Amelogenesis Imperfecta

Mendelian MONDO:0019507 Pathograph 27 Show in embeddings browser Ectodermal Dysplasia Oral Cavity Disease

Amelogenesis imperfecta (AI) is a clinically and genetically heterogeneous group of inherited disorders of tooth enamel formation, in which the enamel is abnormal in quantity, structure, and/or mineral content in the absence of a generalized systemic disorder. Enamel is the most highly mineralized tissue in the body and is produced by ameloblasts, epithelial cells of ectodermal origin that secrete a protein-rich enamel matrix (amelogenin, enamelin, ameloblastin) and then orchestrate its proteolytic processing and progressive mineralization during the secretory and maturation stages of amelogenesis. AI arises when mutations disrupt the genes encoding these matrix proteins (AMELX, ENAM) or the proteases that process them (MMP20, KLK4), or other regulators of the secretory/maturation program (FAM83H, WDR72, DLX3 and others). Because the dental phenotype reflects which stage of amelogenesis is disrupted, AI is conventionally classified into hypoplastic (reduced enamel thickness, a secretory-stage quantitative defect), hypomaturation (normal-thickness but soft, mottled enamel from defective maturation), and hypocalcified/hypomineralized (poorly mineralized, rapidly attriting enamel) types, with X-linked, autosomal dominant, and autosomal recessive inheritance. AI is mechanistically and clinically distinct from acquired developmental defects of enamel such as dental fluorosis (excess fluoride) and from molar-incisor hypomineralization.

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3
Inheritance
7
Pathophys.
4
Phenotypes
27
Pathograph
17
Genes
2
Medical Actions
21
Subtypes
1
Datasets
24
References
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Inheritance

3
X-linked inheritance HP:0001417
AMELX (amelogenin) is located on the X chromosome; mutations cause X-linked AI, with males more severely and uniformly affected than heterozygous females.
X-linked inheritance
Show evidence (1 reference)
PMID:16304440 SUPPORT Human Clinical
"Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
Establishes the X-linked inheritance of AMELX-related AI versus autosomal inheritance of ENAM-related AI.
Autosomal dominant inheritance HP:0000006
Autosomal dominant AI is caused by mutations in genes such as ENAM and FAM83H.
Autosomal dominant inheritance
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"Autosomal dominant, recessive, and X-linked types have been previously described."
Documents the full range of Mendelian inheritance patterns described for AI.
Autosomal recessive inheritance HP:0000007
Autosomal recessive AI is caused by biallelic mutations in genes such as MMP20, KLK4, and WDR72, which mediate enamel matrix processing and maturation.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"Autosomal dominant, recessive, and X-linked types have been previously described."
Documents autosomal recessive inheritance as one of the established AI patterns.
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Subtypes

21
Hypoplastic AI (secretory-stage quantitative defect)
Reduced enamel thickness due to a defect during the secretory stage of amelogenesis, when the enamel matrix is laid down. Classically associated with AMELX and ENAM mutations.
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
Defines the hypoplastic type as a defect in a specific stage of enamel synthesis.
Hypomaturation AI (maturation-stage defect)
Enamel of relatively normal thickness but soft and mottled, due to defective maturation-stage processing of the enamel matrix. Classically associated with MMP20 and KLK4 protease mutations.
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
Defines the hypomature type as a maturation-stage defect of enamel synthesis.
Hypocalcified AI (mineralization defect)
Enamel of normal thickness but poorly mineralized, soft, and rapidly lost to attrition. FAM83H mutations are a common cause of autosomal dominant hypocalcified AI.
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
Defines the hypocalcified type as a defect in the enamel synthesis process.
AI type 1A (LAMB3, autosomal dominant hypoplastic) MONDO:0007094
LAMB3 hgnc:6490 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in LAMB3 (hgnc:6490). hgnc:6490 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal dominant hypoplastic AI caused by heterozygous LAMB3 variants that truncate the laminin beta-3 chain near its C-terminus. Biallelic loss of LAMB3 instead causes junctional epidermolysis bullosa, so the AI-only phenotype is allele- and dose-specific rather than a simple null.
Show evidence (2 references)
PMID:30905256 SUPPORT Human Clinical
"We identified 2 families segregating autosomal dominant AI with variable degrees of a distinctive hypoplastic phenotype due to pathogenic variants in LAMB3."
Establishes dominantly inherited hypoplastic AI as the LAMB3 phenotype in two families, which is the concept MONDO:0007094 denotes.
PMID:30905256 SUPPORT BACKGROUND Human Clinical
"In contrast, biallelic loss-of-function variants in LAMB3 cause recessive junctional epidermolysis bullosa, characterized by life-threatening skin fragility."
Source for the contrast with junctional epidermolysis bullosa drawn in this subtype's description.
AI type 1B (ENAM, autosomal dominant localized hypoplastic) MONDO:0007092
ENAM hgnc:3344 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in ENAM (hgnc:3344). hgnc:3344 is a gene from the HUGO Gene Nomenclature Committee.
The dominant, heterozygous end of the ENAM allelic series: carriers of a single ENAM insertion or nonsense allele show localized enamel pitting or local hypoplastic AI. MONDO carries "hereditary localised enamel hypoplasia" as a synonym of this term, matching that phenotype.
Show evidence (1 reference)
PMID:16246937 SUPPORT Human Clinical
"A novel nonsense mutation (g.12663C>A; p.S246X) was identified in one family segregating local hypoplastic AI as a dominant trait."
Documents the dominant, localized hypoplastic ENAM phenotype that distinguishes AI1B from the recessive generalized form (AI1C).
AI type 1C (ENAM, autosomal recessive generalized hypoplastic) MONDO:0008770
ENAM hgnc:3344 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in ENAM (hgnc:3344). hgnc:3344 is a gene from the HUGO Gene Nomenclature Committee.
The recessive end of the same ENAM allelic series: biallelic ENAM defects produce generalized hypoplastic AI with a class II open-bite malocclusion. AI1B and AI1C are one gene separated by dose, not two genes, which is why both MONDO terms list ENAM.
Show evidence (1 reference)
PMID:14684688 SUPPORT Human Clinical
"The phenotype associated with the g.13185_13186insAG ENAM mutation is dose dependent such that ARAI with openbite malocclusion segregates as a recessive trait, and enamel pitting as a dominant trait."
States the dose dependence directly, supporting the split of the ENAM allelic series into a recessive generalized type and a dominant localized one.
AI type 1E (AMELX, X-linked) MONDO:0010521
AMELX hgnc:461 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in AMELX (hgnc:461). hgnc:461 is a gene from the HUGO Gene Nomenclature Committee.
X-linked AI from AMELX variants. The enamel defect is not purely quantitative: reported phenotypes span thin poorly mineralized enamel with a "snow-capped" appearance through to severe hypoplasia, which is why Witkop assigned AMELX cases to types IE, IIB and IIC.
Show evidence (2 references)
PMID:38892321 SUPPORT Human Clinical
"AMELX mutations cause X-linked amelogenesis imperfecta (AI), known as AI types IE, IIB, and IIC in Witkop's classification, characterized by hypoplastic (reduced thickness) and/or hypomaturation (reduced hardness) enamel defects."
Names AMELX as the X-linked AI gene and places type IE within its phenotypic range, supporting both the gene binding and the mixed hypoplastic/hypomaturation description.
PMID:38892321 SUPPORT Human Clinical
"The affected individuals exhibited enamel malformations, ranging from thin, poorly mineralized enamel with a "snow-capped" appearance to severe hypoplastic defects with minimal enamel."
Source for the phenotypic range, including the snow-capped appearance, described for this subtype.
AI type 1F (AMBN, autosomal recessive hypoplastic) MONDO:0014560
AMBN hgnc:452 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in AMBN (hgnc:452). hgnc:452 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive hypoplastic AI from biallelic ameloblastin defects. Ameloblastin is a secreted enamel matrix protein whose essential functions are enamel-specific, so the phenotype is confined to the dentition.
Show evidence (2 references)
PMID:31402633 SUPPORT Human Clinical
"Biallelic AMBN defects cause non-syndromic autosomal recessive amelogenesis imperfecta."
States the gene-disease relationship and the recessive, non-syndromic mode that MONDO:0014560 denotes.
PMID:31402633 SUPPORT BACKGROUND Other
"Ameloblastin (AMBN) is a secreted matrix protein that is critical for the formation of dental enamel and is enamel-specific with respect to its essential functions."
Source for the description of ameloblastin as a secreted, enamel-specific matrix protein.
AI type 1G / enamel renal syndrome (FAM20A, autosomal recessive) MONDO:0008771
FAM20A hgnc:23015 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in FAM20A (hgnc:23015). hgnc:23015 is a gene from the HUGO Gene Nomenclature Committee.
Biallelic FAM20A variants cause enamel renal syndrome, which OMIM and MONDO number as amelogenesis imperfecta type 1G. Unlike the other rows here it is syndromic: ectopic mineralization extends beyond enamel to dental pulp, follicle and gingiva, and to the kidney as nephrocalcinosis.
Show evidence (1 reference)
PMID:40089179 SUPPORT Human Clinical
"This autosomal recessive condition, caused by pathogenic variants in the FAM20A gene, is linked to ectopic mineralisation in tissues such as dental pulp, follicles, gingiva, and kidneys."
Establishes FAM20A as the cause and records the extra-enamel involvement that makes this subtype syndromic.
AI type 1H (ITGB6, autosomal recessive hypoplastic) MONDO:0014540
ITGB6 hgnc:6161 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in ITGB6 (hgnc:6161). hgnc:6161 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive generalized hypoplastic AI from loss-of-function variants in the integrin beta-6 subunit, which in mouse localizes to the distal membrane of differentiating ameloblasts. The lesion is in ameloblast attachment to its own matrix rather than in a matrix protein or protease.
Show evidence (2 references)
PMID:24305999 SUPPORT Human Clinical
"We recruited two Hispanic families with generalized hypoplastic amelogenesis imperfecta (AI). Analysis of whole-exome sequences identified three integrin beta 6 (ITGB6) mutations responsible for their enamel malformations."
First report of disease-causing ITGB6 mutations, in generalized hypoplastic AI, which is the concept MONDO:0014540 denotes.
PMID:24305999 SUPPORT Model Organism
"Immunohistochemistry of mouse mandibular incisors localized ITGB6 to the distal membrane of differentiating ameloblasts and pre-ameloblasts, and then ITGB6 appeared to be internalized by secretory stage ameloblasts."
Source for the distal-membrane localization stated in this subtype's description; the localization is mouse rather than human data.
AI type 1J (ACP4, autosomal recessive hypoplastic) MONDO:0015008
ACP4 hgnc:14376 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in ACP4 (hgnc:14376). hgnc:14376 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive generalized hypoplastic AI from biallelic ACP4 variants. ACP4 is the acid phosphatase previously symbolized ACPT (testicular acid phosphatase); in mouse, it localizes to secretory-stage ameloblasts.
Show evidence (2 references)
PMID:27843125 SUPPORT Human Clinical
"In this study, we identified ACPT (testicular acid phosphatase) biallelic mutations causing non-syndromic, generalized hypoplastic autosomal-recessive amelogenesis imperfecta (AI) in individuals from six apparently unrelated Turkish families."
Establishes the recessive ACP4/ACPT-AI relationship in six families.
PMID:27843125 SUPPORT Model Organism
"Immunohistochemical analysis confirmed localization of ACPT in secretory-stage ameloblasts."
Source for the secretory-stage ameloblast localization stated above; the staining was performed on mouse molar tissue.
AI type 1K (SP6, autosomal dominant hypoplastic) MONDO:0031084
SP6 hgnc:14530 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in SP6 (hgnc:14530). hgnc:14530 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal dominant hypoplastic AI from a missense change in the first zinc finger of the SP6 transcription factor. The lesion is upstream of enamel matrix production: SP6 drives proliferation of the inner enamel epithelium and its differentiation into ameloblasts.
Show evidence (1 reference)
PMID:32167558 SUPPORT Human Clinical
"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."
Establishes SP6 as the gene and autosomal dominant hypoplastic AI as the phenotype.
AI type 2A1 (KLK4, autosomal recessive hypomaturation) MONDO:0008772
KLK4 hgnc:6365 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in KLK4 (hgnc:6365). hgnc:6365 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive hypomaturation AI from inactivating KLK4 variants. Kallikrein-4 is the maturation-stage protease that clears residual enamel matrix, so the enamel reaches normal thickness but stays soft and discolored.
Show evidence (2 references)
PMID:35207639 SUPPORT Human Clinical
"These analyses revealed two novel homozygous mutations in the KLK4 gene: a nonsense mutation in exon 3 (NM_004917.4:c.170C>A, p.(Ser57*)) was found in families 1, 2 and 3 and a missense mutation in exon 6 (c.637T>C, p.(Cys213Arg)) in family 4."
Identifies biallelic inactivating KLK4 variants in four families recruited for hypomaturation AI.
PMID:35207639 SUPPORT BACKGROUND Human Clinical
"Even though there are some overlapping phenotypes, hypomaturation AI enamel typically has a yellow to brown discoloration with a dull appearance but a normal thickness indicating a less mineralized enamel matrix."
Source for describing hypomaturation enamel as normal in thickness but soft and discolored.
AI type 2A2 (MMP20, autosomal recessive hypomaturation) MONDO:0012926
MMP20 hgnc:7167 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in MMP20 (hgnc:7167). hgnc:7167 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive hypomaturation AI from biallelic MMP20 variants. MMP20 (enamelysin) is the protease that cleaves the developing extracellular enamel matrix, a step required for normal enamel crystal growth.
Show evidence (1 reference)
PMID:33600052 SUPPORT Human Clinical
"MMP20 encodes a protease that cleaves the developing extracellular enamel matrix and is necessary for normal enamel crystal growth during amelogenesis."
States the protease function whose loss produces the hypomaturation phenotype of this subtype.
AI type 2A3 (WDR72, autosomal recessive hypomaturation) MONDO:0013181
WDR72 hgnc:26790 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in WDR72 (hgnc:26790). hgnc:26790 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive hypomaturation AI from biallelic WDR72 defects: enamel of normal thickness that is severely hypomineralized, orange-brown, and prone to attrition. Some affected individuals also have distal renal tubular acidosis, so a low serum pH is a recognized extra-dental finding in this subtype.
Show evidence (2 references)
PMID:30779877 SUPPORT Human Clinical
"Defects in WDR72 (WD repeat-containing protein 72; OMIM *613214) cause AI, type IIA3 (OMIM #613211), which follows an autosomal recessive pattern of inheritance."
Names the gene, the OMIM type IIA3 designation that MONDO:0013181 mirrors, and the recessive inheritance.
PMID:30779877 SUPPORT Human Clinical
"Three of the affected patients showed decreased serum pH, consistent with a diagnosis of renal tubular acidosis."
Records the acidosis finding in a minority of affected individuals, which is why this subtype's description notes an extra-dental feature.
AI type 2A4 (ODAPH, autosomal recessive) MONDO:0013906
ODAPH hgnc:26300 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in ODAPH (hgnc:26300). hgnc:26300 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive AI from biallelic ODAPH defects. ODAPH was previously symbolized C4orf26; in mouse, Odaph is expressed by ameloblasts at the onset of the post-secretory transition. The reported human enamel phenotype is extensive post-eruptive failure and discoloration, which the authors classify as hypocalcified AI and explicitly not as the hypomaturation type this MONDO term is named for.
Show evidence (4 references)
PMID:38303846 SUPPORT Human Clinical
"A novel homozygous ODAPH (previously designated C4orf26) mutation of single-nucleotide deletion (NG_032974.1:g.5103del, NM_178497.5:c.67+1del) was identified to be disease-causing."
Identifies a biallelic ODAPH mutation as the cause in a consanguineous family, and records the previous C4orf26 symbol.
PMID:38303846 SUPPORT Human Clinical
"The defective enamel of erupted teeth showed extensive post-eruptive failure and discoloration."
Source for the post-eruptive enamel failure described for this subtype.
PMID:38303846 SUPPORT Human Clinical
"Loss-of-function ODAPH mutations can cause AI type IIIB (the hypocalcified, autosomal recessive type), rather than type IIA4 (the hypomaturation, pigmented autosomal recessive type)."
Supports ODAPH as the causal gene, and is the source for this subtype's statement that the authors reject the type IIA4 (hypomaturation) label that MONDO:0013906 carries.
+ 1 more reference
AI type 2A5 (SLC24A4, autosomal recessive hypomaturation) MONDO:0014385
SLC24A4 hgnc:10978 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in SLC24A4 (hgnc:10978). hgnc:10978 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive hypomaturation AI from biallelic SLC24A4 defects. The function lost is calcium transport at the maturation stage, so this subtype's lesion is in calcium delivery to the maturing matrix rather than in a matrix protein or protease.
Show evidence (1 reference)
PMID:24532815 SUPPORT Human Clinical
"This is the first report of exonal deletion in SLC24A4 providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis."
Confirms the gene-disease relationship and names calcium transport at the maturation stage as the function lost.
AI type 2A6 (GPR68, autosomal recessive hypomaturation) MONDO:0014971
GPR68 hgnc:4519 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in GPR68 (hgnc:4519). hgnc:4519 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive hypomaturation AI from loss-of-function GPR68 variants. GPR68 is a proton-sensing G-protein-coupled receptor active over the pH range the enamel matrix passes through during maturation, so this subtype's lesion is in sensing matrix pH rather than in transporting an ion.
Show evidence (1 reference)
PMID:27693231 SUPPORT Human Clinical
"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."
Establishes biallelic GPR68 variants as a cause of AI in three families.
AI type 3A (FAM83H, autosomal dominant hypocalcified) MONDO:0007538
FAM83H hgnc:24797 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in FAM83H (hgnc:24797). hgnc:24797 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal dominant hypocalcified AI. Only truncating FAM83H alleles cause it, and knockout and knock-in mouse models argue the mechanism is neomorphic rather than simple loss of function.
Show evidence (2 references)
PMID:33034243 SUPPORT Human Clinical
"Truncation mutations in FAM83H (OMIM *611927) are hitherto the sole cause of ADHCAI."
States that only truncating FAM83H alleles cause autosomal dominant hypocalcified AI, the concept MONDO:0007538 denotes.
PMID:33034243 SUPPORT REVIEW SYNTHESIS Model Organism
"With human genetic studies, Fam83h knockout and mutation-knock-in mouse models indicated that FAM83H does not serve a critical physiologic function during enamel formation and suggested a neomorphic mutation mechanism causing ADHCAI."
Source for describing the FAM83H mechanism as neomorphic rather than loss-of-function. The claim rests on Fam83h knockout and knock-in mouse models, and this review is restating them rather than reporting them.
AI type 3C (RELT, autosomal recessive) MONDO:0032717
RELT hgnc:13764 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in RELT (hgnc:13764). hgnc:13764 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive AI from homozygous RELT defects, reported as generalized irregular hypoplastic enamel that attrits rapidly. RELT is a tumor necrosis factor receptor superfamily member expressed by secretory-stage ameloblasts and by odontoblasts.
Show evidence (2 references)
PMID:30506946 SUPPORT Human Clinical
"We characterized three consanguineous AI families with generalized irregular hypoplastic enamel with rapid attrition that perfectly segregated with homozygous defects in a novel gene: RELT that is a member of the tumor necrosis factor receptor superfamily (TNFRSF)."
Establishes RELT as a recessive AI gene and describes the enamel phenotype quoted in this subtype's description.
PMID:30506946 SUPPORT Model Organism
"RNAscope in situ hybridization of wild-type mouse molars and incisors showed specific Relt mRNA expression by secretory stage ameloblasts and by odontoblasts."
Source for the expression statement in this subtype's description; the data are mouse rather than human.
Hypomaturation-hypoplastic AI with taurodontism (DLX3, autosomal dominant) MONDO:0007093
DLX3 hgnc:2916 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in DLX3 (hgnc:2916). hgnc:2916 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal dominant AI combining hypomaturation and hypoplastic enamel defects with taurodont molars, caused by DLX3 homeodomain frameshifts. Like SP6, DLX3 is a transcription factor, so the lesion precedes matrix production.
Show evidence (1 reference)
PMID:15666299 SUPPORT Human Clinical
"In this study, we mapped an AIHHT family to human chromosome 17 q21-q22 (lod score 3.3) and identify a two basepair deletion (CT) at nucleotide 560 in DLX3 associated with the disease."
Maps and identifies the DLX3 homeodomain frameshift in an AIHHT family, supporting the gene binding for this subtype.
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Pathophysiology

