OBJECTIVE: To identify the genetic cause of a Chinese family with hypomaturation amelogenesis imperfecta (AI) and to characterize the structure of GPR68 mutated enamel in order to develop a deeper understanding of the role of the GPR68 protein during the intricate process of amelogenesis.
METHODS: One Chinese family with generalized hypomaturation AI was recruited. Two of the third molars from the proband were subjected to scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Whole exome sequencing (WES) was performed, and the identified mutation was confirmed by Sanger sequencing. Bioinformatics studies were further conducted to analyze the potential deleterious effects of the mutation.
RESULTS: The proband presented with a hypomaturation AI phenotype, characterized by fragile and discolored enamel surface. The AI enamel showed prismatic structure, which was sporadically obscured by areas of amorphous material and porous structure. EDX analysis showed the proband\'s enamel demonstrated a significant decrease in calcium and phosphorus content and a significant increase in oxygen compared with normal enamel. A novel homozygous mutation of G protein-coupled receptor 68 (GPR68) (c .149 T > A, p.Ile50Asn) was identified in the proband. Bioinformatics analysis indicated that the mutation site displayed a high level of evolutionary conservation among species, and the mutation might impact the stability and conformation of the protein.
CONCLUSIONS: The novel homozygous GPR68 mutation resulted in hypomaturation AI. We first described the effect of GPR68 mutation on enamel structure. Our results provide new genetic evidence that mutations involved in GPR68 contribute to hypomaturation AI.

本文报道了1例Heimler综合征患儿，并确定了该家系的分子遗传基础，先证者携带NM_000466.3（PEX1）：c.2966T>C（p.Ile989Thr）和c.2783+2T>C两个变异位点。经Sanger测序验证c.2966T>C位点变异遗传自其母亲，c.2783+2T>C变异位点遗传自其父亲，并结合RNA测序进行变异功能验证，两个变异评级为致病。.

BACKGROUND: Heimler syndrome (HS) is a rare disorder that includes sensorineural hearing loss (SNHL), nail abnormalities, and enamel hypoplasia. Patients with this syndrome can also exhibit ocular manifestations. At present, only a few cases of HS have been reported, existing knowledge of this syndrome is limited, and many cases have been misdiagnosed or even missed. This is the first report of Heimler syndrome with blurred vision as the first complaint, which was diagnosed by genetic analysis in the ophthalmology department.
METHODS: An 8-year-old girl complained of bilateral visual blur and night blindness from birth. Ophthalmic examinations revealed bilateral retinitis pigmentosa with cystoid macular edema, visual impairment with hyperopia and astigmatism. Hearing test revealed bilateral severe sensorineural hearing loss. Dental examinations revealed enamel hypoplasia. In addition, whole-exome sequencing (WES) identified two pathogenic variants in PEX1: the previously reported missense variant c.2966T > C (p.I989 T), and the novel frameshift variant c.1671_1672del (p.G558Sfs*33).
CONCLUSIONS: Heimler syndrome is caused by compound heterozygous PEX1 pathogenic variants, c.2966T > C (p.I989 T) and c.1671_1672del (p.G558Sfs*33), which contributed to the diversity of clinical and genetic profiles in this patient. The main clinical manifestations include bilateral retinitis pigmentosa with cystoid macular edema, sensorineural hearing loss, and enamel hypoplasia. Systemic examinations are suggested for patients suspected of having pigmentary retinal dystrophy, especially combined with hearing-related impairments. Genetic testing can help us to make a definitive diagnosis.

