Eye movement defects in KO zebrafish reveals SRPK3 as a causative gene for an X-linked intellectual disability.

Intellectual disability (ID) is a common neurodevelopmental disorder characterized by significantly impaired intellectual and adaptive functioning. X-linked ID (XLID) disorders, caused by defects in genes on the X chromosome, affect 1.7 out of 1,000 males. Employing exome sequencing, we identified three missense mutations (c.475C>G; p.H159D, c.1373C>A; p.T458N, and c.1585G>A; p.E529K) in the SRPK3 gene in seven XLID patients from three independent families. Clinical features common to the patients are intellectual disability, agenesis of the corpus callosum, abnormal smooth pursuit eye movement, and ataxia. SRPK proteins are known to be involved in mRNA processing and, recently, synaptic vesicle and neurotransmitter release. In order to validate SRPK3 as a novel XLID gene, we established a knockout (KO) model of the SRPK3 orthologue in zebrafish. In day 5 of larval stage, KO zebrafish showed significant defects in spontaneous eye movement and swim bladder inflation. In adult KO zebrafish, we found agenesis of cerebellar structures and impairments in social interaction. These results suggest an important role of SRPK3 in eye movements, which might reflect learning problems, intellectual disability, and other psychiatric disorders.

Utility of Measuring Fetal Cavum Septum Pellucidum (CSP) Width During Routine Obstetrical Ultrasound for Improving Diagnosis of 22q11.2 Deletion Syndrome: A Case-Control Study.

Objective: To evaluate the utility of measuring fetal cavum septum pellucidum (CSP) width during routine, mid-pregnancy ultrasound for improving diagnosis of 22q11.2 deletion syndrome amongst fetuses with and without conotruncal anomalies. Patients and Methods: This was a retrospective case-control study (2005-2016). Fetuses and newborns with 22q11.2 deletion and/or conotruncal cardiac anomalies were identified using a regional, clinical database. A control group was assembled in a 2:1 ratio to create three groups for comparison: i) 22q11.2 deletion syndrome; ii) isolated conotruncal anomalies; and iii) controls. Eligibility was restricted to those with stored ultrasound images between 18-22 weeks' gestation and a minimum biparietal diameter of 40 mm. Post-processing measurement of CSP width was performed in a standardized fashion by two blinded and independent study personnel. Descriptive and inferential statistics, regression modeling, and receiver operator curves (ROC) were used to compare outcomes between groups and evaluate sensitivity/specificity of CSP width as a marker of 22q11.2 deletion syndrome. Results: Twenty-nine cases of 22q11.2 deletion and 64 cases of isolated conotruncal anomalies were matched to 186 healthy controls. Cases with 22q11.2 deletion syndrome had significantly larger CSP widths (5.36 mm; SD=1.2) compared to those with isolated conotruncal anomalies (3.75 mm; SD=1.11) and healthy controls (2.93 mm; SD=0.57; p<0.0001). There was no difference in CSP width amongst those with 22q11.2 deletion irrespective of the presence/absence of a conotruncal anomaly (p=0.362), or by type of conotruncal anomaly (p=0.211). Using a CSP width cutoff >4.3 mm, fetuses with 22q11.2 deletion can be accurately identified with good sensitivity (89.7%) and specificity (84%). Conclusion: Fetuses with 22q11.2 deletion syndrome have dilated CSPs when compared to those with isolated conotruncal anomalies or controls. Because CSP dilation can be evaluated during routine mid-pregnancy ultrasound using standard images of the fetal head, measurement could easily be incorporated to enhance prenatal diagnosis of this phenotypically diverse condition.

Neuroimaging Findings and Repeat Neuroimaging Value in Pediatric Chronic Ataxia.

