Cone-rod dystrophy and amelogenesis imperfecta (Jalili syndrome): phenotypes and environs

Dentofacial manifestations in a child with Jalili syndrome

Jalili syndrome (JS) (MIM#217080) is a rare autosomal recessive disorder with oculo-dental malformations. The clinical phenotype is characterized by the presence of Cone-Rod Dystrophy (CRD) and Amelogenesis Imperfecta (AI). Genetic mechanism entails a mutation in the CNNM4, a metal transporter gene located on Chromosome 2q11.2. A high fluoride concentration in groundwater has also been identified as an epigenetic factor in this syndrome. JS draws the attention of dentists due to its distinct oral manifestations. To the best of our knowledge, this is the first genetically confirmed pediatric case report from the Indian subcontinent emphasizing the clinical and radiographic features of this condition and its management in a 6-year-old child.

Association between malocclusions and amelogenesis imperfecta genotype and phenotype: A systematic review

INTRODUCTION

The aim of this systematic review (Prospero CRD42022323188) is to investigate whether an association exists in patients with amelogenesis imperfecta (AI) between occlusal characteristics and genotype on the one hand and enamel structural phenotype on the other.

MATERIAL AND METHODS

Reports up to May 2023 assessing occlusion of individuals with AI were browsed in a systematic search using Medline, Embase, ISI Web of Science, and the grey literature. Randomised control trials, case control studies, and case series specifying both occlusion, assessed by cephalometric or clinical analysis, and genotype or dental phenotype in patients with AI were included without any age limitation. Two authors independently selected the publications and extracted the data in accordance with the PRISMA statement. The risk of bias was assessed with the Critical Appraisal Checklists from the Johanna Briggs Institute.

RESULTS

Twenty-five articles were chosen from the 261 results. Most of the included publications were case series (n=22) and case control studies (n=3). Thirteen studies reported both a genotype (ENAM, FAM83H, FAM20A, DLX3, CNMM4, WDR72) and occlusal diagnostic. The methodological quality of the studies was moderate. All AI phenotypes showed an open bite (OB) rate around 35%, except mixed form. The other malocclusions were not often mentioned. No correlation between occlusal phenotype and genotype or AI phenotype could be identified in patients with AI, as most studies had short occlusal descriptions and small sample sizes.

CONCLUSION

OB malocclusions were more frequently reported in AI. This review highlighted the need for a more accurate description of orofacial features associated with AI, to better clarify the role of amelogenesis genes in the regulation of craniofacial morphogenesis and identify patients requiring orthognathic surgery at an early stage.

Novel homozygous nonsynonymous variant of CNNM4 gene in a Chinese family with Jalili syndrome

Background

Jalili syndrome (JS) is a rare autosomal‐recessive inherited disorder characterized by cone‐rod dystrophy and amelogenesis imperfecta. It is often misdiagnosed in clinical practice due to its heterogeneity and rarity.

Methods

Two JS patients from a consanguineous family were included in this study. Detailed ophthalmic examinations were performed. Oral photography was taken. The DNA sample of the proband was sequenced using the customized capture panel, which includes 338 retinal disease genes. Sanger sequencing was performed for validation and segregation.

Results

The patients had poor vision, photophobia, and nystagmus from childhood. Fundus examination revealed diffused chorioretinal atrophy with a prominent macular coloboma. OCT showed a deep staphyloma, severely reduced retinal thickness, retinoschisis, loss of photoreceptor layer, and retinal pigment epithelium in the macular region. Amelogenesis imperfecta, dental decay, staining, irregular shapes, and loss of teeth were present. Next‐generation sequencing combined with Sanger validation identified a novel homozygous nonsynonymous variant c.598T>C (p.S200P) in CNNM4 gene (NM_020184.3).

Conclusions

We described the clinical features of a Chinese family with JS and identified a novel disease‐causing mutation. Our findings broadened the phenotypes and mutation spectrums of JS in Chinese population, as well as are helpful in the diagnosis of this rare disease.

