Joubert Syndrome and related disorders

The splice c.1815G>A variant in KIAA0586 results in a phenotype bridging short-rib-polydactyly and oral-facial-digital syndrome: A case report and literature review

INTRODUCTION

KIAA0586 variants have been associated to short-rib thoracic dysplasia, an autosomal recessive skeletal ciliopathy characterized by a narrow thorax, short limbs, and radiological skeletal abnormalities.

PATIENT CONCERNS

Patients 1 and 2 were two Roma Gypsy siblings presenting thoracic dysplasia and a combination of oral cavity anomalies.

DIAGNOSIS

A custom NGS gene panel, including genes associated to skeletal ciliopathies, identified the homozygous KIAA0586 splicing variant c.1815G>A (p.Gln605Gln) in both siblings, confirming the clinical diagnosis of short-rib-polydactyly.

INTERVENTION

Patients were transferred to neonatal intensive care unit and received life-support treatment.

OUTCOMES

Patients 1 and 2 died after few hours and 1 month of birth, respectively, because of respiratory failure related with the disease.

CONCLUSION

We report two patients affected by short-rib polydactyly syndrome and overlapping phenotype with oral-facial-digital syndrome associated with the c.1815G>A variant in KIAA0586, suggesting a quite peculiar genotype-phenotype correlation.

Embryonic and foetal expression patterns of the ciliopathy gene CEP164

Nephronophthisis-related ciliopathies (NPHP-RC) are a group of inherited genetic disorders that share a defect in the formation, maintenance or functioning of the primary cilium complex, causing progressive cystic kidney disease and other clinical manifestations. Mutations in centrosomal protein 164 kDa (CEP164), also known as NPHP15, have been identified as a cause of NPHP-RC. Here we have utilised the MRC-Wellcome Trust Human Developmental Biology Resource (HDBR) to perform immunohistochemistry studies on human embryonic and foetal tissues to determine the expression patterns of CEP164 during development. Notably expression is widespread, yet defined, in multiple organs including the kidney, retina and cerebellum. Murine studies demonstrated an almost identical Cep164 expression pattern. Taken together, these data support a conserved role for CEP164 throughout the development of numerous organs, which, we suggest, accounts for the multi-system disease phenotype of CEP164-mediated NPHP-RC.

Primary cilia control cell alignment and patterning in bone development via ceramide-PKCζ-β-catenin signaling

Intraflagellar transport (IFT) proteins are essential for cilia assembly and function. IFT protein mutations lead to ciliopathies, which manifest as variable skeletal abnormalities. However, how IFT proteins regulate cell alignment during bone development is unknown. Here, we show that the deletion of IFT20 in osteoblast lineage using Osterix-Cre and inducible type I Collagen-CreERT cause a compromised cell alignment and a reduced bone mass. This finding was validated by the disorganized collagen fibrils and decreased bone strength and stiffness in IFT20-deficient femurs. IFT20 maintains cilia and cell alignment in osteoblasts, as the concentric organization of three-dimensional spheroids was disrupted by IFT20 deletion. Mechanistically, IFT20 interacts with the ceramide-PKCζ complex to promote PKCζ phosphorylation in cilia and induce the apical localization of β-catenin in osteoblasts, both of which were disrupted in the absence of IFT20. These results reveal that IFT20 regulates polarity and cell alignment via ceramide-pPKCζ-β-catenin signaling during bone development.

Pediatric liver diseases and ocular changes: What hepatologists and ophthalmologists should know and share with each other

Several rare pediatric liver disorders are accompanied by ophthalmic signs whose awareness and early identification may be of value in confirming/accelerating their diagnosis. Many of these signs are asymptomatic and can only be detected with an ophthalmological examination. Corneal signs are described in patients with Wilson's disease, Alagille's syndrome and some liver storage diseases. Cataract plays an important role to diagnose galactosemia. Retinal involvement is seen in some peroxisomal disorders (e.g. Zellweger's syndrome), in mucopolysaccharidoses (pigmentary retinopathy), and in Niemann-Pick disease (macular cherry red spot). In mucopolysaccharidoses optic nerve can be involved as optic atrophy secondary to pigmentary retinopathy or to chronic papilledema. Children with neonatal cholestasis due to hypopituitarism may present septo-optic dysplasia. Several infectious agents have an ophthalmological/hepatic involvement in the fetal life and/or thereafter. Some mitochondrial liver diseases, such as Pearson's syndrome, present pigmentary retinopathy and a chronic progressive external ophthalmoplegia. Finally, some drugs while protecting the liver may damage the ocular system as seen with long-term glucocorticoids and Nitisinone administration. This review provides a synopsis of those conditions that hepatologists and ophthalmologists should share among themselves to better take care of patients. Synoptic tables are presented to facilitate the mutual understanding of the issues.

Joubert Syndrome: A Rare Radiological Case

Joubert syndrome is a rare autosomal recessive neurodevelopmental disease characterized by abnormal breathing patterns composed of episodic tachypnea/apnea, hypotonia, ataxia, developmental delay, intellectual impairment, ocular impairment, renal cysts, and hepatic fibrosis. We report the case of a 4-year-old boy who presented with global developmental delay, bilateral nystagmus, and gaze instability with difficulty walking and maintaining an upright posture. A detailed examination revealed facial dysmorphic features with a depressed nasal bridge and deepened orbital sockets. Neurological examination yielded positive results for hypotonia, gait ataxia, bilateral horizontal pendular nystagmus, and a grade 1 ptosis more prominent in the right eye. However, no abnormal breathing patterns were observed in our case. Magnetic resonance imaging revealed the characteristic molar tooth sign and a batwing appearance of the fourth ventricle.

MICAL-L1 coordinates ciliogenesis by recruiting EHD1 to the primary cilium

The endocytic protein EHD1 plays an important role in ciliogenesis by facilitating fusion of the ciliary vesicle and removal of CP110 (also known as CCP110) from the mother centriole, as well as removal of Cep215 (also known as CDK5RAP2) from centrioles to permit disengagement and duplication. However, the mechanism of its centrosomal recruitment remains unknown. Here, we address the role of the EHD1 interaction partner MICAL-L1 in ciliogenesis. MICAL-L1 knockdown impairs ciliogenesis in a similar manner to EHD1 knockdown, and MICAL-L1 localizes to cilia and centrosomes in both ciliated and non-ciliated cells. Consistent with EHD1 function, MICAL-L1-depletion prevents CP110 removal from the mother centriole. Moreover, upon MICAL-L1-depletion, EHD1 fails to localize to basal bodies. Since MICAL-L1 localizes to the centrosome even in non-ciliated cells, we hypothesized that it might be anchored to the centrosome via an interaction with centrosomal proteins. By performing mass spectrometry, we identified several tubulins as potential MICAL-L1 interaction partners, and found a direct interaction between MICAL-L1 and both α-tubulin-β-tubulin heterodimers and γ-tubulin. Our data support the notion that a pool of centriolar γ-tubulin and/or α-tubulin-β-tubulin heterodimers anchor MICAL-L1 to the centriole, where it might recruit EHD1 to promote ciliogenesis.