BACKGROUND: Chronic ataxia, greater than two months in duration, is encountered relatively commonly in clinical pediatric neurology practise and presents with diagnostic challenges. It is caused by multiple and diverse disorders. Our aims were to describe the neuroimaging features and the value of repeat neuroimaging in pediatric chronic ataxia to ascertain their contribution to the diagnosis and management. MATERIALS AND METHODS: A retrospective charts and neuroimaging reports review was undertaken in 177 children with chronic ataxia. Neuroimaging in 130 of 177 patients was also reviewed. RESULTS: Nineteen patients had head computed tomography only, 103 brain magnetic resonance imaging only, and 55 had both. Abnormalities in the cerebellum or other brain regions were associated with ataxia. Neuroimaging was helpful in 73 patients with 30 disorders: It was diagnostic in 9 disorders, narrowed down the diagnostic possibilities in 14 disorders, and revealed important but non-diagnostic abnormalities, e.g. cerebellar atrophy in 7 disorders. Having a normal magnetic resonance imaging scan was mostly seen in genetic diseases or in the early course of ataxia telangiectasia. Repeat neuroimaging, performed in 108 patients, was generally helpful in monitoring disease evolution and in making a diagnosis. Neuroimaging was not directly helpful in 36 patients with 10 disorders or by definition the 55 patients with unknown disease etiology. CONCLUSIONS: Normal or abnormal neuroimaging findings and repeat neuroimaging are very valuable in the diagnosis and management of disorders associated with pediatric chronic ataxia.

Prenatal Diagnosis of Walker-Warburg Syndrome Using Single Nucleotide Polymorphism Array: A Clinical Experience from Three Related Palestinian Families with Congenital Hydrocephalus.

Background Congenital hydrocephalus is a common and often disabling disorder. Various syndromic forms of hydrocephalus have been reported in the Palestinian population including Walker-Warburg syndrome (WWS), Carpenter syndrome, and Meckel syndrome. Aim In this report we discuss the antenatal diagnosis of congenital hydrocephalus in three related Palestinian families. Method Single nucleotide polymorphism (SNP) array was performed prenatally for the third affected fetus. Results A diagnosis of WWS was found and molecular testing revealed a known pathogenic mutation in the POMT2 gene. An affected fetus from the other family was diagnosed and tested postnatally in light of this finding. Testing of another affected stillborn offspring was performed and revealed the same mutation. Conclusions Here, we show that the use of prenatal SNP array testing can be helpful in elucidating the etiology of congenital hydrocephalus and in guiding appropriate perinatal care. Also, testing for this specific POMT2 mutation should be considered in cases of prenatally detected hydrocephalus in Palestinian families.

An siRNA-based functional genomics screen for the identification of regulators of ciliogenesis and ciliopathy genes.

Defects in primary cilium biogenesis underlie the ciliopathies, a growing group of genetic disorders. We describe a whole-genome siRNA-based reverse genetics screen for defects in biogenesis and/or maintenance of the primary cilium, obtaining a global resource. We identify 112 candidate ciliogenesis and ciliopathy genes, including 44 components of the ubiquitin-proteasome system, 12 G-protein-coupled receptors, and 3 pre-mRNA processing factors (PRPF6, PRPF8 and PRPF31) mutated in autosomal dominant retinitis pigmentosa. The PRPFs localize to the connecting cilium, and PRPF8- and PRPF31-mutated cells have ciliary defects. Combining the screen with exome sequencing data identified recessive mutations in PIBF1, also known as CEP90, and C21orf2, also known as LRRC76, as causes of the ciliopathies Joubert and Jeune syndromes. Biochemical approaches place C21orf2 within key ciliopathy-associated protein modules, offering an explanation for the skeletal and retinal involvement observed in individuals with C21orf2 variants. Our global, unbiased approaches provide insights into ciliogenesis complexity and identify roles for unanticipated pathways in human genetic disease.

Neuro-Ophthalmological Findings in Children and Adolescents with Chronic Ataxia.

