Heterozygous COL17A1 variants are a frequent cause of amelogenesis imperfecta.

BACKGROUND: Collagen XVII is most typically associated with human disease when biallelic COL17A1 variants (>230) cause junctional epidermolysis bullosa (JEB), a rare, genetically heterogeneous, mucocutaneous blistering disease with amelogenesis imperfecta (AI), a developmental enamel defect. Despite recognition that heterozygous carriers in JEB families can have AI, and that heterozygous COL17A1 variants also cause dominant corneal epithelial recurrent erosion dystrophy (ERED), the importance of heterozygous COL17A1 variants causing dominant non-syndromic AI is not widely recognised. METHODS: Probands from an AI cohort were screened by single molecule molecular inversion probes or targeted hybridisation capture (both a custom panel and whole exome sequencing) for COL17A1 variants. Patient phenotypes were assessed by clinical examination and analyses of affected teeth. RESULTS: Nineteen unrelated probands with isolated AI (no co-segregating features) had 17 heterozygous, potentially pathogenic COL17A1 variants, including missense, premature termination codons, frameshift and splice site variants in both the endo-domains and the ecto-domains of the protein. The AI phenotype was consistent with enamel of near normal thickness and variable focal hypoplasia with surface irregularities including pitting. CONCLUSION: These results indicate that COL17A1 variants are a frequent cause of dominantly inherited non-syndromic AI. Comparison of variants implicated in AI and JEB identifies similarities in type and distribution, with five identified in both conditions, one of which may also cause ERED. Increased availability of genetic testing means that more individuals will receive reports of heterozygous COL17A1 variants. We propose that patients with isolated AI or ERED, due to COL17A1 variants, should be considered as potential carriers for JEB and counselled accordingly, reflecting the importance of multidisciplinary care.

Biallelic variants in Plexin B2 (PLXNB2) cause amelogenesis imperfecta, hearing loss and intellectual disability.

BACKGROUND: Plexins are large transmembrane receptors for the semaphorin family of signalling proteins. Semaphorin-plexin signalling controls cellular interactions that are critical during development as well as in adult life stages. Nine plexin genes have been identified in humans, but despite the apparent importance of plexins in development, only biallelic PLXND1 and PLXNA1 variants have so far been associated with Mendelian genetic disease. METHODS: Eight individuals from six families presented with a recessively inherited variable clinical condition, with core features of amelogenesis imperfecta (AI) and sensorineural hearing loss (SNHL), with variable intellectual disability. Probands were investigated by exome or genome sequencing. Common variants and those unlikely to affect function were excluded. Variants consistent with autosomal recessive inheritance were prioritised. Variant segregation analysis was performed by Sanger sequencing. RNA expression analysis was conducted in C57Bl6 mice. RESULTS: Rare biallelic pathogenic variants in plexin B2 (PLXNB2), a large transmembrane semaphorin receptor protein, were found to segregate with disease in all six families. The variants identified include missense, nonsense, splicing changes and a multiexon deletion. Plxnb2 expression was detected in differentiating ameloblasts. CONCLUSION: We identify rare biallelic pathogenic variants in PLXNB2 as a cause of a new autosomal recessive, phenotypically diverse syndrome with AI and SNHL as core features. Intellectual disability, ocular disease, ear developmental abnormalities and lymphoedema were also present in multiple cases. The variable syndromic human phenotype overlaps with that seen in Plxnb2 knockout mice, and, together with the rarity of human PLXNB2 variants, may explain why pathogenic variants in PLXNB2 have not been reported previously.

A missense variant in specificity protein 6 (SP6) is associated with amelogenesis imperfecta.