Healthcare recommendations for Joubert syndrome

Joubert syndrome (JS) is a recessive neurodevelopmental disorder defined by a characteristic cerebellar and brainstem malformation recognizable on axial brain magnetic resonance imaging as the "Molar Tooth Sign". Although defined by the neurological features, JS is associated with clinical features affecting many other organ systems, particularly progressive involvement of the retina, kidney, and liver. JS is a rare condition; therefore, many affected individuals may not have easy access to subspecialty providers familiar with JS (e.g., geneticists, neurologists, developmental pediatricians, ophthalmologists, nephrologists, hepatologists, psychiatrists, therapists, and educators). Expert recommendations can enable practitioners of all types to provide quality care to individuals with JS and know when to refer for subspecialty care. This need will only increase as precision treatments targeting specific genetic causes of JS emerge. The goal of these recommendations is to provide a resource for general practitioners, subspecialists, and families to maximize the health of individuals with JS throughout the lifespan.

Whole exome sequencing reveals novel CEP104 mutations in a Chinese patient with Joubert syndrome

Background

Joubert syndrome (JS, OMIM: 213300) is a recessive developmental disorder characterized by cerebellar vermis hypoplasia and a distinctive mid‐hindbrain malformation called the “molar tooth sign” on axial magnetic resonance imaging. To date, more than 35 ciliary genes have been identified as the causative genes of JS.

Methods

Whole exome sequencing was performed to detect the causative gene mutations in a Chinese patient with JS followed by Sanger sequencing. RT‐PCR and Sanger sequencing were used to confirm the abnormal transcript of centrosomal protein 104 (CEP104, OMIM: 616690).

Results

We identified two novel heterozygous mutations of CEP104 in the proband, which were c.2364+1G>A and c.414delC (p.Asn138Lysfs*11) (GenBank: NM_014704.3) and consistent with the autosomal recessive inheritance mode.

Conclusion

Our study reported the fourth case of JS patients with CEP104 mutations, which expands the mutation spectrum of CEP104 and elucidates the clinical heterogeneity of JS.

An Unusual Case of Congenital Hepatic Fibrosis with Retinitis Pigmentosa

Congenital hepatic fibrosis (CHF) is a rare hereditary autosomal recessive disorder due to periportal fibrosis and ductal plate malformation. It is just one of many different malformations collectively named oculo-encephalo-hepato-renal syndrome. The major presenting feature is upper gastrointestinal bleeding due to portal hypertension secondary to the development of esophageal varices. Herein we report a case of CHF with retinitis pigmentosa but lacking the distinctive multisystem malformations associated with other well-known syndromes associated with CHF. In cases of CHF, search for other organ involvement is important at the time of presentation as well as during follow-up.

Ahi1 promotes Arl13b ciliary recruitment, regulates Arl13b stability and is required for normal cell migration

Mutations in the Abelson-helper integration site 1 (AHI1) gene are associated with neurological/neuropsychiatric disorders, and cause the neurodevelopmental ciliopathy Joubert syndrome (JBTS). Here, we show that deletion of the transition zone (TZ) protein Ahi1 in mouse embryonic fibroblasts (MEFs) has a small effect on cilia formation. However, Ahi1 loss in these cells results in: (1) reduced localization of the JBTS-associated protein Arl13b to the ciliary membrane, (2) decreased sonic hedgehog signaling, (3) and an abnormally elongated ciliary axoneme accompanied by an increase in ciliary IFT88 concentrations. While no changes in Arl13b levels are detected in crude cell membrane extracts, loss of Ahi1 significantly reduced the level of non-membrane-associated Arl13b and its stability via the proteasome pathway. Exogenous expression of Ahi1-GFP in Ahi1^-/- MEFs restored ciliary length, increased ciliary recruitment of Arl13b and augmented Arl13b stability. Finally, Ahi1^-/- MEFs displayed defects in cell motility and Pdgfr-α-dependent migration. Overall, our findings support molecular mechanisms underlying JBTS etiology that involve: (1) disruptions at the TZ resulting in defects of membrane- and non-membrane-associated proteins to localize to primary cilia, and (2) defective cell migration.This article has an associated First Person interview with the first author of the paper.

Joubert Syndrome with Orofacial Digital Features

Joubert syndrome (JS) is an autosomal recessive inherited disorder characterized by hypotonia, cerebellar vermis hypoplasia, ocular abnormalities (e.g., pigmentary retinopathy, oculomotor apraxia, and nystagmus), renal cysts, and hepatic fibrosis. Respiratory abnormalities, as apnea and hyperpnea, may be present, as well as mental retardation. Since the clinical findings of JS are quite heterogeneous, determination of radiological findings is essential.

Congenital hepatic fibrosis and coexistent retinal macular degeneration: A case report

RATIONALE

Congenital hepatic fibrosis (CHF) is an autosomal recessive disease characterized by periportal fibrosis, portal hypertension, and renal cystic disease. Essentially, CHF is a variant of fibrocystic disorder in which liver and kidney are commonly affected. Other frequently associated conditions include Caroli syndrome and polycystic kidney disease. CHF is also a known accompaniment in an array of inherited disorders with multiorgan involvement.

PATIENT CONCERNS

The 20-year-old male patient with declining vision (14 years duration), intermittent gingival bleeding (7 years duration), and abdominal distension (5 years duration), presented with exacerbation of these symptoms during the prior 2 months. The patient had been previously diagnosed with retinal macular degeneration, idiopathic thrombocytopenic purpura, and hepatosplenomegaly.

DIAGNOSES

Liver biopsy showed disordered hepatic acini and fibrous parenchymal banding, indicative of CHF.

INTERVENTIONS

After the treatment of diuresis and liver protectants, the clinical symptoms of the patients were improved. We subsequently recommend chromosomal analysis, although the family refused.

OUTCOMES

Three months after discharge, the patient was followed up by telephone. The patient had obvious abdominal distension and we advised that he should be admitted again. But the family refused.

LESSONS

CHF is an AR disease resulting in portal hypertension and often associated with renal malformations. CHF is also linked to a number of other disorders, many of which are ciliopathies. Because the clinical manifestations of CHF are nonspecific or lacking, its diagnosis is problematic, relying largely on liver biopsy. Once CHF is identified, physicians are obligated to investigate other organ systems, particularly a search for neuromuscular, retina or renal involvement. This case underscores the value of radiologic imaging, pathologic examination, and genetic testing in successfully diagnosing a rare disease.

