Joubert syndrome: a review

A Brief Focus on Joubert Syndrome and Related Acute Complications

Joubert syndrome (JS) and related disorders are a group of congenital anomalies syndromes in which the obligatory hallmark is the molar tooth sign, a complex midbrain–hindbrain malformation. Moreover, JS may be associated with multiorgan involvement, mainly nephronophthisis, hepatic fibrosis, retinal dystrophy, and other abnormalities with both inter- and intra-familial variability. Therefore, these patients should be followed by both diagnostic protocol and multidisciplinary approach to assess multiorgan involvement. Here, we briefly summarize the possible complications in patients with JS.

Joubert Syndrome and Renal Implication

Twenty-five to 30% of patients with Joubert syndrome (JS) have renal involvement. Two forms of renal disease (RD) have traditionally been described. The less common form is the Dekaban–Arima syndrome, a JS RD that includes congenital blindness and occasional encephalocele. The other, more common RD is juvenile nephronophthisis (NPHP), that presents a progressive interstitial fibrosis, associated with small cysts at the corticomedullary junction. NPHP is the most frequent genetic cause for end-stage RD in the first three decades of life. Symptoms start at approximately 6 years of age with urine concentrating defects, polydipsia, polyuria, and secondary enuresis.

New insights intoCC2D2A-related Joubert syndrome

Purpose

In this study, we describe the phenotype and genotype of the largest cohort of patients with Joubert syndrome (JS) carrying pathogenic variants on one of the most frequent causative genes,CC2D2A.

Methods

We selected 53 patients with pathogenic variants onCC2D2A, compiled and analysed their clinical, neuroimaging and genetic information and compared it to previous literature.

Results

Developmental delay (motor and language) was nearly constant but patients had normal intellectual efficiency in 74% of cases (20/27 patients) and 68% followed mainstream schooling despite learning difficulties. Epilepsy was found in only 13% of cases. Only three patients had kidney cysts, only three had genuine retinal dystrophy and no subject had liver fibrosis or polydactyly. Brain MRIs showed typical signs of JS with rare additional features. Genotype–phenotype correlation findings demonstrate a homozygous truncating variant p.Arg950* linked to a more severe phenotype.

Conclusion

This study contradicts previous literature stating an association betweenCC2D2A-related JS and ventriculomegaly. Our study implies thatCC2D2A-related JS is linked to positive neurodevelopmental outcome and low rate of other organ defects except for homozygous pathogenic variant p.Arg950*. This information will help modulate patient follow-up and provide families with accurate genetic counselling.

Neonatal Joubert Syndrome With Renal Involvement and Respiratory Distress

Joubert syndrome (JS) is a rare autosomal recessive neurodevelopmental disorder with characteristic clinical presentation of hyperpnea-apnea spells, hypotonia, dysmorphic facies, and nystagmus and imaging features of molar tooth sign and cerebellar vermian hypoplasia-dysplasia. Early diagnosis is needed for timely management and favorable outcome. We present a case of neonatal JS with renal involvement presenting with respiratory distress and highlight the characteristic clinical and imaging findings. On examination, the baby had low set ears, a large protruding tongue, hypertelorism, and a depressed nasal bridge. Ultrasonography (USG) abdomen showed echogenic kidneys with cortical and medullary cysts. Magnetic Resonance Imaging (MRI) brain showed classical molar tooth sign, vermian hypoplasia-dysplasia, and thinning of the corpus callosum.

TUBB4B gene mutation in Leber phenotype of congenital amaurosis syndrome associated with early-onset deafness

Beta-tubulin 4B isotype is one of the subunits of microtubules encoded by TUBB4B gene on chromosome 9, which is responsible for the maintenance of microtubule stability. In humans, mutations in microtubule-encoding genes have been associated with several tubulinopathies with very heterogeneous symptoms. So far, only two missense mutations in TUBB4B gene have been found to have pathological implications in this disorder. Here we report a Hungarian family with three affected members, mother and her 12- and 14-year-old children, who suffer from ophthalmologic and hearing impairments probably due to c.1171C > T missense variant in the TUBB4B gene. The presented case is the second report, and unique in the literature because of three affected family members carrying the same mutation and the family provides evidence for a quite similar but not identical phenotype of LCAEOD in subjects carrying this mutation.

Turning the Curve Into Straight: Phenogenetics of the Spine Morphology and Coordinate Maintenance in the Zebrafish

The vertebral column, or spine, provides mechanical support and determines body axis posture and motion. The most common malformation altering spine morphology and function is adolescent idiopathic scoliosis (AIS), a three-dimensional spinal deformity that affects approximately 4% of the population worldwide. Due to AIS genetic heterogenicity and the lack of suitable animal models for its study, the etiology of this condition remains unclear, thus limiting treatment options. We here review current advances in zebrafish phenogenetics concerning AIS-like models and highlight the recently discovered biological processes leading to spine malformations. First, we focus on gene functions and phenotypes controlling critical aspects of postembryonic aspects that prime in spine architecture development and straightening. Second, we summarize how primary cilia assembly and biomechanical stimulus transduction, cerebrospinal fluid components and flow driven by motile cilia have been implicated in the pathogenesis of AIS-like phenotypes. Third, we highlight the inflammatory responses associated with scoliosis. We finally discuss recent innovations and methodologies for morphometrically characterize and analyze the zebrafish spine. Ongoing phenotyping projects are expected to identify novel and unprecedented postembryonic gene functions controlling spine morphology and mutant models of AIS. Importantly, imaging and gene editing technologies are allowing deep phenotyping studies in the zebrafish, opening new experimental paradigms in the morphometric and three-dimensional assessment of spinal malformations. In the future, fully elucidating the phenogenetic underpinnings of AIS etiology in zebrafish and humans will undoubtedly lead to innovative pharmacological treatments against spinal deformities.

