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.

Novel variant CPLANE 1: c.5051C>A (p.Ser1684Ter) in an Indian neonate with Joubert syndrome

Joubert syndrome (JS) is a rare ciliopathy that presents with the triad of hypotonia, developmental delay and molar tooth sign (MTS) in brain MRI. Next-generation sequencing has identified about 35 genes which are known to cause JS of which CPLANE 1 mutation is found in 8%-10% of cases. We report a case of JS in an Indian neonate who presented with hypotonia, dysmorphic facies, polydactyly, syndactyly and occipital encephalocele. MRI of the brain revealed MTS, and compound heterozygous mutations in CPLANE 1 gene were detected by clinical exome sequencing, one of them a novel variant CPLANE 1: c.5051C>A (p.Ser1684Ter) in exon 26, which was inherited from the parents.

A temporal single cell transcriptome atlas of zebrafish anterior segment development

Anterior segment dysgenesis (ASD), resulting in vision impairment, stems from maldevelopment of anterior segment (AS) tissues. Incidence of ASD has been linked to malfunction of periocular mesenchyme cells (POM). POM cells specify into anterior segment mesenchyme (ASM) cells which colonize and produce AS tissues. In this study we uncover ASM developmental trajectories associated with formation of the AS. Using a transgenic line of zebrafish that fluorescently labels the ASM throughout development, Tg[foxc1b:GFP], we isolated GFP+ ASM cells at several developmental timepoints (48-144 hpf) and performed single cell RNA sequencing. Clustering analysis indicates subdifferentiation of ASM as early as 48 hpf and subsequent diversification into corneal epithelium/endothelium/stroma, or annular ligament (AL) lineages. Tracking individual clusters reveals common developmental pathways, up to 72 hpf, for the AL and corneal endothelium/stroma and distinct pathways for corneal epithelium starting at 48 hpf. Spatiotemporal validation of over 80 genes found associated with AS development demonstrates a high degree of conservation with mammalian trabecular meshwork and corneal tissues. In addition, we characterize thirteen novel genes associated with annular ligament and seven with corneal development. Overall, the data provide a molecular verification of the long-standing hypothesis that POM derived ASM give rise to AS tissues and highlight the high degree of conservation between zebrafish and mammals.

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.