Bony Congenital Nasolacrimal Duct Obstruction: A Novel Phenotype of Aplasia of Lacrimal and Major Salivary Glands

PURPOSE

Aplasia of lacrimal and salivary glands (ALSG) is a syndromic disorder characterized by aplasia of lacrimal and salivary systems. Reported ophthalmic manifestations of ALSG include aplasia of lacrimal glands, punctal agenesis, lacrimal sac mucocele, and membranous congenital nasolacrimal duct obstruction (CNLDO). Bony CNLDO, a rare clinical entity, has not been associated with any syndromic disorder. This study investigated the relationship between genetic mutations and bony CNLDO in 3 Chinese families with ALSG.

DESIGN

Single-center observational case study.

PARTICIPANTS

Three Chinese families with bony CNLDO, including 7 affected and 9 healthy family members.

METHODS

Slit-lamp ophthalmic examination, comprehensive physical examination, orbital computed tomography (CT) imaging, cervicofacial magnetic resonance imaging, audiometry, and whole exome sequencing on periphery blood were performed. Variants were cross-referenced with 1000 control genomes and various population databases. Pathologic variants were identified using bioinformatic tools.

MAIN OUTCOME MEASURES

Clinical examination, diagnostic imaging, whole exome sequencing, and bioinformatic analysis findings.

RESULTS

Affected patients showed decreased tear production on the Schimer I test and reduced tear breakup time. Bony CNLDO was observed on CT, showing unilateral or bilateral bony termination at the middle or terminal segment of the nasolacrimal canal. Magnetic resonance imaging showed aplasia or absence of lacrimal, parotid, and submandibular glands. Physical examination revealed normal ears, digits, and facial morphology. Audiometry and dental assessment were conducted on the pediatric patients and yielded normal results. The clinical characteristics of patients aligned with a diagnosis of ALSG. Genomic analysis revealed 3 novel heterozygous missense mutations of the Fgf10 gene: c.316T→C, c.327C→G, and c.332T→G. The inheritance pattern was autosomal dominant with variable penetrance. These variants were not observed in 1000 control genomes and population databases. These variant positions also were shown to be highly conserved across various animal species. Mutated genes and proteins were predicted as deleterious with most computational models, with a few suggesting they may be benign.

CONCLUSIONS

Bony CNLDO was identified as a novel phenotype of ALSG implicated by missense mutations of highly conserved residues in the Fgf10 gene. These cases broadened our knowledge of Fgf10-related phenotypes and prompted clinicians to consider syndromic associations in patients with bony CNLDO.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Complex balanced intrachromosomal rearrangement involving PITX2 identified as a cause of Axenfeld-Rieger Syndrome

Axenfeld-Rieger Syndrome (ARS) type 1 is a rare autosomal dominant condition characterized by anterior chamber anomalies, umbilical defects, dental hypoplasia, and craniofacial anomalies, with Meckel's diverticulum in some individuals. Here, we describe a clinically ascertained female of childbearing age with ARS for whom clinical targeted sequencing and deletion/duplication analysis followed by clinical exome and genome sequencing resulted in no pathogenic variants or variants of unknown significance in PITX2 or FOXC1. Advanced bioinformatic analysis of the genome data identified a complex, balanced rearrangement disrupting PITX2. This case is the first reported intrachromosomal rearrangement leading to ARS, illustrating that for patients with compelling clinical phenotypes but negative genomic testing, additional bioinformatic analysis are essential to identify subtle genomic abnormalities in target genes.

Joubert syndrome-derived induced pluripotent stem cells show altered neuronal differentiation in vitro

Joubert syndrome (JS) is a recessively inherited congenital ataxia characterized by hypotonia, psychomotor delay, abnormal ocular movements, intellectual disability, and a peculiar cerebellar and brainstem malformation, the "molar tooth sign." Over 40 causative genes have been reported, all encoding for proteins implicated in the structure or functioning of the primary cilium, a subcellular organelle widely present in embryonic and adult tissues. In this paper, we developed an in vitro neuronal differentiation model using patient-derived induced pluripotent stem cells (iPSCs), to evaluate possible neurodevelopmental defects in JS. To this end, iPSCs from four JS patients harboring mutations in distinct JS genes (AHI1, CPLANE1, TMEM67, and CC2D2A) were differentiated alongside healthy control cells to obtain mid-hindbrain precursors and cerebellar granule cells. Differentiation was monitored over 31 days through the detection of lineage-specific marker expression by qRT-PCR, immunofluorescence, and transcriptomics analysis. All JS patient-derived iPSCs, regardless of the mutant gene, showed a similar impairment to differentiate into mid-hindbrain and cerebellar granule cells when compared to healthy controls. In addition, analysis of primary cilium count and morphology showed notable ciliary defects in all differentiating JS patient-derived iPSCs compared to controls. These results confirm that patient-derived iPSCs are an accessible and relevant in vitro model to analyze cellular phenotypes connected to the presence of JS gene mutations in a neuronal context.

Joubert syndrome presenting bilateral peroneal neuropathies: A case report

RATIONALE

Joubert syndrome (JS) is a rare genetic disorder that presents with various neurological symptoms, primarily involving central nervous system dysfunction. Considering the etiology of JS, peripheral nervous system abnormalities cannot be excluded; however, cases of JS accompanied by peripheral nervous system abnormalities have not yet been reported. Distinct radiological findings on brain magnetic resonance imaging were considered essential for the diagnosis of JS. However, recently, cases of JS with normal or nearly normal brain morphology have been reported. To date, there is no consensus on the most appropriate diagnostic method for JS when imaging-based diagnostic approach is challenging. This report describes the case of an adult patient who exhibited bilateral peroneal neuropathies and was finally diagnosed with JS through genetic testing.

PATIENT CONCERNS AND DIAGNOSIS

A 27-year-old man visited our outpatient clinic due to a gait disturbance that started at a very young age. The patient exhibited difficulty maintaining balance, especially when walking slowly. Oculomotor apraxia was observed on ophthalmic evaluation. During diagnostic workups, including brain imaging and direct DNA sequencing, no conclusive findings were detected. Only nerve conduction studies revealed profound bilateral peroneal neuropathies. We performed whole genome sequencing to obtain a proper diagnosis and identify the gene mutation responsible for JS.

LESSONS

This case represents the first instance of peripheral nerve dysfunction in JS. Further research is needed to explore the association between JS and peripheral nervous system abnormalities. Detailed genetic testing may serve as a valuable tool for diagnosing JS when no prominent abnormalities are detected in brain imaging studies.

Syndromic ciliopathy: a taiwanese single-center study

BACKGROUND

Syndromic ciliopathies are a group of congenital disorders characterized by broad clinical and genetic overlap, including obesity, visual problems, skeletal anomalies, mental retardation, and renal diseases. The hallmark of the pathophysiology among these disorders is defective ciliary functions or formation. Many different genes have been implicated in the pathogenesis of these diseases, but some patients still remain unclear about their genotypes.

METHODS

The aim of this study was to identify the genetic causes in patients with syndromic ciliopathy. Patients suspected of or meeting clinical diagnostic criteria for any type of syndromic ciliopathy were recruited at a single diagnostic medical center in Southern Taiwan. Whole exome sequencing (WES) was employed to identify their genotypes and elucidate the mutation spectrum in Taiwanese patients with syndromic ciliopathy. Clinical information was collected at the time of patient enrollment.