Chronic ataxia is a challenging problem in paediatric neurology. It is caused by a multitude of disorders that at least initially have similar or non-specific phenotype. Some of these disorders have associated neuro-ophthalmological signs (N-OS). The aims of this study are to describe the N-OS and their frequencies in general and by disease aetiology in paediatric patients with chronic ataxia. The authors identified 184 patients under age 17 years with chronic ataxia (>2 months duration or recurrent) during 1991-2008 from multiple sources. Diagnoses and N-OS were ascertained following charts review. Mean age (SD) was 15 (7.7) years. Median duration of follow-up was 6.4 years. There were 214 N-OS in 115 patients (median = 2, range = 1-5 N-OS/patient). Strabismus was present in 29.3% of patients, nystagmus 27.7%, impaired smooth pursuit 23.4%, hypometric saccades 10.3%, decreased visual acuity 9.2%, abnormal optic discs 8.7%, abnormal pupillary examination 2.7%, hypermetric saccades 2.2%, impaired ductions 1.6%, and abnormal visual fields in 1.1% of patients. N-OS were reported most commonly among patients with the following disorders (commonest N-OS): hypoxic-ischaemic encephalopathy following birth (strabismus), episodic ataxia (nystagmus), neuronal ceroid lipofuscinosis (abnormal optic discs), neuronal migration disorder (strabismus), ischaemic stroke (nystagmus), Joubert syndrome-related disorders (strabismus), leukodystrophy (nystagmus), Friedreich ataxia (hypometric saccades, impaired smooth pursuit, nystagmus), mitochondrial disease (strabismus, nystagmus), ataxia telangiectasia (impaired smooth pursuit), and Angelman syndrome (strabismus). N-OS occur commonly in children with chronic ataxia. Although non-specific, they vary with disease aetiology, potentially aiding in the assessment of these patients.

Disrupted auto-regulation of the spliceosomal gene SNRPB causes cerebro-costo-mandibular syndrome.

Elucidating the function of highly conserved regulatory sequences is a significant challenge in genomics today. Certain intragenic highly conserved elements have been associated with regulating levels of core components of the spliceosome and alternative splicing of downstream genes. Here we identify mutations in one such element, a regulatory alternative exon of SNRPB as the cause of cerebro-costo-mandibular syndrome. This exon contains a premature termination codon that triggers nonsense-mediated mRNA decay when included in the transcript. These mutations cause increased inclusion of the alternative exon and decreased overall expression of SNRPB. We provide evidence for the functional importance of this conserved intragenic element in the regulation of alternative splicing and development, and suggest that the evolution of such a regulatory mechanism has contributed to the complexity of mammalian development.

Evaluation of a clinical genetics service--a quality initiative.

Paper-based surveys are an effective means of evaluating the quality of a clinical service. As part of ongoing quality improvement initiatives within our Genetics Program, new patients were invited to participate in a paper-based survey. Issues related to the quality of counseling based on educational/informational aspects (e.g. whether testing was explained fully, testing options, the meaning of normal/abnormal testing), competency, respect and nondirectiveness of counseling in addition to clinical environment/setting were evaluated. Data related to demographics, discipline seen within the program and whether the patient was seen by a physician or genetic counselor were also captured. Five hundred questionnaires were distributed. One hundred and forty-seven questionnaires were returned, with a response rate of 29.4 %. The majority of patients seen were prenatal (pregnant) patients and comprised a heterogeneous group including those seen for advanced maternal age and abnormal maternal serum screening. Overall, 98.6 % of respondents felt their appointment in genetics was a positive experience. Issues related to confidentiality, pros and cons of testing, meaning of an abnormal test result and time allotted for decision making were significantly different in some disciplines between genetic counselor and geneticist. However, when controlling for referral indication, these differences lost significance with the exception of issues relating to confidentiality and perceived time allotted to organize thoughts and questions. This survey provided valuable information to allow for improvement in the quality of the provision of service.

Ethnicity and geographic distribution of pediatric chronic ataxia in Manitoba.