Expanding the genotypic spectrum of Jalili syndrome: Novel CNNM4 variants and uniparental isodisomy in a north American patient cohort

Jalili syndrome is a rare multisystem disorder with the most prominent features consisting of cone-rod dystrophy and amelogenesis imperfecta. Few cases have been reported in the Americas. Here we describe a case series of patients with Jalili syndrome examined at the National Eye Institute’s Ophthalmic Genetics clinic between 2016 and 2018. Three unrelated sporadic cases were systematically evaluated for ocular phenotype and determined to have cone-rod dystrophy with bull’s eye maculopathy, photophobia, and nystagmus. All patients had amelogenesis imperfecta. Two of these patients had Guatemalan ancestry and the same novel homozygous CNNM4 variant (p.Arg236Trp c.706C > T) without evidence of consanguinity. This variant met likely pathogenic criteria by the American College of Medical Genetics guidelines. An additional patient had a homozygous deleterious variant in CNNM4 (c.279delC p.Phe93Leufs*31), which resulted from paternal uniparental isodisomy for chromosome 2p22–2q37. This individual had additional syndromic features including developmental delay and spastic diplegia, likely related to mutations at other loci. Our work highlights the genotypic variability of Jalili syndrome and expands the genotypic spectrum of this condition by describing the first series of patients seen in the United States.

Features, genetics and their correlation in Jalili syndrome: a systematic review

Jalili syndrome is a rare genetic disorder first identified by Jalili in Gaza. Amelogenesis imperfecta and cone-rode dystrophy are simultaneously seen in Jalili syndrome patients as the main and primary manifestations. Molecular analysis has revealed that theCNNM4gene is responsible for this rare syndrome. Jalili syndrome has been observed in many countries around the world, especially in the Middle East and North Africa. In the current scoping systematic review we searched electronic databases to find studies related to Jalili syndrome. In this review we summarise the reported clinical symptoms,CNNM4gene and protein structure,CNNM4mutations, attempts to reach a genotype-phenotype correlation, the functional role ofCNNM4mutations, and epidemiological aspects of Jalili syndrome. In addition, we have analysed the reported mutations in mutation effect prediction databases in order to gain a better understanding of the mutation’s outcomes.

Jalili Syndrome: Cross-sectional and Longitudinal Features of Seven Patients With Cone-Rod Dystrophy and Amelogenesis Imperfecta

PURPOSE

To characterize a series of 7 patients with cone-rod dystrophy (CORD) and amelogenesis imperfecta (AI) owing to confirmed mutations in CNNM4, first described as "Jalili Syndrome."

DESIGN

Retrospective observational case series.

METHODS

Seven patients from 6 families with Jalili Syndrome were identified at 3 tertiary referral centers. We systematically reviewed their available medical records, spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence imaging (FAF), color fundus photography, and electrophysiological assessments.

RESULTS

The mean age at presentation was 6.7 years (range 3-16 years), with 6 male and 1 female patient. CNNM4 mutations were identified in all patients. The mean Snellen best-corrected visual acuity (BCVA) at presentation was 20/246 (range 20/98 to 20/399) in the right eye and 20/252 (range 20/98 to 20/480) in the left. Nystagmus was observed in all 7 patients, and photophobia was present in 6. Funduscopic findings at presentation were variable, ranging from only mild disc pallor to retinal vascular attenuation and macular atrophy. Multimodal imaging demonstrated disease progression in all 7 patients over time. Electroretinography uniformly revealed progressive cone-rod dysfunction.

CONCLUSIONS

Jalili Syndrome is a rare CORD associated with AI. We have further characterized its ocular phenotype, including describing SD-OCT, FAF, and electrophysiological features; and report several novel disease-causing sequence variants. Moreover, this study presents novel longitudinal data demonstrating structural and functional progression over time, allowing better informed advice on prognosis.