BACKGROUND: Short stature, amelogenesis imperfecta, and skeletal dysplasia with scoliosis is a rare, autosomal recessive, skeletal disorder first described in 2018. This syndrome starts with pre- and postnatal developmental delay, and gradually presents with variable facial dysmorphisms, a short stature, amelogenesis imperfecta, and progressive skeletal dysplasia affecting the limbs, joints, hands, feet, and spine.
METHODS: We identified a homozygous novel nonsense mutation in exon 1 of SLC10A7 (NM_001300842.2: c.100G > T / p.Gly34*) segregating with the typical disease phenotype in a Han Chinese family. We reviewed the 12-year surgical treatment history with seven interventions on spine.
CONCLUSIONS: To date, only 12 cases of the SLC10A7 mutation have been reported, mainly from consanguineous families. Our patient showed a relatively severe and broad clinical phenotype compared with previously reported cases. In this patient, annual check-ups and timely surgeries led to a good outcome.

Amelogenesis imperfecta (AI) is a developmental enamel defect affecting the structure of enamel, esthetic appearance, and the tooth masticatory function. Gene mutations are reported to be relevant to AI. However, the mechanism underlying AI caused by different mutations is still unclear. This study aimed to reveal the molecular pathogenesis in AI families with 2 novel pre-mRNA splicing mutations.
Two Chinese families with AI were recruited. Whole-exome sequencing and Sanger sequencing were performed to identify mutations in candidate genes. Minigene splicing assays were performed to analyze the mutation effects on mRNA splicing alteration. Furthermore, three-dimensional structures of mutant proteins were predicted by AlphaFold2 to evaluate the detrimental effect.
The affected enamel in family 1 was thin, rough, and stained, which was diagnosed as hypoplastic-hypomature AI. Genomic analysis revealed a novel splicing mutation (NM_001142.2: c.570 + 1G > A) in the intron 6 of amelogenin (AMELX) gene in family 1, resulting in a partial intron 6 retention effect. The proband in family 2 exhibited a typical hypoplastic AI, and the splicing mutation (NM_031889.2: c.123 + 4 A > G) in the intron 4 of enamelin (ENAM) gene was observed in the proband and her father. This mutation led to exon 4 skipping. The predicted structures showed that there were obvious differences in the mutation proteins compared with wild type, leading to impaired function of mutant proteins.
In this study, we identified two new splicing mutations in AMELX and ENAM genes, which cause hypoplastic-hypomature and hypoplastic AI, respectively. These results expand the spectrum of genes causing AI and broaden our understanding of molecular genetic pathology of enamel formation.

This study reported the first case of Kohlschütter-Tönz syndrome (KTS) in China and reviewed the literature of the reported cases.
This patient was registered at the Children\'s Hospital of Chongqing Medical University. The patient\'s symptoms and treatments were recorded in detail, and the patient was monitored for six years. We employed a combination of the following search terms and Boolean operators in our search strategy: Kohlschütter-Tönz syndrome, KTS, and ROGDI. These terms were carefully selected to capture a broad range of relevant publications in PubMed, Web of Science, WHO Global Health Library, and China National Knowledge Infrastructure, including synonyms, variations, and specific terms related to KTS. The pathogenicity of the variants was predicted using SpliceAI and MutationTaster, and the structures of the ROGDI mutations were constructed using I-TASSER.
This is the first case report of KTS in China. Our patient presented with epilepsy, global developmental delay, and amelogenesis imperfecta. A trio-WES revealed homozygous mutations in ROGDI (c.46-37_46-30del). The brain magnetic resonance imaging (MRI) and video electroencephalogram (VEEG) were normal. The efficacy of perampanel (PMP) in treating seizures and intellectual disability was apparent. Furthermore, 43 cases of ROGDI-related KTS were retrieved. 100% exhibited epilepsy, global developmental delay, and amelogenesis imperfecta. 17.2% received a diagnosis of attention deficit hyperactivity disorder (ADHD), and 3.4% were under suspicion of autism spectrum disorder (ASD). Language disorders were observed in all patients. Emotional disorders, notably self-harm behaviors (9.1%), were also reported.
ROGDI-related KTS is a rare neurodegenerative disorder, characterized by three classic clinical manifestations: epilepsy, global developmental delay, and amelogenesis imperfecta. Moreover, patients could present comorbidities, including ADHD, ASD, emotional disorders, and language disorders. PMP may be a potential drug with relatively good efficacy, but long-term clinical trials are still needed.