BACKGROUND: Genetic and environmental factors are important determinants of disease distribution. Several disorders associated with ataxia are known to occur more commonly in certain ethnic groups; for example, the disequilibrium syndrome in the Hutterites. The aim of this study was to determine the ethnic and geographic distribution of pediatric patients with chronic ataxia in Manitoba, Canada. METHODS: We identified 184 patients less than 17 years-of-age with chronic ataxia during 1991-2008 from multiple sources. Their diagnosis, ethnicity and place of residence were determined following a chart review. RESULTS: Most patients resided in Manitoba (N=177) and the majority in Winnipeg, the provincial capital. Thirty five Aboriginal, 29 Mennonite and 11 Hutterite patients resided in Manitoba. The latter two groups were significantly overrepresented in our cohort. Ataxia telangiectasia, mitochondrial disorders, and non-progressive ataxia of unknown etiology associated with pyramidal tracts signs and developmental delay were significantly more common in Mennonite patients. Four of five patients with neuronal migration disorders associated with chronic ataxia were Aboriginal. Few isolated disorders with chronic ataxia occurred in the 11 Hutterite patients including a Joubert syndrome related disorder. CONCLUSIONS: Three disorders associated with chronic ataxia were more prevalent than expected in Mennonites in Manitoba. Few rare disorders were more prevalent in the Hutterite and Aboriginal population. Further research is needed to determine the risk factors underlying these variations in prevalence within different ethnic groups. The unique risk factor profiles of each ethnic group need to be considered in health promotion endeavors.Ethnie et distribution géographique de l'ataxie chronique chez des patients d'âge pédiatrique au Manitoba.

Mutations in CSPP1, encoding a core centrosomal protein, cause a range of ciliopathy phenotypes in humans.

Ciliopathies are characterized by a pattern of multisystem involvement that is consistent with the developmental role of the primary cilium. Within this biological module, mutations in genes that encode components of the cilium and its anchoring structure, the basal body, are the major contributors to both disease causality and modification. However, despite rapid advances in this field, the majority of the genes that drive ciliopathies and the mechanisms that govern the pronounced phenotypic variability of this group of disorders remain poorly understood. Here, we show that mutations in CSPP1, which encodes a core centrosomal protein, are disease causing on the basis of the independent identification of two homozygous truncating mutations in three consanguineous families (one Arab and two Hutterite) affected by variable ciliopathy phenotypes ranging from Joubert syndrome to the more severe Meckel-Gruber syndrome with perinatal lethality and occipital encephalocele. Consistent with the recently described role of CSPP1 in ciliogenesis, we show that mutant fibroblasts from one affected individual have severely impaired ciliogenesis with concomitant defects in sonic hedgehog (SHH) signaling. Our results expand the list of centrosomal proteins implicated in human ciliopathies.

Lissencephaly with brainstem and cerebellar hypoplasia and congenital cataracts.

Classical lissencephaly may be associated with cerebellar hypoplasia and when significant cerebellar abnormalities occur, defects in proteins encoded by TUBA1A, RELN, and very-low-density lipoprotein receptor (VLDLR) genes have been reported. We present a neonate with a severe neurologic phenotype associated with hypotonia, oropharyngeal incoordination that required a gastric tube for feeding, intractable epilepsy, and congenital cataracts. Her brain magnetic resonance imaging (MRI) showed classical lissencephaly, ventriculomegaly, absent corpus callosum, globular and vertical hippocampi, and severe cerebellar and brainstem hypoplasia. She died at 6 weeks of age. No specific molecular diagnosis was made. This likely represents a previously undescribed genetic lissencephaly syndrome.

Radiographic characterization of the hands in Ritscher-Schinzel/3-C syndrome.

ABSTRACT: Ritscher-Schinzel Syndrome (RSS) is a clinically variable, autosomal recessive disorder, involving cardiac, cerebellar and craniofacial abnormalities. Numerous reports describe hand changes in RSS patients; however, a detailed characterization of the hands has not previously been performed. OBJECTIVE: The purpose of this study was to identify whether specific radiographic hand changes were characteristic of RSS and could serve as a diagnostic tool. MATERIALS AND METHODS: We performed a detailed radiographic hand characterization of 8 RSS patients. The patient population consisted of 5 males and 3 females from ages one month to 26 years, 7 months. The hands were characterized using metacarpophalangeal pattern (MCPP) profiles, carpal height and bone age analyses and assessment of bone morphology. RESULTS: There was generalized brachydactyly with the second ray being the most severely affected. There was significant shortening of the first metacarpal and the fifth distal phalanx. The MCPP profile generated showed a consistent wavy pattern with average Z-scores ranging from -0.15 (4(th) proximal phalanx) to -2.13 (1(st) metacarpal) and 0.53 (4(th) middle phalanx) to -1.73 (2(nd) proximal phalanx) for the left and right hands, respectively. Six of eight patients showed a decreased carpal height. Bone age was within normal limits for all patients. Our study population showed consistent radiographic changes including: overtubulation of the bones (especially metacarpals 2-4), prominent tufts of the distal phalanges and a hypoplastic fifth distal phalanx. CONCLUSION: The hand findings identified in this study can provide helpful diagnostic tools to clinicians when the diagnosis of RSS is being considered.