Joubert syndrome: a case report

Background

Joubert syndrome (JS) is a rare autosomal recessive genetic heterogeneously inherited disorder characterized by neurological features that include hypotonia, ataxia, developmental delay, intellectual disability, abnormal eye movements, and neonatal breathing dysregulation.

Case presentation

The main purposes of the case report are to highlight the benefit of multidisciplinary rehabilitation team approach and describe the clinical features associated with Joubert syndrome. In this case report, we have discussed a 9-month-old girl who presented with developmental delay, impaired vision, and a history of recurrent respiratory infection with respiratory distress. On examination, she had facial dysmorphism, myopia, and hypotonia. Brain magnetic resonance imaging showed a thick, elongated, and abnormally oriented superior cerebellar peduncle showing molar tooth appearance with elongated bat-wing shaped 4th ventricle and hypoplasia of the vermis suggestive of JS. The patient has been treated at Garden Reach Institute for the Rehabilitation and Research (GRIRR), Kolkata, India, by a multidisciplinary team of physiotherapist, speech therapist, special educator, orthotist, medical officer, and social worker that shown excellent improvement in her condition, and she has achieved good sitting balance, able to sit without support, stand with wall support, and able to walk using bilateral AFO and reverse walker.

Conclusion

Knowledge of characteristic clinical and radiological findings in JS will help in early diagnosis and successful rehabilitation.

Fetal ciliopathies: a retrospective observational single-center study

Purpose

Report on the diagnosis of prenatally suspected multisystem ciliopathies in a single center between 2002 and 2020.

Methods

Retrospective observational single-center study including pregnancies with prenatal ultrasound features of multisystem ciliopathies, such as hyperechogenic kidneys together with polydactyly and/or other skeletal and extraskeletal findings. Cases were compared according to their prenatal findings and outcomes.

Results

36 cases of multisystem ciliopathies were diagnosed. Meckel-Gruber syndrome (MKS) was the most common ciliopathy (n = 19/36, 52.8%), followed by disorders that belong to the group of short-rib thoracic dysplasia (SRTD, n = 10/36, 27.8%) McKusick–Kaufmann syndrome (MKKS, n = 4/36, 11.1%), Bardet–Biedl syndrome (BBS, n = 2/36, 5.5%) and Joubert syndrome (n = 1/36, 2.8%). All cases showed abnormalities of the kidneys, most often hyperechogenic parenchyma (n = 26/36, 72.2%), cystic dysplasia (n = 24/36, 66.7%), and/or bilateral kidney enlargement (n = 22/36, 61.1%). Oligohydramnios was mainly present in fetuses with MKS. Polydactyly (n = 18/36), abnormalities of the CNS (n = 25/36), and heart defects (n = 10/36) were associated in 50%, 69.4%, and 27.8%, respectively.

Conclusion

Prenatal detection of renal abnormalities associated with skeletal or brain abnormalities should raise the suspicion for multisystem ciliopathies. Prenatal ultrasound can help to differentiate between different diseases and pave the way for subsequent targeted genetic testing.

AHI1 gene mutation in a consanguineous Iranian family affected by Joubert syndrome: A case report

This point of detected mutation could be considered as a novel mutational hotspot point that carried in patient ancestors. Moreover, the obtained results and family history suggest a precise genetic consulting and molecular prenatal evaluation for suspect individuals with a family history of mental and physical abnormalities.

Papillorenal syndrome: a systemic diagnosis not to be missed on funduscopy

A 45-year-old man presented to the ophthalmology department with visual symptoms in his left eye. Almost two decades ago, he required a renal transplant for focal segmental glomerular sclerosis and a detailed enquiry revealed a strong family history of renal and ocular disease. Fundus examination demonstrated significant optic disc dysplasia in his left eye and optical coherence tomography showed intraretinal fluid bilaterally. The diagnosis of papillorenal syndrome was suspected and genetic testing identified a heterozygous pathogenic variant in the PAX2 gene c.76dupG, p.Val26Glyfs*28, confirming the diagnosis. The patient was treated conservatively, and his vision eventually improved and stabilised. His renal disease and transplant were concurrently monitored by nephrologists. In this case, history-taking and ophthalmic examination raised suspicion of this rare systemic condition, which led to genetic testing and molecular confirmation of the diagnosis. We therefore highlight this case to raise awareness of papillorenal syndrome, which has significant systemic implications and also impacts familial screening and genetic counselling.