7
Ameloblast Dysfunction and Defective Enamel Biomineralization
AI is fundamentally a disorder of the ameloblast, the ectoderm-derived epithelial cell that builds enamel. Enamel formation is a tightly staged biomineralization process in which ameloblasts first secrete an organic enamel matrix and then drive its mineralization. Mutations in the genes critical for this process disrupt ameloblast function and produce structurally and/or quantitatively abnormal enamel. The specific inherited dental phenotype maps onto the developmental stage at which the mutated gene is critically required.
Ameloblast CL:0000059 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Ameloblast (CL:0000059). CL:0000059 is a cell type from the Cell Ontology.
FAM83H hgnc:24797 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves FAM83H (hgnc:24797). hgnc:24797 is a gene from the HUGO Gene Nomenclature Committee.
Amelogenesis GO:0097186 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Amelogenesis (GO:0097186). GO:0097186 is a biological process from the Gene Ontology. ↓ DECREASED Biomineral tissue development GO:0031214 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal Biomineral tissue development (GO:0031214). GO:0031214 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Defective Enamel Matrix Secretion
Defective Enamel Matrix Processing and Maturation
iPSC-Derived Ameloblast Enamel-Formation Defect (Organoid Model) Human iPSC-derived ameloblast models recapitulate the same ameloblast enamel-formation defect represented by the upstream cellular mechanism.
Show evidence (3 references)
PMID:16304440 SUPPORT Human Clinical
"Dental enamel formation is a remarkable example of a biomineralization process."
Frames enamel formation as a biomineralization process whose disruption underlies AI.
PMID:17552940 SUPPORT Human Clinical
"The type of inherited dental malformations observed in a given kindred relate to when, during odontogenesis, the defective gene is critically expressed."
Establishes the central principle that the AI phenotype reflects the developmental stage of ameloblast function that the mutated gene disrupts.
PMID:33034243 SUPPORT Human Clinical
"The function of FAM83H remains obscure."
FAM83H is bound to this general ameloblast-dysfunction node rather than to one of the staged nodes below precisely because the step at which it acts is not established; this sentence is the source for leaving it unplaced.
Defective Enamel Matrix Secretion
During the secretory stage, ameloblasts deposit an enamel matrix rich in amelogenin (AMELX) and enamelin (ENAM) that templates the elongating enamel crystallites. Mutations in AMELX (X-linked) and ENAM (autosomal) impair matrix deposition, reducing enamel thickness and producing the hypoplastic AI phenotype.
Ameloblast CL:0000059 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Ameloblast (CL:0000059). CL:0000059 is a cell type from the Cell Ontology.
AMELX hgnc:461 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves AMELX (hgnc:461). hgnc:461 is a gene from the HUGO Gene Nomenclature Committee. ENAM hgnc:3344 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ENAM (hgnc:3344). hgnc:3344 is a gene from the HUGO Gene Nomenclature Committee. AMBN hgnc:452 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves AMBN (hgnc:452). hgnc:452 is a gene from the HUGO Gene Nomenclature Committee. ACP4 hgnc:14376 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ACP4 (hgnc:14376). hgnc:14376 is a gene from the HUGO Gene Nomenclature Committee. RELT hgnc:13764 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves RELT (hgnc:13764). hgnc:13764 is a gene from the HUGO Gene Nomenclature Committee.
Enamel mineralization GO:0070166 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Enamel mineralization (GO:0070166). GO:0070166 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Enamel Structural Failure
Enamel hypoplasia Secretory-stage matrix deposition failure reduces enamel thickness, producing hypoplastic enamel.
Show evidence (4 references)
PMID:16304440 SUPPORT Human Clinical
"Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
Links secretory-stage matrix protein genes AMELX and ENAM to AI.
PMID:31402633 SUPPORT BACKGROUND Other
"Ameloblastin (AMBN) is a secreted matrix protein that is critical for the formation of dental enamel and is enamel-specific with respect to its essential functions."
Places ameloblastin among the secreted enamel matrix proteins deposited at this step, which is why AMBN is bound here rather than to a processing node. Graded OTHER because the quoted sentence states established protein biology rather than a result of the citing study.
PMID:27843125 SUPPORT Model Organism
"Immunohistochemical analysis confirmed localization of ACPT in secretory-stage ameloblasts."
Localizes ACP4 (ACPT) protein to secretory-stage ameloblasts, supporting placement of ACP4 at this step of the cascade. The staining was performed on a developing molar from 8-day-old mice, so this is animal rather than human or cell-culture evidence.
+ 1 more reference
Defective Enamel Matrix Processing and Maturation
During the maturation stage, the enamel proteases MMP20 (enamelysin) and KLK4 (kallikrein-4) progressively degrade and remove the enamel matrix, allowing crystallites to grow and the tissue to harden. Biallelic mutations in MMP20 and KLK4 impair matrix processing, leaving residual protein and soft, hypomineralized/hypomature enamel.
Ameloblast CL:0000059 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Ameloblast (CL:0000059). CL:0000059 is a cell type from the Cell Ontology.
MMP20 hgnc:7167 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves MMP20 (hgnc:7167). hgnc:7167 is a gene from the HUGO Gene Nomenclature Committee. KLK4 hgnc:6365 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves KLK4 (hgnc:6365). hgnc:6365 is a gene from the HUGO Gene Nomenclature Committee. WDR72 hgnc:26790 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves WDR72 (hgnc:26790). hgnc:26790 is a gene from the HUGO Gene Nomenclature Committee. ODAPH hgnc:26300 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ODAPH (hgnc:26300). hgnc:26300 is a gene from the HUGO Gene Nomenclature Committee.
Enamel mineralization GO:0070166 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Enamel mineralization (GO:0070166). GO:0070166 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Enamel Structural Failure
Enamel hypomineralization Defective matrix processing and maturation leave enamel under-mineralized and structurally weak.
Show evidence (3 references)
PMID:17552940 SUPPORT Human Clinical
"Genes expressed by odontoblasts (COL1A1, COL1A2, and DSPP), and ameloblasts (AMELX, ENAM, MMP20, and KLK4) during the crown formation stage, are associated with dentinogenesis imperfecta, dentin dysplasia, and amelogenesis imperfecta."
Identifies the ameloblast-expressed processing genes MMP20 and KLK4 as AI genes acting during crown formation.
PMID:30779877 SUPPORT Human Clinical
"The defective enamel is normal in thickness, severely hypomineralized, orange-brown stained, and susceptible to attrition."
The normal-thickness, severely hypomineralized enamel of WDR72 defects is a maturation-stage rather than secretory-stage failure, which is why WDR72 is bound to this node.
PMID:38303846 SUPPORT BACKGROUND Model Organism
"It was demonstrated that Odaph is expressed by the ameloblasts at the onset of post-secretory transition in mouse mandibular incisors."
Places ODAPH's expression at the onset of the post-secretory transition, which is the step this node covers. The earlier phrasing of this item quoted the human enamel phenotype instead, which argues for hypoplasia or hypocalcification rather than for a maturation-stage placement. Mouse data.
Transcriptional Control of Ameloblast Differentiation
Before any enamel matrix is laid down, the inner enamel epithelium must proliferate and differentiate into secretory ameloblasts. Two AI genes encode the transcription factors that drive this step rather than any structural or enzymatic component of enamel: SP6, whose first zinc finger is altered in autosomal dominant hypoplastic AI, and DLX3, whose DNA-binding homeodomain is truncated in AI with taurodontism. A lesion here is upstream of every matrix and processing defect below.
Ameloblast CL:0000059 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Ameloblast (CL:0000059). CL:0000059 is a cell type from the Cell Ontology.
SP6 hgnc:14530 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves SP6 (hgnc:14530). hgnc:14530 is a gene from the HUGO Gene Nomenclature Committee. DLX3 hgnc:2916 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves DLX3 (hgnc:2916). hgnc:2916 is a gene from the HUGO Gene Nomenclature Committee.
Ameloblast differentiation GO:0036305 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Ameloblast differentiation (GO:0036305). GO:0036305 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Ameloblast Dysfunction and Defective Enamel Biomineralization Failure to produce a competent secretory ameloblast population is one route into the general ameloblast dysfunction that underlies every form of AI.
Show evidence (3 references)
PMID:32167558 SUPPORT BACKGROUND Other
"SP6 has been shown to be crucial to both proliferation of the IEE and to its differentiation into ameloblasts."
States the step SP6 acts at: proliferation of the inner enamel epithelium and its differentiation into ameloblasts, which is what this node models.
PMID:32167558 SUPPORT In Vitro
"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."
Surface plasmon resonance binding data showing the AI-associated SP6 variant binds a promoter of an enamel matrix gene less well than wild type, which is the transcriptional lesion this node asserts.
PMID:15666299 SUPPORT Human Clinical
"This mutation causes a frameshift altering the last two amino acids of the DNA-binding homeodomain introducing a premature stop codon truncating the protein by 88 amino acids."
Places the AI-causing DLX3 lesion in the DNA-binding homeodomain, supporting DLX3's membership of this transcriptional-control node.
Defective Ameloblast Cell-Matrix Adhesion
Amelogenesis also depends on the ameloblast staying correctly attached to the matrix it is building. In mouse, ITGB6 localizes to the distal membrane of differentiating ameloblasts and is expressed most strongly by maturation-stage ameloblasts; in humans its loss causes generalized hypoplastic AI. LAMB3, a subunit of the laminin 332 complex, is grouped here on the same axis, although the specific ameloblast-matrix step it disrupts is proposed rather than demonstrated.
Ameloblast CL:0000059 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Ameloblast (CL:0000059). CL:0000059 is a cell type from the Cell Ontology.
ITGB6 hgnc:6161 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ITGB6 (hgnc:6161). hgnc:6161 is a gene from the HUGO Gene Nomenclature Committee. LAMB3 hgnc:6490 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves LAMB3 (hgnc:6490). hgnc:6490 is a gene from the HUGO Gene Nomenclature Committee.
Cell-matrix adhesion GO:0007160 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Cell-matrix adhesion (GO:0007160). GO:0007160 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Enamel Structural Failure
Enamel hypoplasia Both genes bound to this node present clinically as hypoplastic, thin enamel.
Show evidence (4 references)
PMID:24305999 SUPPORT Human Clinical
"Our findings demonstrate that early and late amelogenesis depend upon cell-matrix interactions."
The authors' conclusion from human ITGB6 mutations plus ameloblast immunohistochemistry, and the core claim of this node.
PMID:24305999 SUPPORT Model Organism
"Immunohistochemistry of mouse mandibular incisors localized ITGB6 to the distal membrane of differentiating ameloblasts and pre-ameloblasts, and then ITGB6 appeared to be internalized by secretory stage ameloblasts."
Mouse localization data placing ITGB6 at the ameloblast-matrix interface during the stages this node covers.
PMID:24305999 SUPPORT Model Organism
"ITGB6 expression was strongest in the maturation stage and its localization was associated with ameloblast modulation."
Source for the statement that ITGB6 is expressed most strongly by maturation-stage ameloblasts.
+ 1 more reference
Defective Ameloblast Ion Transport and Enamel Matrix pH Regulation
Maturation-stage ameloblasts must move calcium into the enamel matrix and manage the pH swings that accompany hydroxyapatite deposition. Two AI genes act on this axis rather than on matrix protein or its proteolysis: SLC24A4, whose function in calcium transport is crucial at the maturation stage, and GPR68, a proton-sensing G-protein-coupled receptor tuned to the pH range the maturing matrix passes through.
Ameloblast CL:0000059 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Ameloblast (CL:0000059). CL:0000059 is a cell type from the Cell Ontology.
SLC24A4 hgnc:10978 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves SLC24A4 (hgnc:10978). hgnc:10978 is a gene from the HUGO Gene Nomenclature Committee. GPR68 hgnc:4519 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves GPR68 (hgnc:4519). hgnc:4519 is a gene from the HUGO Gene Nomenclature Committee.
Calcium ion transmembrane transport GO:0070588 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Calcium ion transmembrane transport (GO:0070588). GO:0070588 is a biological process from the Gene Ontology. ↓ DECREASED Regulation of enamel matrix pH GO:0006885 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal Regulation of enamel matrix pH, annotated with regulation of pH (GO:0006885). GO:0006885 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Enamel Structural Failure
Enamel hypomineralization Both genes bound to this node present as hypomaturation AI, in which enamel of normal thickness fails to mineralize fully.
Show evidence (3 references)
PMID:27693231 SUPPORT BACKGROUND Other
"This process requires the intricate regulation of ion transport and controlled changes to the pH of the developing enamel matrix."
States the ion-transport and pH-regulation requirement of amelogenesis that this node represents.
PMID:27693231 SUPPORT Human Clinical
"GPR68 encodes a proton-sensing G-protein-coupled receptor with sensitivity in the pH range that occurs in the developing enamel matrix during amelogenesis."
Identifies GPR68's function as matrix pH sensing, the basis for binding it to this node rather than to a matrix or protease node.
PMID:24532815 SUPPORT Human Clinical
"This is the first report of exonal deletion in SLC24A4 providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis."
Names calcium transport at the maturation stage as SLC24A4's function, supporting its placement on this node.
Enamel Structural Failure
The proximate consequence of disrupted secretion, processing, or mineralization is enamel that is thin, soft, discolored, and/or rapidly worn. This is the structural phenotype underlying the clinical presentation of AI: hypoplastic, hypomature, or hypocalcified enamel with attendant sensitivity, attrition, and esthetic impairment.
Enamel mineralization GO:0070166 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Enamel mineralization (GO:0070166). GO:0070166 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Amelogenesis imperfecta The downstream structural enamel failure is the defining clinical dental phenotype of amelogenesis imperfecta.
Show evidence (1 reference)
PMID:16838342 SUPPORT Human Clinical
"The amelogenesis imperfectas (AIs) are a clinically and genetically diverse group of conditions that are caused by mutations in a variety of genes that are critical for normal enamel formation."
Frames the diverse AI phenotypes as the downstream result of disrupted normal enamel formation.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Amelogenesis Imperfecta Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