Truncating mutations in exons 20 and 21 of OFD1 can cause primary ciliary dyskinesia without associated syndromic symptoms

BACKGROUND

Primary ciliary dyskinesia (PCD) is a motile ciliopathy, whose symptoms include airway infections, male infertility and situs inversus. Apart from the typical forms of PCD, rare syndromic PCD forms exist. Mutations of the X-linked OFD1 gene cause several syndromic ciliopathies, including oral-facial-digital syndrome type 1, Joubert syndrome type 10 (JBTS10), and Simpson-Golabi-Behmel syndrome type 2, the latter causing the X-linked syndromic form of PCD. Neurological and skeletal symptoms are characteristic for these syndromes, with their severity depending on the location of the mutation within the gene.

OBJECTIVES

To elucidate the role of motile cilia defects in the respiratory phenotype of PCD patients with C-terminal OFD1 mutations.

METHODS

Whole-exome sequencing in a group of 120 Polish PCD patients, mutation screening of the OFD1 coding sequence, analysis of motile cilia, and magnetic resonance brain imaging.

RESULTS

Four novel hemizygous OFD1 mutations, in exons 20 and 21, were found in men with a typical PCD presentation but without severe neurological, skeletal or renal symptoms characteristic for other OFD1-related syndromes. Magnetic resonance brain imaging in two patients did not show a molar tooth sign typical for JBTS10. Cilia in the respiratory epithelium were sparse, unusually long and displayed a defective motility pattern.

CONCLUSION

Consistent with the literature, truncations of the C-terminal part of OFD1 (exons 16-22) almost invariably cause a respiratory phenotype (due to motile cilia defects) while their impact on the primary cilia function is limited. We suggest that exons 20-21 should be included in the panel for regular mutation screening in PCD.

The molecular genetics of Joubert syndrome and related ciliopathies: The challenges of genetic and phenotypic heterogeneity

Joubert syndrome (JS; MIM PS213300) is a rare, typically autosomal recessive disorder characterized by cerebellar vermis hypoplasia and a distinctive malformation of the cerebellum and brainstem identified as the “molar tooth sign” on brain MRI. Other universal features include hypotonia with later ataxia and intellectual disability/developmental delay, with additional features consisting of oculomotor apraxia and abnormal respiratory pattern. Notably, other, more variable features include renal cystic disease, typically nephronophthisis, retinal dystrophy, and congenital hepatic fibrosis; skeletal changes such as polydactyly and findings consistent with short-rib skeletal dysplasias are also seen in many subjects. These pleiotropic features are typical of a number of disorders of the primary cilium, and make the identification of causal genes challenging given the significant overlap between JS and other ciliopathy conditions such as nephronophthisis and Meckel, Bardet-Biedl, and COACH syndromes. This review will describe the features of JS, characterize the 35 known genes associated with the condition, and describe some of the genetic conundrums of JS, such as the heterogeneity of founder effects, lack of genotype-phenotype correlations, and role of genetic modifiers. Finally, aspects of JS and related ciliopathies that may pave the way for development of therapeutic interventions, including gene therapy, will be described.

Joubert syndrome with multiple pituitary hormone deficiency

Joubert syndrome (JS) and JS-related disorders are a group of developmental delay, multiple congenital anomalies and complex midbrain-hindbrain malformations. A few cases of JS with multiple pituitary hormone deficiency (MPHD) have been reported in literature. Here, we presented an unusual presentation of JS in a newborn with MPHD. This case is intended to draw attention to the rare association of JS and MDPH by increasing the awareness of this syndrome.

A novel pathogenic variant in OFD1 results in X-linked Joubert syndrome with orofaciodigital features and pituitary aplasia

Orofaciodigital syndrome type I and X-linked recessive Joubert syndrome are known ciliopathic disorders that are caused by pathogenic variants in OFD1 gene. Endocrine system involvement with these conditions is not well described. We present the first report of a newborn male with a novel hemizygous variant in OFD1 gene c.515T>C, (p.Leu172Pro) resulting in X-linked Joubert syndrome and orofaciodigital features with complete pituitary gland aplasia and subsequent severe hypoplasia of peripheral endocrine glands. This clinical report expands the phenotypic spectrum of endocrine system involvement in OFD1-related disorders and suggests that OFD1 gene may be related to pituitary gland development.

Primary Cilia-An Underexplored Topic in Major Mental Illness

Though much progress has been made in recent years towards understanding the function and physiology of primary cilia, they remain a somewhat elusive organelle. Some studies have explored the role of primary cilia in the developing nervous system, and their dysfunction has been linked with several neurosensory deficits. Yet, very little has been written on their potential role in psychiatric disorders. This article provides an overview of some of the functions of primary cilia in signalling pathways, and demonstrates that they are a worthy candidate in psychiatric research. The links between primary cilia and major mental illness have been demonstrated to exist at several levels, spanning genetics, signalling pathways, and pharmacology as well as cell division and migration. The primary focus of this review is on the sensory role of the primary cilium and the neurodevelopmental hypothesis of psychiatric disease. As such, the primary cilium is demonstrated to be a key link between the cellular environment and cell behaviour, and hence of key importance in the considerations of the nature and nurture debate in psychiatric research.

Loss of the neurodevelopmental Joubert syndrome causing protein, Ahi1, causes motor and muscle development delays independent of central nervous system involvement

Joubert syndrome (JBTS) is a predominantly autosomal recessive neurodevelopmental disorder that presents with characteristic malformations of the cerebellar vermis, superior cerebellar peduncles and midbrain in humans. Accompanying these malformations are a heterogeneous set of clinical symptoms, which frequently include deficits in motor and muscle function, such as hypotonia (low muscle tone) and ataxia (clumsiness). These symptoms are attributed to improper development of the hindbrain, but no direct evidence has been reported linking these in JBTS. Here, we describe muscle developmental defects in a mouse with a targeted deletion of the Abelson helper integration site 1 gene, Ahi1, one of the genes known to cause JBTS in humans. While FVB/NJ Ahi1^-/- mice display no gross malformations of the cerebellum, deficits are observed in several measures of motor function, strength, and body development. Specifically, Ahi1^-/- mice show delayed physical development, delays in surface reflex righting as neonates, and reductions in grip strength and spontaneous locomotor activity as adults. Additionally, Ahi1^-/- mice showed evidence of muscle-specific contributions to this phenotype, such as reductions in 1) myoblast differentiation potential in vitro, 2) muscle desmin expression, and 3) overall muscle mass, myonuclear domain, and muscle fiber cross-sectional area. Together, these data suggest that loss of Ahi1 may cause abnormalities in the differentiation of myoblasts to mature muscle cells. Moreover, Ahi1 loss impacts muscle development directly, outside of any indirect impact of cerebellar malformations, revealing a novel myogenic cause for hypotonia in JBTS.