The Major Ciliary Isoforms of RPGR Build Different Interaction Complexes with INPP5E and RPGRIP1L

X-linked retinitis pigmentosa (XLRP) is frequently caused by mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene. A complex splicing process acts on the RPGR gene resulting in three major isoforms: RPGR^ex1-19, RPGR^ORF15 and RPGR^skip14/15. We characterized the widely expressed, alternatively spliced transcript RPGR^skip14/15 lacking exons 14 and 15. Using the CRISPR/eSpCas9 system, we generated HEK293T cell lines exclusively expressing the RPGR^skip14/15 transcript from the endogenous RPGR gene. RPGR^ex1-19 and RPGR^ORF15 were knocked out. Immunocytochemistry demonstrated that the RPGR^skip14/15 protein localizes along primary cilia, resembling the expression pattern of RPGR^ex1-19. The number of cilia-carrying cells was not affected by the absence of the RPGR^ex1-19 and RPGR^ORF15 isoforms. Co-immunoprecipitation assays demonstrated that both RPGR^ex1-19 and RPGR^skip14/15 interact with PDE6D, further supporting that RPGR^skip14/15 is associated with the protein networks along the primary cilium. Interestingly, interaction complexes with INPP5E or RPGRIP1L were only detectable with isoform RPGR^ex1-19, but not with RPGR^skip14/15, demonstrating distinct functional properties of the major RPGR isoforms in spite of their similar subcellular localization. Our findings lead to the conclusion that protein binding sites within RPGR are mediated through alternative splicing. A tissue-specific expression ratio between RPGR^skip14/15 and RPGR^ex1-19 seems required to regulate the ciliary concentration of RPGR interaction partners.

The Emerging Roles of Axonemal Glutamylation in Regulation of Cilia Architecture and Functions

Cilia, which either generate coordinated motion or sense environmental cues and transmit corresponding signals to the cell body, are highly conserved hair-like structures that protrude from the cell surface among diverse species. Disruption of ciliary functions leads to numerous human disorders, collectively referred to as ciliopathies. Cilia are mechanically supported by axonemes, which are composed of microtubule doublets. It has been recognized for several decades that tubulins in axonemes undergo glutamylation, a post-translational polymodification, that conjugates glutamic acid chains onto the C-terminal tail of tubulins. However, the physiological roles of axonemal glutamylation were not uncovered until recently. This review will focus on how cells modulate glutamylation on ciliary axonemes and how axonemal glutamylation regulates cilia architecture and functions, as well as its physiological importance in human health. We will also discuss the conventional and emerging new strategies used to manipulate glutamylation in cilia.

An Atypical Presentation of Joubert Syndrome Due to a Novel Mutation in ZNF423 Gene

Joubert syndrome is a rare brain malformation characterized by the absence or underdevelopment of the cerebellar vermis. Infants with Joubert syndrome usually present with hypotonia, developmental delay, oculomotor apraxia, and respiratory abnormalities. Seizures in Joubert syndrome are not uncommon. Infantile spasms as presentation are hitherto unreported. Here we present a rare case of an 8-month-old infant diagnosed as Joubert syndrome with ZNF423 mutation who presented with West syndrome. Early diagnosis and appropriate management of the child effectively reduced the spasms.

Any modality of renal replacement therapy can be a treatment option for Joubert syndrome

Joubert syndrome (JS) is an inherited ciliopathy characterized by a distinctive cerebellar and brain stem malformation which is known as the "molar tooth sign" on axial brain images, hypotonia, and developmental delay. Approximately 25-30% of patients with JS have kidney disease and many of them progress to end-stage kidney disease (ESKD). However, there are few reports on the outcomes of renal replacement therapy (RRT) in patients with JS and ESKD. In this study, we clarified the clinical features, treatment, and outcomes of patients with JS who underwent RRT. We retrospectively analyzed the medical records and clinical characteristics of 11 patients with JS who underwent RRT between June 1994 and July 2019. Data are shown as the median (range). Gene analysis was performed in 8 of the 11 cases, and CEP290 mutations were found in four patients, two had TMEM67 mutations, one had a RPGRIP1L mutation, and one patient showed no mutation with the panel exome analysis. Complications in other organs included hydrocephalus in two cases, retinal degeneration in eight cases, coloboma in one case, liver diseases in four cases, and polydactyly in one case. Peritoneal dialysis (PD) was introduced in seven cases, with a median treatment duration of 5.4 (3.4-10.7) years. Hemodialysis was performed using arteriovenous fistula in two cases, and kidney transplantation was performed 9 times in eight cases. Only one of the grafts failed during the observation period of 25.6 (8.2-134.2) months. The glomerular filtration rate at the final observation was 78.1 (41.4-107.7) mL/min/1.73 m². The median age at the final observation was 13.4 (5.6-25.1) years, and all patients were alive except one who died of hepatic failure while on PD. Any type of RRT modality can be a treatment option for patients with JS and ESKD.

Three Cases of Joubert Syndrome in a Consanguineous Syrian Family and a Interesting Case of Multinational Collaboration

Joubert syndrome (JS) is a rare congenital, autosomal recessive disorder characterized by a distinctive brain malformation, developmental delay, ocular motor apraxia, breathing abnormalities, and high clinical and genetic heterogeneity. We are reporting three siblings with JS from consanguineous parents in Syria. Two of them had the same homozygous c.2172delA (p.Trp725Glyfs*) AHI1 mutation and the third was diagnosed prenatally with magnetic resonance imaging. This pathogenic variant is very rare and described in only a few cases in the literature. Multinational collaboration could be of benefit for the patients from undeveloped, low-income countries that have a low-quality health care system, especially for the diagnosis of rare diseases.

Prenatal genetic considerations in congenital ventriculomegaly and hydrocephalus

BACKGROUND

Fetal ventriculomegaly (VM) is a frequent finding in prenatal ultrasound. Rather than a proper diagnosis, VM is a sonographic sign, making prenatal counseling a complex and challenging undertaking. VM can range from severe pathologic processes leading to severe neurodevelopmental delay to normal variants.