4
Amelogenesis imperfecta Dental HP:0000705 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Amelogenesis imperfecta (HP:0000705). HP:0000705 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:16838342 SUPPORT Human Clinical
"The amelogenesis imperfectas (AIs) are a clinically and genetically diverse group of conditions that are caused by mutations in a variety of genes that are critical for normal enamel formation."
Directly characterizes AI as a hereditary disorder of enamel formation.
Enamel hypoplasia Dental HP:0006297 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Enamel hypoplasia (HP:0006297). HP:0006297 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
The hypoplastic type corresponds to reduced enamel (enamel hypoplasia).
Enamel hypomineralization Dental HP:0006285 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Enamel hypomineralization (HP:0006285). HP:0006285 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39321764 SUPPORT Human Clinical
"AI phenotypes, whether hypoplastic or hypomineralised, entail mutations in genes, such as AMELX, ENAM, MMP20, KLK4, WDR72, FAM83H, C4ORF26, amelotin, GPR68, and ACPT."
Documents hypomineralized enamel as a core AI phenotype linked to the maturation/ mineralization genes.
iPSC-Derived Ameloblast Enamel-Formation Defect (Organoid Model) Cellular HP:0000705 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Defective iPSC-derived ameloblast enamel formation, annotated with Amelogenesis imperfecta (HP:0000705). HP:0000705 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37582367 SUPPORT In Vitro
"We furthermore develop a disease model of amelogenesis imperfecta in a three-dimensional (3D) organoid system and show AM maturation to mineralized structure in vivo."
A 3D organoid system serves as an in vitro disease model of AI, recapitulating defective ameloblast-driven enamel formation in human cells.
PMID:37582367 SUPPORT In Vitro
"We identify key signaling pathways involved between the support cells and ameloblasts during fetal development and recapitulate those findings in human ameloblast in vitro differentiation from induced pluripotent stem cells (iPSCs). We furthermore develop a disease model of amelogenesis..."
Confirms that human ameloblast differentiation is modeled in vitro from iPSCs, the basis for the AI organoid disease model.
🧬

Genetic Associations

17
AMELX (Causative)
Gene: AMELX hgnc:461 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is AMELX (hgnc:461). hgnc:461 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:16304440 SUPPORT Human Clinical
"Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
Identifies AMELX as the X-linked AI gene.
ENAM (Causative)
Gene: ENAM hgnc:3344 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is ENAM (hgnc:3344). hgnc:3344 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:16304440 SUPPORT Human Clinical
"Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
Identifies ENAM as the cause of autosomal-inherited AI.
MMP20 (Causative)
Gene: MMP20 hgnc:7167 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is MMP20 (hgnc:7167). hgnc:7167 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:16838342 SUPPORT Human Clinical
"To date, mutations have been identified in four genes (AMELX, ENAM, KLK4, MMP20) known to be involved in enamel formation."
Identifies MMP20 as one of the established AI genes.
KLK4 (Causative)
Gene: KLK4 hgnc:6365 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is KLK4 (hgnc:6365). hgnc:6365 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:16838342 SUPPORT Human Clinical
"To date, mutations have been identified in four genes (AMELX, ENAM, KLK4, MMP20) known to be involved in enamel formation."
Identifies KLK4 as one of the established AI genes.
FAM83H (Causative)
Gene: FAM83H hgnc:24797 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is FAM83H (hgnc:24797). hgnc:24797 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"These disorders are considered clinically and genetically heterogeneous in etiology, involving a variety of genes, such as AMELX, ENAM, DLX3, FAM83H, MMP-20, KLK4, and WDR72."
Lists FAM83H among the established AI genes.
WDR72 (Causative)
Gene: WDR72 hgnc:26790 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is WDR72 (hgnc:26790). hgnc:26790 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"These disorders are considered clinically and genetically heterogeneous in etiology, involving a variety of genes, such as AMELX, ENAM, DLX3, FAM83H, MMP-20, KLK4, and WDR72."
Lists WDR72 among the established AI genes.
LAMB3 (Causative)
Gene: LAMB3 hgnc:6490 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is LAMB3 (hgnc:6490). hgnc:6490 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:30905256 SUPPORT Human Clinical
"We identified 2 families segregating autosomal dominant AI with variable degrees of a distinctive hypoplastic phenotype due to pathogenic variants in LAMB3."
Establishes dominant hypoplastic AI as the LAMB3-only phenotype.
PMID:30905256 SUPPORT BACKGROUND Human Clinical
"In contrast, biallelic loss-of-function variants in LAMB3 cause recessive junctional epidermolysis bullosa, characterized by life-threatening skin fragility."
Source for the statement that biallelic LAMB3 loss gives a different, and syndromic, disease rather than more severe AI.
AMBN (Causative)
Gene: AMBN hgnc:452 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is AMBN (hgnc:452). hgnc:452 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:31402633 SUPPORT Human Clinical
"Biallelic AMBN defects cause non-syndromic autosomal recessive amelogenesis imperfecta."
States the AMBN gene-disease relationship and its recessive mode.
FAM20A (Causative)
Gene: FAM20A hgnc:23015 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is FAM20A (hgnc:23015). hgnc:23015 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:40089179 SUPPORT Human Clinical
"This autosomal recessive condition, caused by pathogenic variants in the FAM20A gene, is linked to ectopic mineralisation in tissues such as dental pulp, follicles, gingiva, and kidneys."
Establishes FAM20A causation and the extra-enamel tissues involved.
ITGB6 (Causative)
Gene: ITGB6 hgnc:6161 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is ITGB6 (hgnc:6161). hgnc:6161 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:24305999 SUPPORT Human Clinical
"These are the first disease-causing ITGB6 mutations to be reported."
Marks this report as the origin of the ITGB6 gene-disease relationship.
ACP4 (Causative)
Gene: ACP4 hgnc:14376 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is ACP4 (hgnc:14376). hgnc:14376 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:27843125 SUPPORT Human Clinical
"In this study, we identified ACPT (testicular acid phosphatase) biallelic mutations causing non-syndromic, generalized hypoplastic autosomal-recessive amelogenesis imperfecta (AI) in individuals from six apparently unrelated Turkish families."
Establishes the recessive ACP4/ACPT gene-disease relationship.
SP6 (Causative)
Gene: SP6 hgnc:14530 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SP6 (hgnc:14530). hgnc:14530 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:32167558 SUPPORT Human Clinical
"The resulting missense protein change, p.(Ala273Lys), is predicted to alter a DNA-binding residue in the first of three zinc fingers."
Locates the AI-associated SP6 change in a DNA-binding residue, the basis for treating SP6 as a transcriptional lesion.
ODAPH (Causative)
Gene: ODAPH hgnc:26300 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is ODAPH (hgnc:26300). hgnc:26300 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:38303846 SUPPORT Human Clinical
"A novel homozygous ODAPH (previously designated C4orf26) mutation of single-nucleotide deletion (NG_032974.1:g.5103del, NM_178497.5:c.67+1del) was identified to be disease-causing."
Establishes the ODAPH gene-disease relationship and the previous symbol.
SLC24A4 (Causative)
Gene: SLC24A4 hgnc:10978 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SLC24A4 (hgnc:10978). hgnc:10978 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:24532815 SUPPORT Human Clinical
"This is the first report of exonal deletion in SLC24A4 providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis."
Confirms the gene-disease relationship and the calcium-transport function.
GPR68 (Causative)
Gene: GPR68 hgnc:4519 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is GPR68 (hgnc:4519). hgnc:4519 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:27693231 SUPPORT Human Clinical
"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."
Establishes biallelic GPR68 variants as a cause of AI.
RELT (Causative)
Gene: RELT hgnc:13764 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is RELT (hgnc:13764). hgnc:13764 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:30506946 SUPPORT Human Clinical
"We characterized three consanguineous AI families with generalized irregular hypoplastic enamel with rapid attrition that perfectly segregated with homozygous defects in a novel gene: RELT that is a member of the tumor necrosis factor receptor superfamily (TNFRSF)."
Establishes RELT as a recessive AI gene in three consanguineous families.
DLX3 (Causative)
Gene: DLX3 hgnc:2916 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is DLX3 (hgnc:2916). hgnc:2916 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:15666299 SUPPORT Human Clinical
"In this study, we mapped an AIHHT family to human chromosome 17 q21-q22 (lod score 3.3) and identify a two basepair deletion (CT) at nucleotide 560 in DLX3 associated with the disease."
Maps and identifies the causal DLX3 homeodomain frameshift.
PMID:15666299 SUPPORT BACKGROUND Human Clinical
"This is the first report of a mutation within the homeodomain of DLX3."
Source for contrasting the homeodomain AIHHT allele with the previously reported non-homeodomain tricho-dento-osseous allele.
💊