Amelogenesis is the process of enamel formation. For amelogenesis to proceed, the cells of the inner enamel epithelium (IEE) must first proliferate and then differentiate into the enamel-producing ameloblasts. Amelogenesis imperfecta (AI) is a heterogeneous group of genetic conditions that result in defective or absent tooth enamel. We identified a 2 bp variant c.817_818GC>AA in SP6, the gene encoding the SP6 transcription factor, in a Caucasian family with autosomal dominant hypoplastic AI. The resulting missense protein change, p.(Ala273Lys), is predicted to alter a DNA-binding residue in the first of three zinc fingers. SP6 has been shown to be crucial to both proliferation of the IEE and to its differentiation into ameloblasts. SP6 has also been implicated as an AI candidate gene through its study in rodent models. We investigated the effect of the missense variant in SP6 (p.(Ala273Lys)) using surface plasmon resonance protein-DNA binding studies. We identified a potential SP6 binding motif in the AMBN proximal promoter sequence and showed that wild-type (WT) SP6 binds more strongly to it than the mutant protein. We hypothesize that SP6 variants may be a very rare cause of AI due to the critical roles of SP6 in development and that the relatively mild effect of the missense variant identified in this study is sufficient to affect amelogenesis causing AI, but not so severe as to be incompatible with life. We suggest that current AI cohorts, both with autosomal recessive and dominant disease, be screened for SP6 variants.

Spectrum of pathogenic variants and founder effects in amelogenesis imperfecta associated with MMP20.

Amelogenesis imperfecta (AI) describes a heterogeneous group of developmental enamel defects that typically have Mendelian inheritance. Exome sequencing of 10 families with recessive hypomaturation AI revealed four novel and one known variants in the matrix metallopeptidase 20 (MMP20) gene that were predicted to be pathogenic. MMP20 encodes a protease that cleaves the developing extracellular enamel matrix and is necessary for normal enamel crystal growth during amelogenesis. New homozygous missense changes were shared between four families of Pakistani heritage (c.625G>C; p.(Glu209Gln)) and two of Omani origin (c.710C>A; p.(Ser237Tyr)). In two families of UK origin and one from Costa Rica, affected individuals were homozygous for the previously reported c.954-2A>T; p.(Ile319Phefs*19) variant. For each of these variants, microsatellite haplotypes appeared to exclude a recent founder effect, but elements of haplotype were conserved, suggesting more distant founding ancestors. New compound heterozygous changes were identified in one family of the European heritage: c.809_811+12delinsCCAG; p.(?) and c.1122A>C; p.(Gln374His). This report further elucidates the mutation spectrum of MMP20 and the probable impact on protein function, confirms a consistent hypomaturation phenotype and shows that mutations in MMP20 are a common cause of autosomal recessive AI in some communities.

A missense mutation of Leu74Pro of OGR1 found in familial amelogenesis imperfecta actually causes the loss of the pH-sensing mechanism.

Ovarian cancer G protein-coupled receptor 1 (OGR1), also known as GPR68, is a proton-sensing G protein-coupled receptor (GPCR) coupling to Gq/11/phospholipase C/Ca2+ signaling pathways. The specific histidine residues at the extracellular surface of OGR1 are suggested to be involved in the proton sensing. Later, some metal ions, including nickel ion (Ni2+), are also indicated to be OGR1 ligands. OGR1 polymorphic variants have recently been found in three families with amelogenesis imperfecta, which suggested that OGR1 is required for the process of dental enamel formation. One of these families possesses a missense mutation from leucine to proline at 74 (L74P) of OGR1. In the present study, we characterized HEK293 cells with L74P OGR1 (L74P-OGR1) and hemagglutinin (HA)-tag, as compared with cells with wild-type OGR1 (WT-OGR1) and HA-tag. We found that either acidic pH or NiCl2 induced intracellular Ca2+ mobilization and morphological change in WT-OGR1-transfected cells; however, the extracellular stimulus-induced actions were severely damaged in L74P-OGR1-transfected cells. We further confirmed that either WT-OGR1 or L74P-OGR1 is localized mainly in the surface of the cells, but only WT-OGR1 is internalized in response to acidification or NiCl2. Thus, the L74P-OGR1 protein may be distributed in the plasma membranes but severely damaged in the receptor functions. We speculate that L74P in the second transmembrane domain in OGR1 may result in conformational changes in the receptor, thereby disturbing the sensing extracellular signals, i.e., protons or metal ions, and/or transducing them to the intracellular signaling machinery through G proteins.