RESULTS

A total of 14 cases were molecularly diagnosed with syndromic ciliopathy. Among these cases, 10 had Bardet-Biedl syndrome (BBS), comprising eight BBS2 patients and two BBS7 patients. Additionally, two cases were diagnosed with Alström syndrome, one with Oral-facial-digital syndrome type 14, and another with Joubert syndrome type 10. A total of 4 novel variants were identified. A recurrent splice site mutation, BBS2: c.534 + 1G > T, was present in all eight BBS2 patients, suggesting a founder effect. One BBS2 patient with homozygous c.534 + 1G > T mutations carried a third ciliopathic allele, TTC21B: c.264_267dupTAGA, a nonsense mutation resulting in a premature stop codon and protein truncation.

CONCLUSIONS

Whole exome sequencing (WES) assists in identifying molecular pathogenic variants in ciliopathic patients, as well as the genetic hotspot mutations in specific populations. It should be considered as the first-line genetic testing for heterogeneous disorders characterized by the involvement of multiple genes and diverse clinical manifestations.

In Vivo Assessment of Retinal Phenotypes in Axenfeld-Rieger Syndrome

Purpose

Axenfeld-Rieger syndrome (ARS) is characterized by ocular anomalies including posterior embryotoxon, iridocorneal adhesions, corectopia/iris hypoplasia, and developmental glaucoma. Although anterior segment defects and glaucoma contribute to decreased visual acuity, the role of potential posterior segment abnormalities has not been explored. We used high-resolution retinal imaging to test the hypothesis that individuals with ARS have posterior segment pathology.

Methods

Three individuals with FOXC1-ARS and 10 with PITX2-ARS completed slit-lamp and fundus photography, optical coherence tomography (OCT), OCT angiography, and adaptive optics scanning light ophthalmoscopy (AOSLO). Quantitative metrics were compared to previously published values for individuals with normal vision.

Results

All individuals demonstrated typical anterior segment phenotypes. Average ganglion cell and inner plexiform layer thickness was lower in PITX2-ARS, consistent with the glaucoma history in this group. A novel phenotype of foveal hypoplasia was noted in 40% of individuals with PITX2-ARS (but none with FOXC1-ARS). Moreover, the depth and volume of the foveal pit were significantly lower in PITX2-ARS compared to normal controls, even excluding individuals with foveal hypoplasia. Analysis of known foveal hypoplasia genes failed to identify an alternative explanation. Foveal cone density was decreased in one individual with foveal hypoplasia and normal in six without foveal hypoplasia. Two individuals (one from each group) demonstrated non-foveal retinal irregularities with regions of photoreceptor anomalies on OCT and AOSLO.

Conclusions

These findings implicate PITX2 in the development of the posterior segment, particularly the fovea, in humans. The identified posterior segment phenotypes may contribute to visual acuity deficits in individuals with PITX2-ARS.

Novel compound heterozygous variants in ARL13B lead to Joubert syndrome

Joubert syndrome (JBTS) is a systematic developmental disorder mainly characterized by a pathognomonic mid-hindbrain malformation. All known JBTS-associated genes encode proteins involved in the function of antenna-like cellular organelle, primary cilium, which plays essential roles in cellular signal transduction and development. Here, we identified four unreported variants in ARL13B in two patients with the classical features of JBTS. ARL13B is a member of the Ras GTPase family and functions in ciliogenesis and cilia-related signaling. The two missense variants in ARL13B harbored the substitutions of amino acids at evolutionarily conserved positions. Using model cell lines, we found that the accumulations of the missense variants in cilia were impaired and the variants showed attenuated functions in ciliogenesis or the trafficking of INPP5E. Overall, these findings expanded the ARL13B pathogenetic variant spectrum of JBTS.

Rare Association of Ankyloblepharon Filiforme Adnatum (AFA) with Cleft Palate - Case Report

The aim of this article is to discuss about rare representation of ankyloblepharon (an established chromosomal anomaly with aberration of p53 inherited as an autosomal dominant trait) with cleft of palate without any other feature of ectodermal dysplasia. The need to surgically address ankyloblepharon in order to avoid complications is also discussed.

[Embryonic development and congenital diseases of the orbit]

Many neuroradiologists focus primarily on the central nervous system and give little attention to other regions like the eye/orbit. It is easy to be deceived by the pitfall called satisfaction of search (also abbreviated SOS), despite most congenital eye diseases being easily recognized if one is aware of them. In this article, the most common congenital orbital abnormalities are described, and their basic prenatal causes are summarized.

Magnetic Resonance Imaging Findings and Genetic Testing Results in Children With Congenital Corneal Opacities

PURPOSE

This study investigates brain and globe abnormalities identified on magnetic resonance imaging (MRI) in children with congenital corneal opacities (CCO).

DESIGN

Retrospective cohort study.

METHODS

Clinical notes, radiology records, and genetic testing results were reviewed for patients diagnosed with corneal opacification within the first 6 months of life at a tertiary referral academic center between August 2008 and January 2018. Ocular findings, systemic anomalies, neuroimaging, and genetic testing results were summarized.

RESULTS

A total of 135 patients presenting at age 1 day to 12 years (mean age, 1 year) were identified. Children with bilateral CCO were more likely to have systemic disease (P = 0.018). Of the entire cohort, 43 (31.8%) patients received MRI, of whom 27 (62.8%) had abnormal brain findings and 30 (69.7%) had abnormal orbital findings. The most common abnormal brain findings were ventriculomegaly (n = 16, 59.2%) and corpus callosum abnormalities (n = 10, 37.0%) followed by brainstem/pons anomalies (n = 5, 18.5%), and cerebellar anomalies (n = 2, 7.4%). Abnormal brain MRI findings were associated with the presence of neurologic (P = .003) and craniofacial (P = .034) disease. A total of 44 (32.1%) patients underwent genetic testing, of whom 29 (65.9%) had pathogenic results.

CONCLUSIONS

More than 60% of the children with CCO who underwent MRI had abnormal brain and orbit findings that were correlated with significant neurologic disease. Furthermore, almost two-thirds of patients with CCO who underwent genetic testing had pathogenic results. These data demonstrate the value of systemic workup in children with CCO, and highlight the role of ophthalmologists in facilitating the diagnosis of systemic comorbidities associated with CCO.

High Incidence of CPLANE1-Related Joubert Syndrome in the Products of Conceptions from Early Pregnancy Losses

Background

The fetal monogenic causes of early pregnancy losses (EPLs) are mainly unknown, with only a few articles on the subject published. In our previous study of EPLs using whole-exome sequencing analysis, we confirmed a genetic diagnosis of CPLANE1-related Joubert syndrome (JS) in three EPLs from two couples and identified a relatively common CPLANE1 allele among our population (NM_001384732.1:c.1819delT;c.7817T>A, further after referred as “complex allele”). Pathogenic variants in the CPLANE1 (C5orf42) gene are reported to cause JS type 17, a primary ciliopathy with various system defects.

Aims

To examine the hypothesis that the CPLANE1 “complex allele,” whether homozygous or compound heterozygous, is a common cause of EPLs in our population.

Study Design

Cohort study/case-control study.ontrol study.

Methods

In this study, we used polymerase chain reaction-based methods to screen for CPLANE1 “complex allele” presence among 246 euploid EPLs (< 12 gestational weeks) from families in North Macedonia. We also investigated the impact of this allele in 650 women with EPLs versus 646 women with no history of pregnancy loss and at least one livebirth, matched by ethnic origin.

Results

We found a high incidence of JS in the total study group of EPLs (2.03%), with a considerably higher incidence among Albanian families (6.25%). Although not statistically significant, women with EPLs had a higher allele frequency of the CPLANE1 “complex allele” (AF = 1.38%) than the controls (AF = 0.85%; p = 0.2). Albanian women had significantly higher frequency of the “complex allele” than the Macedonians (AF = 1.65% and 0.39%, respectively; p = 0.003).