DISCUSSION

A growing number of genetic conditions with different pathophysiological mechanisms, inheritance patterns, and long-term prognosis have been associated both to isolated and complex fetal VM. These include chromosomal abnormalities, copy number variants, and several single gene diseases. In this review, we describe some of the most common genetic conditions associated with fetal VM and provide a simplified diagnostic workflow for the clinician.

A variable presentation of Joubert syndrome: Case report and a brief review

Joubert syndrome is a rare neurological manifestation usually present in late infancy or early childhood with characteristic episodes of abnormal breathing pattern along with the neurological and other systemic involvement.We report a case of confirmed Joubert syndrome present in the immediate neonatal period with isolated spells of oxygen desaturations not accompanied by the classically described breathing pattern and absent neurological symptoms causing delay in the diagnosis. Isolated oxygen desaturation episodes could be a presenting manifestation of Joubert syndrome in a neonatal period.

Clinical and Molecular Diagnosis of Joubert Syndrome and Related Disorders

BACKGROUND

Joubert syndrome and related disorders are a group of ciliopathies characterized by mid-hindbrain malformation, developmental delay, hypotonia, oculomotor apraxia, and breathing abnormalities. Molar tooth sign in brain imaging is the hallmark for diagnosis. Joubert syndrome is a clinically and genetically heterogeneous disorder involving mutations in 35 ciliopathy-related genes. We present a large cohort of 59 patients with Joubert syndrome from 55 families. Molecular analysis was performed in 35 families (trio).

METHODS

Clinical exome analysis was performed to identify causal mutations, and genotype-phenotype correlations were evaluated.

RESULTS

All of the cases were stratified into pure Joubert syndrome (62.7%), Joubert syndrome with retinal disease (22.0%), polydactyly (8.5%), and liver (1.7%) and kidney (1.7%) involvement. Joubert syndrome-related disorders include Meckel-Gruber syndrome in 5.1% cases and Leber congenital amaurosis (1.7%). Of the 35 Joubert syndrome-related genes, 11 were identified in these patients, i.e., CEP290, C5ORF, TCTN1, CC2D2A, RPGRP1L, TCTN3, AHI1, INPP5E, TCTN2, NPHP1, and TMEM237. For the first time, we identified a ciliopathy gene, CCDC28B, as a causal gene in Joubert syndrome in one family. CEP290 accounted for 37.8% cases of pure Joubert syndrome, Joubert syndrome with retinal and renal disease, and Meckel-Gruber syndrome. The p.G1890∗ allele in CEP290 is highly recurrent. Of the six families with Joubert syndrome who had a prenatal diagnosis, one fetus was normal, two were carriers, and three were affected.

CONCLUSIONS

This is the largest study of Joubert syndrome from India. Although a high degree of locus and allelic heterogeneity was observed, CEP290 variants were the most common among these patients.

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.

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.

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.

IFT80 mutations cause a novel complex ciliopathy phenotype with retinal degeneration

Ciliopathies, a growing pleotropic class of diseases due to mutations in genes that play an important role in primary cilia function. These highly conserved organelles are key to cell signaling. We now know, that mutations in one gene may lead to more than one ciliopathy phenotype and that one ciliopathy phenotype may be due to mutations in more than one gene. We studied the case of a female child with a novel ciliopathy phenotype and identified two novel mutations in the gene IFT80. Previously, mutations in IFT80 have been associated with a very narrow rib cage and failure of the lungs. Bone anomalies are also part of this IFT80-condition but with no vision problems documented. Our case had none of the features known to be associated with IFT80 mutations and had retinal degeneration (RD). This work broadens the IFT80-phenotype spectrum and also shows RD can be a feature of many ciliopathies.

Cerebellar cognitive affective syndrome: insights from Joubert syndrome

BACKGROUND

Joubert syndrome (JS) is a rare, autosomal recessively inherited genetic disorder characterized morphologically by unique developmental malformations of the cerebellum and brainstem (the molar tooth sign), and clinically by impaired motor functions and intellectual disability. Patients with JS often face multiple cognitive challenges, but the neuropsychological profile of this condition has not been well characterized.

METHODS

We performed comprehensive neurological and neuropsychological evaluations in three adult brothers with JS, ages 32, 27, and 25 years.

RESULTS

They all exhibited impaired motor control, global developmental delay most evident in executive function, affect regulation, and social skill set, and similar patterns of neuropsychiatric symptoms.

CONCLUSIONS

These findings provide new insights into the intellectual and neurobehavioral phenotype of JS, which we regard as a developmental form of the cerebellar cognitive affective / Schmahmann syndrome (CCAS). These observations have direct clinical relevance for the diagnosis and care of patients with JS, and they help further the understanding of the multiple manifestations of atypical cerebrocerebellar development.

Prospective Evaluation of Kidney Disease in Joubert Syndrome

BACKGROUND AND OBJECTIVES

Joubert syndrome is a genetically heterogeneous ciliopathy associated with >30 genes. The characteristics of kidney disease and genotype-phenotype correlations have not been evaluated in a large cohort at a single center.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We evaluated 97 individuals with Joubert syndrome at the National Institutes of Health Clinical Center using abdominal ultrasonography, blood and urine chemistries, and DNA sequencing.