New missense variants in RELT causing hypomineralised amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic diseases characterised by dental enamel malformation. Pathogenic variants in at least 33 genes cause syndromic or non-syndromic AI. Recently variants in RELT, encoding an orphan receptor in the tumour necrosis factor (TNF) superfamily, were found to cause recessive AI, as part of a syndrome encompassing small stature and severe childhood infections. Here we describe four additional families with autosomal recessive hypomineralised AI due to previously unreported homozygous mutations in RELT. Three families carried a homozygous missense variant in the fourth exon (c.164C>T, p.(T55I)) and a fourth family carried a homozygous missense variant in the 11th exon (c.1264C>T, p.(R422W)). We found no evidence of additional syndromic symptoms in affected individuals. Analyses of tooth microstructure with computerised tomography and scanning electron microscopy suggest a role for RELT in ameloblasts' coordination and interaction with the enamel matrix. Microsatellite genotyping in families segregating the T55I variant reveals a shared founder haplotype. These findings extend the RELT pathogenic variant spectrum, reveal a founder mutation in the UK Pakistani population and provide detailed analysis of human teeth affected by this hypomineralised phenotype, but do not support a possible syndromic presentation in all those with RELT-variant associated AI.

Amelogenesis imperfecta caused by N-terminal enamelin point mutations in mice and men is driven by endoplasmic reticulum stress.

'Amelogenesis imperfecta' (AI) describes a group of inherited diseases of dental enamel that have major clinical impact. Here, we identify the aetiology driving AI in mice carrying a p.S55I mutation in enamelin; one of the most commonly mutated proteins underlying AI in humans. Our data indicate that the mutation inhibits the ameloblast secretory pathway leading to ER stress and an activated unfolded protein response (UPR). Initially, with the support of the UPR acting in pro-survival mode, Enamp.S55I heterozygous mice secreted structurally normal enamel. However, enamel secreted thereafter was structurally abnormal; presumably due to the UPR modulating ameloblast behaviour and function in an attempt to relieve ER stress. Homozygous mutant mice failed to produce enamel. We also identified a novel heterozygous ENAMp.L31R mutation causing AI in humans. We hypothesize that ER stress is the aetiological factor in this case of human AI as it shared the characteristic phenotype described above for the Enamp.S55I mouse. We previously demonstrated that AI in mice carrying the Amelxp.Y64H mutation is a proteinopathy. The current data indicate that AI in Enamp.S55I mice is also a proteinopathy, and based on comparative phenotypic analysis, we suggest that human AI resulting from the ENAMp.L31R mutation is another proteinopathic disease. Identifying a common aetiology for AI resulting from mutations in two different genes opens the way for developing pharmaceutical interventions designed to relieve ER stress or modulate the UPR during enamel development to ameliorate the clinical phenotype.

Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta.

Amelogenesis is the process of dental enamel formation, leading to the deposition of the hardest tissue in the human body. This process requires the intricate regulation of ion transport and controlled changes to the pH of the developing enamel matrix. The means by which the enamel organ regulates pH during amelogenesis is largely unknown. We identified rare homozygous variants in GPR68 in three families with amelogenesis imperfecta, a genetically and phenotypically heterogeneous group of inherited conditions associated with abnormal enamel formation. Each of these homozygous variants (a large in-frame deletion, a frameshift deletion, and a missense variant) were predicted to result in loss of function. GPR68 encodes a proton-sensing G-protein-coupled receptor with sensitivity in the pH range that occurs in the developing enamel matrix during amelogenesis. Immunohistochemistry of rat mandibles confirmed localization of GPR68 in the enamel organ at all stages of amelogenesis. Our data identify a role for GPR68 as a proton sensor that is required for proper enamel formation.

Novel DLX3 variants in amelogenesis imperfecta with attenuated tricho-dento-osseous syndrome.

OBJECTIVES: Variants in DLX3 cause tricho-dento-osseous syndrome (TDO, MIM #190320), a systemic condition with hair, nail and bony changes, taurodontism and amelogenesis imperfecta (AI), inherited in an autosomal dominant fashion. Different variants found within this gene are associated with different phenotypic presentations. To date, six different DLX3 variants have been reported in TDO. The aim of this paper was to explore and discuss three recently uncovered new variants in DLX3. SUBJECTS AND METHODS: Whole-exome sequencing identified a new DLX3 variant in one family, recruited as part of an ongoing study of genetic variants associated with AI. Targeted clinical exome sequencing of two further families revealed another new variant of DLX3 and complete heterozygous deletion of DLX3. For all three families, the phenotypes were shown to consist of AI and taurodontism, together with other attenuated features of TDO. RESULTS: c.574delG p.(E192Rfs*66), c.476G>T (p.R159L) and a heterozygous deletion of the entire DLX3 coding region were identified in our families. CONCLUSION: These previously unreported variants add to the growing literature surrounding AI, allowing for more accurate genetic testing and better understanding of the associated clinical consequences.