Amelogenesis imperfecta (AI) represents a group of clinically and genetically heterogeneous disorders that affect enamel formation and mineralization. Although AI is commonly considered a monogenic disorder, digenic inheritance is rarely reported. In this study, we recruited two nonconsanguineous Chinese families exhibiting diverse phenotypes of enamel defects among affected family members. Digenic variants were discovered in both probands. In family 1, the proband inherited a paternal frameshift variant in LAMA3 (NM_198129.4:c.3712dup) and a maternal deletion encompassing the entire AMELX gene. This resulted in a combined hypoplastic and hypomineralized AI phenotype, which was distinct from the parents\' manifestations. In family 2, whole-exome sequencing analysis revealed the proband carried a maternal heterozygous splicing variant in COL17A1 (NC_000010.11 (NM_000494.3): c.4156 + 2dup) and compound heterozygous variants in RELT (paternal: NM_032871.4:c.260A > T; maternal: NM_032871.4:c.521 T > G). These genetic changes caused the abundant irregular enamel defects observed in the proband, whereas other affected family members carrying heterozygous variants in both COL17A1 and RELT displayed only horizontal grooves as their phenotype. The pathogenicity of the novel COL17A1 splice site variant was confirmed through RT-PCR and minigene assay. This study enhances our understanding by highlighting the potential association between the co-occurrence of variants in two genes and variable phenotypes observed in AI patients.

Objective: FAM83H is one of the major pathogenic genes of amelogenesis imperfecta (AI). Previous studies focused on the abnormal enamel development and mineralization caused by the mutations in FAM83H. Here we aimed to observe other effects of FAM83H mutations on tooth eruption besides AI through clinical case analysis. Methods: Published AI cases with FAM83H mutations were searched through PubMed database, and the characteristics of tooth eruption of each cases were counted and analyzed. The literature search range was from January 1, 2008 to February 28, 2023, using the keywords FAM83H and amelogenesis imperfecta. The included literature must provide the detailed radiographic imaging or dental eruption information of AI patients, as well as FAM83H gene mutation information. The basic clinical information, tooth phenotypes, and mutations of all the enrolled cases were collected and analyzed in order to find the characteristics of abnormal tooth eruption. Results: Among 45 papers about FAM83H related to AI, twenty meeting the inclusion criteria were selected, involving 50 AI patients carrying FAM83H mutations who had radiographic image data or the detailed description of tooth eruption. A total of 34 abnormal erupted teeth were from 12 patients (12/50, 24%), among which 85% (29/34) had clear eruption path without any eruption obstructions, either embedded (25/34, 74%) or partially erupted (4/34, 12%). Tooth position analysis found that abnormal eruption of canines and second molars accounted for the highest proportion, accounting for 38% (13/34) respectively. Conclusions: The mutations in FAM83H may lead to amelogenesis imperfecta as well as abnormal tooth eruption at specific tooth positions.
目的： 通过分析FAM83H基因突变导致遗传性牙釉质发育不全（amelogenesis imperfecta，AI）病例的牙萌出异常特征，揭示FAM83H基因可能存在的新表型和新功能，为精准诊治AI等遗传性疾病奠定基础。 方法： 通过PubMed数据库检索已发表的FAM83H突变导致的AI病例，检索关键词为“（FAM83H）AND（amelogenesis imperfecta）”，文献发表时间为2008年1月1日至2023年2月28日。文献纳入标准为能够提供患者详细的影像学资料或牙萌出信息以及FAM83H基因突变资料。收集文献来源的每位患者的基本信息、牙齿表型特征和突变基因信息，分析和总结其牙萌出异常的部位和数量特征。 结果： 在检索到的45篇相关文献中，20篇符合纳入标准，并提供了50例具有影像学资料或牙萌出详细资料、携带FAM83H突变的AI患者的相关信息，共有12例（24%）患者出现了牙萌出异常，累计34颗患牙，其中85%（29/34）的患牙无任何萌出阻力，为埋伏牙［74%（25/34）］或部分萌出［12%（4/34）］。牙位分析发现，尖牙和第二磨牙萌出异常占比最高，均占38%（13/34）。 结论： FAM83H基因突变导致AI的同时，还可引起特定牙位牙萌出异常。.