A novel mutation in KIAA0196: identification of a gene involved in Ritscher-Schinzel/3C syndrome in a First Nations cohort.

BACKGROUND: Ritscher-Schinzel syndrome (RSS) is a clinically heterogeneous disorder characterised by distinctive craniofacial features in addition to cerebellar and cardiac anomalies. It has been described in different populations and is presumed to follow autosomal recessive inheritance. In an effort to identify the underlying genetic cause of RSS, affected individuals from a First Nations (FN) community in northern Manitoba, Canada, were enrolled in this study. METHODS: Homozygosity mapping by SNP array and Sanger sequencing of the candidate genes in a 1Mb interval on chromosome 8q24.13 were performed on genomic DNA from eight FN RSS patients, eight of their parents and five unaffected individuals (control subjects) from this geographic isolate. RESULTS: All eight patients were homozygous for a novel splice site mutation in KIAA0196. RNA analysis revealed an approximate eightfold reduction in the relative amount of a KIAA0196 transcript lacking exon 27. A 60% reduction in the amount of strumpellin protein was observed on western blot. CONCLUSIONS: We have identified a mutation in KIAA0196 as the cause of the form of RSS characterised in our cohort. The ubiquitous expression and highly conserved nature of strumpellin, the product of KIAA0196, is consistent with the complex and multisystem nature of this disorder.

The epidemiology of intermittent and chronic ataxia in children in Manitoba, Canada.

AIM: To determine the epidemiology of chronic ataxia in children in Manitoba, Canada. METHOD: A retrospective study using multiple sources and disease codes identified children (age 0-16y) with chronic ataxia (>2mo duration or recurrent episodes of ataxia) seen at Winnipeg Children's Hospital from 1991 to 2008. Patients with isolated peripheral nerve diseases, vestibular disorders, or brain tumors were excluded. RESULTS: We identified 184 patients (males=females; mean age 15y, SD 7y 8mo) with chronic ataxia. Median age at the presenting symptom onset was 1 year 3 months and at ataxia onset 3 years 1 month. Median duration of follow-up was 6 years 5 months. During the study period, the crude incidence rate was 5.77 in 10,000; the crude prevalence rate was 6.59 in 10,000; and the crude mortality rate 0.446 in 10,000. The most common presenting symptoms were developmental delay, ataxia, or seizures. The most common diagnoses (known in 129) were Angelman syndrome (n=16), ataxia telangiectasia (n=13), mitochondrial disease (n=9), Friedreich ataxia (n=7), stroke (n=7), and familial/genetic episodic ataxia (n=7). INTERPRETATION: Chronic ataxia is a relatively common early-presenting symptom in childhood. A specific diagnosis is possible in 70% of patients after extensive investigations. The mortality rate is relatively low and the disease burden is high with significant comorbidities including developmental delay and epilepsy.

Prenatal screening characteristics in Emanuel syndrome: a case series and review of the literature.

PURPOSE: Emanuel syndrome is a rare chromosomal disorder characterized by severe mental retardation and multiple anomalies. The syndrome is caused by chromosomal imbalance due to a supernumerary derivative chromosome 22. Little is known regarding the characteristics of prenatal biochemical screening, or ultrasonographic markers in this syndrome. We aimed to identify a prenatal screening pattern characteristic of Emanuel Syndrome. METHODS: We report the prenatal characteristics of five fetuses with Emanuel syndrome, four of which were diagnosed prenatally. RESULTS: We found no consistent pattern of prenatal biochemical markers or other prenatal characteristics. Nevertheless, increased NT, low PAPP-A and ultrasound features such as intra uterine growth restriction, posterior fossa, cardiac and bowel abnormalities may be helpful in raising the suspicion for this rare genetic syndrome. CONCLUSION: Review of the biochemical screening results, ultrasound findings, and demographic characteristics of this Emanuel syndrome case series, as well as of the relevant literature fail to suggest a characteristic prenatal pattern.