Conclusion

To the best of our knowledge, this is the highest reported incidence of fetal monogenic disease that might cause EPLs. Targeted screening for the CPLANE1 “complex allele” would be warranted in Albanian ethnic couples because it would detect one JS in every 16 euploid EPLs. Our findings have a larger impact on the pathogenesis of pregnancy loss and contribute to a better understanding of the pathogenicity of the variants in the CPLANE1 gene.

Joubert syndrome causing mutation in C2 domain of CC2D2A affects structural integrity of cilia and cellular signaling molecules

Cilia are organelles extend from cells to sense external signals for tuning intracellular signaling for optimal cellular functioning. They have evolved sensory and motor roles in various cells for tissue organization and homeostasis in development and post-development. More than a thousand genes are required for cilia function. Mutations in them cause multisystem disorders termed ciliopathies. The null mutations in CC2D2A result in Meckel syndrome (MKS), which is embryonic lethal, whereas patients who have missense mutations in the C2 domain of CC2D2A display Joubert syndrome (JBTS). They survive with blindness and mental retardation. How C2 domain defects cause disease conditions is not understood. To answer this question, C2 domain of Cc2d2a (mice gene) was knocked down (KD) in IMCD-3 cells by shRNA. This resulted in defective cilia morphology observed by immunofluorescence analysis. To further probe the cellular signaling alteration in affected cells, gene expression profiling was done by RNAseq and compared with the controls. Bioinformatics analysis revealed that the differentially expressed genes (DEGs) have functions in cilia. Among the 61 cilia DEGs identified, 50 genes were downregulated and 11 genes were upregulated. These cilia genes are involved in cilium assembly, protein trafficking to the cilium, intraflagellar transport (IFT), cellular signaling like polarity patterning, and Hedgehog signaling pathway. This suggests that the C2 domain of CC2D2A plays a critical role in cilia assembly and molecular signaling hosted in cilia for cellular homeostasis. Taken together, the missense mutations in the C2 domain of CC2D2A seen in JBTS might have affected cilia-mediated signaling in neurons of the retina and brain.

Short-read whole genome sequencing identifies causative variants in most individuals with previously unexplained aniridia

BACKGROUND

Classic aniridia is a highly penetrant autosomal dominant disorder characterised by congenital absence of the iris, foveal hypoplasia, optic disc anomalies and progressive opacification of the cornea. >90% of cases of classic aniridia are caused by heterozygous, loss-of-function variants affecting the PAX6 locus.

METHODS

Short-read whole genome sequencing was performed on 51 (39 affected) individuals from 37 different families who had screened negative for mutations in the PAX6 coding region.

RESULTS

Likely causative mutations were identified in 22 out of 37 (59%) families. In 19 out of 22 families, the causative genomic changes have an interpretable deleterious impact on the PAX6 locus. Of these 19 families, 1 has a novel heterozygous PAX6 frameshift variant missed on previous screens, 4 have single nucleotide variants (SNVs) (one novel) affecting essential splice sites of PAX6 5' non-coding exons and 2 have deep intronic SNV (one novel) resulting in gain of a donor splice site. In 12 out of 19, the causative variants are large-scale structural variants; 5 have partial or whole gene deletions of PAX6, 3 have deletions encompassing critical PAX6 cis-regulatory elements, 2 have balanced inversions with disruptive breakpoints within the PAX6 locus and 2 have complex rearrangements disrupting PAX6. The remaining 3 of 22 families have deletions encompassing FOXC1 (a known cause of atypical aniridia). Seven of the causative variants occurred de novo and one cosegregated with familial aniridia. We were unable to establish inheritance status in the remaining probands. No plausibly causative SNVs were identified in PAX6 cis-regulatory elements.

CONCLUSION

Whole genome sequencing proves to be an effective diagnostic test in most individuals with previously unexplained aniridia.

Generation of iPSC line from a Joubert syndrome patient with compound heterozygous mutations in CPLANE1 gene

We generated iPSC line using skin fibroblasts obtained from a female patient affected by Joubert syndrome, caused by two compound heterozygous variants (c.143G > A; p.Gly48Glu and c.1784 T > G; p.Leu595Ter) in CPLANE1. We used Sendai-virus-based technique for reprogramming and then we applied karyotype analysis, to exclude possible acquired big rearrangements. We verified the presence of the same STR profile as fibroblasts, the stem cell state (by immunofluorescence and qPCR) and, finally, the pluripotency state (by in vitro trilineage differentiation).

Phenotypic variability in Joubert syndrome is partially explained by ciliary pathophysiology

INTRODUCTION

Joubert syndrome (JS) arises from defects of primary cilia resulting in potential malformations of the brain, kidneys, eyes, liver, and limbs. Several of the 35+ genes associated with JS have recognized genotype/phenotype correlations, but most genes have not had enough reported individuals to draw meaningful conclusions.

METHODS

A PubMed literature review identified 688 individuals with JS across 32 genes and 112 publications to bolster known genotype/phenotype relationships and identify new correlations. All included patients had the "molar tooth sign" and a confirmed genetic diagnosis. Individuals were categorized by age, ethnicity, sex and the presence of developmental disability/intellectual disability, hypotonia, abnormal eye movements, ataxia, visual impairment, renal impairment, polydactyly, and liver abnormalities.

RESULTS

Most genes demonstrated unique phenotypic profiles. Grouping proteins based on physiologic interactions established stronger phenotypic relationships that reflect known ciliary pathophysiology. Age-stratified data demonstrated that end-organ disease is progressive in JS. Most genes demonstrated a significant skew towards having variants with either residual protein function or no residual protein function.

CONCLUSION

This cohort demonstrates that clinically meaningful genotype/phenotype relationships exist within most JS-related genes and can be referenced to allow for more personalized clinical care.

Penetrating keratoplasty in brittle Cornea syndrome: Case series and review of the literature

It concerns three siblings (two 28 year old twin boys and a 25 year old woman) who presented a previous history of rupture of eyeball in one eye and very poor vision in the other. At the first ophthalmoscopic and instrumental evaluation, three patients presented with bluish sclera and keratoglobus in the intact eye. A genetic analysis with whole exome sequencing was then performed on the three siblings, identifying a biallelic variant of the PRDM5 gene that led to the diagnosis of Brittle Cornea Syndrome (BCS), a rare autosomal recessive disorder characterized by corneal thinning and blue sclera. To preserve the only intact eye from possible breakage, the three siblings were trained in using protective measures (polycarbonate goggles etc.) to carry out close monitoring of symptoms and were asked to continue with follow-up visits for ocular and systemic diseases associated with BCS. Given the poor best corrected visual acuity achievable with glasses and contact lenses, penetrating keratoplasty was performed, achieving good visual acuity maintained in the 2-year follow-up in two of the three patients. Knowledge of this pathology and its clinical manifestations is essential for early diagnosis and correct management of this rare but very debilitating pathology. To our knowledge, this is the first case series of BCS reported in an Albanian population.

Novel mutation in RPGRIP1L gene causing Joubert syndrome: A case report

INTRODUCTION

Joubert syndrome is a rare disease of genetic origin with autosomal recessive inheritance and extreme genetic heterogeneity with more than 40 causative genes. Joubert syndrome 7 is caused by mutations in the RPGRIP1L gene.

PATIENT CONCERNS

Our report describes a pediatric patient with clinical features compatible with JS type 7 such as hypotonia, developmental delay and aplasia of the cerebellar vermis.

DIAGNOSIS

The clinical features and the MRI of the head and neck which showed alterations at the level of the posterior fossa, with absence of the vermis and horizontal disposition of the cerebellar peduncles, were compatible with Joubert syndrome. Whole exome sequencing detected the variants RPGRIP1L (NM_015272.2) c.697A > T (p. Lys233Ter) and RPGRIP1L (NM_015272.2) c.3545 del (p.Pro1182LeufsTer25).