RESULTS

Patients were ages 0.6-36 years old (mean of 9.0±7.6 years old); 41 were female. Mutations were identified in 19 genes in 92 patients; two thirds of the mutations resided in six genes: TMEM67, C5orf42, CC2D2A, CEP290, AHI1, and KIAA0586. Kidney disease was detected in 30%, most commonly in association with the following genes: CEP290 (six of six), TMEM67 (11 of 22), and AHI1 (three of six). No kidney disease was identified in patients with mutations in C5orf42 (zero of 15) or KIAA0586 (zero of six). Prenatal ultrasonography of kidneys was normal in 72% of patients with kidney disease. Specific types of kidney disease included nephronophthisis (31%), an overlap phenotype of autosomal recessive polycystic kidney disease/nephronophthisis (35%), unilateral multicystic dysplastic kidney (10%), and indeterminate-type cystic kidney disease (24%). Early-onset hypertension occurred in 24% of patients with kidney disease. Age at ESRD (n=13) ranged from 6 to 24 years old (mean of 11.3±4.8 years old).

CONCLUSIONS

Kidney disease occurs in up to one third of patients with Joubert syndrome, most commonly in those with mutations in CEP290, TMEM67, and AHI1. Patients with mutations in C5orf42 or KIAA0586 are less likely to develop kidney disease. Prenatal ultrasonography is a poor predictor of kidney involvement in Joubert syndrome. Unilateral multicystic dysplastic kidney and autosomal recessive polycystic kidney disease-like enlarged kidneys with early-onset hypertension can be part of the Joubert syndrome kidney phenotype.

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.

Keeping an Eye on Bardet-Biedl Syndrome: A Comprehensive Review of the Role of Bardet-Biedl Syndrome Genes in the Eye

Upwards of 90% of individuals with Bardet-Biedl syndrome (BBS) display rod-cone dystrophy with early macular involvement. BBS is an autosomal recessive, genetically heterogeneous, pleiotropic ciliopathy for which 21 causative genes have been discovered to date. In addition to retinal degeneration, the cardinal features of BBS include obesity, cognitive impairment, renal anomalies, polydactyly, and hypogonadism. Here, we review the genes, proteins, and protein complexes involved in BBS and the BBS model organisms available for the study of retinal degeneration. We include comprehensive lists for all known BBS genes, their known phenotypes, and the model organisms available. We also review the molecular mechanisms believed to lead to retinal degeneration. We provide an overview of the mode of inheritance and describe the relationships between BBS genes and Joubert syndrome, Leber Congenital Amaurosis, Senior-Løken syndrome, and non-syndromic retinitis pigmentosa. Finally, we propose ways that new advances in technology will allow us to better understand the role of different BBS genes in retinal formation and function.

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.

Mortality in Joubert syndrome

Joubert syndrome (JS) is a rare, recessively inherited neurodevelopmental disorder characterized by a distinctive mid-hindbrain malformation. Little is known about mortality in affected individuals. Identifying the timing and causes of death will allow for development of healthcare guidelines for families and providers and, thus, help to prolong and improve the lives of patients with JS. We evaluated information on 40 deceased individuals with JS to characterize age and cause of death. We compared this population with 525 living individuals with JS to estimate associations between risk of death and extra-neurological features. Genetic causes were examined in both groups. Mean age of death in this cohort was 7.2 years, and the most prevalent causes of death were respiratory failure (35%), particularly in individuals younger than 6 years, and kidney failure (37.5%), which was more common in older individuals. We identified possible associations between risk of death and kidney disease, liver fibrosis, polydactyly, occipital encephalocele, and genetic cause. This work highlights factors (genetic cause, extra-neurological organ involvement, and other malformations) likely to be associated with higher risk of mortality in JS, which should prompt increased monitoring for respiratory issues, kidney disease, and liver fibrosis.

Ciliopathies

Nephronophthisis-related ciliopathies (NPHP-RC) are a group of inherited diseases that affect genes encoding proteins that localize to primary cilia or centrosomes. With few exceptions, ciliopathies are inherited in an autosomal recessive manner, and affected individuals manifest early during childhood or adolescence. NPHP-RC are genetically very heterogeneous, and, currently, mutations in more than 90 genes have been described as single-gene causes. The phenotypes of NPHP-RC are very diverse, and include cystic-fibrotic kidney disease, brain developmental defects, retinal degeneration, skeletal deformities, facial dimorphism, and, in some cases, laterality defects, and congenital heart disease. Mutations in the same gene can give rise to diverse phenotypes depending on the mutated allele. At the same time, there is broad phenotypic overlap between different monogenic genes. The identification of monogenic causes of ciliopathies has furthered the understanding of molecular mechanism and cellular pathways involved in the pathogenesis.

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.

Molecular genetic findings and clinical correlations in 100 patients with Joubert syndrome and related disorders prospectively evaluated at a single center

PURPOSE

Joubert syndrome (JS) is a genetically and clinically heterogeneous ciliopathy characterized by distinct cerebellar and brainstem malformations resulting in the diagnostic "molar tooth sign" on brain imaging. To date, more than 30 JS genes have been identified, but these do not account for all patients.

METHODS

In our cohort of 100 patients with JS from 86 families, we prospectively performed extensive clinical evaluation and provided molecular diagnosis using a targeted 27-gene Molecular Inversion Probes panel followed by whole-exome sequencing (WES).

RESULTS

We identified the causative gene in 94% of the families; 126 (27 novel) unique potentially pathogenic variants were found in 20 genes, including KIAA0753 and CELSR2, which had not previously been associated with JS. Genotype-phenotype correlation revealed the absence of retinal degeneration in patients with TMEM67, C5orf52, or KIAA0586 variants. Chorioretinal coloboma was associated with a decreased risk for retinal degeneration and increased risk for liver disease. TMEM67 was frequently associated with kidney disease.