Linear and whorled nevoid hypermelanosis and Joubert syndrome: a novel association: A case report and literature review

This report discusses a case of linear and whorled nevoid hypermelanosis associated with cerebellar atrophy, ocular and developmental anomalies compatible with Joubert syndrome. Linear and whorled nevoid hypermelanosis is a rare disorder of skin pigmentation characterized by swirls and whorls of hyperpigmented macules in a reticulate pattern along Blaschko’s lines. Neurologic, cardiac, skeletal and developmental anomalies have been reported. We present a case of linear and whorled nevoid hypermelanosis on an 18-year-old woman who also presented with cerebellar atrophy, jerk nystagmus, macrocephaly and developmental delay. Those symptoms were compatible with Joubert syndrome. A complete work-up failed to reveal other systemic or skeletal anomalies. No chromosomal alteration was found on karyotyping carried out on a skin specimen. Much remains to be known about linear and whorled nevoid hypermelanosis. It is generally a benign condition but association with various congenital anomalies have been reported. Proper work-up is advised in order to exclude congenital anomalies.

Review of Ocular Manifestations of Joubert Syndrome

Joubert syndrome is a group of rare disorders that stem from defects in a sensory organelle, the primary cilia. Affected patients often present with disorders involving multiple organ systems, including the brain, eyes, and kidneys. Common symptoms include breathing abnormalities, mental developmental delays, loss of voluntary muscle coordination, and abnormal eye movements, with a diagnostic “molar tooth” sign observed by magnetic resonance imaging (MRI) of the midbrain. We reviewed the ocular phenotypes that can be found in patients with Joubert syndrome. Ocular motor apraxia is the most frequent (80% of patients), followed by strabismus (74%) and nystagmus (72%). A minority of patients also present with ptosis (43%), chorioretinal coloboma (30%), and optic nerve atrophy (22%). Although mutations in 34 genes have been found to be associated with Joubert syndrome, retinal degeneration has been reported in only 38% of patients. Mutations in AHI1 and CEP290, genes critical to primary cilia function, have been linked to retinal degeneration. In conclusion, Joubert syndrome is a rare pleiotropic group of disorders with variable ocular presentations.

Missense variants in TMEM67 in a patient with Joubert syndrome

We present a patient with a clinical diagnosis of Joubert syndrome with COACH phenotype who carries two TMEM67 variants of uncertain significance (VUS). One VUS can be reclassified as "likely pathogenic" by adding clinical data. As genetic testing becomes more accessible, more VUS will require clinical correlation for accurate classification.

Idiopathic Scoliosis Families Highlight Actin-Based and Microtubule-Based Cellular Projections and Extracellular Matrix in Disease Etiology

Idiopathic scoliosis (IS) is a structural lateral spinal curvature of ≥10° that affects up to 3% of otherwise healthy children and can lead to life-long problems in severe cases. It is well-established that IS is a genetic disorder. Previous studies have identified genes that may contribute to the IS phenotype, but the overall genetic etiology of IS is not well understood. We used exome sequencing to study five multigenerational families with IS. Bioinformatic analyses identified unique and low frequency variants (minor allele frequency ≤5%) that were present in all sequenced members of the family. Across the five families, we identified a total of 270 variants with predicted functional consequences in 246 genes, and found that eight genes were shared by two families. We performed GO term enrichment analyses, with the hypothesis that certain functional annotations or pathways would be enriched in the 246 genes identified in our IS families. Using three complementary programs to complete these analyses, we identified enriched categories that include stereocilia and other actin-based cellular projections, cilia and other microtubule-based cellular projections, and the extracellular matrix (ECM). Our results suggest that there are multiple paths to IS and provide a foundation for future studies of IS pathogenesis.

Joubert Syndrome: Ophthalmological Findings in Correlation with Genotype and Hepatorenal Disease in 99 Patients Prospectively Evaluated at a Single Center

PURPOSE

Joubert syndrome (JS) is caused by mutations in >34 genes that encode proteins involved with primary (nonmotile) cilia and the cilium basal body. This study describes the varying ocular phenotypes in JS patients, with correlation to systemic findings and genotype.

DESIGN

Patients were systematically and prospectively examined at the National Institutes of Health (NIH) Clinical Center in the setting of a dedicated natural history clinical trial.

PARTICIPANTS

Ninety-nine patients with JS examined at a single center.

METHODS

All patients underwent genotyping for JS, followed by complete age-appropriate ophthalmic examinations at the NIH Clinical Center, including visual acuity (VA), fixation behavior, lid position, motility assessment, slit-lamp biomicroscopy, dilated fundus examination with an indirect ophthalmoscope, and retinoscopy. Color and fundus autofluorescence imaging, Optos wide-field photography (Dunfermline, Scotland, UK), and electroretinography (ERG) were performed when possible.

MAIN OUTCOME MEASURES

The VA (with longitudinal follow-up where possible), ptosis, extraocular muscle function, retinal and optic nerve status, and retinal function as measured by ERG.

RESULTS

Among patients with JS with quantifiable VA (68/99), values ranged from 0 logarithm of the minimum angle of resolution (logMAR) (Snellen 20/20) to 1.5 logMAR (Snellen 20/632). Strabismus (71/98), nystagmus (66/99), oculomotor apraxia (60/77), ptosis (30/98), coloboma (28/99), retinal degeneration (20/83), and optic nerve atrophy (8/86) were identified.

CONCLUSIONS

We recommend regular monitoring for ophthalmological manifestations of JS beginning soon after birth or diagnosis. We demonstrate delayed visual development and note that the amblyogenic time frame may last significantly longer in JS than is typical. In general, patients with coloboma were less likely to display retinal degeneration, and those with retinal degeneration did not have coloboma. Severe retinal degeneration that is early and aggressive is seen in disease caused by specific genes, such as CEP290- and AHI1-associated JS. Retinal degeneration in INPP5E-, MKS1-, and NPHP1-associated JS was generally milder. Finally, ptosis surgery can be helpful in a subset of patients with JS; decisions as to timing and benefit/risk ratio need to be made on an individual basis according to expert consultation.

Macular staphyloma in patients affected by Joubert syndrome with retinal dystrophy: a new finding detected by SD-OCT

PURPOSE

Joubert syndrome (JS) is an inherited autosomal recessive or X-lined disorder characterized by a congenital malformation of the mid-hindbrain and a large spectrum of clinical features. It is estimated that retinal dystrophy is present in association with the typical neurological findings in about one-third of the patients. The aim of this study is to better characterize the macular region in JS patients with and without retinal dystrophy.

METHODS

We describe six individuals affected by JS as demonstrated by the presence of the typical "molar tooth sign" on MRI. The presence of retinal dystrophy was assessed by fundus examination and electrophysiology by means of full-field electroretinogram (ERG) and visual evoked potentials (VEP) at five spatial frequencies (300-15 min of arc). The macular region was examined with spectral domain optical coherence tomography (SD-OCT). All the exams were performed in awake conditions. All the patients underwent next-generation-sequencing analysis of known JS genes.