INTERVENTIONS

Resection was performed to correct the polydactyly. At age 2 years umbilical hernia, adenoid surgery and ventilatory tubes surgery were performed. Renal biopsy confirmed interstitial fibrosis and focally accentuated mild tubular atrophy with focal tubular hypertrophy, compatible with the clinical suspicion of Joubert syndrome. Congenital hip dislocation surgery was performed. The patient underwent surgery for correction of concomitant divergent strabismus and continued with glasses for astigmatism and hyperopia.

OUTCOMES

Sanger sequencing confirmed the patient´s results and the father was found to be a carrier of RPGRIP1L (NM_015272.2) c.697A > T (p. Lys233Ter) and the mother and maternal grandmother as carriers of RPGRIP1L (NM_015272.2) c.3545del (p.Pro1182LeufsTer25). RPGRIP1L:c.3545del novel variant is a deletion which changes the reading frame, altering the RPGR1_C terminal domain and giving rise to an incomplete protein whose functions will be altered.

CONCLUSION

This is the first genetically confirmed case of JS in Colombia, the first carrier of biallelic RPGRIP1L gene mutations with hip dislocation and incomplete glottic closure and the first report of the novel c.3545del likely pathogenic variant causing JS.

A novel mutation of the RPGRIP1L gene in a Chinese boy with Joubert syndrome with oculorenal involvement

BACKGROUND

Joubert syndrome (JS) is a rare genetically heterogeneous primary ciliopathy characterized by a pathognomonic cerebellar and brainstem malformation, the "molar tooth sign", and variable organ involvement (such as eye, kidney, liver, and skeleton). Here, we present a case of JS in a Chinese boy.

CASE PRESENTATION

An 11-year-old Chinese boy presented with neonatal asphyxiation and hypoxia, strabismus, subsequent developmental delay, ataxia and end-stage kidney disease (ESKD). Routine blood tests showed severe anemia, increasing blood urea nitrogen and creatinine, elevated parathyroid hormone, hypocalcemia, hypokalemia and metabolic acidosis. Urine tests showed mild proteinuria. Ultrasound showed two small kidneys. Brain magnetic resonance imaging (MRI) showed dysplasia of the cerebellar vermis and extension of the upper cerebellar feet with the "molar tooth sign". Genetic analysis showed novel compound heterozygous mutations in the RPGRIP1L gene [p.L447fs*7(p.Leu447fsTer7) and p.G908V (p.Gly908Val)].

CONCLUSION

In the present study, we identified novel compound heterozygous mutations in the RPGRIP1L gene in a Chinese boy. The clinical and genetic findings of this study will expand the understanding of JS.

Alternative Genetic Diagnoses in Axenfeld-Rieger Syndrome Spectrum

Axenfeld-Rieger anomaly (ARA) is a specific ocular disorder that is frequently associated with other systemic abnormalities. PITX2 and FOXC1 variants explain the majority of individuals with Axenfeld-Rieger syndrome (ARS) but leave ~30% unsolved. Here, we present pathogenic/likely pathogenic variants in nine families with ARA/ARS or similar phenotypes affecting five different genes/regions. USP9X and JAG1 explained three families each. USP9X was recently linked with syndromic cognitive impairment that includes hearing loss, dental defects, ventriculomegaly, Dandy-Walker malformation, skeletal anomalies (hip dysplasia), and other features showing a significant overlap with FOXC1-ARS. Anterior segment anomalies are not currently associated with USP9X, yet our cases demonstrate ARA, congenital glaucoma, corneal neovascularization, and cataracts. The identification of JAG1 variants, linked with Alagille syndrome, in three separate families with a clinical diagnosis of ARA/ARS highlights the overlapping features and high variability of these two phenotypes. Finally, intragenic variants in CDK13, BCOR, and an X chromosome deletion encompassing HCCS and AMELX (linked with ocular and dental anomalies, correspondingly) were identified in three additional cases with ARS. Accurate diagnosis has important implications for clinical management. We suggest that broad testing such as exome sequencing be applied as a second-tier test for individuals with ARS with normal results for PITX2/FOXC1 sequencing and copy number analysis, with attention to the described genes/regions.

A case of Joubert syndrome caused by novel compound heterozygous variants in the TMEM67 gene

Joubert syndrome (JS) is a recessive disorder that is characterized by midbrain-hindbrain malformation and shows the "molar tooth sign" on magnetic resonance imaging. Mutations in 40 genes, including Abelson helper integration site 1 (AHI1), inositol polyphosphate-5-phosphatase (INPP5E), coiled-coil and c2 domain-containing protein 2A (CC2D2A), and ARL2-like protein 1 (ARL13B), can cause JS. Classic JS is a part of a group of diseases associated with JS, and its manifestations include various neurological signs such as skeletal abnormalities, ocular coloboma, renal disease, and hepatic fibrosis. Here, we present a proband with the molar tooth sign, ataxia, and developmental and psychomotor delays in a Dagestan family from Russia. Molecular genetic testing revealed two novel heterozygous variants, c.2924G>A (p.Arg975His) in exon 28 and c.1241C>G (p.Pro414Arg) in exon 12 of the transmembrane protein 67 (TMEM67) gene. These TMEM67 gene variants significantly affected the development of JS type 6. This case highlights the importance of whole exome sequencing for a proper clinical diagnosis of children with complex motor and psycho-language delays. This case also expands the clinical phenotype and genotype of TMEM67-associated diseases.

Oculoauriculofrontonasal syndrome: Refining the phenotype through a new case series and literature review

The oculoauriculofrontonasal syndrome (OAFNS) is a rare condition, with unknown etiology, characterized by the association of frontonasal dysplasia (FND) and oculoauriculovertebral spectrum (OAVS). Main clinical findings include widely spaced eyes, epibulbar dermoid, broad nose, mandibular hypoplasia, and preauricular tags. Here, we describe a case series of 32 Brazilian individuals with OAFNS and review the literature ascertaining individuals presenting phenotypes compatible with the diagnosis of OAFNS, aiming to refine the phenotype. This series emphasizes the phenotypic variability of the OAFNS and highlights the occurrence of rare craniofacial clefts as a part of the phenotype. The ectopic nasal bone, a hallmark of OAFNS, was frequent in our series, reinforcing the clinical diagnosis. The absence of recurrence, consanguinity, chromosomal, and genetic abnormalities reinforces the hypothesis of a nontraditional inheritance model. The phenotypic refinement provided by this series contributes to an investigation regarding the etiology of OAFNS.

Novel variants identified in five Chinese families with Joubert Syndrome: a case report

BACKGROUND

Joubert syndrome (JS) is a group of rare ciliopathies, mainly characterized by cerebellar dysplasia representing the "molar tooth sign (MTS)" on neuroimaging, hypotonia, and developmental delay. Having a complicated genotype-phenotype correlation due to its rich genetic heterogeneity, JS is usually combined with other organic defects affecting the retina, kidney, and liver. This report aimed to present new cases and novel variants of JS.

CASE PRESENTATION

Five unrelated patients who were diagnosed with JS, with or without typical clinical characteristics, received integrated examinations, including whole-exome sequencing (WES) and Sanger sequencing. We identified nine pathogenic variants in the TCTN2, CPLANE1, INPP5E, NPHP1, and CC2D2A genes.

CONCLUSION

Four novel pathogenic mutations in the TCTN2, CPLANE1, and INPP5E genes were reported. The findings broadened the genotypic spectrum of JS and contributed to a better understanding of genotype-phenotype correlation.

Recurrent, founder and hypomorphic variants contribute to the genetic landscape of Joubert syndrome

BACKGROUND

Joubert syndrome (JS) is a neurodevelopmental ciliopathy characterised by a distinctive mid-hindbrain malformation, the 'molar tooth sign'. Over 40 JS-associated genes are known, accounting for two-thirds of cases.

