH) transcription factor linked to multiple neurodevelopmental disorders, including schizophrenia, 18q deletion syndrome, and Pitt Hopkins syndrome (PTHS). In vivo suppression of Tcf4 by shRNA or mutation by CRISPR/Cas9 in the developing rat prefrontal cortex resulted in attenuated action potential output. To explain this intrinsic excitability deficit, we demonstrated that haploinsufficiency of TCF4 lead to the ectopic expression of two ion channels, Scn10a and Kcnq1. These targets of TCF4 regulation were identified through molecular profiling experiments that used translating ribosome affinity purification to enrich mRNA from genetically manipulated neurons.Using a mouse model of PTHS (Tcf4+/tr), we observed a similar intrinsic excitability deficit, however the underlying mechanism appeared slightly different than our rat model - as Scn10a expression was similarly increased but Kcnq1 expression was decreased. Here, we show that the truncated TCF4 protein expressed in our PTHS mouse model binds to wild-type TCF4 protein, and we suggest the difference in Kcnq1 expression levels between these two rodent models appears to be explained by a dominant-negative function of the truncated TCF4 protein. Despite the differences in the underlying molecular mechanisms, we observed common underlying intrinsic excitability deficits that are consistent with ectopic expression of Scn10a. The converging molecular function of TCF4 across two independent rodent models indicates SCN10a is a potential therapeutic target for Pitt-Hopkins syndrome.

Asthma and hypoxia

More or less severe asthma attacks can damage the CNS and peripheral system in adults and children, both directly causing hypoxia and indirectly with the production of autoimmune antibodies. The pathogenic mechanism is still unknown; cytokines, TNFs, interleukins, free radicals and nitric oxide are often involved as causative factors for the disorders [1,2]. In this review we focus our attention on the relationship between atopy and CNS (central) or PNS (peripheral system) involvement. The main disorders associated with atopic disease are: Atopic myelitis Hopkins syndrome Hirayama disease Spinal progressive muscular atrophy (SPMA) The occurrence of myelitis in patients with atopic diathesis (atopic myelitis) affecting young adults has been widely reported especially in Japan.[2,3] In general, the disorders affect the posterior column of the cervical spinal cord, as shown clinically and by an MRI, and are characterized by hyperIgEaemia and the presence of light antigen-specific IgE. Another disease that has been reported in association with atopic disorders is Hirayama disease, a juvenile muscular atrophy of the distal upper extremity, which is also associated with airway allergies such as allergic rhinitis and atopic asthma. Our group reported on a 13-year-old girl who had recurrent acute episodes of myelitis after asthma attacks; the patient showed to be affected by Hopkins syndrome [4] (HS); a flaccid paralysis affecting one or more limbs after an asthma attack. It is a poliomyelitis-like illness, with frequent recurrences in which a possible link between the disease and atopic myelitis was reported, but until now the precise etiopathogenetic mechanism still remains unknown. Prospective study on the history of allergic disorders in known neurological diseases, an association between spinal progressive muscular atrophy and asthma as well as between myelitis and atopic dermatitis has been demonstrated. Central nervous system damage associated with atopic diathesis may be classified into two categories: eosinophilic myelitis mainly affecting the cervical spinal cord and those lower motor neuron, such as Hopkins syndrome, Hirayama disease and SPMA [2,4]. Recently we reported children with epileptic crisis related to cow's milk protein allergy; this disease can manifest itself with skin reactions, failure to thrive, and anaphylaxis as well as gastrointestinal and respiratory disorders [5]. In conclusion, the aim of this report is to analyse current data on the link between asthma and CNS/or PNS involvement and also, cow's milk protein allergy and epileptic events, highlighting the presence and scientific evidence for any potential pathogenetic mechanism.