Medical Actions

2
Restorative and Prosthetic Rehabilitation
Action: dental restorationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is dental restoration, annotated with Dental Procedure (NCIT:C38052). NCIT:C38052 is a clinical intervention from the NCI Thesaurus. Ontology label: Dental Procedure NCIT:C38052
Full-coverage crowns, composite restorations, overlays, and prosthetic rehabilitation restore function, protect remaining enamel/dentin, reduce sensitivity, and improve esthetics in AI.
Genetic Counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Genetic counseling addresses the X-linked, autosomal dominant, and autosomal recessive inheritance patterns and recurrence risk for affected families.
Show evidence (1 reference)
PMID:21127961 SUPPORT Human Clinical
"Autosomal dominant, recessive, and X-linked types have been previously described."
The Mendelian inheritance of AI supports genetic counseling for affected families.
📊

Related Datasets

1
Single-cell census of human tooth development enables generation of human enamel. PMID:37582367
Single-cell (sci-RNA-seq) atlas of human tooth development with iPSC-derived ameloblast differentiation and a 3D organoid disease model of amelogenesis imperfecta.
human SINGLE CELL RNA SEQ
PMID:37582367
{ }

Source YAML

click to show 
name: Amelogenesis Imperfecta
creation_date: "2026-06-17T00:00:00Z"
category: Mendelian
disease_term:
  preferred_term: amelogenesis imperfecta
  term:
    id: MONDO:0019507
    label: amelogenesis imperfecta
parents:
- Ectodermal Dysplasia
- Oral Cavity Disease
synonyms:
- AI
- Hereditary enamel dysplasia
- Amelogenesis imperfecta, hereditary

description: >
  Amelogenesis imperfecta (AI) is a clinically and genetically heterogeneous group of
  inherited disorders of tooth enamel formation, in which the enamel is abnormal in
  quantity, structure, and/or mineral content in the absence of a generalized systemic
  disorder. Enamel is the most highly mineralized tissue in the body and is produced by
  ameloblasts, epithelial cells of ectodermal origin that secrete a protein-rich enamel
  matrix (amelogenin, enamelin, ameloblastin) and then orchestrate its proteolytic
  processing and progressive mineralization during the secretory and maturation stages of
  amelogenesis. AI arises when mutations disrupt the genes encoding these matrix proteins
  (AMELX, ENAM) or the proteases that process them (MMP20, KLK4), or other regulators of
  the secretory/maturation program (FAM83H, WDR72, DLX3 and others). Because the dental
  phenotype reflects which stage of amelogenesis is disrupted, AI is conventionally
  classified into hypoplastic (reduced enamel thickness, a secretory-stage quantitative
  defect), hypomaturation (normal-thickness but soft, mottled enamel from defective
  maturation), and hypocalcified/hypomineralized (poorly mineralized, rapidly attriting
  enamel) types, with X-linked, autosomal dominant, and autosomal recessive inheritance.
  AI is mechanistically and clinically distinct from acquired developmental defects of
  enamel such as dental fluorosis (excess fluoride) and from molar-incisor hypomineralization.

inheritance:
- name: X-linked inheritance
  inheritance_term:
    preferred_term: X-linked inheritance
    term:
      id: HP:0001417
      label: X-linked inheritance
  description: >
    AMELX (amelogenin) is located on the X chromosome; mutations cause X-linked AI, with
    males more severely and uniformly affected than heterozygous females.
  evidence:
  - reference: PMID:16304440
    reference_title: "Genes and related proteins involved in amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
    explanation: >
      Establishes the X-linked inheritance of AMELX-related AI versus autosomal
      inheritance of ENAM-related AI.
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >
    Autosomal dominant AI is caused by mutations in genes such as ENAM and FAM83H.
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autosomal dominant, recessive, and X-linked types have been previously described."
    explanation: >
      Documents the full range of Mendelian inheritance patterns described for AI.
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >
    Autosomal recessive AI is caused by biallelic mutations in genes such as MMP20, KLK4,
    and WDR72, which mediate enamel matrix processing and maturation.
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autosomal dominant, recessive, and X-linked types have been previously described."
    explanation: >
      Documents autosomal recessive inheritance as one of the established AI patterns.

has_subtypes:
- name: Hypoplastic
  display_name: Hypoplastic AI (secretory-stage quantitative defect)
  description: >
    Reduced enamel thickness due to a defect during the secretory stage of amelogenesis,
    when the enamel matrix is laid down. Classically associated with AMELX and ENAM
    mutations.
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
    explanation: >
      Defines the hypoplastic type as a defect in a specific stage of enamel synthesis.
- name: Hypomaturation
  display_name: Hypomaturation AI (maturation-stage defect)
  description: >
    Enamel of relatively normal thickness but soft and mottled, due to defective
    maturation-stage processing of the enamel matrix. Classically associated with MMP20
    and KLK4 protease mutations.
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
    explanation: >
      Defines the hypomature type as a maturation-stage defect of enamel synthesis.
- name: Hypocalcified
  display_name: Hypocalcified AI (mineralization defect)
  description: >
    Enamel of normal thickness but poorly mineralized, soft, and rapidly lost to
    attrition. FAM83H mutations are a common cause of autosomal dominant hypocalcified AI.
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
    explanation: >
      Defines the hypocalcified type as a defect in the enamel synthesis process.