METHODS

While most variants are novel or extremely rare, we report on 11 recurring variants in seven genes, including three known 'founder variants' in the Ashkenazi Jewish, Hutterite and Finnish populations. We evaluated variant frequencies in ~550 European patients with JS and compared them with controls (>15 000 Italian plus gnomAD), and with an independent cohort of ~600 JS probands from the USA.

RESULTS

All variants were markedly enriched in the European JS cohort compared with controls. When comparing allele frequencies in the two JS cohorts, the Ashkenazim founder variant (TMEM216 c.218G>T) was significantly enriched in American compared with European patients with JS, while MKS1 c.1476T>G was about 10 times more frequent among European JS. Frequencies of other variants were comparable in the two cohorts. Genotyping of several markers identified four novel European founder haplotypes.Two recurrent variants (MKS1 c.1476T>G and KIAA0586 c.428delG), have been detected in homozygosity in unaffected individuals, suggesting they could act as hypomorphic variants. However, while fibroblasts from a MKS1 c.1476T>G healthy homozygote showed impaired ability to form primary cilia and mildly reduced ciliary length, ciliary parameters were normal in cells from a KIAA0586 c.428delG healthy homozygote.

CONCLUSION

This study contributes to understand the complex genetic landscape of JS, explain its variable prevalence in distinct geographical areas and characterise two recurrent hypomorphic variants.

The molecular genetics of anterior segment dysgenesis

Anterior segment dysgenesis is a severe developmental eye disorder that leads to blindness in children. The exact mechanisms underlying this condition remain elusive. Recently, an increasing amount of studies have focused on genes and signal transduction pathways that affect anterior segment dysgenesis;these factors include transcription factors, developmental regulators, extracellular matrix genes, membrane-related proteins, cytoskeleton proteins and other associated genes. To date, dozens of gene variants have been found to cause anterior segment dysgenesis. However, there is still a lack of effective treatments. With a broader and deeper understanding of the molecular mechanisms underlying anterior segment development in the future, gene editing technology and stem cell technology may be new treatments for anterior segment dysgenesis. Further studies on the mechanisms of how different genes influence the onset and progression of anterior segment dysgenesis are still needed.

TOPORS as a novel causal gene for Joubert syndrome

Joubert syndrome (JBTS) is a Mendelian disorder of the primary cilium defined by the clinical triad of hypotonia, developmental delay, and a distinct cerebellar malformation called the molar tooth sign. JBTS is inherited in an autosomal recessive, autosomal dominant, or X-linked recessive manner. Though over 40 genes have been identified as causal for JBTS, molecular diagnosis is not made in 30%-40% of individuals who meet clinical criteria. TOPORS encodes topoisomerase I-binding arginine/serine-rich protein, and homozygosity for a TOPORS missense variant (c.29C > A; p.(Pro10Gln)) was identified in individuals with the ciliopathy oral-facial-digital syndrome in two families of Dominican descent. Here, we report an additional proband of Dominican ancestry with JBTS found by exome sequencing to be homozygous for the identical p.(Pro10Gln) TOPORS missense variant. Query of the Mount Sinai BioMe biobank, which includes 1880 individuals of Dominican ancestry, supports a high carrier frequency of the TOPORS p.(Pro10Gln) variant in individuals of Dominican descent. Our data nominates TOPORS as a novel causal gene for JBTS and suggests that TOPORS variants should be considered in the differential of ciliopathy-spectrum disease in individuals of Dominican ancestry.

Traboulsi syndrome without features of Marfan syndrome caused by a novel homozygous ASPH variant associated with a heterozygous FBN1 variant

BACKGROUND

Traboulsi syndrome is a rare disease clinically characterized by facial dysmorphism, abnormal spontaneous filtering blebs, ectopia lentis (EL) and multiple anterior segment abnormalities.

MATERIAL AND METHODS

An 18-year-old female was referred to the Emergency Service of Hospital São Geraldo (HSG) claiming decreased right eye (RE) visual acuity associated with ocular pain that was noticed approximately 2 months earlier. She underwent a complete ophthalmic and physical examination including hands, ankle, wrist and chest X-ray, abdominal ultrasound, echocardiogram and genetic analysis (whole-exome sequencing).

RESULTS

The ophthalmic examination revealed a high myopia with spherical equivalent of - 9.50 D and best corrected visual acuity (BCVA) of 20/60 in RE and - 9.25 D with BCVA of 20/30 in the left eye (LE). Slit-lamp examination showed normal conjunctiva in both eyes (BE) and a superior-temporal cystic lesion in RE and nasal in LE; the flat anterior chamber in BE with the transparent crystalline lens touches the central corneal endothelium in the RE. Fundoscopy suggested glaucoma as the cup/disc ratio was 0.7, although the intraocular pressure (IOP) was 10 mmHg in BE without medication. Validation of data from whole exome demonstrated a novel splicing homozygous pathogenic variant (PV) (c.1765-1G>A) of the ASPH gene as well as a heterozygous variant of unknown significance (VUS) of the FBN1 gene (c.6832C>T).

CONCLUSION

We here report a novel splice-affecting homozygous pathogenic variant in the ASPH gene that was detected in a Brazilian patient with clinical features of Traboulsi syndrome.

SOX2 pathogenic variants with normal eyes: Expanding the phenotypic spectrum

SOX2 pathogenic variants, though rare, constitute the most commonly known genetic cause of clinical anophthalmia and microphthalmia. However, patients without major ocular malformation, but with multi-system developmental disorders, have been reported, suggesting that the range of clinical phenotypes is broader than previously appreciated. We detail two patients with bilateral structurally normal eyes along with 11 other previously published patients. Our findings suggest that there is no obvious phenotypic or genotypic pattern that may help set apart patients with normal eyes. Our patients provide further evidence for broadening the phenotypic spectrum of SOX2 mutations and re-appraising the designation of SOX2 disorder as an anophthalmia/microphthalmia syndrome. We emphasize the importance of considering SOX2 pathogenic variants in the differential diagnoses of individuals with normal eyes, who may have varying combinations of features such as developmental delay, urogenital abnormalities, gastro-intestinal anomalies, pituitary dysfunction, midline structural anomalies, and complex movement disorders, seizures or other neurological issues.

Biallelic intragenic tandem duplication of CPLANE1 in Joubert syndrome: A case report

Joubert syndrome (JS) is a clinically and genetically heterogeneous genetic disorder. To date, 40 JS-causing genes have been reported and CPLANE1 is one of the most frequently mutated, with biallelic pathogenic missense and truncating variants explaining up to 14% of JS cases. We present a case of JS diagnosed after the identification of a novel biallelic intragenic duplication of exons 20-46 of CPLANE1. The quadruplication was identified by short-read sequencing and copy number variant analysis and confirmed in tandem by long PCR with the breakpoints defined by a nanopore-based long-read sequencing approach. Based on the genetic findings and the clinical presentation of the patient, a brain MRI was ordered, evidencing the molar tooth sign, which confirmed the diagnosis of JS in the patient. This is, to the best of our knowledge, the first report of an intragenic duplication in this gene as the potential molecular mechanism of JS.

Axenfeld-Rieger syndrome: more than meets the eye

BACKGROUND

Axenfeld-Rieger syndrome (ARS) is characterised by typical anterior segment anomalies, with or without systemic features. The discovery of causative genes identified ARS subtypes with distinct phenotypes, but our understanding is incomplete, complicated by the rarity of the condition.

METHODS

Genetic and phenotypic characterisation of the largest reported ARS cohort through comprehensive genetic and clinical data analyses.