RESULTS

Pathogenic biallelic variants in either the INPP5E gene or the AHI1 gene were detected in two pairs of siblings, all positive for retinal dystrophy. Genetic testing yielded no results in the remaining two patients, one with bilateral coloboma and retinal dystrophy and the other with normal fundus appearance. Decimal best-corrected visual acuity was between 0.1 and 1.0. In the two pairs of siblings, SD-OCT revealed a posterior staphyloma centred on the fovea, in one case associated with cystoid macular oedema. Macular morphology was just slightly altered in the fifth patient and completely normal in the last patient. Refractive error was between + 2.50 diopter sphere (DS) and - 8 DS and - 4 diopter cylinder ax 45°. ERG waves were markedly lower than the normal limits in both scotopic and photopic components in the two pairs of siblings and in the fifth subject, with VEP P100 latencies and amplitudes delayed and reduced in all spatial frequencies. ERG and VEP were within normal limits in the last patient.

CONCLUSIONS

To our knowledge, macular staphyloma has not been described before in JS. Further work is warranted to assess the true prevalence of staphyloma in JS and its connection to retinal dystrophy.

Late-onset hydrocephalus in a child with Joubert syndrome: a case report

INTRODUCTION

The ciliopathy "Joubert syndrome" was first described in 1969 by Dr. Marie Joubert and most subtypes follow an autosomal recessive inheritance. The complex disorder shows typical clinical features, such as hyperventilation, abnormal eye movements, and retardation. A pathognomonic midbrain-hindbrain malformation, the molar tooth sign, can be found on magnetic resonance imaging of the brainstem. There are a little more than 200 reports of Joubert syndrome in the literature.

CASE PRESENTATION

We report a case of a 9-year-old boy who developed a progressive hydrocephalus starting from the age of 4. He underwent VP shunt placement at 8 years, which relieved hydrocephalus-related clinical symptoms and put development of the macrocephalus to a halt.

CONCLUSION

Neonatal hydrocephalus due to the altered anatomy of the posterior fossa has been reported earlier, but to our knowledge, this is the first case of a delayed onset of hydrocephalus in a patient with Joubert syndrome.

Uncovering the genetic lesions underlying the most severe form of Hirschsprung disease by whole-genome sequencing

Hirschsprung disease (HSCR) is a complex birth defect characterized by the lack of ganglion cells along a variable length of the distal intestine. A large proportion of HSCR patients remain genetically unexplained. We applied whole-genome sequencing (WGS) on 9 trios where the probands are sporadically affected with the most severe form of the disorder and harbor no coding sequence variants affecting the function of known HSCR genes. We found de novo protein-altering variants in three intolerant to change genes-CCT2, VASH1, and CYP26A1-for which a plausible link with the enteric nervous system (ENS) exists. De novo single-nucleotide and indel variants were present in introns and non-coding neighboring regions of ENS-related genes, including NRG1 and ERBB4. Joint analysis with those inherited rare variants found under recessive and/or digenic models revealed both patient-unique and shared genetic features where rare variants were found to be enriched in the extracellular matrix-receptor (ECM-receptor) pathway (p = 3.4 × 10-11). Delineation of the genetic profile of each patient might help finding common grounds that could lead to the discovery of shared molecules that could be used as drug targets for the currently ongoing cell therapy effort which aims at providing an alternative to the surgical treatment.

Prenatal Diagnosis and Genetic Analysis of a Fetus with Joubert Syndrome

Objective

To diagnose and explore the genetic cause of Joubert syndrome (JS) in a fetus.

Methods

Prenatal ultrasound and magnetic resonance imaging (MRI) examinations were performed, and genetic analysis was conducted using targeted next-generation sequencing (NGS) and Sanger sequencing.

Results

Prenatal ultrasound and MRI examinations showed cerebellar vermis hypoplasia and molar tooth sign (MTS); hence the fetus was diagnosed with JS. Further genetic analysis revealed a known missense variant (c.3599C>T, p.A1200V) and a novel missense variant (c.3857G>A, p.R1286H) in the C5orf42 gene of the fetus.

Conclusion

Our study provides insights into prenatal and early diagnosis of JS and expands the variation spectrum of C5orf42 gene.

Primary cilia proteins: ciliary and extraciliary sites and functions

Primary cilia are immotile organelles known for their roles in development and cell signaling. Defects in primary cilia result in a range of disorders named ciliopathies. Because this organelle can be found singularly on almost all cell types, its importance extends to most organ systems. As such, elucidating the importance of the primary cilium has attracted researchers from all biological disciplines. As the primary cilia field expands, caution is warranted in attributing biological defects solely to the function of this organelle, since many of these "ciliary" proteins are found at other sites in cells and likely have non-ciliary functions. Indeed, many, if not all, cilia proteins have locations and functions outside the primary cilium. Extraciliary functions are known to include cell cycle regulation, cytoskeletal regulation, and trafficking. Cilia proteins have been observed in the nucleus, at the Golgi apparatus, and even in immune synapses of T cells (interestingly, a non-ciliated cell). Given the abundance of extraciliary sites and functions, it can be difficult to definitively attribute an observed phenotype solely to defective cilia rather than to some defective extraciliary function or a combination of both. Thus, extraciliary sites and functions of cilia proteins need to be considered, as well as experimentally determined. Through such consideration, we will understand the true role of the primary cilium in disease as compared to other cellular processes' influences in mediating disease (or through a combination of both). Here, we review a compilation of known extraciliary sites and functions of "cilia" proteins as a means to demonstrate the potential non-ciliary roles for these proteins.

Renal cystic disease and associated ciliopathies

PURPOSE OF REVIEW

To review disorders that are associated with renal cystic disease during prenatal life and to highlight the strong association between renal cystic disease and ciliopathies.

RECENT FINDINGS

There are numerous causative genes for ciliopathies that can present with cystic kidney disease. In the group of single gene ciliopathies, autosomal dominant polycystic kidney disease is by far the most prevalent one. Other examples are autosomal recessive polycystic kidney disease, nephronophthisis, Bardet-Biedl syndrome, Meckel-Gruber syndrome, Joubert syndrome and related disorders as well as X-linked orofaciodigital syndrome type 1, respectively. The prevalence of these inherited disorders sums up to about in 1 : 2000 people. These disorders with their hepatorenal fibrocystic character should be classified as multisystem diseases.

SUMMARY

Understanding of the origin of renal cystic disease and associated disorders is important to make the appropriate prenatal diagnosis and for counseling affected parents. In the future, understanding of the pathophysiology may help to develop new treatment strategies.

X-linked ataxias

X-linked cerebellar ataxias (XLCA) are an expanding group of genetically heterogeneous and clinically variable conditions characterized by cerebellar dysgenesis (hypoplasia, atrophy, or dysplasia) caused by gene mutations or genomic imbalances on the X chromosome. The neurologic features of XLCA include hypotonia, developmental delay, intellectual disability, ataxia, and other cerebellar signs. Normal cognitive development has also been reported. Cerebellar defects may be isolated or associated with other brain malformations or extraneurologic involvement. More than 20 genes on the X chromosome, mainly encoding for proteins involved in brain development and synaptic function that have been constantly or occasionally associated with a pathologic cerebellar phenotype, and several families with X-linked inheritance have been reported. Given the excess of males with ataxia, this group of conditions is probably underestimated and families of patients with neuroradiologic and clinical evidence of a cerebellar disorder should be counseled for high risk of X-linked inheritance.