Report of two unrelated families with Jalili syndrome and a novel nonsense heterozygous mutation in CNNM4 gene

Jalili syndrome (JS) is an autosomal recessive disease characterized by a combination of cone-rode retinal dytrophy (CRD) and amelogenesis imperfect (AI). Mutations in cyclin and CBS domain divalent metal cation transport mediator 4 (CNNM4) gene cause JS. Here we described 2 families (3 members) affected by JS. In the first family, JS was caused by the homozygous p.Leu324Pro (c.971T > C) missense mutation and the affected patient developed both CRD and AI. In the second family, a specific combination of a compound heterozygous mutation was found - the p.Leu324Pro (c.971T > C) missense transition and the novel p.Tyr581* (c.1743C > G) nonsense mutation. The proband showed CRD and AI, but her father just developed eye alterations. Together, these findings suggest that the p.Leu324Pro mutation in homozygosis induces a complete phenotype with both CRD and AI, but in heterozygosis and in composition with the novel p.Tyr581* nonsense mutation in CNNM4 promotes variable clinical expressivity, particularly with lack of dental phenotypes. These different phenotypes could be explained by deletions affecting the proband's homologous allele, epistasia or interactions with environmental factors leading to residual activity of protein.

Identification of a mutation in CNNM4 by whole exome sequencing in an Amish family and functional link between CNNM4 and IQCB1

We investigated an Amish family in which three siblings presented with an early-onset childhood retinal dystrophy inherited in an autosomal recessive fashion. Genome-wide linkage analysis identified significant linkage to marker D2S2216 on 2q11 with a two-point LOD score of 1.95 and a multi-point LOD score of 3.76. Whole exome sequencing was then performed for the three affected individuals and identified a homozygous nonsense mutation (c.C1813T, p.R605X) in the cyclin and CBS domain divalent metal cation transport mediator 4 (CNNM4) gene located within the 2p14-2q14 Jalili syndrome locus. The initial assessment and collection of the family were performed before the clinical delineation of Jalili syndrome. Another assessment was made after the discovery of the responsible gene and the dental abnormalities characteristic of Jalili syndrome were retrospectively identified. The p.R605X mutation represents the first probable founder mutation of Jalili syndrome identified in the Amish community. The molecular mechanism underlying Jalili syndrome is unknown. Here we show that CNNM4 interacts with IQCB1, which causes Leber congenital amaurosis (LCA) when mutated. A truncated CNNM4 protein starting at R605 significantly increased the rate of apoptosis, and significantly increased the interaction between CNNM4 and IQCB1. Mutation p.R605X may cause Jalili syndrome by a nonsense-mediated decay mechanism, affecting the function of IQCB1 and apoptosis, or both. Our data, for the first time, functionally link Jalili syndrome gene CNNM4 to LCA gene IQCB1, providing important insights into the molecular pathogenic mechanism of retinal dystrophy in Jalili syndrome.

Practical approach to syndromic pediatric retinal dystrophies

PURPOSE OF REVIEW

The purpose of this review is to outline those systemic disorders that are associated with pediatric retinal dystrophy, summarize important retinal, and nonretinal clues that aid in syndromic diagnosis, provide an approach for ophthalmic and systematic systemic examination, describe the important systemic findings seen in pediatric syndromic retinal dystrophies and highlight the role of genetic testing.

RECENT FINDINGS

With profound advances being made in the field of molecular genetics, a definitive molecular etiology is increasingly being made even in rare and unusual forms of retinal dystrophies. Early recognition and precise diagnosis of a syndromic association has major clinical implications. It not only ensures early and holistic care to the child but also provides an opportunity for the parents in better understanding the nature and course of the disorder. It greatly aids in genetic counseling.

SUMMARY

Many syndromic retinal dystrophies may present initially to the ophthalmologist long before they present to the pediatrician with systemic symptoms. The intent of this article is to act as a resource in assisting the ophthalmologist to arrive at an early systemic diagnosis.