RESULTS

128 individuals with causative variants in PITX2 or FOXC1, including 81 new cases, were investigated. Ocular anomalies showed significant overlap but with broader variability and earlier onset of glaucoma for FOXC1-related ARS. Systemic anomalies were seen in all individuals with PITX2-related ARS and the majority of those with FOXC1-related ARS. PITX2-related ARS demonstrated typical umbilical anomalies and dental microdontia/hypodontia/oligodontia, along with a novel high rate of Meckel diverticulum. FOXC1-related ARS exhibited characteristic hearing loss and congenital heart defects as well as previously unrecognised phenotypes of dental enamel hypoplasia and/or crowding, a range of skeletal and joint anomalies, hypotonia/early delay and feeding disorders with structural oesophageal anomalies in some. Brain imaging revealed highly penetrant white matter hyperintensities, colpocephaly/ventriculomegaly and frequent arachnoid cysts. The expanded phenotype of FOXC1-related ARS identified here was found to fully overlap features of De Hauwere syndrome. The results were used to generate gene-specific management plans for the two types of ARS.

CONCLUSION

Since clinical features of ARS vary significantly based on the affected gene, it is critical that families are provided with a gene-specific diagnosis, PITX2-related ARS or FOXC1-related ARS. De Hauwere syndrome is proposed to be a FOXC1opathy.

Exome Analysis Reveals Novel Missense and Deletion Variants in the CC2D2A Gene as Causative of Joubert Syndrome

The CC2D2A gene is essential for primary cilia formation, and its disruption has been associated with Joubert Syndrome-9 (JBTS9), a ciliopathy with typical neurodevelopmental features. Here, we describe an Italian pediatric patient with typical features of Joubert Syndrome (JBTS): “Molar Tooth Sign”, global developmental delay, nystagmus, mild hypotonia, and oculomotor apraxia. Whole exome sequencing and segregation analysis identified in our infant patient a novel heterozygous germline missense variant c.3626C > T; p.(Pro1209Leu) inherited from the father and a novel 7.16 kb deletion inherited from the mother. To the best of our knowledge, this is the first report showing a novel missense and deletion variant involving exon 30 of the CC2D2A gene.

ARHGAP35 is a novel factor disrupted in human developmental eye phenotypes

ARHGAP35 has known roles in cell migration, invasion and division, neuronal morphogenesis, and gene/mRNA regulation; prior studies indicate a role in cancer in humans and in the developing eyes, neural tissue, and renal structures in mice. We identified damaging variants in ARHGAP35 in five individuals from four families affected with anophthalmia, microphthalmia, coloboma and/or anterior segment dysgenesis disorders, together with variable non-ocular phenotypes in some families including renal, neurological, or cardiac anomalies. Three variants affected the extreme C-terminus of the protein, with two resulting in a frameshift and C-terminal extension and the other a missense change in the Rho-GAP domain; the fourth (nonsense) variant affected the middle of the gene and is the only allele predicted to undergo nonsense-mediated decay. This study implicates ARHGAP35 in human developmental eye phenotypes. C-terminal clustering of the identified alleles indicates a possible common mechanism for ocular disease but requires further studies.

The murine ortholog of Kaufman oculocerebrofacial syndrome gene Ube3b is crucial for the maintenance of the excitatory synapses in the young adult stage

Kaufman oculocerebrofacial syndrome (KOS) is an autosomal recessive developmental disorder. Inactivating mutations in UBE3B, an E3 ubiquitin ligase gene are causative for KOS. We have reported that towards postnatal week three, its murine ortholog, Ube3b, acts as a negative regulator of the number of dendritic spines. In this study, we investigated the role of Ube3b at the synapse in the young adult mice. With an improved estimation method, images from the hippocampal CA1 and CA2 regions acquired with 3D Stimulated Emission Depletion (3D-STED) microscopy were used to quantify the excitatory synapse numbers. In the young adult mice, the excitatory synapse density was decreased in brain-specific Ube3b conditional knockout mice as compared to the control. Our results indicate the novel role of Ube3b in the maintenance of synapse numbers in the young adult period.

Genome-wide screening reveals the genetic basis of mammalian embryonic eye development

BACKGROUND

Microphthalmia, anophthalmia, and coloboma (MAC) spectrum disease encompasses a group of eye malformations which play a role in childhood visual impairment. Although the predominant cause of eye malformations is known to be heritable in nature, with 80% of cases displaying loss-of-function mutations in the ocular developmental genes OTX2 or SOX2, the genetic abnormalities underlying the remaining cases of MAC are incompletely understood. This study intended to identify the novel genes and pathways required for early eye development. Additionally, pathways involved in eye formation during embryogenesis are also incompletely understood. This study aims to identify the novel genes and pathways required for early eye development through systematic forward screening of the mammalian genome.

RESULTS

Query of the International Mouse Phenotyping Consortium (IMPC) database (data release 17.0, August 01, 2022) identified 74 unique knockout lines (genes) with genetically associated eye defects in mouse embryos. The vast majority of eye abnormalities were small or absent eyes, findings most relevant to MAC spectrum disease in humans. A literature search showed that 27 of the 74 lines had previously published knockout mouse models, of which only 15 had ocular defects identified in the original publications. These 12 previously published gene knockouts with no reported ocular abnormalities and the 47 unpublished knockouts with ocular abnormalities identified by the IMPC represent 59 genes not previously associated with early eye development in mice. Of these 59, we identified 19 genes with a reported human eye phenotype. Overall, mining of the IMPC data yielded 40 previously unimplicated genes linked to mammalian eye development. Bioinformatic analysis showed that several of the IMPC genes colocalized to several protein anabolic and pluripotency pathways in early eye development. Of note, our analysis suggests that the serine-glycine pathway producing glycine, a mitochondrial one-carbon donator to folate one-carbon metabolism (FOCM), is essential for eye formation.

CONCLUSIONS

Using genome-wide phenotype screening of single-gene knockout mouse lines, STRING analysis, and bioinformatic methods, this study identified genes heretofore unassociated with MAC phenotypes providing models to research novel molecular and cellular mechanisms involved in eye development. These findings have the potential to hasten the diagnosis and treatment of this congenital blinding disease.

Distinct Roles of Histone Lysine Demethylases and Methyltransferases in Developmental Eye Disease

Histone lysine methyltransferase and demethylase enzymes play a central role in chromatin organization and gene expression through the dynamic regulation of histone lysine methylation. Consistent with this, genes encoding for histone lysine methyltransferases (KMTs) and demethylases (KDMs) are involved in complex human syndromes, termed congenital regulopathies. In this report, we present several lines of evidence for the involvement of these genes in developmental ocular phenotypes, suggesting that individuals with structural eye defects, especially when accompanied by craniofacial, neurodevelopmental and growth abnormalities, should be examined for possible variants in these genes. We identified nine heterozygous damaging genetic variants in KMT2D (5) and four other histone lysine methyltransferases/demethylases (KMT2C, SETD1A/KMT2F, KDM6A and KDM5C) in unrelated families affected with developmental eye disease, such as Peters anomaly, sclerocornea, Axenfeld-Rieger spectrum, microphthalmia and coloboma. Two families were clinically diagnosed with Axenfeld-Rieger syndrome and two were diagnosed with Peters plus-like syndrome; others received no specific diagnosis prior to genetic testing. All nine alleles were novel and five of them occurred de novo; five variants resulted in premature truncation, three were missense changes and one was an in-frame deletion/insertion; and seven variants were categorized as pathogenic or likely pathogenic and two were variants of uncertain significance. This study expands the phenotypic spectra associated with KMT and KDM factors and highlights the importance of genetic testing for correct clinical diagnosis.