Joubert’s syndrome and related disorders and home-based peritoneal dialysis in East Africa: a case report

Background

Joubert’s syndrome is a rare condition affecting an estimated 1:80,000–1:100,000 individuals. There is underdevelopment of the cerebellar vermis resulting in a characteristic molar tooth sign on cross sectional axial magnetic resonance imaging. It can occur in association with multi-organ involvement; in such cases it is classified as Joubert’s syndrome and related disorders. To date, there are no cases of Joubert’s syndrome and related disorders from sub-Saharan Africa described in the literature.

Case presentation

An 8 year old black Kenyan female child was diagnosed in Joubert’s syndrome in her first year of life. She was noted to have dysmorphic facies and hypotonia in the neonatal period and cranial MRI showed dysplasia of the cerebellar vermis and typical molar tooth malformation. She was subsequently lost to follow up for several years and later presented with anaemia. Further investigation revealed bilateral multicystic kidneys and significant renal impairment consistent with a diagnosis of end stage renal failure and polycystic kidney disease. She underwent home peritoneal dialysis for 7 months.

Conclusions

Joubert’s syndrome and related disorders is a rare condition. This case report demonstrates that home peritoneal dialysis is feasible in a low resource setting. Although it is scarcely provided in African countries, it is an effective renal replacement strategy for patients with end stage renal disease.

Prenatal diagnosis of Joubert syndrome: A case report and literature review

INTRODUCTION

Joubert syndrome (JS) is a rare autosomal recessive inherited disease belonging to ciliopathy with the causative mutation of genes. Except for X-linked inheritance, the high recurrence rate of a family is about 25%. After birth, it may cause a series of neurological symptoms, even with retina, kidney, liver, and other organ abnormalities, which is defined as Joubert syndrome and related disorders (JSRD). Molecular genetics research contributes to disease prediction and genetic counseling. Prenatal diagnosis is rare. Magnetic resonance imaging (MRI) is usually the first-choice diagnostic modality with typical brain images characterized by the molar tooth sign. We describe a case of JS prenatally and Dandy-Walker malformation for the differential diagnosis based on ultrasonograms. We also review the etiology, imaging features, clinical symptoms, and diagnosis of JSRD.

CASE PRESENTATION

A 22-year-old woman was pregnant at 27 1/7 weeks' gestation with fetal cerebellar vermis hypoplasia. Fetal ultrasonography and MRI confirmed a diagnosis of JS at our center. The couple finally opted to terminate the fetus, which had a normal appearance and growth parameters. The couple also had an AHI1 gene mutation on chromosome 6.

CONCLUSIONS

Currently, a diagnosis of JS is commonly made after birth. Fewer cases of prenatal diagnosis by ultrasonography have been made, and they are more liable to be misdirected because of some nonspecial features that also manifest in Dandy-Walker malformation, cranio-cerebello-cardiac syndrome, and so on.

Physiotherapy and Rehabilitation in a Child with Joubert Syndrome

Objective

Joubert syndrome (JS) is a rare autosomal recessive genetic disorder characterized by brain malformation, hypotonia, breathing abnormalities, ataxia, oculomotor apraxia, and developmental delay. The purpose of this study was to report the efficiency of the physiotherapy and rehabilitation program in a child with JS.

Materials and Methods

Our case is a 19-month-old female child with mild clinical signs of JS. The pretreatment and posttreatment motor functioning level of the case was evaluated through the Gross Motor Function Measure (GMFM), whereas the independence level was evaluated through the Pediatric Functional Independence Measure (WeeFIM). The case was included in the rehabilitation program by the physiotherapist for one hour for five days a week throughout the period of 13 months in accordance with the neurodevelopmental treatment principles.

Results

The case was able to turn around from the supine position to the reverse direction by oneself, and she was able to rise on her forearms facedown and was able to sit, crawl, and walk independently. The GMFM score was 210, whereas WeeFIM score was 65.

Discussion

In the direction of those findings, in Joubert Syndrome, physiotherapy and rehabilitation can be effective in coping with the symptoms causing developmental delay.

Defective ciliogenesis in INPP5E-related Joubert syndrome

Joubert syndrome is a neurodevelopmental disorder, characterized by malformation of the mid and hindbrain leading to the pathognomonic molar tooth appearance of the brainstem and cerebellum on axial MRI. Core clinical manifestations include hypotonia, tachypnea/apnea, ataxia, ocular motor apraxia, and developmental delay of varying degrees. In addition, a subset of patients has retinal dystrophy, chorioretinal colobomas, hepatorenal fibrocystic disease, and polydactyly. Joubert syndrome exhibits genetic heterogeneity, with mutations identified in more than 30 genes, including INPP5E, a gene encoding inositol polyphosphate 5-phosphatase E, which is important in the development and stability of the primary cilium. Here, we report the detailed clinical phenotypes of two sisters with a novel homozygous variant in INPP5E (NM_019892.4: c.1565G>C, NP_063945.2: p.Gly552Ala), expanding the phenotype associated with Joubert syndrome type 1. Expression studies using patient-derived fibroblasts showed changes in mRNA and protein levels. Analysis of fibroblasts from patients revealed that a significant number of cells had shorter or no cilia, indicating defects in ciliogenesis, and cilia maintenance.

A Homozygous Missense Variant in INPP5E Associated with Joubert Syndrome and Related Disorders

Joubert syndrome and related disorders (JSRD; ORPHA 140874) is a complex set of neurodevelopmental disorders with multiple organ involvement. JSRD is a type of ciliopathy which is caused by the presence of defective primary cilia in an individual. JSRD is commonly inherited in an autosomal recessive pattern, and more than 23 genes are known to be associated with JSRD. We report a novel homozygous mutation identified in the INPP5E gene, c.1303C>T, which leads to a change of an amino acid from arginine to tryptophan at residue 435 in the protein chain. In silico analysis indicates that p.Arg435Trp substitution affects the functionality of the protein product of the gene. Our result adds to the growing body of evidences that underlines the clinical utility of next-generation sequencing in the diagnosis of a genetic disorder when clinical features are inconclusive.