# Gene-defined subtypes. The three rows above classify AI on the Witkop
# phenotype axis (which stage of amelogenesis is disrupted); the rows below
# classify it on the genetic axis, one row per MONDO/OMIM gene-defined type.
# The two axes are orthogonal and deliberately coexist in this list: each
# gene-defined row states in its description which Witkop class it presents as.
- name: AI1A
  display_name: AI type 1A (LAMB3, autosomal dominant hypoplastic)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 1A
    term:
      id: MONDO:0007094
      label: amelogenesis imperfecta type 1A
  genes:
  - preferred_term: LAMB3
    term:
      id: hgnc:6490
      label: LAMB3
  description: >
    Autosomal dominant hypoplastic AI caused by heterozygous LAMB3 variants that
    truncate the laminin beta-3 chain near its C-terminus. Biallelic loss of
    LAMB3 instead causes junctional epidermolysis bullosa, so the AI-only
    phenotype is allele- and dose-specific rather than a simple null.
  evidence:
  - reference: PMID:30905256
    reference_title: "Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified 2 families segregating autosomal dominant AI with variable degrees of a distinctive hypoplastic phenotype due to pathogenic variants in LAMB3."
    explanation: >
      Establishes dominantly inherited hypoplastic AI as the LAMB3 phenotype in
      two families, which is the concept MONDO:0007094 denotes.
  - reference: PMID:30905256
    reference_title: "Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "In contrast, biallelic loss-of-function variants in LAMB3 cause recessive junctional epidermolysis bullosa, characterized by life-threatening skin fragility."
    explanation: >
      Source for the contrast with junctional epidermolysis bullosa drawn in this
      subtype's description.
- name: AI1B
  display_name: AI type 1B (ENAM, autosomal dominant localized hypoplastic)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 1B
    term:
      id: MONDO:0007092
      label: amelogenesis imperfecta type 1B
  genes:
  - preferred_term: ENAM
    term:
      id: hgnc:3344
      label: ENAM
  description: >
    The dominant, heterozygous end of the ENAM allelic series: carriers of a
    single ENAM insertion or nonsense allele show localized enamel pitting or
    local hypoplastic AI. MONDO carries "hereditary localised enamel hypoplasia"
    as a synonym of this term, matching that phenotype.
  evidence:
  - reference: PMID:16246937
    reference_title: "Phenotype of ENAM mutations is dosage-dependent."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A novel nonsense mutation (g.12663C>A; p.S246X) was identified in one family segregating local hypoplastic AI as a dominant trait."
    explanation: >
      Documents the dominant, localized hypoplastic ENAM phenotype that
      distinguishes AI1B from the recessive generalized form (AI1C).
- name: AI1C
  display_name: AI type 1C (ENAM, autosomal recessive generalized hypoplastic)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 1C
    term:
      id: MONDO:0008770
      label: amelogenesis imperfecta type 1C
  genes:
  - preferred_term: ENAM
    term:
      id: hgnc:3344
      label: ENAM
  description: >
    The recessive end of the same ENAM allelic series: biallelic ENAM defects
    produce generalized hypoplastic AI with a class II open-bite malocclusion.
    AI1B and AI1C are one gene separated by dose, not two genes, which is why
    both MONDO terms list ENAM.
  evidence:
  - reference: PMID:14684688
    reference_title: "Novel ENAM mutation responsible for autosomal recessive amelogenesis imperfecta and localised enamel defects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The phenotype associated with the g.13185_13186insAG ENAM mutation is dose dependent such that ARAI with openbite malocclusion segregates as a recessive trait, and enamel pitting as a dominant trait."
    explanation: >
      States the dose dependence directly, supporting the split of the ENAM
      allelic series into a recessive generalized type and a dominant localized one.
- name: AI1E
  display_name: AI type 1E (AMELX, X-linked)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 1E
    term:
      id: MONDO:0010521
      label: amelogenesis imperfecta type 1E
  genes:
  - preferred_term: AMELX
    term:
      id: hgnc:461
      label: AMELX
  description: >
    X-linked AI from AMELX variants. The enamel defect is not purely
    quantitative: reported phenotypes span thin poorly mineralized enamel with a
    "snow-capped" appearance through to severe hypoplasia, which is why Witkop
    assigned AMELX cases to types IE, IIB and IIC.
  review_notes: >
    MONDO parents this type-1-labelled term under MONDO:0015048 "amelogenesis
    imperfecta type 2" rather than under MONDO:0015047 "amelogenesis imperfecta
    type 1" (checked at the OLS MONDO endpoint, 2026-09-23). The binding is still
    correct — the term is xref'd to OMIM:301200, the X-linked AMELX phenotype —
    but the parentage is internally inconsistent with the label. Reported for an
    upstream decision rather than worked around here.
  evidence:
  - reference: PMID:38892321
    reference_title: "AMELX Mutations and Genotype-Phenotype Correlation in X-Linked Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AMELX mutations cause X-linked amelogenesis imperfecta (AI), known as AI types IE, IIB, and IIC in Witkop's classification, characterized by hypoplastic (reduced thickness) and/or hypomaturation (reduced hardness) enamel defects."
    explanation: >
      Names AMELX as the X-linked AI gene and places type IE within its
      phenotypic range, supporting both the gene binding and the mixed
      hypoplastic/hypomaturation description.
  - reference: PMID:38892321
    reference_title: "AMELX Mutations and Genotype-Phenotype Correlation in X-Linked Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The affected individuals exhibited enamel malformations, ranging from thin, poorly mineralized enamel with a \"snow-capped\" appearance to severe hypoplastic defects with minimal enamel."
    explanation: >
      Source for the phenotypic range, including the snow-capped appearance,
      described for this subtype.
- name: AI1F
  display_name: AI type 1F (AMBN, autosomal recessive hypoplastic)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 1F
    term:
      id: MONDO:0014560
      label: amelogenesis imperfecta type 1F
  genes:
  - preferred_term: AMBN
    term:
      id: hgnc:452
      label: AMBN
  description: >
    Autosomal recessive hypoplastic AI from biallelic ameloblastin defects.
    Ameloblastin is a secreted enamel matrix protein whose essential functions
    are enamel-specific, so the phenotype is confined to the dentition.
  evidence:
  - reference: PMID:31402633
    reference_title: "AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biallelic AMBN defects cause non-syndromic autosomal recessive amelogenesis imperfecta."
    explanation: >
      States the gene-disease relationship and the recessive, non-syndromic mode
      that MONDO:0014560 denotes.
  - reference: PMID:31402633
    reference_title: "AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "Ameloblastin (AMBN) is a secreted matrix protein that is critical for the formation of dental enamel and is enamel-specific with respect to its essential functions."
    explanation: >
      Source for the description of ameloblastin as a secreted, enamel-specific
      matrix protein.
- name: AI1G
  display_name: AI type 1G / enamel renal syndrome (FAM20A, autosomal recessive)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 1G
    term:
      id: MONDO:0008771
      label: amelogenesis imperfecta type 1G
  genes:
  - preferred_term: FAM20A
    term:
      id: hgnc:23015
      label: FAM20A
  description: >
    Biallelic FAM20A variants cause enamel renal syndrome, which OMIM and MONDO
    number as amelogenesis imperfecta type 1G. Unlike the other rows here it is
    syndromic: ectopic mineralization extends beyond enamel to dental pulp,
    follicle and gingiva, and to the kidney as nephrocalcinosis.
  review_notes: >
    Kept as a subtype row because OMIM and MONDO both file this concept as an
    amelogenesis imperfecta type, but flagged as the one syndromic member of the
    list. Its renal and gingival manifestations exceed the non-syndromic scope
    this entry's description states, and a separate Enamel_Renal_Syndrome Disease
    entry is the likely future split. No such entry or stub exists today
    (checked kb/disorders/ and stubs/ for enamel/renal/FAM20A, 2026-09-23).
  evidence:
  - reference: PMID:40089179
    reference_title: "The craniofacial, dental and systemic manifestations of Enamel Renal Syndrome: A Scoping review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This autosomal recessive condition, caused by pathogenic variants in the FAM20A gene, is linked to ectopic mineralisation in tissues such as dental pulp, follicles, gingiva, and kidneys."
    explanation: >
      Establishes FAM20A as the cause and records the extra-enamel involvement
      that makes this subtype syndromic.
- name: AI1H
  display_name: AI type 1H (ITGB6, autosomal recessive hypoplastic)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 1H
    term:
      id: MONDO:0014540
      label: amelogenesis imperfecta type 1H
  genes:
  - preferred_term: ITGB6
    term:
      id: hgnc:6161
      label: ITGB6
  description: >
    Autosomal recessive generalized hypoplastic AI from loss-of-function variants
    in the integrin beta-6 subunit, which in mouse localizes to the distal membrane
    of differentiating ameloblasts. The lesion is in ameloblast attachment to its own
    matrix rather than in a matrix protein or protease.
  evidence:
  - reference: PMID:24305999
    reference_title: "ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We recruited two Hispanic families with generalized hypoplastic amelogenesis imperfecta (AI). Analysis of whole-exome sequences identified three integrin beta 6 (ITGB6) mutations responsible for their enamel malformations."
    explanation: >
      First report of disease-causing ITGB6 mutations, in generalized hypoplastic
      AI, which is the concept MONDO:0014540 denotes.
  - reference: PMID:24305999
    reference_title: "ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Immunohistochemistry of mouse mandibular incisors localized ITGB6 to the distal membrane of differentiating ameloblasts and pre-ameloblasts, and then ITGB6 appeared to be internalized by secretory stage ameloblasts."
    explanation: >
      Source for the distal-membrane localization stated in this subtype's
      description; the localization is mouse rather than human data.
- name: AI1J
  display_name: AI type 1J (ACP4, autosomal recessive hypoplastic)
  subtype_term:
    preferred_term: amelogenesis imperfecta, type 1J
    term:
      id: MONDO:0015008
      label: amelogenesis imperfecta, type 1J
  genes:
  - preferred_term: ACP4
    term:
      id: hgnc:14376
      label: ACP4
  description: >
    Autosomal recessive generalized hypoplastic AI from biallelic ACP4 variants.
    ACP4 is the acid phosphatase previously symbolized ACPT (testicular acid
    phosphatase); in mouse, it localizes to secretory-stage ameloblasts.
  evidence:
  - reference: PMID:27843125
    reference_title: "Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we identified ACPT (testicular acid phosphatase) biallelic mutations causing non-syndromic, generalized hypoplastic autosomal-recessive amelogenesis imperfecta (AI) in individuals from six apparently unrelated Turkish families."
    explanation: >
      Establishes the recessive ACP4/ACPT-AI relationship in six families.
  - reference: PMID:27843125
    reference_title: "Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Immunohistochemical analysis confirmed localization of ACPT in secretory-stage ameloblasts."
    explanation: >
      Source for the secretory-stage ameloblast localization stated above; the
      staining was performed on mouse molar tissue.
- name: AI1K
  display_name: AI type 1K (SP6, autosomal dominant hypoplastic)
  subtype_term:
    preferred_term: amelogenesis imperfecta, IIa 1K
    term:
      id: MONDO:0031084
      label: amelogenesis imperfecta, IIa 1K
  genes:
  - preferred_term: SP6
    term:
      id: hgnc:14530
      label: SP6
  description: >
    Autosomal dominant hypoplastic AI from a missense change in the first zinc
    finger of the SP6 transcription factor. The lesion is upstream of enamel
    matrix production: SP6 drives proliferation of the inner enamel epithelium
    and its differentiation into ameloblasts.
  review_notes: >
    MONDO's primary label for this term, "amelogenesis imperfecta, IIa 1K",
    mixes a type-II prefix with the AI1K designation; MONDO's own synonym list
    carries "amelogenesis imperfecta, hypoplastic IIa 1K" and "AI1K", and the
    cited study reports a hypoplastic (type I) phenotype. The short name here
    follows the AI1K synonym. Label copied verbatim from the OLS MONDO record.
  evidence:
  - reference: PMID:32167558
    reference_title: "A missense variant in specificity protein 6 (SP6) is associated with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: >
      Establishes SP6 as the gene and autosomal dominant hypoplastic AI as the
      phenotype.
- name: AI2A1
  display_name: AI type 2A1 (KLK4, autosomal recessive hypomaturation)
  subtype_term:
    preferred_term: amelogenesis imperfecta type 2A1
    term:
      id: MONDO:0008772
      label: amelogenesis imperfecta type 2A1
  genes:
  - preferred_term: KLK4
    term:
      id: hgnc:6365
      label: KLK4
  description: >
    Autosomal recessive hypomaturation AI from inactivating KLK4 variants.
    Kallikrein-4 is the maturation-stage protease that clears residual enamel
    matrix, so the enamel reaches normal thickness but stays soft and discolored.
  evidence:
  - reference: PMID:35207639
    reference_title: "Novel KLK4 Mutations Cause Hypomaturation Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These analyses revealed two novel homozygous mutations in the KLK4 gene: a nonsense mutation in exon 3 (NM_004917.4:c.170C>A, p.(Ser57*)) was found in families 1, 2 and 3 and a missense mutation in exon 6 (c.637T>C, p.(Cys213Arg)) in family 4."
    explanation: >
      Identifies biallelic inactivating KLK4 variants in four families recruited
      for hypomaturation AI.
  - reference: PMID:35207639
    reference_title: "Novel KLK4 Mutations Cause Hypomaturation Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Even though there are some overlapping phenotypes, hypomaturation AI enamel typically has a yellow to brown discoloration with a dull appearance but a normal thickness indicating a less mineralized enamel matrix."
    explanation: >
      Source for describing hypomaturation enamel as normal in thickness but soft
      and discolored.
- name: AI2A2
  display_name: AI type 2A2 (MMP20, autosomal recessive hypomaturation)
  subtype_term:
    preferred_term: amelogenesis imperfecta hypomaturation type 2A2
    term:
      id: MONDO:0012926
      label: amelogenesis imperfecta hypomaturation type 2A2
  genes:
  - preferred_term: MMP20
    term:
      id: hgnc:7167
      label: MMP20
  description: >
    Autosomal recessive hypomaturation AI from biallelic MMP20 variants. MMP20
    (enamelysin) is the protease that cleaves the developing extracellular enamel
    matrix, a step required for normal enamel crystal growth.
  evidence:
  - reference: PMID:33600052
    reference_title: "Spectrum of pathogenic variants and founder effects in amelogenesis imperfecta associated with MMP20."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MMP20 encodes a protease that cleaves the developing extracellular enamel matrix and is necessary for normal enamel crystal growth during amelogenesis."
    explanation: >
      States the protease function whose loss produces the hypomaturation
      phenotype of this subtype.
- name: AI2A3
  display_name: AI type 2A3 (WDR72, autosomal recessive hypomaturation)
  subtype_term:
    preferred_term: amelogenesis imperfecta hypomaturation type 2A3
    term:
      id: MONDO:0013181
      label: amelogenesis imperfecta hypomaturation type 2A3
  genes:
  - preferred_term: WDR72
    term:
      id: hgnc:26790
      label: WDR72
  description: >
    Autosomal recessive hypomaturation AI from biallelic WDR72 defects: enamel of
    normal thickness that is severely hypomineralized, orange-brown, and prone to
    attrition. Some affected individuals also have distal renal tubular acidosis,
    so a low serum pH is a recognized extra-dental finding in this subtype.
  evidence:
  - reference: PMID:30779877
    reference_title: "WDR72 Mutations Associated with Amelogenesis Imperfecta and Acidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Defects in WDR72 (WD repeat-containing protein 72; OMIM *613214) cause AI, type IIA3 (OMIM #613211), which follows an autosomal recessive pattern of inheritance."
    explanation: >
      Names the gene, the OMIM type IIA3 designation that MONDO:0013181 mirrors,
      and the recessive inheritance.
  - reference: PMID:30779877
    reference_title: "WDR72 Mutations Associated with Amelogenesis Imperfecta and Acidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Three of the affected patients showed decreased serum pH, consistent with a diagnosis of renal tubular acidosis."
    explanation: >
      Records the acidosis finding in a minority of affected individuals, which
      is why this subtype's description notes an extra-dental feature.
- name: AI2A4
  display_name: AI type 2A4 (ODAPH, autosomal recessive)
  subtype_term:
    preferred_term: amelogenesis imperfecta hypomaturation type 2A4
    term:
      id: MONDO:0013906
      label: amelogenesis imperfecta hypomaturation type 2A4
  genes:
  - preferred_term: ODAPH
    term:
      id: hgnc:26300
      label: ODAPH
  description: >
    Autosomal recessive AI from biallelic ODAPH defects. ODAPH was previously
    symbolized C4orf26; in mouse, Odaph is expressed by ameloblasts at the onset
    of the post-secretory transition. The reported human enamel phenotype is
    extensive post-eruptive failure and discoloration, which the authors classify
    as hypocalcified AI and explicitly not as the hypomaturation type this MONDO
    term is named for.
  review_notes: >
    Direct disagreement between MONDO and the cited report, recorded rather than
    resolved. MONDO:0013906 is labelled "amelogenesis imperfecta hypomaturation
    type 2A4"; the report cited below concludes that loss-of-function ODAPH
    mutations cause AI type IIIB, the hypocalcified autosomal recessive type,
    "rather than type IIA4". The term is still the right identifier for
    ODAPH-related AI and the label is copied verbatim from MONDO, but the type
    assignment inside that label is contradicted by the primary literature.
  evidence:
  - reference: PMID:38303846
    reference_title: "A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A novel homozygous ODAPH (previously designated C4orf26) mutation of single-nucleotide deletion (NG_032974.1:g.5103del, NM_178497.5:c.67+1del) was identified to be disease-causing."
    explanation: >
      Identifies a biallelic ODAPH mutation as the cause in a consanguineous
      family, and records the previous C4orf26 symbol.
  - reference: PMID:38303846
    reference_title: "A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The defective enamel of erupted teeth showed extensive post-eruptive failure and discoloration."
    explanation: >
      Source for the post-eruptive enamel failure described for this subtype.
  - reference: PMID:38303846
    reference_title: "A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Loss-of-function ODAPH mutations can cause AI type IIIB (the hypocalcified, autosomal recessive type), rather than type IIA4 (the hypomaturation, pigmented autosomal recessive type)."
    explanation: >
      Supports ODAPH as the causal gene, and is the source for this subtype's
      statement that the authors reject the type IIA4 (hypomaturation) label that
      MONDO:0013906 carries.
  - reference: PMID:38303846
    reference_title: "A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: BACKGROUND
    snippet: "It was demonstrated that Odaph is expressed by the ameloblasts at the onset of post-secretory transition in mouse mandibular incisors."
    explanation: >
      Source for the expression timing given in this subtype's description; the
      data are mouse rather than human.
- name: AI2A5
  display_name: AI type 2A5 (SLC24A4, autosomal recessive hypomaturation)
  subtype_term:
    preferred_term: amelogenesis imperfecta hypomaturation type 2A5
    term:
      id: MONDO:0014385
      label: amelogenesis imperfecta hypomaturation type 2A5
  genes:
  - preferred_term: SLC24A4
    term:
      id: hgnc:10978
      label: SLC24A4
  description: >
    Autosomal recessive hypomaturation AI from biallelic SLC24A4 defects. The
    function lost is calcium transport at the maturation stage, so this subtype's
    lesion is in calcium delivery to the maturing matrix rather than in a matrix
    protein or protease.
  evidence:
  - reference: PMID:24532815
    reference_title: "Exonal deletion of SLC24A4 causes hypomaturation amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first report of exonal deletion in SLC24A4 providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis."
    explanation: >
      Confirms the gene-disease relationship and names calcium transport at the
      maturation stage as the function lost.
- name: AI2A6
  display_name: AI type 2A6 (GPR68, autosomal recessive hypomaturation)
  subtype_term:
    preferred_term: amelogenesis imperfecta, hypomaturation type, IIa6
    term:
      id: MONDO:0014971
      label: amelogenesis imperfecta, hypomaturation type, IIa6
  genes:
  - preferred_term: GPR68
    term:
      id: hgnc:4519
      label: GPR68
  description: >
    Autosomal recessive hypomaturation AI from loss-of-function GPR68 variants.
    GPR68 is a proton-sensing G-protein-coupled receptor active over the pH range
    the enamel matrix passes through during maturation, so this subtype's lesion
    is in sensing matrix pH rather than in transporting an ion.
  evidence:
  - reference: PMID:27693231
    reference_title: "Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: >
      Establishes biallelic GPR68 variants as a cause of AI in three families.
- name: AI3A
  display_name: AI type 3A (FAM83H, autosomal dominant hypocalcified)
  subtype_term:
    preferred_term: amelogenesis imperfecta, type 3A
    term:
      id: MONDO:0007538
      label: amelogenesis imperfecta, type 3A
  genes:
  - preferred_term: FAM83H
    term:
      id: hgnc:24797
      label: FAM83H
  description: >
    Autosomal dominant hypocalcified AI. Only truncating FAM83H alleles cause it,
    and knockout and knock-in mouse models argue the mechanism is neomorphic
    rather than simple loss of function.
  review_notes: >
    HGNC has renamed this gene: hgnc:24797 is now symbolized SACK1H
    (scaffolding CK1 anchoring protein H), with FAM83H recorded as a previous
    symbol (rest.genenames.org, read 2026-09-23). The repository's
    cache/hgnc/terms.csv still carries FAM83H for hgnc:24797, so FAM83H is the
    label that validates here and is kept for consistency with the rest of the
    entry and the AI literature.
  evidence:
  - reference: PMID:33034243
    reference_title: "FAM83H and Autosomal Dominant Hypocalcified Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Truncation mutations in FAM83H (OMIM *611927) are hitherto the sole cause of ADHCAI."
    explanation: >
      States that only truncating FAM83H alleles cause autosomal dominant
      hypocalcified AI, the concept MONDO:0007538 denotes.
  - reference: PMID:33034243
    reference_title: "FAM83H and Autosomal Dominant Hypocalcified Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: REVIEW_SYNTHESIS
    snippet: "With human genetic studies, Fam83h knockout and mutation-knock-in mouse models indicated that FAM83H does not serve a critical physiologic function during enamel formation and suggested a neomorphic mutation mechanism causing ADHCAI."
    explanation: >
      Source for describing the FAM83H mechanism as neomorphic rather than
      loss-of-function. The claim rests on Fam83h knockout and knock-in mouse
      models, and this review is restating them rather than reporting them.
- name: AI3C
  display_name: AI type 3C (RELT, autosomal recessive)
  subtype_term:
    preferred_term: amelogenesis imperfecta, type 3C
    term:
      id: MONDO:0032717
      label: amelogenesis imperfecta, type 3C
  genes:
  - preferred_term: RELT
    term:
      id: hgnc:13764
      label: RELT
  description: >
    Autosomal recessive AI from homozygous RELT defects, reported as generalized
    irregular hypoplastic enamel that attrits rapidly. RELT is a tumor necrosis
    factor receptor superfamily member expressed by secretory-stage ameloblasts
    and by odontoblasts.
  review_notes: >
    MONDO parents this term under MONDO:0968955 "hypocalcified amelogenesis
    imperfecta", whereas the report cited here describes the enamel as
    generalized irregular hypoplastic with rapid attrition. The description
    follows the cited report; the binding follows MONDO's own term for AI3C.
  evidence:
  - reference: PMID:30506946
    reference_title: "Mutations in RELT cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We characterized three consanguineous AI families with generalized irregular hypoplastic enamel with rapid attrition that perfectly segregated with homozygous defects in a novel gene: RELT that is a member of the tumor necrosis factor receptor superfamily (TNFRSF)."
    explanation: >
      Establishes RELT as a recessive AI gene and describes the enamel phenotype
      quoted in this subtype's description.
  - reference: PMID:30506946
    reference_title: "Mutations in RELT cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "RNAscope in situ hybridization of wild-type mouse molars and incisors showed specific Relt mRNA expression by secretory stage ameloblasts and by odontoblasts."
    explanation: >
      Source for the expression statement in this subtype's description; the data
      are mouse rather than human.
- name: AIHHT
  display_name: Hypomaturation-hypoplastic AI with taurodontism (DLX3, autosomal dominant)
  subtype_term:
    preferred_term: hypomaturation-hypoplastic amelogenesis imperfecta with taurodontism
    term:
      id: MONDO:0007093
      label: hypomaturation-hypoplastic amelogenesis imperfecta with taurodontism
  genes:
  - preferred_term: DLX3
    term:
      id: hgnc:2916
      label: DLX3
  description: >
    Autosomal dominant AI combining hypomaturation and hypoplastic enamel defects
    with taurodont molars, caused by DLX3 homeodomain frameshifts. Like SP6, DLX3
    is a transcription factor, so the lesion precedes matrix production.
  review_notes: >
    MONDO:0007093 is also named in kb/disorders/Taurodontism.yaml, as a
    differential diagnosis of isolated taurodontism. That is a contrast, not a
    claim on the concept, so the two entries do not compete for the term.
  evidence:
  - reference: PMID:15666299
    reference_title: "DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we mapped an AIHHT family to human chromosome 17 q21-q22 (lod score 3.3) and identify a two basepair deletion (CT) at nucleotide 560 in DLX3 associated with the disease."
    explanation: >
      Maps and identifies the DLX3 homeodomain frameshift in an AIHHT family,
      supporting the gene binding for this subtype.