[Clinical features and genetic analysis of two Chinese pedigrees affected with Joubert syndrome]

OBJECTIVE

To explore the clinical characteristics and genetic basis of two Chinese pedigrees affected with Joubert syndrome.

METHODS

Clinical data of the two pedigrees was collected. Genomic DNA was extracted from peripheral blood samples and subjected to high-throughput sequencing. Candidate variants were verified by Sanger sequencing. Prenatal diagnosis was carried out for a high-risk fetus from pedigree 2.

RESULTS

The proband of pedigree 1 was a fetus at 23⁺⁵ weeks gestation, for which both ultrasound and MRI showed "cerebellar vermis malformation" and "molar tooth sign". No apparent abnormality was noted in the fetus after elected abortion. The fetus was found to harbor c.812+3G>T and c.1828G>C compound heterozygous variants of the INPP5E gene, which have been associated with Joubert syndrome type 1. The proband from pedigree 2 had growth retardation, mental deficiency, peculiar facial features, low muscle tone and postaxial polydactyly of right foot. MRI also revealed "cerebellar dysplasia" and "molar tooth sign". The proband was found to harbor c.485C>G and c.1878+1G>A compound heterozygous variants of the ARMC9 gene, which have been associated with Joubert syndrome type 30. Prenatal diagnosis found that the fetus only carried the c.485C>G variant. A healthy infant was born, and no anomalies was found during the follow-up.

CONCLUSION

The compound heterozygous variants of the INPP5E and ARMC9 genes probably underlay the disease in the two pedigrees. Above finding has expanded the spectrum of pathogenic variants underlying Joubert syndrome and provided a basis for genetic counseling and prenatal diagnosis.

Non-syndromic Retinal Degeneration Caused by Pathogenic Variants in Joubert Syndrome Genes

Inherited retinal degenerations (IRDs) are a group of genetic disorders characterized by progressive dysfunction and loss of photoreceptors. IRDs are classified as non-syndromic or syndromic, depending on whether retinal degeneration manifests alone or in combination with other associated symptoms. Joubert syndrome (JBTS) is a genetically and clinically heterogeneous disorder affecting the central nervous system and other organs and tissues, including the neuroretina. To date, 39 genes have been associated with JBTS, a majority of which encode structural or functional components of the primary cilium, a specialized sensory organelle present in most post-mitotic cells, including photoreceptors. The use of whole exome and IRD panel next-generation sequencing in routine diagnostics of non-syndromic IRD cases led to the discovery of pathogenic variants in JBTS genes that cause photoreceptor loss without other syndromic features. Here, we recapitulate these findings, describing the JBTS gene defects leading to non-syndromic IRDs.

Congenital corneal opacities as a new feature in an unusual case of White-Sutton syndrome

A 2-week-old girl presented with bilateral congenital corneal opacities. Additional systemic manifestations included microcephaly, patent foramen ovale, and poor feeding. Patient and parents underwent whole exome sequencing trio analysis that revealed a de novo pathogenic variant in POGZ (p.Val1150GlyfsX8), which is causative of the White-Sutton syndrome. This rare genetic condition is usually associated with intellectual and developmental delay, facial dysmorphism, strabismus, refractive error, and retinal changes. To our knowledge, this is the first reported case of White-Sutton syndrome presenting with congenital corneal opacities.

Comparison of Anterior Segment Abnormalities in Individuals With FOXC1 and PITX2 Variants

PURPOSE

Axenfeld-Rieger syndrome encompasses a group of developmental disorders affecting the anterior chamber structures of the eye, with associated systemic features in some cases. This study aims to compare the difference in anterior segment phenotypes such as those involving the cornea, iris, lens, and anterior chamber angle between cases with disease-causing sequence variations in FOXC1 and PITX2 .

METHODS

This cross-sectional study involved 61 individuals, from 32 families with pathogenic FOXC1 or PITX2 variants, who were registered with the Australian and New Zealand Registry of Advanced Glaucoma.

RESULTS

The median age of the cohort was 39 years at the time of last assessment (range 3-85 years; females, 54%). Thirty-two patients had pathogenic variants in the FOXC1 gene, and 29 patients had pathogenic variants in the PITX2 gene. Corneal abnormalities were more common in individuals with FOXC1 variants (18/36, 50%) than those with PITX2 variants (4/25, 16%; P = 0.007). Iris abnormalities such as hypoplasia ( P = 0.008) and pseudopolycoria ( P = 0.001) were more common in individuals with PITX2 variants than those with FOXC1 variants. Glaucoma was present in 72% of participants. Corneal decompensation was positively associated with corneal abnormalities ( P < 0.001), glaucoma surgery ( P = 0.025), and cataract surgery ( P = 0.002).

CONCLUSIONS

Corneal abnormalities were more common in individuals with FOXC1 than in those with PITX2 variants and were often associated with early onset glaucoma. These findings highlight that patients with FOXC1 variations require close follow-up and monitoring throughout infancy and into adulthood.

Molecular diagnoses in the congenital malformations caused by ciliopathies cohort of the 100,000 Genomes Project

BACKGROUND

Primary ciliopathies represent a group of inherited disorders due to defects in the primary cilium, the 'cell's antenna'. The 100,000 Genomes Project was launched in 2012 by Genomics England (GEL), recruiting National Health Service (NHS) patients with eligible rare diseases and cancer. Sequence data were linked to Human Phenotype Ontology (HPO) terms entered by recruiting clinicians.

METHODS

Eighty-three prescreened probands were recruited to the 100,000 Genomes Project suspected to have congenital malformations caused by ciliopathies in the following disease categories: Bardet-Biedl syndrome (n=45), Joubert syndrome (n=14) and 'Rare Multisystem Ciliopathy Disorders' (n=24). We implemented a bespoke variant filtering and analysis strategy to improve molecular diagnostic rates for these participants.

RESULTS

We determined a research molecular diagnosis for n=43/83 (51.8%) probands. This is 19.3% higher than previously reported by GEL (n=27/83 (32.5%)). A high proportion of diagnoses are due to variants in non-ciliopathy disease genes (n=19/43, 44.2%) which may reflect difficulties in clinical recognition of ciliopathies. n=11/83 probands (13.3%) had at least one causative variant outside the tiers 1 and 2 variant prioritisation categories (GEL's automated triaging procedure), which would not be reviewed in standard 100,000 Genomes Project diagnostic strategies. These include four structural variants and three predicted to cause non-canonical splicing defects. Two unrelated participants have biallelic likely pathogenic variants in LRRC45, a putative novel ciliopathy disease gene.

CONCLUSION

These data illustrate the power of linking large-scale genome sequence to phenotype information. They demonstrate the value of research collaborations in order to maximise interpretation of genomic data.

Toward clinical and molecular dissection of frontonasal dysplasia with facial skin polyps: From Pai syndrome to differential diagnosis through a series of 27 patients

Unique or multiple congenital facial skin polyps are features of several rare syndromes, from the most well-known Pai syndrome (PS), to the less recognized oculoauriculofrontonasal syndrome (OAFNS), encephalocraniocutaneous lipomatosis (ECCL), or Sakoda complex (SC). We set up a research project aiming to identify the molecular bases of PS. We reviewed 27 individuals presenting with a syndromic frontonasal polyp and initially referred for PS. Based on strict clinical classification criteria, we could confirm only nine (33%) typical and two (7%) atypical PS individuals. The remaining ones were either OAFNS (11/27-41%) or presenting with an overlapping syndrome (5/27-19%). Because of the phenotypic overlap between these entities, OAFNS, ECCL, and SC can be either considered as differential diagnosis of PS or part of the same spectrum. Exome and/or genome sequencing from blood DNA in 12 patients and from affected tissue in one patient failed to identify any replication in candidate genes. Taken together, our data suggest that conventional approaches routinely utilized for the identification of molecular etiologies responsible for Mendelian disorders are inconclusive. Future studies on affected tissues and multiomics studies will thus be required in order to address either the contribution of mosaic or noncoding variation in these diseases.