Pitt–Hopkins Syndrome and Differential Diagnosis: A Molecular and Clinical Challenge

Pitt-Hopkins syndrome is an emerging neurodevelopmental disorder caused by haploinsufficiency of the TCF4 gene on chromosome 18q21. It is characterized by severe intellectual disability, seizures, microcephaly, constipation and a distinctive facial gestalt. Although the overlapping phenotype of microcephaly, epilepsy, absent speech and constipation represents a challenge for the differential diagnosis with Angelman syndrome, Rett syndrome and Mowat-Wilson syndrome, distinctive of Pitt-Hopkins syndrome are breathing abnormalities, that can occur as either hyperventilation episodes or apnea crises, and a typical facial dysmorphism, including bitemporal narrowing, squared forehead, deep-set eyes, peculiar nose conformation, with broad nasal bridge, down-turned nasal tip and flaring nostrils, typical shape of the mouth, with a tented and M shaped upper lip, and widely spaced teeth. The occurrence of these signs in variable association of uncoordinated movements, microcephaly of postnatal onset, eye abnormalities, constipation, epilepsy and subtle brain abnormalities is highly predictive of a TCF4 mutation, making it possible to plan a genetic test of choice among severe encephalopathies. Angelman syndrome represents the nosological condition closest to Pitt-Hopkins syndrome.

Free muscle transfer for challenging and rare upper limb disorders

Free innervated muscle transfer (FMT) achieves functional restoration following not only traumatic brachial plexus injury, but also intractable rare upper limb disorders, such Hopkins' syndrome, myoplasia in arthrogryposis and radition neuropathy. I introduce our current experience of FMT for these disorders. Hopkins syndrome is a rare cause of poliomyelitis-like paralysis affecting one or more extremities after an acute attack of asthma. The exact etiology of Hopkins syndrome is not known. Two children developed acute asthma followed by complete flaccid paralysis of the the upper extremity. They underwent staged reconstruction using FMT. Rigorous postoperative physiotherapy was carried out to achieve a good functional outcome. At recent follow-up, they were able to effectively use the reconstructed hand for most of their daily activities. They had good control and could perform 2-handed activities. The selection of a suitable operative treatment and suitable donor nerves is critical, and there are no clear guidelines in the literature. FMT can be effectively employed in similar cases to restore grasping function. Arthrogryposis is a collective term applied to a variety of different syndromes characterized by nonprogressive, multiple joint contractures present at birth due to neurogenic, myopathic (amyoplasia), or connective-tissue disorders. The most serious impairment of amyoplasia in the upper extremity is an inability to flex the elbow due to extension contracture of the elbow. The ability to flex one elbow is essential to enable a child to become functionally independent with self-feeding and self-care of the face and hair; extension of the other elbow is necessary for independent toileting. Active elbow flexion is the definitive goal of surgical intervention. Multiple procedures, including triceps transfer, pectoralis major transfer, latissimus dorsi transfer, and the Steindler flexorplasty, have been used to provide active elbow flexion in patients with arthrogryposis. However, these conventional procedures do not always provide satisfactory long-term function and may result in a decreased arc of elbow flexion and in flexion contracture because of weakness of the donor muscles. We present the long-term results of a functioning free muscle transfer with use of the gracilis muscle for restoration of elbow flexion in three patients with arthrogryposis. Radiation-induced brachial plexopathy is a delayed complication of radiation treatment for tumors involving the neck and chest area and is progressive. A 56 year-old woman presented to us with loss of elbow flexion and weak wrist and finger extension 15 years after she received external beam radiation to the left chest, axilla, and supraclavicular region for the treatment of breast cancer. She was managed with a gracilis free muscle transfer for elbow flexion and hand prehension. By 2 years after surgery she regained elbow range of motion of 40 to 110 degrees and improved her hand function. She was able to perform her activities of daily living. Her Disabilities of the Arm, Shoulder, and Hand Score improved from 56 to 20.