Novel splice site mutation in CNNM4 gene in a family with Jalili syndrome

Jalili syndrome is a rare autosomal recessive genetic disease characterized by the association of amelogenesis imperfecta and cone-rod retinal dystrophy. This syndrome is caused by mutations in the CNNM4 gene. Different types of CNNM4 mutations have been reported; missense, nonsense, large deletions, single base insertion, and duplication. We used Sanger sequencing to analyze a large consanguineous family with three siblings affected with Jalili syndrome, suspected clinically after dental and ophthalmological examination. These patients are carrying a novel homozygous mutation in the splice site acceptor of intron 3 (c.1682-1G > C) in the CNNM4 gene. We compare the findings of the present family to those from literature, in order to further delineate Jalili syndrome.

A novel mutation and variable phenotypic expression in a large consanguineous pedigree with Jalili syndrome

PurposeJalili syndrome is an autosomal recessive disorder characterized by simultaneous appearance of cone-rod dystrophy (CRD) and amelogenesis imperfecta (AI). Mutations in CNNM4 gene have been identified as the underlying cause of the syndrome. In this study, we investigated a large affected family to identify the causative mutation.Patients and MethodsA seven-generation family with 24 members affected with Jalili syndrome were enrolled in the study. Comprehensive ophthalmologic and dental examinations were performed on them. The entire coding region of CNNM4 gene was sequenced for detection of potential mutations.ResultsOcular examinations showed nystagmus and photophobia along with early onset visual impairment. Fundoscopic exams revealed a spectrum of macular dystrophies in different family members, from macular coloboma and advanced form of beaten bronze macular dystrophy (bull's eye) to milder form of macular thinning along with a range of pigmentary changes and vascular attenuation in the posterior pole and periphery. Scotopic and photopic electro-retinographic responses (ERGs) were extinguished or significantly depressed. Mutation analysis revealed a novel mutation (c.1091delG) in homozygous form in the patients and as a heterozygous form in the normal carrier subjects.ConclusionWe identified a novel homozygous deleterious mutation in CNNM4 gene which causes Jalili syndrome.

A new familial case of Jalili syndrome caused by a novel mutation in CNNM4

Jalili syndrome (JS) is a rare autosomal recessive disorder characterized by the combination of cone-rod dystrophy (CRD) and amelogenesis imperfecta. To date, 18 families with JS have been reported, 16 of which were found to have a mutation in CNNM4. We describe three siblings with clinical features of JS with a homozygous missense mutation in exon 4 of CNNM4, c.1781A>G (p.N594S). They demonstrated phenotypic variability in terms of ocular and dental findings. Although fundus examination and optical coherence tomography results were normal, the electroretinogram was compatible with CRD, supporting the diagnosis of JS. The dental phenotype severity also varied among the siblings.

Amelogenesis imperfecta and anterior open bite: Etiological, classification, clinical and management interrelationships

Although amelogenesis imperfecta is not a common dental pathological condition, its etiological, classification, clinical and management aspects have been addressed extensively in the scientific literature. Of special clinical consideration is the frequent co-existence of amelogenesis imperfecta with the anterior open bite. This paper provides an updated review on amelogenesis imperfecta as well as anterior open bite, in general, and documents the association of these two separate entities, in particular. Diagnosis and treatment of amelogenesis imperfecta patients presenting also with anterior open bite require a lengthy, comprehensive and multidisciplinary approach, which should aim to successfully address all dental, occlusal, developmental, skeletal and soft tissue problems associated with these two serious clinical conditions.