Mutations in SRCAP, encoding SNF2-related CREBBP activator protein, cause Floating-Harbor syndrome.

Floating-Harbor syndrome (FHS) is a rare condition characterized by short stature, delayed osseous maturation, expressive-language deficits, and a distinctive facial appearance. Occurrence is generally sporadic, although parent-to-child transmission has been reported on occasion. Employing whole-exome sequencing, we identified heterozygous truncating mutations in SRCAP in five unrelated individuals with sporadic FHS. Sanger sequencing identified mutations in SRCAP in eight more affected persons. Mutations were de novo in all six instances in which parental DNA was available. SRCAP is an SNF2-related chromatin-remodeling factor that serves as a coactivator for CREB-binding protein (CREBBP, better known as CBP, the major cause of Rubinstein-Taybi syndrome [RTS]). Five SRCAP mutations, two of which are recurrent, were identified; all are tightly clustered within a small (111 codon) region of the final exon. These mutations are predicted to abolish three C-terminal AT-hook DNA-binding motifs while leaving the CBP-binding and ATPase domains intact. Our findings show that SRCAP mutations are the major cause of FHS and offer an explanation for the clinical overlap between FHS and RTS.

Trends in telehealth versus on-site clinical genetics appointments in Manitoba: a comparative study.

Telehealth involves the use of information and communications technology to deliver health services to patients over distance. Canada is well suited to benefit from telehealth since many individuals live in remote, rural and isolated locations. Manitoba is the easternmost prairie province and MBTelehealth is an active Canadian program that currently has 105 sites in 73 communities. Although studies of patient satisfaction comparing telehealth to on-site clinical visits have been conducted, a comparative study of the types of genetics patients seen via these two modalities has not been performed previously. In this study we: (1) examined the uptake of telehealth in Genetics in Manitoba; (2) contrasted telehealth usage in Genetics with other clinical programs; and (3) performed a comparative study of the types of Genetics referrals seen in 2008 on-site versus via telehealth. Results indicate the uptake of telehealth is increasing and has made genetics outreach clinics unnecessary. The Program of Genetics and Metabolism is consistently one of the top ten utilizers of telehealth within the province. With respect to discipline, chi square analysis revealed the trends were not significantly different for on-site and telehealth encounters, with prenatal referrals being the most common and Hereditary Breast and Ovarian Cancer referrals being the least common. Referrals within each discipline varied depending on the need for fetal assessment and physical examination. Telehealth was utilized regularly for test results sessions across all disciplines.

TMEM237 is mutated in individuals with a Joubert syndrome related disorder and expands the role of the TMEM family at the ciliary transition zone.

Joubert syndrome related disorders (JSRDs) have broad but variable phenotypic overlap with other ciliopathies. The molecular etiology of this overlap is unclear but probably arises from disrupting common functional module components within primary cilia. To identify additional module elements associated with JSRDs, we performed homozygosity mapping followed by next-generation sequencing (NGS) and uncovered mutations in TMEM237 (previously known as ALS2CR4). We show that loss of the mammalian TMEM237, which localizes to the ciliary transition zone (TZ), results in defective ciliogenesis and deregulation of Wnt signaling. Furthermore, disruption of Danio rerio (zebrafish) tmem237 expression produces gastrulation defects consistent with ciliary dysfunction, and Caenorhabditis elegans jbts-14 genetically interacts with nphp-4, encoding another TZ protein, to control basal body-TZ anchoring to the membrane and ciliogenesis. Both mammalian and C. elegans TMEM237/JBTS-14 require RPGRIP1L/MKS5 for proper TZ localization, and we demonstrate additional functional interactions between C. elegans JBTS-14 and MKS-2/TMEM216, MKSR-1/B9D1, and MKSR-2/B9D2. Collectively, our findings integrate TMEM237/JBTS-14 in a complex interaction network of TZ-associated proteins and reveal a growing contribution of a TZ functional module to the spectrum of ciliopathy phenotypes.