CONCLUSION

In JS, WES significantly increases the yield for molecular diagnosis, which is essential for reproductive counseling and the option of preimplantation and prenatal diagnosis as well as medical management and prognostic counseling for the age-dependent and progressive organ-specific manifestations, including retinal, liver, and kidney disease.Genet Med advance online publication 26 January 2017.

Congenital Cytomegalovirus Infection and Brain Anomalies

The spectrum of brain anomalies caused by cytomegalovirus (CMV) infection is discussed. Seven patients (four girls, three boys, ages ranging from 2 to 14 months) are included in this study. In the children and mothers serologic tests studied for CMV infection including IgG and IgM titres, and viral cultures for inclusion bodies, were positive. Cranial CT and MR imaging studies were performed. In all the patients, periventricular calcifications were evident on CT scans. CT and MR imaging revealed three patients with neuronal migrational disorders (pachygyria (n?2), and schizencephaly (n=1)). One patient had hydranencephaly. Of particular note, there were two patients with rhombencephalosynapsis, and one with Joubert's syndrome. CMV infection is known to cause some of the disorders of neuronal migration and organization in early gestation, and some encephaloclastic lesions (e.g. hydranencephaly) in late gestation. Its possible association with relatively rare cerebellar malformations (Joubert's syndrome, and rhombencephalosynapsis) as noted in this study, indicates further clinicoradiologic studies.

Revealing new candidate genes for reproductive traits in pigs: combining Bayesian GWAS and functional pathways

Background

Reproductive traits such as number of stillborn piglets (SB) and number of teats (NT) have been evaluated in many genome-wide association studies (GWAS). Most of these GWAS were performed under the assumption that these traits were normally distributed. However, both SB and NT are discrete (e.g. count) variables. Therefore, it is necessary to test for better fit of other appropriate statistical models based on discrete distributions. In addition, although many GWAS have been performed, the biological meaning of the identified candidate genes, as well as their functional relationships still need to be better understood. Here, we performed and tested a Bayesian treatment of a GWAS model assuming a Poisson distribution for SB and NT in a commercial pig line. To explore the biological role of the genes that underlie SB and NT and identify the most likely candidate genes, we used the most significant single nucleotide polymorphisms (SNPs), to collect related genes and generated gene-transcription factor (TF) networks.

Results

Comparisons of the Poisson and Gaussian distributions showed that the Poisson model was appropriate for SB, while the Gaussian was appropriate for NT. The fitted GWAS models indicated 18 and 65 significant SNPs with one and nine quantitative trait locus (QTL) regions within which 18 and 57 related genes were identified for SB and NT, respectively. Based on the related TF, we selected the most representative TF for each trait and constructed a gene-TF network of gene-gene interactions and identified new candidate genes.

Conclusions

Our comparative analyses showed that the Poisson model presented the best fit for SB. Thus, to increase the accuracy of GWAS, counting models should be considered for this kind of trait. We identified multiple candidate genes (e.g. PTP4A2, NPHP1, and CYP24A1 for SB and YLPM1, SYNDIG1L, TGFB3, and VRTN for NT) and TF (e.g. NF-κB and KLF4 for SB and SOX9 and ELF5 for NT), which were consistent with known newborn survival traits (e.g. congenital heart disease in fetuses and kidney diseases and diabetes in the mother) and mammary gland biology (e.g. mammary gland development and body length).

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-016-0189-x) contains supplementary material, which is available to authorized users.

Nystagmus in a newborn: a manifestation of Joubert syndrome in the neonatal period

Joubert syndrome is a rare disorder, usually autosomal recessive, with a prevalence of 1:80,000 to 1:100,000. This disease presents most commonly as breathing irregularities, although the two major clinical criteria are hypotonia and developmental delay, sometimes associated with ocular movement abnormalities. The severity of the presentation varies, ranging from mild cases with normal intelligence to severe developmental delays associated with early death. We report a case of a newborn who presented to the emergency department for absent ocular fixation and torsional nystagmus without other neurological abnormalities. Her cranial MR showed cerebellar vermis agenesis and a molar tooth sign. Her laboratory evaluation, and renal and abdominal ultrasound were normal. An electroretinogram showed mixed retinal dystrophy and an AHI1 homozygous missense c.1981T>C mutation was identified (parents are carriers). Throughout infancy, she has shown mild developmental delay and hypotonia, but no respiratory abnormalities. Owing to variable expressivity, a high level of suspicion is required.

MKS1 regulates ciliary INPP5E levels in Joubert syndrome

BACKGROUND

Joubert syndrome (JS) is a recessive ciliopathy characterised by a distinctive brain malformation 'the molar tooth sign'. Mutations in >27 genes cause JS, and mutations in 12 of these genes also cause Meckel-Gruber syndrome (MKS). The goals of this work are to describe the clinical features of MKS1-related JS and determine whether disease causing MKS1 mutations affect cellular phenotypes such as cilium number, length and protein content as potential mechanisms underlying JS.

METHODS

We measured cilium number, length and protein content (ARL13B and INPP5E) by immunofluorescence in fibroblasts from individuals with MKS1-related JS and in a three-dimensional (3D) spheroid rescue assay to test the effects of disease-related MKS1 mutations.