Deletion of amelotin exons 3-6 is associated with amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic conditions that result in defective dental enamel formation. Amelotin (AMTN) is a secreted protein thought to act as a promoter of matrix mineralization in the final stage of enamel development, and is strongly expressed, almost exclusively, in maturation stage ameloblasts. Amtn overexpression and Amtn knockout mouse models have defective enamel with no other associated phenotypes, highlighting AMTN as an excellent candidate gene for human AI. However, no AMTN mutations have yet been associated with human AI. Using whole exome sequencing, we identified an 8,678 bp heterozygous genomic deletion encompassing exons 3-6 of AMTN in a Costa Rican family segregating dominant hypomineralised AI. The deletion corresponds to an in-frame deletion of 92 amino acids, shortening the protein from 209 to 117 residues. Exfoliated primary teeth from an affected family member had enamel that was of a lower mineral density compared to control enamel and exhibited structural defects at least some of which appeared to be associated with organic material as evidenced using elemental analysis. This study demonstrates for the first time that AMTN mutations cause non-syndromic human AI and explores the human phenotype, comparing it with that of mice with disrupted Amtn function.

Heimler Syndrome Is Caused by Hypomorphic Mutations in the Peroxisome-Biogenesis Genes PEX1 and PEX6.

Heimler syndrome (HS) is a rare recessive disorder characterized by sensorineural hearing loss (SNHL), amelogenesis imperfecta, nail abnormalities, and occasional or late-onset retinal pigmentation. We ascertained eight families affected by HS and, by using a whole-exome sequencing approach, identified biallelic mutations in PEX1 or PEX6 in six of them. Loss-of-function mutations in both genes are known causes of a spectrum of autosomal-recessive peroxisome-biogenesis disorders (PBDs), including Zellweger syndrome. PBDs are characterized by leukodystrophy, hypotonia, SNHL, retinopathy, and skeletal, craniofacial, and liver abnormalities. We demonstrate that each HS-affected family has at least one hypomorphic allele that results in extremely mild peroxisomal dysfunction. Although individuals with HS share some subtle clinical features found in PBDs, the diagnosis was not suggested by routine blood and skin fibroblast analyses used to detect PBDs. In conclusion, our findings define HS as a mild PBD, expanding the pleiotropy of mutations in PEX1 and PEX6.

A missense mutation in ITGB6 causes pitted hypomineralized amelogenesis imperfecta.

We identified a family in which pitted hypomineralized amelogenesis imperfecta (AI) with premature enamel failure segregated in an autosomal recessive fashion. Whole-exome sequencing revealed a missense mutation (c.586C>A, p.P196T) in the I-domain of integrin-ß6 (ITGB6), which is consistently predicted to be pathogenic by all available programmes and is the only variant that segregates with the disease phenotype. Furthermore, a recent study revealed that mice lacking a functional allele of Itgb6 display a hypomaturation AI phenotype. Phenotypic characterization of affected human teeth in this study showed areas of abnormal prismatic organization, areas of low mineral density and severe abnormal surface pitting in the tooth's coronal portion. We suggest that the pathogenesis of this form of AI may be due to ineffective ligand binding of ITGB6 resulting in either compromised cell-matrix interaction or compromised ITGB6 activation of transforming growth factor-ß (TGF-ß) impacting indirectly on ameloblast-ameloblast interactions and proteolytic processing of extracellular matrix proteins via MMP20. This study adds to the list of genes mutated in AI and further highlights the importance of cell-matrix interactions during enamel formation.

Deletion of ameloblastin exon 6 is associated with amelogenesis imperfecta.