pathophysiology:
- name: Ameloblast Dysfunction and Defective Enamel Biomineralization
  description: >
    AI is fundamentally a disorder of the ameloblast, the ectoderm-derived epithelial cell
    that builds enamel. Enamel formation is a tightly staged biomineralization process in
    which ameloblasts first secrete an organic enamel matrix and then drive its
    mineralization. Mutations in the genes critical for this process disrupt ameloblast
    function and produce structurally and/or quantitatively abnormal enamel. The specific
    inherited dental phenotype maps onto the developmental stage at which the mutated gene
    is critically required.
  cell_types:
  - preferred_term: Ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  biological_processes:
  - preferred_term: Amelogenesis
    term:
      id: GO:0097186
      label: amelogenesis
    modifier: DECREASED
  - preferred_term: Biomineral tissue development
    term:
      id: GO:0031214
      label: biomineral tissue development
    modifier: ABNORMAL
  genes:
  - preferred_term: FAM83H
    term:
      id: hgnc:24797
      label: FAM83H
  downstream:
  - target: Defective Enamel Matrix Secretion
    causal_link_type: DIRECT
  - target: Defective Enamel Matrix Processing and Maturation
    causal_link_type: DIRECT
  - target: iPSC-Derived Ameloblast Enamel-Formation Defect (Organoid Model)
    causal_link_type: DIRECT
    description: >
      Human iPSC-derived ameloblast models recapitulate the same ameloblast
      enamel-formation defect represented by the upstream cellular mechanism.
  evidence:
  - reference: PMID:16304440
    reference_title: "Genes and related proteins involved in amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Dental enamel formation is a remarkable example of a biomineralization process."
    explanation: >
      Frames enamel formation as a biomineralization process whose disruption underlies AI.
  - reference: PMID:17552940
    reference_title: "Developmental biology and genetics of dental malformations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The type of inherited dental malformations observed in a given kindred relate to when, during odontogenesis, the defective gene is critically expressed."
    explanation: >
      Establishes the central principle that the AI phenotype reflects the developmental
      stage of ameloblast function that the mutated gene disrupts.
  - reference: PMID:33034243
    reference_title: "FAM83H and Autosomal Dominant Hypocalcified Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The function of FAM83H remains obscure."
    explanation: >
      FAM83H is bound to this general ameloblast-dysfunction node rather than to
      one of the staged nodes below precisely because the step at which it acts
      is not established; this sentence is the source for leaving it unplaced.

- name: Defective Enamel Matrix Secretion
  description: >
    During the secretory stage, ameloblasts deposit an enamel matrix rich in amelogenin
    (AMELX) and enamelin (ENAM) that templates the elongating enamel crystallites.
    Mutations in AMELX (X-linked) and ENAM (autosomal) impair matrix deposition, reducing
    enamel thickness and producing the hypoplastic AI phenotype.
  cell_types:
  - preferred_term: Ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  biological_processes:
  - preferred_term: Enamel mineralization
    term:
      id: GO:0070166
      label: enamel mineralization
    modifier: DECREASED
  genes:
  - preferred_term: AMELX
    term:
      id: hgnc:461
      label: AMELX
  - preferred_term: ENAM
    term:
      id: hgnc:3344
      label: ENAM
  - preferred_term: AMBN
    term:
      id: hgnc:452
      label: AMBN
  - preferred_term: ACP4
    term:
      id: hgnc:14376
      label: ACP4
  - preferred_term: RELT
    term:
      id: hgnc:13764
      label: RELT
  downstream:
  - target: Enamel Structural Failure
    causal_link_type: DIRECT
  - target: Enamel hypoplasia
    causal_link_type: DIRECT
    description: >
      Secretory-stage matrix deposition failure reduces enamel thickness,
      producing hypoplastic enamel.
  evidence:
  - reference: PMID:16304440
    reference_title: "Genes and related proteins involved in amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
    explanation: >
      Links secretory-stage matrix protein genes AMELX and ENAM to AI.
  - reference: PMID:31402633
    reference_title: "AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "Ameloblastin (AMBN) is a secreted matrix protein that is critical for the formation of dental enamel and is enamel-specific with respect to its essential functions."
    explanation: >
      Places ameloblastin among the secreted enamel matrix proteins deposited at
      this step, which is why AMBN is bound here rather than to a processing node.
      Graded OTHER because the quoted sentence states established protein biology
      rather than a result of the citing study.
  - reference: PMID:27843125
    reference_title: "Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Immunohistochemical analysis confirmed localization of ACPT in secretory-stage ameloblasts."
    explanation: >
      Localizes ACP4 (ACPT) protein to secretory-stage ameloblasts, supporting
      placement of ACP4 at this step of the cascade. The staining was performed on
      a developing molar from 8-day-old mice, so this is animal rather than human
      or cell-culture evidence.
  - reference: PMID:30506946
    reference_title: "Mutations in RELT cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "RNAscope in situ hybridization of wild-type mouse molars and incisors showed specific Relt mRNA expression by secretory stage ameloblasts and by odontoblasts."
    explanation: >
      Mouse expression data placing Relt in secretory-stage ameloblasts; this is
      the basis for binding RELT to the secretory node, and is model-organism
      rather than human evidence.

- name: Defective Enamel Matrix Processing and Maturation
  description: >
    During the maturation stage, the enamel proteases MMP20 (enamelysin) and KLK4
    (kallikrein-4) progressively degrade and remove the enamel matrix, allowing crystallites
    to grow and the tissue to harden. Biallelic mutations in MMP20 and KLK4 impair matrix
    processing, leaving residual protein and soft, hypomineralized/hypomature enamel.
  cell_types:
  - preferred_term: Ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  biological_processes:
  - preferred_term: Enamel mineralization
    term:
      id: GO:0070166
      label: enamel mineralization
    modifier: DECREASED
  genes:
  - preferred_term: MMP20
    term:
      id: hgnc:7167
      label: MMP20
  - preferred_term: KLK4
    term:
      id: hgnc:6365
      label: KLK4
  - preferred_term: WDR72
    term:
      id: hgnc:26790
      label: WDR72
  - preferred_term: ODAPH
    term:
      id: hgnc:26300
      label: ODAPH
  downstream:
  - target: Enamel Structural Failure
    causal_link_type: DIRECT
  - target: Enamel hypomineralization
    causal_link_type: DIRECT
    description: >
      Defective matrix processing and maturation leave enamel under-mineralized
      and structurally weak.
  evidence:
  - reference: PMID:17552940
    reference_title: "Developmental biology and genetics of dental malformations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genes expressed by odontoblasts (COL1A1, COL1A2, and DSPP), and ameloblasts (AMELX, ENAM, MMP20, and KLK4) during the crown formation stage, are associated with dentinogenesis imperfecta, dentin dysplasia, and amelogenesis imperfecta."
    explanation: >
      Identifies the ameloblast-expressed processing genes MMP20 and KLK4 as AI genes
      acting during crown formation.
  - reference: PMID:30779877
    reference_title: "WDR72 Mutations Associated with Amelogenesis Imperfecta and Acidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The defective enamel is normal in thickness, severely hypomineralized, orange-brown stained, and susceptible to attrition."
    explanation: >
      The normal-thickness, severely hypomineralized enamel of WDR72 defects is a
      maturation-stage rather than secretory-stage failure, which is why WDR72 is
      bound to this node.
  - reference: PMID:38303846
    reference_title: "A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: BACKGROUND
    snippet: "It was demonstrated that Odaph is expressed by the ameloblasts at the onset of post-secretory transition in mouse mandibular incisors."
    explanation: >
      Places ODAPH's expression at the onset of the post-secretory transition,
      which is the step this node covers. The earlier phrasing of this item quoted
      the human enamel phenotype instead, which argues for hypoplasia or
      hypocalcification rather than for a maturation-stage placement. Mouse data.

- name: Transcriptional Control of Ameloblast Differentiation
  description: >
    Before any enamel matrix is laid down, the inner enamel epithelium must
    proliferate and differentiate into secretory ameloblasts. Two AI genes encode
    the transcription factors that drive this step rather than any structural or
    enzymatic component of enamel: SP6, whose first zinc finger is altered in
    autosomal dominant hypoplastic AI, and DLX3, whose DNA-binding homeodomain is
    truncated in AI with taurodontism. A lesion here is upstream of every matrix
    and processing defect below.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  biological_processes:
  - preferred_term: Ameloblast differentiation
    term:
      id: GO:0036305
      label: ameloblast differentiation
    modifier: DECREASED
  downstream:
  - target: Ameloblast Dysfunction and Defective Enamel Biomineralization
    causal_link_type: DIRECT
    description: >
      Failure to produce a competent secretory ameloblast population is one route
      into the general ameloblast dysfunction that underlies every form of AI.
  genes:
  - preferred_term: SP6
    term:
      id: hgnc:14530
      label: SP6
  - preferred_term: DLX3
    term:
      id: hgnc:2916
      label: DLX3
  evidence:
  - reference: PMID:32167558
    reference_title: "A missense variant in specificity protein 6 (SP6) is associated with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "SP6 has been shown to be crucial to both proliferation of the IEE and to its differentiation into ameloblasts."
    explanation: >
      States the step SP6 acts at: proliferation of the inner enamel epithelium
      and its differentiation into ameloblasts, which is what this node models.
  - reference: PMID:32167558
    reference_title: "A missense variant in specificity protein 6 (SP6) is associated with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "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."
    explanation: >
      Surface plasmon resonance binding data showing the AI-associated SP6 variant
      binds a promoter of an enamel matrix gene less well than wild type, which is
      the transcriptional lesion this node asserts.
  - reference: PMID:15666299
    reference_title: "DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This mutation causes a frameshift altering the last two amino acids of the DNA-binding homeodomain introducing a premature stop codon truncating the protein by 88 amino acids."
    explanation: >
      Places the AI-causing DLX3 lesion in the DNA-binding homeodomain, supporting
      DLX3's membership of this transcriptional-control node.