Causes and consequences of inherited cone disorders

Hereditary cone disorders (CDs) are characterized by defects of the cone photoreceptors or retinal pigment epithelium underlying the macula, and include achromatopsia (ACHM), cone dystrophy (COD), cone-rod dystrophy (CRD), color vision impairment, Stargardt disease (STGD) and other maculopathies. Forty-two genes have been implicated in non-syndromic inherited CDs. Mutations in the 5 genes implicated in ACHM explain ∼93% of the cases. On the contrary, only 21% of CRDs (17 genes) and 25% of CODs (8 genes) have been elucidated. The fact that the large majority of COD and CRD-associated genes are yet to be discovered hints towards the existence of unknown cone-specific or cone-sensitive processes. The ACHM-associated genes encode proteins that fulfill crucial roles in the cone phototransduction cascade, which is the most frequently compromised (10 genes) process in CDs. Another 7 CD-associated proteins are required for transport processes towards or through the connecting cilium. The remaining CD-associated proteins are involved in cell membrane morphogenesis and maintenance, synaptic transduction, and the retinoid cycle. Further novel genes are likely to be identified in the near future by combining large-scale DNA sequencing and transcriptomics technologies. For 31 of 42 CD-associated genes, mammalian models are available, 14 of which have successfully been used for gene augmentation studies. However, gene augmentation for CDs should ideally be developed in large mammalian models with cone-rich areas, which are currently available for only 11 CD genes. Future research will aim to elucidate the remaining causative genes, identify the molecular mechanisms of CD, and develop novel therapies aimed at preventing vision loss in individuals with CD in the future.

Dental phenotype in Jalili syndrome due to a c.1312 dupC homozygous mutation in the CNNM4 gene

Jalili syndrome denotes a recessively inherited combination of an eye disease (cone-rod dystrophy) and a dental disorder (amelogenesis imperfecta), which is caused by mutations in the CNNM4 gene. Whereas the ophthalmic consequences of these mutations have been studied comprehensively, the dental phenotype has obtained less attention. A defective transport of magnesium ions by the photoreceptors of the retina is assumed to account for the progressive visual impairment. Since magnesium is also incorporated in the mineral of dental hard tissues, we hypothesized that magnesium concentrations in defective enamel resulting from mutations in CNNM4 would be abnormal, if a similar deficiency of magnesium transport also accounted for the amelogenesis imperfecta. Thus, a detailed analysis of the dental hard tissues was performed in two boys of Kosovan origin affected by Jalili syndrome. Retinal dystrophy of the patients was diagnosed by a comprehensive eye examination and full-field electroretinography. A mutational analysis revealed a c.1312 dupC homozygous mutation in CNNM4, a genetic defect which had already been identified in other Kosovan families and putatively results in loss-of-function of the protein. The evaluation of six primary teeth using light and scanning electron microscopy as well as energy-dispersive X-ray spectroscopy showed that dental enamel was thin and deficient in mineral, suggesting a hypoplastic/hypomineralized type of amelogenesis imperfecta. The reduced mineral density of enamel was accompanied by decreased amounts of calcium, but significantly elevated levels of magnesium. In dentin, however, a similar mineral deficiency was associated with reduced magnesium and normal calcium levels. It is concluded that the c.1312 dupC mutation of CNNM4 results in mineralization defects of both enamel and dentin, which are associated with significantly abnormal magnesium concentrations. Thus, we could not disprove the hypothesis that a disrupted magnesium transport is involved in the development of the dental abnormalities observed in Jalili syndrome.

Molecular genetics of achromatopsia in Newfoundland reveal genetic heterogeneity, founder effects and the first cases of Jalili syndrome in North America

Achromatopsia (ACHM) is a severe retinal disorder characterized by an inability to distinguish colors, impaired visual acuity, photophobia and nystagmus. This rare autosomal recessive disorder of the cone photoreceptors is best known for its increased frequency due to founder effect in the Pingelapese population of the Pacific islands. Sixteen patients from Newfoundland, Canada were sequenced for mutations in the four known achromatopsia genes CNGA3, CNGB3, GNAT2, and PDE6C. The majority (n = 12) of patients were either homozygotes or compound heterozygotes for known achromatopsia alleles, two in CNGB3 (p.T383fsX and p.T296YfsX9) and three in CNGA3 (p.R283Q, p.R427C and p.L527R). Haplotype reconstruction showed that recurrent mutations p.T383fsX and p.L527R were due to a founder effect. Aggregate data from exome sequencing, segregation analysis and archived medical records support a rediagnosis of Jalili syndrome in affected siblings (n = 4) from Family 0094, which to our knowledge is the first family identified with Jalili Syndrome in North America.