Amelogenesis imperfecta (AI) describes a heterogeneous group of inherited dental enamel defects reflecting failure of normal amelogenesis. Ameloblastin (AMBN) is the second most abundant enamel matrix protein expressed during amelogenesis. The pivotal role of AMBN in amelogenesis has been confirmed experimentally using mouse models. However, no AMBN mutations have been associated with human AI. Using autozygosity mapping and exome sequencing, we identified genomic deletion of AMBN exon 6 in a second cousin consanguineous family with three of the six children having hypoplastic AI. The genomic deletion corresponds to an in-frame deletion of 79 amino acids, shortening the protein from 447 to 368 residues. Exfoliated primary teeth (unmatched to genotype) were available from family members. The most severely affected had thin, aprismatic enamel (similar to that reported in mice homozygous for Ambn lacking exons 5 and 6). Other teeth exhibited thicker but largely aprismatic enamel. One tooth had apparently normal enamel. It has been suggested that AMBN may function in bone development. No clinically obvious bone or other co-segregating health problems were identified in the family investigated. This study confirms for the first time that AMBN mutations cause non-syndromic human AI and that mouse models with disrupted Ambn function are valid.

Identification of mutations in SLC24A4, encoding a potassium-dependent sodium/calcium exchanger, as a cause of amelogenesis imperfecta.

A combination of autozygosity mapping and exome sequencing identified a null mutation in SLC24A4 in a family with hypomineralized amelogenesis imperfect a (AI), a condition in which tooth enamel formation fails. SLC24A4 encodes a calcium transporter upregulated in ameloblasts during the maturation stage of amelogenesis. Screening of further AI families identified a missense mutation in the ion-binding site of SLC24A4 expected to severely diminish or abolish the ion transport function of the protein. Furthermore, examination of previously generated Slc24a4 null mice identified a severe defect in tooth enamel that reflects impaired amelogenesis. These findings support a key role for SLC24A4 in calcium transport during enamel formation.

Mutations in C4orf26, encoding a peptide with in vitro hydroxyapatite crystal nucleation and growth activity, cause amelogenesis imperfecta.

Autozygosity mapping and clonal sequencing of an Omani family identified mutations in the uncharacterized gene, C4orf26, as a cause of recessive hypomineralized amelogenesis imperfecta (AI), a disease in which the formation of tooth enamel fails. Screening of a panel of 57 autosomal-recessive AI-affected families identified eight further families with loss-of-function mutations in C4orf26. C4orf26 encodes a putative extracellular matrix acidic phosphoprotein expressed in the enamel organ. A mineral nucleation assay showed that the protein's phosphorylated C terminus has the capacity to promote nucleation of hydroxyapatite, suggesting a possible function in enamel mineralization during amelogenesis.

Variability of systemic and oro-dental phenotype in two families with non-lethal Raine syndrome with FAM20C mutations.

BACKGROUND: Raine syndrome (RS) is a rare autosomal recessive bone dysplasia typified by osteosclerosis and dysmorphic facies due to FAM20C mutations. Initially reported as lethal in infancy, survival is possible into adulthood. We describe the molecular analysis and clinical phenotypes of five individuals from two consanguineous Brazilian families with attenuated Raine Syndrome with previously unreported features. METHODS: The medical and dental clinical records were reviewed. Extracted deciduous and permanent teeth as well as oral soft tissues were analysed. Whole exome sequencing was undertaken and FAM20C cDNA sequenced in family 1. RESULTS: Family 1 included 3 siblings with hypoplastic Amelogenesis Imperfecta (AI) (inherited abnormal dental enamel formation). Mild facial dysmorphism was noted in the absence of other obvious skeletal or growth abnormalities. A mild hypophosphataemia and soft tissue ectopic mineralization were present. A homozygous FAM20C donor splice site mutation (c.784 + 5 g > c) was identified which led to abnormal cDNA sequence. Family 2 included 2 siblings with hypoplastic AI and tooth dentine abnormalities as part of a more obvious syndrome with facial dysmorphism. There was hypophosphataemia, soft tissue ectopic mineralization, but no osteosclerosis. A homozygous missense mutation in FAM20C (c.1487C > T; p.P496L) was identified. CONCLUSIONS: The clinical phenotype of non-lethal Raine Syndrome is more variable, including between affected siblings, than previously described and an adverse impact on bone growth and health may not be a prominent feature. By contrast, a profound failure of dental enamel formation leading to a distinctive hypoplastic AI in all teeth should alert clinicians to the possibility of FAM20C mutations.

Review of 1.75 million referrals over 34 months identifies the disruptive impact of the SARS-CoV-2 pandemic on oral surgery care in England: a service evaluation.