- name: Defective Ameloblast Cell-Matrix Adhesion
  description: >
    Amelogenesis also depends on the ameloblast staying correctly attached to the
    matrix it is building. In mouse, ITGB6 localizes to the distal membrane of
    differentiating ameloblasts and is expressed most strongly by maturation-stage
    ameloblasts; in humans its loss causes generalized hypoplastic AI. LAMB3, a subunit of the
    laminin 332 complex, is grouped here on the same axis, although the specific
    ameloblast-matrix step it disrupts is proposed rather than demonstrated.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  biological_processes:
  - preferred_term: Cell-matrix adhesion
    term:
      id: GO:0007160
      label: cell-matrix adhesion
    modifier: DECREASED
  downstream:
  - target: Enamel Structural Failure
    causal_link_type: DIRECT
  - target: Enamel hypoplasia
    causal_link_type: DIRECT
    description: >
      Both genes bound to this node present clinically as hypoplastic, thin enamel.
  genes:
  - preferred_term: ITGB6
    term:
      id: hgnc:6161
      label: ITGB6
  - preferred_term: LAMB3
    term:
      id: hgnc:6490
      label: LAMB3
  evidence:
  - reference: PMID:24305999
    reference_title: "ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our findings demonstrate that early and late amelogenesis depend upon cell-matrix interactions."
    explanation: >
      The authors' conclusion from human ITGB6 mutations plus ameloblast
      immunohistochemistry, and the core claim of this node.
  - reference: PMID:24305999
    reference_title: "ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Immunohistochemistry of mouse mandibular incisors localized ITGB6 to the distal membrane of differentiating ameloblasts and pre-ameloblasts, and then ITGB6 appeared to be internalized by secretory stage ameloblasts."
    explanation: >
      Mouse localization data placing ITGB6 at the ameloblast-matrix interface
      during the stages this node covers.
  - reference: PMID:24305999
    reference_title: "ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "ITGB6 expression was strongest in the maturation stage and its localization was associated with ameloblast modulation."
    explanation: >
      Source for the statement that ITGB6 is expressed most strongly by
      maturation-stage ameloblasts.
  - reference: PMID:30905256
    reference_title: "Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "If mutant LAMB3 affects secretory ameloblast-matrix interactions, this may underlie the abnormal enamel architecture seen near the EDJ."
    explanation: >
      The authors advance an ameloblast-matrix mechanism for LAMB3 as a
      conditional hypothesis, not a demonstrated result; it is cited here as the
      stated basis for grouping LAMB3 on this node and graded INDIRECT for that
      reason.

- name: Defective Ameloblast Ion Transport and Enamel Matrix pH Regulation
  description: >
    Maturation-stage ameloblasts must move calcium into the enamel matrix and
    manage the pH swings that accompany hydroxyapatite deposition. Two AI genes
    act on this axis rather than on matrix protein or its proteolysis: SLC24A4,
    whose function in calcium transport is crucial at the maturation stage, and
    GPR68, a proton-sensing G-protein-coupled receptor tuned to the pH range the
    maturing matrix passes through.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  biological_processes:
  - preferred_term: Calcium ion transmembrane transport
    term:
      id: GO:0070588
      label: calcium ion transmembrane transport
    modifier: DECREASED
  - preferred_term: Regulation of enamel matrix pH
    term:
      id: GO:0006885
      label: regulation of pH
    modifier: ABNORMAL
  downstream:
  - target: Enamel Structural Failure
    causal_link_type: DIRECT
  - target: Enamel hypomineralization
    causal_link_type: DIRECT
    description: >
      Both genes bound to this node present as hypomaturation AI, in which enamel
      of normal thickness fails to mineralize fully.
  genes:
  - preferred_term: SLC24A4
    term:
      id: hgnc:10978
      label: SLC24A4
  - preferred_term: GPR68
    term:
      id: hgnc:4519
      label: GPR68
  evidence:
  - reference: PMID:27693231
    reference_title: "Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "This process requires the intricate regulation of ion transport and controlled changes to the pH of the developing enamel matrix."
    explanation: >
      States the ion-transport and pH-regulation requirement of amelogenesis that
      this node represents.
  - reference: PMID:27693231
    reference_title: "Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GPR68 encodes a proton-sensing G-protein-coupled receptor with sensitivity in the pH range that occurs in the developing enamel matrix during amelogenesis."
    explanation: >
      Identifies GPR68's function as matrix pH sensing, the basis for binding it
      to this node rather than to a matrix or protease node.
  - reference: PMID:24532815
    reference_title: "Exonal deletion of SLC24A4 causes hypomaturation amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first report of exonal deletion in SLC24A4 providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis."
    explanation: >
      Names calcium transport at the maturation stage as SLC24A4's function,
      supporting its placement on this node.

- name: Enamel Structural Failure
  description: >
    The proximate consequence of disrupted secretion, processing, or mineralization is
    enamel that is thin, soft, discolored, and/or rapidly worn. This is the structural
    phenotype underlying the clinical presentation of AI: hypoplastic, hypomature, or
    hypocalcified enamel with attendant sensitivity, attrition, and esthetic impairment.
  biological_processes:
  - preferred_term: Enamel mineralization
    term:
      id: GO:0070166
      label: enamel mineralization
    modifier: DECREASED
  downstream:
  - target: Amelogenesis imperfecta
    causal_link_type: DIRECT
    description: >
      The downstream structural enamel failure is the defining clinical dental
      phenotype of amelogenesis imperfecta.
  evidence:
  - reference: PMID:16838342
    reference_title: "The molecular etiologies and associated phenotypes of amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The amelogenesis imperfectas (AIs) are a clinically and genetically diverse group of conditions that are caused by mutations in a variety of genes that are critical for normal enamel formation."
    explanation: >
      Frames the diverse AI phenotypes as the downstream result of disrupted normal enamel
      formation.

phenotypes:
- category: Dental
  name: Amelogenesis imperfecta
  diagnostic: true
  description: >
    The defining phenotype: hereditary abnormal enamel formation affecting the primary
    and/or permanent dentition, encompassing hypoplastic, hypomature, and hypocalcified
    enamel.
  phenotype_term:
    preferred_term: Amelogenesis imperfecta
    term:
      id: HP:0000705
      label: Amelogenesis imperfecta
  evidence:
  - reference: PMID:16838342
    reference_title: "The molecular etiologies and associated phenotypes of amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The amelogenesis imperfectas (AIs) are a clinically and genetically diverse group of conditions that are caused by mutations in a variety of genes that are critical for normal enamel formation."
    explanation: >
      Directly characterizes AI as a hereditary disorder of enamel formation.

- category: Dental
  name: Enamel hypoplasia
  description: >
    Reduced thickness of enamel, the quantitative defect characteristic of secretory-stage
    (hypoplastic) AI caused by AMELX/ENAM mutations.
  phenotype_term:
    preferred_term: Enamel hypoplasia
    term:
      id: HP:0006297
      label: Enamel hypoplasia
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis."
    explanation: >
      The hypoplastic type corresponds to reduced enamel (enamel hypoplasia).

- category: Dental
  name: Enamel hypomineralization
  description: >
    Reduced mineral content of enamel, producing soft, discolored, attrition-prone enamel
    characteristic of hypomature and hypocalcified AI from MMP20/KLK4/FAM83H defects.
  phenotype_term:
    preferred_term: Enamel hypomineralization
    term:
      id: HP:0006285
      label: Enamel hypomineralization
  evidence:
  - reference: PMID:39321764
    reference_title: "Developmental Defects of Enamel."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AI phenotypes, whether hypoplastic or hypomineralised, entail mutations in genes, such as AMELX, ENAM, MMP20, KLK4, WDR72, FAM83H, C4ORF26, amelotin, GPR68, and ACPT."
    explanation: >
      Documents hypomineralized enamel as a core AI phenotype linked to the maturation/
      mineralization genes.

- category: Cellular
  name: iPSC-Derived Ameloblast Enamel-Formation Defect (Organoid Model)
  description: >
    A human induced pluripotent stem cell (iPSC)-derived ameloblast model reproduces the
    differentiation program of human ameloblasts and, in a three-dimensional organoid
    system, recapitulates amelogenesis imperfecta as a disease model — providing a
    human cellular platform for AI mechanism and regenerative studies. This organoid
    model is the cellular counterpart of the in vivo ameloblast dysfunction that drives AI.
  phenotype_term:
    preferred_term: Defective iPSC-derived ameloblast enamel formation
    term:
      id: HP:0000705
      label: Amelogenesis imperfecta
  evidence:
  - reference: PMID:37582367
    reference_title: "Single-cell census of human tooth development enables generation of human enamel."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We furthermore develop a disease model of amelogenesis imperfecta in a three-dimensional (3D) organoid system and show AM maturation to mineralized structure in vivo."
    explanation: >
      A 3D organoid system serves as an in vitro disease model of AI, recapitulating
      defective ameloblast-driven enamel formation in human cells.
  - reference: PMID:37582367
    reference_title: "Single-cell census of human tooth development enables generation of human enamel."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We identify key signaling pathways involved between the support cells and ameloblasts during
      fetal development and recapitulate those findings in human ameloblast in vitro differentiation
      from induced pluripotent stem cells (iPSCs). We furthermore develop a disease model of
      amelogenesis imperfecta in a three-dimensional (3D) organoid system and show AM maturation to
      mineralized structure in vivo.
    explanation: >
      Confirms that human ameloblast differentiation is modeled in vitro from iPSCs,
      the basis for the AI organoid disease model.

genetic:
- name: AMELX
  gene_term:
    preferred_term: AMELX
    term:
      id: hgnc:461
      label: AMELX
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1E
  notes: >
    Amelogenin, X-linked; the major secretory enamel matrix protein. Mutations cause
    X-linked AI, typically hypoplastic.
  evidence:
  - reference: PMID:16304440
    reference_title: "Genes and related proteins involved in amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
    explanation: >
      Identifies AMELX as the X-linked AI gene.
- name: ENAM
  gene_term:
    preferred_term: ENAM
    term:
      id: hgnc:3344
      label: ENAM
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1C
  notes: >
    ENAM spans two subtype rows because its phenotype is dose dependent: the
    biallelic, generalized hypoplastic form is AI1C, which this record is keyed
    to, and the heterozygous carrier phenotype of localized enamel pitting is
    AI1B. `subtype` is single-valued, so only the recessive row can be named here.
    Enamelin, the largest secretory enamel matrix protein; mutations cause
    autosomal-inherited (dominant and recessive) hypoplastic AI.
  evidence:
  - reference: PMID:16304440
    reference_title: "Genes and related proteins involved in amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta."
    explanation: >
      Identifies ENAM as the cause of autosomal-inherited AI.
- name: MMP20
  gene_term:
    preferred_term: MMP20
    term:
      id: hgnc:7167
      label: MMP20
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI2A2
  notes: >
    Enamelysin, a matrix metalloproteinase that cleaves the enamel matrix during the
    secretory/transition stages; biallelic mutations cause autosomal recessive
    hypomaturation AI.
  evidence:
  - reference: PMID:16838342
    reference_title: "The molecular etiologies and associated phenotypes of amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "To date, mutations have been identified in four genes (AMELX, ENAM, KLK4, MMP20) known to be involved in enamel formation."
    explanation: >
      Identifies MMP20 as one of the established AI genes.
- name: KLK4
  gene_term:
    preferred_term: KLK4
    term:
      id: hgnc:6365
      label: KLK4
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI2A1
  notes: >
    Kallikrein-4, the maturation-stage protease that degrades residual enamel matrix to
    allow full mineralization; biallelic mutations cause autosomal recessive
    hypomaturation AI.
  evidence:
  - reference: PMID:16838342
    reference_title: "The molecular etiologies and associated phenotypes of amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "To date, mutations have been identified in four genes (AMELX, ENAM, KLK4, MMP20) known to be involved in enamel formation."
    explanation: >
      Identifies KLK4 as one of the established AI genes.
- name: FAM83H
  gene_term:
    preferred_term: FAM83H
    term:
      id: hgnc:24797
      label: FAM83H
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI3A
  notes: >
    FAM83H mutations are a common cause of autosomal dominant hypocalcified AI.
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These disorders are considered clinically and genetically heterogeneous in etiology, involving a variety of genes, such as AMELX, ENAM, DLX3, FAM83H, MMP-20, KLK4, and WDR72."
    explanation: >
      Lists FAM83H among the established AI genes.
- name: WDR72
  gene_term:
    preferred_term: WDR72
    term:
      id: hgnc:26790
      label: WDR72
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI2A3
  notes: >
    WDR72 is required for maturation-stage ameloblast function; biallelic mutations cause
    autosomal recessive hypomaturation AI.
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These disorders are considered clinically and genetically heterogeneous in etiology, involving a variety of genes, such as AMELX, ENAM, DLX3, FAM83H, MMP-20, KLK4, and WDR72."
    explanation: >
      Lists WDR72 among the established AI genes.