RESULTS

We report MKS1 mutations (eight of them previously unreported) in nine individuals with JS. A minority of the individuals with MKS1-related JS have MKS features. In contrast to the truncating mutations associated with MKS, all of the individuals with MKS1-related JS carry ≥ 1 non-truncating mutation. Fibroblasts from individuals with MKS1-related JS make normal or fewer cilia than control fibroblasts, their cilia are more variable in length than controls, and show decreased ciliary ARL13B and INPP5E. Additionally, MKS1 mutant alleles have similar effects in 3D spheroids.

CONCLUSIONS

MKS1 functions in the transition zone at the base of the cilium to regulate ciliary INPP5E content, through an ARL13B-dependent mechanism. Mutations in INPP5E also cause JS, so our findings in patient fibroblasts support the notion that loss of INPP5E function, due to either mutation or mislocalisation, is a key mechanism underlying JS, downstream of MKS1 and ARL13B.

A homozygous AHI1 gene mutation (p.Thr304AsnfsX6) in a consanguineous Moroccan family with Joubert syndrome: a case report

Introduction

Joubert syndrome is a rare congenital disorder characterized by brain malformation, developmental delay with hypotonia, ocular motor apraxia, and breathing abnormalities. Joubert syndrome is a genetically highly heterogeneous ciliopathy disorder with 23 identified causative genes. The diagnosis is based on brain imaging showing the “molar tooth sign” with cerebellar vermis agenesis. We describe a consanguineous Moroccan family with three affected siblings (18-year-old boy, 13-year-old girl, and 10-year-old boy) showing typical signs of Joubert syndrome, and attempt to identify the underlying genetic defect in this family.

Methods

We performed genome-wide homozygosity mapping using a high-resolution array followed by targeted Sanger sequencing to identify the causative gene.

Results

This approach found three homozygous regions, one including the AHI1 gene. Direct sequencing of the 26 coding exons of AHI1 revealed a homozygous mutation (p.Thr304AsnfsX6) located in exon 7 present in the three Joubert syndrome-affected Moroccan siblings. Of more interest, this truncating mutation was previously reported in patients with compound heterozygous Joubert syndrome originating from Spain (one patient) and from the Netherlands (two patients), suggesting a possible founder effect or mutational hotspot.

Conclusions

Combined homozygosity mapping and targeted sequencing allowed the rapid detection of the disease-causing mutation in the AHI1 gene in this family affected with a highly genetically heterogeneous disorder. Carriers of the same truncating mutation (p.Thr304AsnfsX6), originating from Spain and the Netherlands, presented variable clinical characteristics, thereby corroborating the extreme heterogeneity of Joubert syndrome.

Novel variant syndrome associated with congenital hepatic fibrosis

Congenital hepatic fibrosis is part of many different malformation syndromes, of which oculo-encephalo-hepato-renal syndrome is the most common. These syndromes largely overlap, and so accurate classification of individual patients may be difficult. We present herein three syndromic siblings who were products of a consanguineous marriage. We investigated in detail at least six organ systems in these patients, namely the liver, brain, eye, kidneys, skeleton, and gonads. The common features observed in these three cases were congenital hepatic fibrosis, retinitis pigmentosa, truncal obesity, rotatory nystagmus, mental retardation, advanced myopia, and high-arched palate. The clinical dysmorphology in these patients was distinct and lacked the major features of the known syndromes associated with congenital hepatic fibrosis. Although some features of these presented cases are similar to those found in Bardet-Biedl syndrome (BBS), the absence of some major criteria of BBS (polydactyly, renal abnormality, and hypogonadism) suggests that this may be a new syndrome. All three patients remain under follow-up in the departments of Gastroenterology, Ophthalmology, and Neurology at Hacettepe University.

Novel KIF7 Mutation in a Tunisian Boy with Acrocallosal Syndrome: Case Report and Review of the Literature

Acrocallosal syndrome (ACLS) is a rare autosomal recessive disorder characterized by agenesis of the corpus callosum, facial dysmorphism, postaxial polydactyly of the hands as well as preaxial polydactyly of the feet, and developmental delay. Mutations in the KIF7 gene, encoding a molecule within the Sonic hedgehog (SHH) pathway, have been identified as causative for ACLS but also for the fatal hydrolethalus syndrome and some cases of Joubert syndrome. We report here on a Tunisian boy who shows the clinical characteristics of ACLS and was found to have a novel homozygous KIF7 nonsense mutation. Further, we summarize the current knowledge about the clinical spectrum associated with KIF7 mutations as well as genetic and/or phenotypic overlap with ciliopathies and other mutations in the SHH pathway.

Joubert syndrome: genotyping a Northern European patient cohort

Joubert syndrome (JBS) is a rare neurodevelopmental disorder belonging to the group of ciliary diseases. JBS is genetically heterogeneous, with >20 causative genes identified to date. A molecular diagnosis of JBS is essential for prediction of disease progression and genetic counseling. We developed a targeted next-generation sequencing (NGS) approach for parallel sequencing of 22 known JBS genes plus 599 additional ciliary genes. This method was used to genotype a cohort of 51 well-phenotyped Northern European JBS cases (in some of the cases, Sanger sequencing of individual JBS genes had been performed previously). Altogether, 21 of the 51 cases (41%) harbored biallelic pathogenic mutations in known JBS genes, including 14 mutations not previously described. Mutations in C5orf42 (12%), TMEM67 (10%), and AHI1 (8%) were the most prevalent. C5orf42 mutations result in a purely neurological Joubert phenotype, in one case associated with postaxial polydactyly. Our study represents a population-based cohort of JBS patients not enriched for consanguinity, providing insight into the relative importance of the different JBS genes in a Northern European population. Mutations in C5orf42 are relatively frequent (possibly due to a Dutch founder mutation) and mutations in CEP290 are underrepresented compared with international cohorts. Furthermore, we report a case with heterozygous mutations in CC2D2A and B9D1, a gene associated with the more severe Meckel-Gruber syndrome that was recently published as a potential new JBS gene, and discuss the significance of this finding.