Joubert syndrome: Molecular basis and treatment

Joubert syndrome (JS; MIM PS213300) is a rare genetic autosomal recessive disease characterized by cerebellar vermis hypoplasia, a distinctive malformation of the cerebellum and the so-called "molar tooth sign." Other characteristic features are hypotonia with lateral ataxia, intellectual disability/mental retardation, oculomotor apraxia, retinal dystrophy, abnormalities in the respiratory system, renal cysts, hepatic fibrosis, and skeletal changes. Such pleiotropic characteristics are typical of many disorders involving primary cilium aberrations, providing a significant overlap between JS and other ciliopathies such as nephronophthisis, Meckel syndrome, and Bardet-Biedl syndrome. This review will describe some characteristics of JS associated with changes in 35 genes, and will also address subtypes of JS, clinical diagnosis, and the future of therapeutic developments.

Systematic analysis of physical examination characteristics of 94 individuals with Joubert syndrome: Keys to suspecting the diagnosis

Joubert syndrome (JS) is a neurodevelopmental disorder characterized by hypotonia and developmental delay, as well as the obligatory molar tooth sign on brain imaging. Since hypotonia and developmental delay are nonspecific features, there must be a high level of clinical suspicion of JS so that the diagnostic brain imaging and/or molecular testing for the >38 genes associated with JS is/are obtained. The goal of this study was to analyze clinical photographs of a cohort of patients with JS to define a list of physical examination features that should prompt investigation for JS. Analysis of photographs from 94 individuals with JS revealed that there is a recognizable pattern of facial features in JS that changes over time as individuals age. Macrocephaly, head tilting even when looking straight ahead, eye movement abnormalities (oculomotor apraxia, nystagmus, strabismus), and ptosis are common in those with JS. Distinctive features in younger children include triangular-shaped open mouth with tongue protrusion; in older children and adults, mandibular prognathia and prominent nasal bridge are common.

Variable Anterior Segment Dysgenesis and Cardiac Anomalies Caused by a Novel Truncating Variant of FOXC1

Anterior segment dysgenesis (ASD) encompasses a wide spectrum of developmental abnormalities of the anterior ocular segment, including congenital cataract, iris hypoplasia, aniridia, iridocorneal synechiae, as well as Peters, Axenfeld, and Rieger anomalies. Here, we report a large five-generation Caucasian family exhibiting atypical syndromic ASD segregating with a novel truncating variant of FOXC1. The family history is consistent with highly variable autosomal dominant symptoms including isolated glaucoma, iris hypoplasia, aniridia, cataract, hypothyroidism, and congenital heart anomalies. Whole-exome sequencing revealed a novel variant [c.313_314insA; p.(Tyr105*)] in FOXC1 that disrupts the α-helical region of the DNA-binding forkhead box domain. In vitro studies using a heterologous cell system revealed aberrant cytoplasmic localization of FOXC1 harboring the Tyr105* variant, likely precluding downstream transcription function. Meta-analysis of the literature highlighted the intrafamilial variability related to FOXC1 truncating alleles. This study highlights the clinical variability in ASD and signifies the importance of combining both clinical and molecular analysis approaches to establish a complete diagnosis.

Compound heterozygous ADAMTS9 variants in Joubert syndrome-related disorders without renal manifestation

BACKGROUND

Ciliopathies are the outcomes of defects of primary cilia structures and functions which cause multisystemic developmental disorders, such as polycystic kidney disease, nephronophthisis, retinitis pigmentosa, Joubert syndrome (JS), and JS-related disorders (JSRD) with additional organ involvement including oral-facial-digital syndrome and so on. They often share common and unexpected phenotypic features.

CASE PRESENTATION

We report a 4-year-old-boy case with compound heterozygous variants of ADAMTS9. Unlike the cases with ADAMTS9 variants in the previous report, which identified that homozygous variants of ADAMTS9 were responsible for nephronophthisis-related ciliopathies in two cases, the current case did not have nephronophthisis nor renal dysfunction, and his clinical features, such as oculomotor apraxia, hypotonia, developmental delay, bifid tongue, and mild hypoplasia of cerebellar vermis indicated JSRD.

CONCLUSIONS

The case suggested a possible association between the clinical presentation of JSRD and ADAMTS9-related disease, and it shows a wide spectrum of ADAMTS9 phenotype.

Using in vivo cerebellar electroporation to study neuronal cell proliferation and differentiation in a Joubert syndrome mouse model

Joubert syndrome (JS) is an autosomal recessive ciliopathy that mainly affects the morphogenesis of the cerebellum and brain stem. To date, mutations in at least 39 genes have been identified in JS; all these gene-encoding proteins are involved in the biogenesis of the primary cilium and centrioles. Recent studies using the mouse model carrying deleted or mutated JS-related genes exhibited cerebellar hypoplasia with a reduction in neurogenesis; however, investigating specific neuronal behaviors during their development in vivo remains challenging. Here, we describe an in vivo cerebellar electroporation technique that can be used to deliver plasmids carrying GFP and/or shRNAs into the major cerebellar cell type, granule neurons, from their progenitor state to their maturation in a spatiotemporal-specific manner. By combining this method with cerebellar immunostaining and EdU incorporation, these approaches enable the investigation of the cell-autonomous effect of JS-related genes in granule neuron progenitors, including the pathogenesis of ectopic neurons and the defects in neuronal differentiation. This approach provides information toward understanding the multifaceted roles of JS-related genes during cerebellar development in vivo.

[Joubert syndrome type 5 caused by a new compound heterozygous mutation in CEP290]

Joubert syndrome (JS) is a recessive neurodegenerative disease characterized by hypotonia, ataxia, psychomotor delay, oculomotor and visual impairments. JS shows clinically variability and genetic heterogeneity. In this article, we report a case of a 14-year-old female patient with JS 5 type associated with a new compound-heterozygous mutation c.2991+1655A>G + c.6604delA (p.Ile2202fs) in CEP290. Clinical and genetic data of JS 5 type can be useful in the diagnosis of disease.

Precision Medicine through Next-Generation Sequencing in Inherited Eye Diseases in a Korean Cohort

In this study, we investigated medically or surgically actionable genes in inherited eye disease, based on clinical phenotype and genomic data. This retrospective consecutive case series included 149 patients with inherited eye diseases, seen by a single pediatric ophthalmologist, who underwent genetic testing between 1 March 2017 and 28 February 2018. Variants were detected using a target enrichment panel of 429 genes and known deep intronic variants associated with inherited eye disease. Among 149 patients, 38 (25.5%) had a family history, and this cohort includes heterogeneous phenotype including anterior segment dysgenesis, congenital cataract, infantile nystagmus syndrome, optic atrophy, and retinal dystrophy. Overall, 90 patients (60.4%) received a definite molecular diagnosis. Overall, NGS-guided precision care was provided to 8 patients (5.4%). The precision care included cryotherapy to prevent retinal detachment in COL2A1 Stickler syndrome, osteoporosis management in patients with LRP5-associated familial exudative vitreoretinopathy, and avoidance of unnecessary phlebotomy in hyperferritinemia-cataract syndrome. A revision of the initial clinical diagnosis was made in 22 patients (14.8%). Unexpected multi-gene deletions and dual diagnosis were noted in 4 patients (2.7%). We found that precision medical or surgical managements were provided for 8 of 149 patients (5.4%), and multiple locus variants were found in 2.7% of cases. These findings are important because individualized management of inherited eye diseases can be achieved through genetic testing.