- name: LAMB3
  gene_term:
    preferred_term: LAMB3
    term:
      id: hgnc:6490
      label: LAMB3
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1A
  notes: >
    Laminin subunit beta 3, part of the laminin 332 complex. Heterozygous
    C-terminal truncating alleles cause isolated dominant hypoplastic AI (AI1A),
    while biallelic loss of the same gene causes junctional epidermolysis
    bullosa, so AI is not simply the mild end of a single loss-of-function series.
  evidence:
  - reference: PMID:30905256
    reference_title: "Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified 2 families segregating autosomal dominant AI with variable degrees of a distinctive hypoplastic phenotype due to pathogenic variants in LAMB3."
    explanation: >
      Establishes dominant hypoplastic AI as the LAMB3-only phenotype.
  - reference: PMID:30905256
    reference_title: "Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "In contrast, biallelic loss-of-function variants in LAMB3 cause recessive junctional epidermolysis bullosa, characterized by life-threatening skin fragility."
    explanation: >
      Source for the statement that biallelic LAMB3 loss gives a different, and
      syndromic, disease rather than more severe AI.
- name: AMBN
  gene_term:
    preferred_term: AMBN
    term:
      id: hgnc:452
      label: AMBN
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1F
  notes: >
    Ameloblastin, a secreted enamel matrix protein whose essential functions are
    enamel-specific; biallelic defects cause autosomal recessive hypoplastic AI.
  evidence:
  - reference: PMID:31402633
    reference_title: "AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biallelic AMBN defects cause non-syndromic autosomal recessive amelogenesis imperfecta."
    explanation: >
      States the AMBN gene-disease relationship and its recessive mode.
- name: FAM20A
  gene_term:
    preferred_term: FAM20A
    term:
      id: hgnc:23015
      label: FAM20A
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1G
  notes: >
    Biallelic FAM20A variants cause enamel renal syndrome, numbered AI type 1G.
    This is the one syndromic member of this entry's subtype list.
  review_notes: >
    Deliberately not bound to a pathophysiology node. The source cited here
    establishes the gene-disease relationship and the tissues affected, but the
    ameloblast-level step FAM20A acts at is not stated in it. PubMed was searched
    for FAM20A with amelogenesis imperfecta and with enamel renal syndrome, and
    the sources returned describe the ectopic mineralization phenotype and the
    renal involvement rather than a step of ameloblast function, so there is no
    basis here for placing FAM20A on the secretory, processing, adhesion,
    transport or transcriptional node. Recorded as an open wiring gap rather than
    guessed at.
  evidence:
  - reference: PMID:40089179
    reference_title: "The craniofacial, dental and systemic manifestations of Enamel Renal Syndrome: A Scoping review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This autosomal recessive condition, caused by pathogenic variants in the FAM20A gene, is linked to ectopic mineralisation in tissues such as dental pulp, follicles, gingiva, and kidneys."
    explanation: >
      Establishes FAM20A causation and the extra-enamel tissues involved.
- name: ITGB6
  gene_term:
    preferred_term: ITGB6
    term:
      id: hgnc:6161
      label: ITGB6
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1H
  notes: >
    Integrin beta-6, which pairs with integrin alpha-V on the ameloblast distal
    membrane; biallelic loss causes generalized hypoplastic AI.
  evidence:
  - reference: PMID:24305999
    reference_title: "ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These are the first disease-causing ITGB6 mutations to be reported."
    explanation: >
      Marks this report as the origin of the ITGB6 gene-disease relationship.
- name: ACP4
  gene_term:
    preferred_term: ACP4
    term:
      id: hgnc:14376
      label: ACP4
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1J
  notes: >
    Acid phosphatase 4, previously symbolized ACPT (testicular acid phosphatase)
    and still cited under that name in much of the AI literature; biallelic
    variants cause generalized hypoplastic autosomal recessive AI. Localization to
    secretory-stage ameloblasts is shown in mouse.
  evidence:
  - reference: PMID:27843125
    reference_title: "Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we identified ACPT (testicular acid phosphatase) biallelic mutations causing non-syndromic, generalized hypoplastic autosomal-recessive amelogenesis imperfecta (AI) in individuals from six apparently unrelated Turkish families."
    explanation: >
      Establishes the recessive ACP4/ACPT gene-disease relationship.
- name: SP6
  gene_term:
    preferred_term: SP6
    term:
      id: hgnc:14530
      label: SP6
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI1K
  notes: >
    Sp6 transcription factor; a missense change in its first zinc finger
    segregates with autosomal dominant hypoplastic AI and reduces binding to a
    candidate SP6 motif in the AMBN promoter.
  evidence:
  - reference: PMID:32167558
    reference_title: "A missense variant in specificity protein 6 (SP6) is associated with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The resulting missense protein change, p.(Ala273Lys), is predicted to alter a DNA-binding residue in the first of three zinc fingers."
    explanation: >
      Locates the AI-associated SP6 change in a DNA-binding residue, the basis
      for treating SP6 as a transcriptional lesion.
- name: ODAPH
  gene_term:
    preferred_term: ODAPH
    term:
      id: hgnc:26300
      label: ODAPH
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI2A4
  notes: >
    Odontogenesis-associated phosphoprotein, previously symbolized C4orf26 and
    cited under that symbol in the older AI literature; biallelic defects cause
    AI with extensive post-eruptive enamel failure.
  evidence:
  - reference: PMID:38303846
    reference_title: "A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A novel homozygous ODAPH (previously designated C4orf26) mutation of single-nucleotide deletion (NG_032974.1:g.5103del, NM_178497.5:c.67+1del) was identified to be disease-causing."
    explanation: >
      Establishes the ODAPH gene-disease relationship and the previous symbol.
- name: SLC24A4
  gene_term:
    preferred_term: SLC24A4
    term:
      id: hgnc:10978
      label: SLC24A4
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI2A5
  notes: >
    Required for calcium transport during the maturation stage of amelogenesis;
    biallelic defects cause hypomaturation AI.
  evidence:
  - reference: PMID:24532815
    reference_title: "Exonal deletion of SLC24A4 causes hypomaturation amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first report of exonal deletion in SLC24A4 providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis."
    explanation: >
      Confirms the gene-disease relationship and the calcium-transport function.
- name: GPR68
  gene_term:
    preferred_term: GPR68
    term:
      id: hgnc:4519
      label: GPR68
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI2A6
  notes: >
    Proton-sensing G-protein-coupled receptor active over the pH range of the
    developing enamel matrix; biallelic loss-of-function variants cause
    hypomaturation AI.
  evidence:
  - reference: PMID:27693231
    reference_title: "Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: >
      Establishes biallelic GPR68 variants as a cause of AI.
- name: RELT
  gene_term:
    preferred_term: RELT
    term:
      id: hgnc:13764
      label: RELT
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AI3C
  notes: >
    RELT TNF receptor, expressed by secretory-stage ameloblasts and odontoblasts;
    homozygous defects cause AI with generalized irregular hypoplastic enamel and
    rapid attrition.
  evidence:
  - reference: PMID:30506946
    reference_title: "Mutations in RELT cause autosomal recessive amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We characterized three consanguineous AI families with generalized irregular hypoplastic enamel with rapid attrition that perfectly segregated with homozygous defects in a novel gene: RELT that is a member of the tumor necrosis factor receptor superfamily (TNFRSF)."
    explanation: >
      Establishes RELT as a recessive AI gene in three consanguineous families.
- name: DLX3
  gene_term:
    preferred_term: DLX3
    term:
      id: hgnc:2916
      label: DLX3
  association: Causative
  relationship_type: CAUSATIVE
  subtype: AIHHT
  notes: >
    Distal-less homeobox 3. A frameshift within the DNA-binding homeodomain
    causes autosomal dominant AI with taurodontism; a DLX3 mutation outside the
    homeodomain instead causes tricho-dento-osseous syndrome.
  evidence:
  - reference: PMID:15666299
    reference_title: "DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we mapped an AIHHT family to human chromosome 17 q21-q22 (lod score 3.3) and identify a two basepair deletion (CT) at nucleotide 560 in DLX3 associated with the disease."
    explanation: >
      Maps and identifies the causal DLX3 homeodomain frameshift.
  - reference: PMID:15666299
    reference_title: "DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "This is the first report of a mutation within the homeodomain of DLX3."
    explanation: >
      Source for contrasting the homeodomain AIHHT allele with the previously
      reported non-homeodomain tricho-dento-osseous allele.

datasets:
- accession: PMID:37582367
  title: "Single-cell census of human tooth development enables generation of human enamel."
  data_type: SINGLE_CELL_RNA_SEQ
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:37582367
  description: >
    Single-cell (sci-RNA-seq) atlas of human tooth development with iPSC-derived ameloblast
    differentiation and a 3D organoid disease model of amelogenesis imperfecta.

treatments:
- name: Restorative and Prosthetic Rehabilitation
  description: >
    Full-coverage crowns, composite restorations, overlays, and prosthetic rehabilitation
    restore function, protect remaining enamel/dentin, reduce sensitivity, and improve
    esthetics in AI.
  treatment_term:
    preferred_term: dental restoration
    term:
      id: NCIT:C38052
      label: Dental Procedure
- name: Genetic Counseling
  description: >
    Genetic counseling addresses the X-linked, autosomal dominant, and autosomal recessive
    inheritance patterns and recurrence risk for affected families.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:21127961
    reference_title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autosomal dominant, recessive, and X-linked types have been previously described."
    explanation: >
      The Mendelian inheritance of AI supports genetic counseling for affected families.

notes: >
  AI is mechanistically distinct from acquired developmental defects of enamel. Dental
  fluorosis (see Dental_Fluorosis) and the demineralization phenotype of dental caries
  (see Dental_Caries) are non-hereditary enamel defects and are curated separately. The
  iPSC-derived ameloblast / 3D enamel organoid system (PMID:37582367) is the first human
  in vitro disease model for AI and is the natural substrate for future MorPhiC-style
  cellular phenotyping of individual AI genes.

  Subtype scope. `has_subtypes` carries two orthogonal axes: the three Witkop
  phenotype classes (hypoplastic, hypomaturation, hypocalcified) and, below them,
  one row per gene-defined MONDO/OMIM type. One of those gene-defined rows, AI1G
  (FAM20A), denotes enamel renal syndrome and is syndromic, which sits awkwardly
  with the description above characterizing AI as an enamel disorder in the
  absence of a generalized systemic disorder. It is retained because OMIM and
  MONDO both number the FAM20A phenotype as an amelogenesis imperfecta type, and
  is flagged in its own `review_notes` as the likely future split into a separate
  Disease entry.

  MONDO observations. The first three below were read from the OLS MONDO endpoint
  on 2026-09-23 rather than from a secondary source; the fourth is a disagreement
  between MONDO and the primary literature.
  MONDO:0010521
  ("amelogenesis imperfecta type 1E", AMELX) is parented under MONDO:0015048
  "amelogenesis imperfecta type 2", not under MONDO:0015047 "amelogenesis
  imperfecta type 1". MONDO:0031084 carries the primary label "amelogenesis
  imperfecta, IIa 1K" while its own synonyms give "amelogenesis imperfecta,
  hypoplastic IIa 1K" and "AI1K", and the cited SP6 report describes a hypoplastic
  phenotype. MONDO:0032717 (AI3C, RELT) is parented under "hypocalcified
  amelogenesis imperfecta" while the cited RELT report describes generalized
  irregular hypoplastic enamel. Separately, MONDO:0013906 is labelled
  "amelogenesis imperfecta hypomaturation type 2A4" while the ODAPH report cited
  on that subtype row concludes that loss-of-function ODAPH mutations cause the
  hypocalcified type "rather than type IIA4". In each case the bound term and its
  label are copied verbatim from MONDO and the disagreement is recorded rather
  than worked around.

references:
- reference: PMID:16838342
  title: "The molecular etiologies and associated phenotypes of amelogenesis imperfecta."
- reference: PMID:16304440
  title: "Genes and related proteins involved in amelogenesis imperfecta."
- reference: PMID:21127961
  title: "Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry."
- reference: PMID:39321764
  title: "Developmental Defects of Enamel."
- reference: PMID:17552940
  title: "Developmental biology and genetics of dental malformations."
- reference: PMID:37582367
  title: "Single-cell census of human tooth development enables generation of human enamel."
- reference: PMID:30905256
  title: "Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta."
- reference: PMID:16246937
  title: "Phenotype of ENAM mutations is dosage-dependent."
- reference: PMID:14684688
  title: "Novel ENAM mutation responsible for autosomal recessive amelogenesis imperfecta and localised enamel defects."
- reference: PMID:38892321
  title: "AMELX Mutations and Genotype-Phenotype Correlation in X-Linked Amelogenesis Imperfecta."
- reference: PMID:31402633
  title: "AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity."
- reference: PMID:40089179
  title: "The craniofacial, dental and systemic manifestations of Enamel Renal Syndrome: A Scoping review."
- reference: PMID:24305999
  title: "ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta."
- reference: PMID:27843125
  title: "Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta."
- reference: PMID:32167558
  title: "A missense variant in specificity protein 6 (SP6) is associated with amelogenesis imperfecta."
- reference: PMID:35207639
  title: "Novel KLK4 Mutations Cause Hypomaturation Amelogenesis Imperfecta."
- reference: PMID:33600052
  title: "Spectrum of pathogenic variants and founder effects in amelogenesis imperfecta associated with MMP20."
- reference: PMID:30779877
  title: "WDR72 Mutations Associated with Amelogenesis Imperfecta and Acidosis."
- reference: PMID:38303846
  title: "A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues."
- reference: PMID:24532815
  title: "Exonal deletion of SLC24A4 causes hypomaturation amelogenesis imperfecta."
- reference: PMID:27693231
  title: "Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta."
- reference: PMID:33034243
  title: "FAM83H and Autosomal Dominant Hypocalcified Amelogenesis Imperfecta."
- reference: PMID:30506946
  title: "Mutations in RELT cause autosomal recessive amelogenesis imperfecta."
- reference: PMID:15666299
  title: "DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism."
📚

References & Deep Research

References

24
PMID:16838342
The molecular etiologies and associated phenotypes of amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:16304440
Genes and related proteins involved in amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:21127961
Defining a new candidate gene for amelogenesis imperfecta: from molecular genetics to biochemistry.
No top-level findings curated for this source.
PMID:39321764
Developmental Defects of Enamel.
No top-level findings curated for this source.
PMID:17552940
Developmental biology and genetics of dental malformations.
No top-level findings curated for this source.
PMID:37582367
Single-cell census of human tooth development enables generation of human enamel.
No top-level findings curated for this source.
PMID:30905256
Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta.
No top-level findings curated for this source.
PMID:16246937
Phenotype of ENAM mutations is dosage-dependent.
No top-level findings curated for this source.
PMID:14684688
Novel ENAM mutation responsible for autosomal recessive amelogenesis imperfecta and localised enamel defects.
No top-level findings curated for this source.
PMID:38892321
AMELX Mutations and Genotype-Phenotype Correlation in X-Linked Amelogenesis Imperfecta.
No top-level findings curated for this source.
PMID:31402633
AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity.
No top-level findings curated for this source.
PMID:40089179
The craniofacial, dental and systemic manifestations of Enamel Renal Syndrome: A Scoping review.
No top-level findings curated for this source.
PMID:24305999
ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:27843125
Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta.
No top-level findings curated for this source.
PMID:32167558
A missense variant in specificity protein 6 (SP6) is associated with amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:35207639
Novel KLK4 Mutations Cause Hypomaturation Amelogenesis Imperfecta.
No top-level findings curated for this source.
PMID:33600052
Spectrum of pathogenic variants and founder effects in amelogenesis imperfecta associated with MMP20.
No top-level findings curated for this source.
PMID:30779877
WDR72 Mutations Associated with Amelogenesis Imperfecta and Acidosis.
No top-level findings curated for this source.
PMID:38303846
A novel ODAPH mutation causing amelogenesis imperfecta and its expression in human dental tissues.
No top-level findings curated for this source.
PMID:24532815
Exonal deletion of SLC24A4 causes hypomaturation amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:27693231
Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta.
No top-level findings curated for this source.
PMID:33034243
FAM83H and Autosomal Dominant Hypocalcified Amelogenesis Imperfecta.
No top-level findings curated for this source.
PMID:30506946
Mutations in RELT cause autosomal recessive amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:15666299
DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism.
No top-level findings curated for this source.