Aims This study aimed to use electronic referral management system (eRMS) oral surgery data across multiple sites in England to evaluate the service over a 34-month period in relation to: 1) pre- and post-pandemic referral rates in oral surgery; 2) examining the data for signs of inequality in obtaining a referral for oral surgery; and 3) considering the impact on service provision for oral surgery in England.Methods Oral surgery referral data were available from an eRMS for areas of England covered by this service for the 34-month period of March 2019 to December 2021 (inclusive), which included 12 months of pre-pandemic data and the first 22 months of the pandemic. The data were from the following regions in England: Central Midlands; Cheshire and Merseyside; East Anglia and Essex; Greater Manchester; Lancashire; Thames Valley; and Yorkshire and the Humber.Results The total number of referrals received was 1,766,895 during this 34-month period, with pre-pandemic referral levels averaging at 25,498 per month, with a reduction to 698 per month in April 2020. Referrals have risen to a peak of 217,646 for the month of November 2021. An average of 1.5% of referrals were rejected pre-pandemic, compared with 2.7% per month post-pandemic.Discussion Pre-pandemic referral numbers were predictably stable within a narrow range which have then increased dramatically post-pandemic. The variations in oral surgery referral patterns place significant strain on oral surgery services across England. This not only has consequences on the patient experience, but also on workforce and workforce development, to ensure that there is not a long-term destabilising impact.Conclusion Analysis of 1.75 million referrals to oral surgery services in England has highlighted the ongoing impact of the pandemic and the need to actively minimise adverse impacts on patients, NHS services and the workforce.

Mutations in the beta propeller WDR72 cause autosomal-recessive hypomaturation amelogenesis imperfecta.

Healthy dental enamel is the hardest and most highly mineralized human tissue. Though acellular, nonvital, and without capacity for turnover or repair, it can nevertheless last a lifetime. Amelogenesis imperfecta (AI) is a collective term for failure of normal enamel development, covering diverse clinical phenotypes that typically show Mendelian inheritance patterns. One subset, known as hypomaturation AI, is characterised by near-normal volumes of organic enamel matrix but with weak, creamy-brown opaque enamel that fails prematurely after tooth eruption. Mutations in genes critical to enamel matrix formation have been documented, but current understanding of other key events in enamel biomineralization is limited. We investigated autosomal-recessive hypomaturation AI in a consanguineous Pakistani family. A whole-genome SNP autozygosity screen identified a locus on chromosome 15q21.3. Sequencing candidate genes revealed a point mutation in the poorly characterized WDR72 gene. Screening of WDR72 in a panel of nine additional hypomaturation AI families revealed the same mutation in a second, apparently unrelated, Pakistani family and two further nonsense mutations in Omani families. Immunohistochemistry confirmed intracellular localization in maturation-stage ameloblasts. WDR72 function is unknown, but as a putative beta propeller is expected to be a scaffold for protein-protein interactions. The nearest homolog, WDR7, is involved in vesicle mobilization and Ca2+-dependent exocytosis at synapses. Vesicle trafficking is important in maturation-stage ameloblasts with respect to secretion into immature enamel and removal of cleaved enamel matrix proteins via endocytosis. This raises the intriguing possibility that WDR72 is critical to ameloblast vesicle turnover during enamel maturation.

Mutations in CNNM4 cause Jalili syndrome, consisting of autosomal-recessive cone-rod dystrophy and amelogenesis imperfecta.

The combination of recessively inherited cone-rod dystrophy (CRD) and amelogenesis imperfecta (AI) was first reported by Jalili and Smith in 1988 in a family subsequently linked to a locus on chromosome 2q11, and it has since been reported in a second small family. We have identified five further ethnically diverse families cosegregating CRD and AI. Phenotypic characterization of teeth and visual function in the published and new families reveals a consistent syndrome in all seven families, and all link or are consistent with linkage to 2q11, confirming the existence of a genetically homogenous condition that we now propose to call Jalili syndrome. Using a positional-candidate approach, we have identified mutations in the CNNM4 gene, encoding a putative metal transporter, accounting for the condition in all seven families. Nine mutations are described in all, three missense, three terminations, two large deletions, and a single base insertion. We confirmed expression of Cnnm4 in the neural retina and in ameloblasts in the developing tooth, suggesting a hitherto unknown connection between tooth biomineralization and retinal function. The identification of CNNM4 as the causative gene for Jalili syndrome, characterized by syndromic CRD with AI, has the potential to provide new insights into the roles of metal transport in visual function and biomineralization.