OBJECTIVE: The current research on single-nucleotide polymorphism (SNP) mutation sites at different positions of the FAM83H gene and their phenotypic changes leading to amelogenesis imperfecta (AI) is inconsistent. We identified a previously reported heterozygous nonsense mutation c.1192C>T (p.Q398*) in the FAM83H gene and conducted a comprehensive analysis of the dental ultrastructure and chemical composition changes induced by this mutation. Additionally, we predicted the protein feature affected by this mutation site. The aim was to further deepen our understanding of the diversity of AI caused by different mutation sites in the FAM83H gene.
METHODS: Whole-exome sequencing (WES) and Sanger sequencing were used to confirm the mutation sites. Physical features of the patient\'s teeth were investigated using various methods including cone beam computer tomography (CBCT), scanning electron microscopy (SEM), contact profilometry (roughness measurement), and a nanomechanical tester (nanoindentation measurement). The protein features of wild-type and mutant FAM83H were predicted using bioinformatics methods.
RESULTS: One previously discovered FAM83H heterozygous nonsense mutation c.1192C>T (p.Q398*) was detected in the patient. SEM revealed inconsistent dentinal tubules, and EDS showed that calcium and phosphorus were lower in the patient\'s dentin but higher in the enamel compared to the control tooth. Roughness measurements showed that AI patients\' teeth had rougher occlusal surfaces than those of the control tooth. Nanoindentation measurements showed that the enamel and dentin hardness values of the AI patients\' teeth were both significantly reduced compared to those of the control tooth. Compared to the wild-type FAM83H protein, the mutant FAM83H protein shows alterations in stability, hydrophobicity, secondary structure, and tertiary structure. These changes could underlie functional differences and AI phenotype variations caused by this mutation site.
CONCLUSIONS: This study expands the understanding of the effects of FAM83H mutations on tooth structure.
CONCLUSIONS: Our study enhances our understanding of the genetic basis of AI and may contribute to improved diagnostics and personalized treatment strategies for patients with FAM83H-related AI.

The rough-toothed dolphin (Steno bredanensis) is characterized by having teeth covered in finely wrinkled vertical ridges, which is a general manifestation of amelogenesis imperfecta. The rough surfaces are hypothesized to be an evolutionary morphological trait of feeding adaptation to increase the dolphin\'s grip on prey. Here, we assembled a rough-toothed dolphin genome and performed the comparative genomic analysis to reveal the genetic basis of the special enamel. Results showed that genes related to enamel development or dental diseases have undergone diversified adaptive changes that may shape the special enamel morphology of this dolphin species, including positive selection (CLDN19, PRKCE, SSUH2, and WDR72), rapid evolution (LAMB3), or unique amino acid substitutions (AMTN, ENAM, MMP20, and KLK4). Meanwhile, the historical demography of rough-toothed dolphin indicated several distinct population fluctuations associated with climate change. The genome-wide heterozygosity of this dolphin is in the middle of all published data for cetaceans. Although the population is considerable, there may be population or subspecies differentiation, and with the global warming and the increasing disturbance of human activities, we should pay more attention to protection in the future. Together, our study brings new insights into the genetic mechanisms that may have driven the evolution of the special enamel morphology in rough-toothed dolphins and provides the first results of genetic heterozygosity and population historical dynamics of this species, which have important guiding implications for the conservation of this dolphin species.