Mutation spectrum of Joubert syndrome and related disorders among Arabs

Joubert syndrome (JS) is a rare autosomal recessive (AR), neurological condition characterized by dysgenesis of the cerebellar vermis with the radiological hallmark of molar tooth sign, oculomotor apraxia, recurrent hyperventilation and intellectual disability. Most cases display a broad spectrum of additional features, including polydactyly, retinal dystrophy and renal abnormalities, which define different subtypes of JS-related disorders (JSRDs). To date, 23 genes have been shown to cause JSRDs, and although most of the identified genes encode proteins involved in cilia function or assembly, the molecular mechanisms associated with ciliary signaling remain enigmatic. Arab populations are ethnically diverse with high levels of consanguinity (20–60%) and a high prevalence of AR disorders. In addition, isolated communities with very-high levels of inbreeding and founder mutations are common. In this article, we review the 70 families reported thus far with JS and JSRDs that have been studied at the molecular level from all the Arabic countries and compile the mutations found. We show that JS and the related JSRDs are genetically heterogeneous in Arabs, with 53 mutations in 15 genes. Thirteen of these mutations are potentially founder mutations for the region.

Ocular findings in two siblings with Joubert syndrome

We describe two brothers with Joubert syndrome (JS). JS diagnosis was made on the basis of neurological findings and the presence of the characteristic “molar tooth sign”, which was subsequently confirmed by magnetic resonance imaging. Both brothers demonstrated ptosis, hypotropia, exotropia, and horizontal pendular nystagmus. The younger brother had mild chorioretinal discoloration at the peripapillary region in both eyes, and a small coloboma at the inferior region of his right optic disc. The elder brother had coloboma in his right eye and a colobomatous optic disc in his left eye. Optical coherence tomography showed that the foveal architecture was preserved in both patients. We discuss the ocular findings, including those from optical coherence tomography, in JS, which has recently been recognized as ciliopathy.

Joubert syndrome: Clinical and radiological characteristics of nine patients

BACKGROUND

Joubert Syndrome (JS) is a rare genetic developmental disorder, first identified in 1969. In patients with JS, certain regions of the brain (mainly cerebellar vermis and brainstem) are underdeveloped or malformed. This can lead to impaired attention, visual, spatial, motor, language and social functional skills. JS is characterized by a host of features, many of which do not occur in every patient.

AIM OF THE STUDY

To spotlight and increase awareness of clinical profile and neuroimaging findings of children with Joubert syndrome.

METHODS

This is a retrospective case series study of patients with JS who attended the Pediatric Neurology Clinic in Aladan and Alfarawanya Hospitals in Kuwait, from September 2007 to September 2012. Clinical and radiological data were obtained from the patient medical records.

RESULTS

Cerebellar vermis hypoplasia/aplasia and apnea were present in all patients, polydactly in 3 of 16, renal problems with cysts in 5 patients and 11 of 16 had abnormal electroretinograms (ERGs). Blood investigations of organic acids, amino acids and very-long-chain fatty acid, were normal in the all the nine patients.

CONCLUSION

JS is a rare genetic brain malformation with association of retinal dystrophy and renal abnormalities. The retinal dystrophy may be progressive. The prognosis of patients depends mainly on the degree of brain malformation.

Joubert syndrome: the molar tooth sign of the mid-brain

Joubert syndrome (JS) is a very rare, autosomal-recessive condition. It is characterized by agenesis of cerebellar vermis, abnormal eye movements with nystagmus, episodes of hyperpnea and apnea, delayed generalized motor development, retinal coloboma and dystrophy and, sometimes, multicystic kidney disease. The importance of recognizing JS is related to the outcome and its potential complications. Prenatal diagnosis by ultarsonography and antenatal magnetic resonance imaging (MRI) is also possible. We have diagnosed a case of JS in a male infant with history of delayed mental and motor milestone development, history of abnormal breathing pattern, abnormal limb movement, generalized hypotonia and abnormal head movements with nystagmus. MRI showed hypoplastic cerebellar vermis with hypoplasia of the superior cerebellar peduncle resembling the "Molar Tooth Sign" in the mid-brain.

[Joubert syndrome and related disorders]

The cerebellum plays a role not only in motor control but also in motor learning and cognition. Joubert syndrome is a rare heterogeneous inherited genetic disorder characterized by ataxia, hypotonia, developmental delay, and at least one of the following features: neonatal respiratory disturbances or abnormal eye movement. The estimated frequency of Joubert syndrome in the United States is around 1 : 100 000. The term Joubert syndrome and related disorders (JSRD) has been recently coined to describe all disorders presenting with molar tooth sign on brain neuroimaging. Joubert syndrome is believed to be a representative of a new group of disorders named ciliopathies. The identification of seven causal genes (NPHP1, AHI1, CEP290, RPGRIP1L, TMEM67/MKS3, ARL13B, CC2D2A) has led to substantial progress in the understanding of the genetic basis of Joubert syndrome. The authors focus on clinical presentation of JSRD, differential diagnosis and molecular background.