PP05.14 – 3044: The use of acetazolamide for severe central apnea in developmental disorders

Objective Breathing disturbances like central apnea, episodic hyperventilation, air swallowing and Valsalva manoeuvres, have a large impact on the quality of life of children. In for instance Rett syndrome, which is characterized by loss of purposeful hand skills, motor and communication functions, cognitive impairment and the development of stereotypic hand function and seizures, they occur mainly when the girl is awake. These breathing disturbances can be severe and life threatening. In Prader-Willi syndrome, a genetic disorder characterized by severe hypotonia, cognitive and behavioral disturbances, the breathing disturbances are sleep related and includes obstructive and central sleep apnea. There's no proven treatment. Acetozolamide, a carbon dioxide hydrase inhibitor changes the Co2 and PH shift in the breathing center, and because of this increases depth of breathing. In adult patients, neonates and Pitt Hopkins syndrome, Acetozolamide has proven to decrease the central apnea's. Side effects like hyponatraemia and metabolic acidosis are rare. The aim of study is to evaluate the effect of Acetozolamide on central apnea's in patients with Rett syndrome, Prader-Willi syndrome and other developmental disorders. Methods All patients experienced extended polysomnographic recording, combined with video-electroencephalography at inclusion and after treatment. Laboratory investigation was performed. Seizure frequency calendars were used if available. Acetozolamide was started if central apnea's were present >3 and lasted for >20 seconds or 2 missed breaths with desaturation. Results All patients experienced severe breathing disturbances. Hyperventilation followed by central apnea's, or sleep related central apnea, with decline of SaO2, were most frequent. Acetozolamide reduced the apnea's and SaO2 declines, substantial. No side effect were reported. Most parents reported less daytime drowsiness, increased alertness and less breathing irregularities. Conclusion Acetozolamide was effective in substantial reducing the central apnea's and SaO2 declines in patients with various developmental disorders.

Genomic characterization of coxsackievirus type A24 strains associated with acute flaccid paralysis and rarely identified Hopkins syndrome.

The full-length genome sequence analysis of four coxsackievirus A24 (CV-A24) strains, detected in three paralytic and one post-asthmatic paralytic (Hopkins syndrome) cases, is reported here for the first time. A phylogenetic tree constructed on the basis of entire genomes displayed topology similar to that of the full-VP1 tree, classifying the study strains in genogroup CV-A24vGIV along with their temporal counterparts in strains from non-paralytic cases. The strains of the study formed a single genetic cluster C4 within CV-A24vGIV and showed 3.5-19.4 % nucleotide sequence divergence, with 2-4 novel nucleotide mutations in the 5'NCR and 3-8 unique amino acid substitutions in the polyprotein, with respect to the CV-A24 strains associated with non-paralytic cases. Among the nucleotide mutations, A299U was identified in the 5'NCRs of all of the study strains. CV-A24v strains of the same genogroup with few genomic variations but different disease manifestations need to be explored to investigate the molecular basis of evolution of neurovirulence.

Monocrural flaccid paralysis following asthmatic attack (post asthmatic amyotrophy) – case report & minireview

Hopkin’s syndrome (HS) is a rare condition characterized by development of flaccid paralysis involving upper, lower limbs or both within 4–11days following an asthmatic attack mimicking poliomyelitis [1]. It commonly occurs in children aged below 13 years. It is due to damage to anterior horn cells of spinal cord, the precise etiopathogenetic mechanism remains unknown. Many postulations like viral infections, atopy and multifactorial immune suppression have been implicated [2,3]. The prognosis for recovery is generally considered poor in these cases. Here, we are reporting a case of left monocrural flaccid paralysis developed during the recovery phase of an acute asthmatic attack in a 5 year old boy. This was confirmed by radiological (MRI) and electrophysiological studies.

Low vision due to cerebral visual impairment: differentiating between acquired and genetic causes