Functional validation of novel MKS3/TMEM67 mutations in COACH syndrome

COACH syndrome is an autosomal recessive developmental disorder, a subtype of Joubert syndrome and related disorders, characterized by cerebellar vermis hypoplasia, oligophrenia, ataxia, coloboma, and hepatic fibrosis. Although mutations in TMEM67 (transmembrane protein 67)/MKS3 (Meckel-Gruber syndrome, type 3) were reported to cause COACH syndrome, this causality has not verified by functional studies. In a 20-year-old Korean man, we found cerebellar ataxia, isolated elevation in serum γ-glutamyl transpeptidase (γ-GTP) activity, oligophrenia, the molar tooth sign (MTS) in the brain MR images and congenital hepatic fibrosis (CHF). Two novel compound heterozygous mutations were found in TMEM67 in the patient: i) missense mutation (c.395 G > C and p.Gly132Ala) in exon 3, and ii) deletion in exon 26 (c.2758delT and p.Tyr920ThrfsX40). Western blotting showed that the p.Tyr920ThrfsX40 mutation accelerates turnover of the TMEM67 protein. Although wild-type human TMEM67 RNA rescued phenotypes of zebrafish embryos injected with anti-sense oligonucleotide morpholinos against tmem67, the two human TMEM67 RNAs individually harboring the two mutations did not. Finally, Wnt signaling, but not Hedgehog signaling, was suppressed in tmem67 morphants. To the best of our knowledge, this is the first report verifying the causality between COACH syndrome and TMEM67, which will further our understanding of molecular pathogenesis of the syndrome.

MicroRNAs 218a-5p, 219a-5p, and 221-3p regulate vestibular compensation

Unilateral vestibular deafferentation (UVD) interrupts afferent signals from one side, resulting in an imbalance of the resting activity between bilateral vestibular nuclei. Vestibular compensation is the process of balancing the resting activity to reestablish homeostasis. Here, we investigated microRNAs (miRNAs) that regulate vestibular compensation using the Sprague-Dawley rat. After determining the progression of vestibular compensation following UVD, microarray analysis was performed and nine miRNAs were selected as candidates. Following validation by quantitative reverse transcription-PCR, three miRNAs remained. We assessed the effect of these miRNAs on vestibular compensation using miRNA oligomers. We compared the results of the rotarod test and 5-bromo-2'-deoxyuridine immunohistochemistry following UVD between the control group and the groups in which the candidate miRNA oligomers were administered. Administration of miR-218a-5p, 219a-5p, and 221-3p oligomers significantly affected vestibular compensation. Target pathway analysis of these miRNAs supported our results. Our findings suggest that the miRNAs 218a-5p, 219a-5p, and 221-3p regulate vestibular compensation.

Lingual Frenectomy in Joubert Syndrome

AIM

Our aim is to present a case of a rare disorder, such as Joubert syndrome (JS) which required oral surgical intervention under general anesthesia at a very young age to help in achieving normal developmental milestones.

BACKGROUND

Ciliopathies are an emerging class of diseases of which JS is a significant member. There have been very few cases of JS with its distinguishing features which have been reported in recent literature.

CASE REPORT

We herewith present a case of JS who reported to our unit with a complaint of speech abnormality. Intraoral examination revealed a tongue-tie which was planned for surgical release. As any drugs that interfere with respiratory depression have to be used with utmost care, adequate precautions were taken in this case and the patient was treated under general anesthesia. The tongue-tie was released and associated ham-artomatous outgrowths from the floor of the mouth were also excised. Appropriate postoperative care was taken and the patient was discharged.

CONCLUSION

The patient treated by us did not reveal any significant intraoperative or postoperative complications. Treatment of cases of JS required a team effort of multiple dental and medical specialists. Long-term follow-up of such patients is required so that they achieve normal chronological development.

CLINICAL SIGNIFICANCE

Joubert syndrome being a rare disorder requires special anesthetic care during any surgical procedure, especially that involving the oral cavity. The need and timing of surgical intervention in such cases should be carefully assessed and appropriate precautions should be taken.

Neuropsychological phenotypes of 76 individuals with Joubert syndrome evaluated at a single center

Joubert syndrome (JS) is a genetically heterogeneous ciliopathy characterized by hypo-dysplasia of the cerebellar vermis, a distinct hindbrain/midbrain malformation (molar tooth sign), and intellectual disability. We evaluated the neuropsychological profiles of 76 participants with JS in the context of molecular genetics and clinical covariates. Evaluations included neuropsychological testing, structured parental interviews, DNA sequencing, brain magnetic resonance imaging (MRI), electroencephalography (EEG), ophthalmologic examination, and assessment for renal and hepatic disease. On average, participants manifested Full Scale Intelligence Quotients (FSIQ) in the moderately to profoundly low range (M = 64.3 ± 15.3). Of the Wechsler index scores, verbal comprehension was least affected and processing speed was most affected. Receptive language was rated as better than expressive language on the Vineland Adaptive Behavior Scales-Second Edition. Those with abnormal EEG had a significantly lower FSIQ (n = 15; M = 50.7 ± 12.9) compared to participants with normal EEG (n = 39; M = 64.7 ± 16.3; p = .004). Participants taking psychiatric medications manifested a lower FSIQ (n = 20; M = 54.8 ± 13.2) than those not taking them (n = 42; M = 65.0 ± 17.2; p = .022). These correlations were also present in the TMEM67-related JS sub-cohort (n = 14). Based on parental assessment, psychiatric and behavioral problems were significantly more common than in the general population for all measures (p < .004 for all). The majority (65%) of individuals with JS have some degree of intellectual disability. Abnormal EEG is associated with lower neuropsychological function. Processing speed is a weakness, while verbal comprehension and receptive language are relative strengths. These findings may guide parents, teachers, therapists, and doctors to determine appropriate therapies, accommodations, and academic goals for individuals with JS.

Joubert syndrome; misleading presentation of two cases as pseudo-tumor cerebri and literature review

Joubert syndrome is a rare autosomal recessive disorder that may have different clinical presentation such as ataxia, hyperpnea, sleep apnea, nystagmus, hypotonia, seizure and retinitis pigmentosa. We present a 22-year-old girl and her older sibling, labeled as cerebral palsy. She had renal transplant years ago without the true diagnosis of the disorder. Brain imaging revealed the classic "molar tooth sign" appearance, and clinical evaluation established the diagnosis for both of the siblings. Imaging should be done to evaluate the neuroradiological findings of Joubert syndrome. With a neonate with Joubert syndrome in a family, antenatal diagnosis by ultrasound is crucial for future siblings.

Missense mutations in the WD40 domain of AHI1 cause non-syndromic retinitis pigmentosa

Background

Recent findings suggesting that Abelson helper integration site 1 (AHI1) is involved in non-syndromic retinal disease have been debated, as the functional significance of identified missense variants was uncertain. We assessed whether AHI1 variants cause non-syndromic retinitis pigmentosa (RP).

Methods

Exome sequencing was performed in three probands with RP. The effects of the identified missense variants in AHI1 were predicted by three-dimensional structure homology modelling. Ciliary parameters were evaluated in patient’s fibroblasts, and recombinant mutant proteins were expressed in ciliated retinal pigmented epithelium cells.