BackgroundTo gain more insight into genetic causes of cerebral visual impairment (CVI) in children and to compare ophthalmological findings between genetic and acquired forms of CVI.MethodsThe clinical data of 309 individuals (mainly children) with CVI, and a visual acuity ≤0.3 were analyzed for etiology and ocular variables. A differentiation was made between acquired and genetic causes. However, in persons with West syndrome or hydrocephalus, it might be impossible to unravel whether CVI is caused by the seizure disorder or increased intracranial pressure or by the underlying disorder (that in itself can be acquired or genetic). In two subgroups, individuals with ‘purely’ acquired CVI and with ‘purely’ genetic CVI, the ocular variables (such as strabismus, pale optic disc and visual field defects) were compared.ResultsIt was possible to identify a putative cause for CVI in 60% (184/309) of the cohort. In the remaining 40% the etiology could not be determined. A ‘purely’ acquired cause was identified in 80 of the patients (26%). West syndrome and/or hydrocephalus was identified in 21 patients (7%), and in 17 patients (6%) both an acquired cause and West and/or hydrocephalus was present. In 66 patients (21%) a genetic diagnosis was obtained, of which 38 (12%) had other possible risk factor (acquired, preterm birth, West syndrome or hydrocephalus), making differentiation between acquired and genetic not possible. In the remaining 28 patients (9%) a ‘purely’ genetic cause was identified.CVI was identified for the first time in several genetic syndromes, such as ATR-X, Mowat-Wilson, and Pitt Hopkins syndrome. In the subgroup with ‘purely’ acquired causes (N = 80) strabismus (88% versus 64%), pale optic discs (65% versus 27%) and visual field defects (72% versus 30%) could be observed more frequent than in the subgroup with ‘purely’ genetic disorders (N = 28).ConclusionsWe conclude that CVI can be part of a genetic syndrome and that abnormal ocular findings are present more frequently in acquired forms of CVI.

If not Angelman, what is it? A review of Angelman-like syndromes.

Angelman syndrome (AS) is caused by a lack of expression of the maternally inherited UBE3A gene in the brain. However, about 10% of individuals with a clinical diagnosis of AS do not have an identifiable molecular defect. It is likely that most of those individuals have an AS-like syndrome that is clinically and molecularly distinct from AS. These AS-like syndromes can be broadly classified into chromosomal microdeletion and microduplication syndromes, and single-gene disorders. The microdeletion/microduplication syndromes are now easily identified by chromosomal microarray analysis and include Phelan–McDermid syndrome (chromosome 22q13.3 deletion), MBD5 haploinsufficiency syndrome (chromosome 2q23.1 deletion), and KANSL1 haploinsufficiency syndrome (chromosome 17q21.31 deletion). The single-gene disorders include Pitt–Hopkins syndrome (TCF4), Christianson syndrome (SLC9A6), Mowat–Wilson syndrome (ZEB2), Kleefstra syndrome (EHMT1), and Rett (MECP2) syndrome. They also include disorders due to mutations in HERC2, adenylosuccinase lyase (ADSL), CDKL5, FOXG1, MECP2 (duplications), MEF2C, and ATRX. Although many of these single-gene disorders can be caused by chromosomal microdeletions resulting in haploinsufficiency of the critical gene, the individual disorders are often caused by intragenic mutations that cannot be detected by chromosomal microarray analysis. We provide an overview of the clinical features of these syndromes, comparing and contrasting them with AS, in the hope that it will help guide clinicians in the diagnostic work-up of individuals with AS-like syndromes.

A survey of rare coding variants in candidate genes in schizophrenia by deep sequencing

The genetic architecture of schizophrenia is likely contributed by both common and rare variants.1 Recent genome-wide studies have revealed that common variants in the major histocompatibility complex (MHC) region, TCF4 and other genes are associated with schizophrenia.1 In addition, rare copy-number variation (CNV) regions in broad regions like 1q21.1, 15q13.3, 15q11.2, 22q111 as well as individual genes such as Neurexin2, 3 have been identified. Unbiased exome or whole genome scanning procedures have the potential to identify novel loci while likely requiring large sample sets to reach a genome-wide significance level. It is possible that the previously identified genes/regions from high-throughput single-nucleotide polymorphisms (SNP) chip genome-wide scanning techniques, in contrast to some ‘classical' candidate genes,4 may harbor rare coding variants that have a role in disease risk. We selected a total of 101 genes from within the 1q21.1, 15q13.3, 22q11 and 15q11.2 regions and a number of other candidate genes, with either a priori knowledge for association with schizophrenia, for example, TCF4/CCDC68, NRXN1, or interesting for drug-discovery efforts, for example, cyclic nucleotide phosphodiesterase genes, and surveyed rare variants in their coding regions through deep sequencing.