Results

In the three patients with RP, three sets of compound heterozygous variants were detected in AHI1 (c.2174G>A; p.Trp725* and c.2258A>T; p.Asp753Val, c.660delC; p.Ser221Glnfs*10 and c.2090C>T; p.Pro697Leu, c.2087A>G; p.His696Arg and c.2429C>T; p.Pro810Leu). All four missense variants were present in the conserved WD40 domain of Jouberin, the ciliary protein encoded by AHI1, with variable predicted implications for the domain structure. No significant changes in the percentage of ciliated cells, nor in cilium length or intraflagellar transport were detected. However, expression of mutant recombinant Jouberin in ciliated cells showed a significantly decreased enrichment at the ciliary base.

Conclusions

This report confirms that mutations in AHI1 can underlie autosomal recessive RP. Moreover, it structurally and functionally validates the effect of the RP-associated AHI1 variants on protein function, thus proposing a new genotype–phenotype correlation for AHI1 mutation associated retinal ciliopathies.

Hassab's operation for Joubert syndrome with congenital hepatic fibrosis: A case report

INTRODUCTION

Joubert syndrome is characterized by psychomotor developmental delay, hypotonia, oculomotor abnormalities, occasional retinal dystrophy and cystic kidneys, and frequent and often, striking breathing abnormalities, especially in the neonatal period, with panting tachypnea followed by apnea. We report a case of Joubert syndrome with hepatic fibrosis, portal hypertension, and pancytopenia treated by Hassab's operation.

PRESENTATION OF CASE

Our patient was a 27-year-old woman with a history of tachypnea, muscle hypotonia, and psychomotor retardation shortly after birth and a diagnosis of Joubert syndrome at 2 years of age. At 19 years of age, she was diagnosed with progressive pancytopenia. At 27 years of age, she visited her local doctor for sudden-onset hematemesis. Endoscopy revealed esophageal varices exhibiting the red color sign and no evidence of recent bleeding. Splenomegaly and development of portal collateral circulation were observed on computed tomography scans. The patient was referred to our hospital, where she was diagnosed with Joubert syndrome and hepatic fibrosis, portal hypertension, and hypersplenism. After performing Hassab's operation, the pancytopenia improved, but anticoagulant therapy was required for splenic vein thrombosis. The patient was discharged on postoperative day 25. Two years following surgery, the gastroesophageal varices were controlled, and no progression of the splenic vein thrombosis or hepatic failure was evident.

CONCLUSION

This is the first case report of Hassab's operation for congenital hepatic fibrosis in a patient with Joubert syndrome, a rare congenital condition. We achieved a favorable clinical outcome.

Whole-exome sequencing and digital PCR identified a novel compound heterozygous mutation in the NPHP1 gene in a case of Joubert syndrome and related disorders

BACKGROUND

Joubert syndrome and related disorders (JSRD) is a clinically and genetically heterogeneous condition with autosomal recessive or X-linked inheritance, which share a distinctive neuroradiological hallmark, the so-called molar tooth sign. JSRD is classified into six clinical subtypes based on associated variable multiorgan involvement. To date, 21 causative genes have been identified in JSRD, which makes genetic diagnosis difficult.

CASE PRESENTATION

We report here a case of a 28-year-old Japanese woman diagnosed with JS with oculorenal defects with a novel compound heterozygous mutation (p.Ser219*/deletion) in the NPHP1 gene. Whole-exome sequencing (WES) of the patient identified the novel nonsense mutation in an apparently homozygous state. However, it was absent in her mother and heterozygous in her father. A read depth-based copy number variation (CNV) detection algorithm using WES data of the family predicted a large heterozygous deletion mutation in the patient and her mother, which was validated by digital polymerase chain reaction, indicating that the patient was compound heterozygous for the paternal nonsense mutation and the maternal deletion mutation spanning the site of the single nucleotide change.

CONCLUSION

It should be noted that analytical pipelines that focus purely on sequence information cannot distinguish homozygosity from hemizygosity because of its inability to detect large deletions. The ability to detect CNVs in addition to single nucleotide variants and small insertion/deletions makes WES an attractive diagnostic tool for genetically heterogeneous disorders.

Neuroimaging findings in Joubert syndrome with C5orf42 gene mutations: A milder form of molar tooth sign and vermian hypoplasia

PURPOSE

Little is known regarding neuroimaging-genotype correlations in Joubert syndrome (JBTS). To elucidate one of these correlations, we investigated the neuroimaging findings of JBTS patients with C5orf42 mutations.

MATERIALS AND METHODS

Neuroimaging findings in five JBTS patients with C5orf42 mutations were retrospectively assessed with regard to the infratentorial and supratentorial structures on T1-magnetization prepared rapid gradient echo (MPRAGE), T2-weighted images, and color-coded fractional anisotropy (FA) maps; the findings were compared to those in four JBTS patients with mutations in other genes (including three with AHI1 and one with TMEM67 mutations).

RESULTS

In C5orf42-mutant patients, the infratentorial magnetic resonance (MR) images showed normal or minimally thickened and minimally elongated superior cerebellar peduncles (SCP), normal or minimally deepened interpeduncular fossa (IF), and mild vermian hypoplasia (VH). However, in other patients, all had severe abnormalities in the SCP and IF, and moderate to marked VH. Supratentorial abnormalities were found in one individual in other JBTS. In JBTS with all mutations, color-coded FA maps showed the absence of decussation of the SCP (DSCP).

CONCLUSION

The morphological neuroimaging findings in C5orf42-mutant JBTS were distinctly mild and made diagnosis difficult. However, the absence of DSCP on color-coded FA maps may facilitate the diagnosis of JBTS.

Disruption of the Photoreceptor Inner Segment-Outer Segment Junction in a 6-Year-Old Girl with Joubert Syndrome

Joubert syndrome (JS) is a spectrum of genetic disorders characterised by cerebellar and brainstem malformation called "molar tooth sign", resulting in hypotonia, developmental delay, and intellectual disability. Here we describe a young female JS patient with "salt-and-pepper" fundus and inner segment-outer segment junction (IS/OS line) discontinuity, with a lack of external limiting membrane. Ocular coherence tomography (OCT) detected blurred external retinal layers in the macula centre. Although JS patients often have retinal degeneration with varying severity, few investigators have utilised OCT in their investigations. Our findings will help clarify the precise mechanisms of retinal involvement in JS.

Orocraniofacial findings of a Pediatric Patient with Joubert Syndrome

Joubert syndrome (JS) is a very rare autosomal recessive disorder, involving agenesis or dysgenesis of cerebellar vermis and brain stem. The neurological features of JS include hypotonia, ataxia, developmental delay, intellectual disability, abnormal eye movements, and neonatal breathing dysregulation. These may be associated with multiorgan involvement, mainly retinal dystrophy, nephronophthisis, hepatic fibrosis, and polydactyly. An obligatory hallmark feature associated with JS is the molar tooth sign (MTS), a complex midbrain-hindbrain malformation visible on brain imaging. This case report presents a pediatric case of JS in a 7-year-old girl. Joubert syndrome cases have been reported by various medical specialties in medical journals; however, this probably could be the first report of this rare developmental disorder in dental and oral health.