Shih-Kai Wang - Academia.edu (original) (raw)

Papers by Shih-Kai Wang

Research paper thumbnail of Institute of Dental and Craniofacial Research

This work was supported by National

Research paper thumbnail of Tooth Development: Learn from "The Normal" and "The Abnormal

Research paper thumbnail of A Genetic Model for the Secretory Stage of Dental Enamel Formation

Journal of Structural Biology

The revolution in genetics has rapidly increased our knowledge of human and mouse genes that are ... more The revolution in genetics has rapidly increased our knowledge of human and mouse genes that are critical for the formation of dental enamel and helps us understand how enamel evolved. In this graphical review we focus on the roles of 41 genes that are essential for the secretory stage of amelogenesis when characteristic enamel mineral ribbons initiate on dentin and elongate to expand the enamel layer to the future surface of the tooth. Based upon ultrastructural analyses of genetically modified mice, we propose a molecular model explaining how a cell attachment apparatus including collagen 17, α6ß4 and αvß6 integrins, laminin 332, and secreted enamel proteins could attach to individual enamel mineral ribbons and mold their cross-sectional dimensions as they simultaneously elongate and orient them in the direction of the retrograde movement of the ameloblast membrane.

Research paper thumbnail of Mouse Dspp frameshift model of human dentinogenesis imperfecta

Scientific Reports

Non-syndromic inherited defects of tooth dentin are caused by two classes of dominant negative/ga... more Non-syndromic inherited defects of tooth dentin are caused by two classes of dominant negative/gain-of-function mutations in dentin sialophosphoprotein (DSPP): 5′ mutations affecting an N-terminal targeting sequence and 3′ mutations that shift translation into the − 1 reading frame. DSPP defects cause an overlapping spectrum of phenotypes classified as dentin dysplasia type II and dentinogenesis imperfecta types II and III. Using CRISPR/Cas9, we generated a Dspp−1fs mouse model by introducing a FLAG-tag followed by a single nucleotide deletion that translated 493 extraneous amino acids before termination. Developing incisors and/or molars from this mouse and a DsppP19L mouse were characterized by morphological assessment, bSEM, nanohardness testing, histological analysis, in situ hybridization and immunohistochemistry. DsppP19L dentin contained dentinal tubules but grew slowly and was softer and less mineralized than the wild-type. DsppP19L incisor enamel was softer than normal, whi...

Research paper thumbnail of Novel REST Truncation Mutations Causing Hereditary Gingival Fibromatosis

Journal of Dental Research

Hereditary gingival fibromatosis (HGF) is a rare genetic disorder featured by nonsyndromic pathol... more Hereditary gingival fibromatosis (HGF) is a rare genetic disorder featured by nonsyndromic pathological overgrowth of gingiva. The excessive gingival tissues can cause dental, masticatory, and phonetic problems, which impose severe functional and esthetic burdens on affected individuals. Due to its high recurrent rate, patients with HGF have to undergo repeated surgical procedures of gingival resection, from childhood to adulthood, which significantly compromises their quality of life. Unraveling the genetic etiology and molecular pathogenesis of HGF not only gains insight into gingival physiology and homeostasis but also opens avenues for developing potential therapeutic strategies for this disorder. Recently, mutations in REST (OMIM *600571), encoding a transcription repressor, were reported to cause HGF (GINGF5; OMIM #617626) in 3 Turkish families. However, the functions of REST in gingival homeostasis and pathogenesis of REST-associated HGF remain largely unknown. In this study,...

Research paper thumbnail of Dental malformations associated with biallelic MMP20 mutations

Molecular Genetics & Genomic Medicine

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial ... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Research paper thumbnail of ENAM mutations and digenic inheritance

Molecular Genetics & Genomic Medicine

Research paper thumbnail of AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout‐NLS‐lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue‐specificity

Molecular Genetics & Genomic Medicine

Research paper thumbnail of Transcriptome analysis of gingival tissues of enamel‐renal syndrome

Journal of Periodontal Research

Background and objective: Biallelic loss-of-function mutations of human FAM20A have been known to... more Background and objective: Biallelic loss-of-function mutations of human FAM20A have been known to cause enamel-renal syndrome (ERS), featured by agenesis of dental enamel, nephrocalcinosis, and other orodental abnormalities, including gingival hyperplasia. However, while the histopathology of this gingival anomaly has been analyzed, its underlying molecular mechanism remains largely unknown. This study aimed to unravel the pathogenesis of gingival hyperplasia in ERS. Methods: Whole exome sequencing was conducted for an ERS case. Transcriptome analyses, using RNA sequencing, of the patient's gingiva were performed to unravel dysregulated molecules and aberrant biological processes underlying the gingival pathology of ERS, which was further confirmed by histology and immunohistochemistry. Results: Two novel frameshift FAM20A mutations in Exon 1 (g.5417delG; c.129delG; p.Cys44Alafs*101) and Exon 5 (g.62248_62249delAG; c.734_735delAG; p.Glu245Glyfs*11) were identified. Transcriptional profiling of patient's gingival tissue revealed a total of 1683 genes whose expression had increased (1129 genes) or decreased (554 genes) at least 2-fold compared to control gingival tissues. There were 951 Gene Ontology (GO) terms of biological process being significantly over-represented or under-represented. While GOs involved in extracellular matrix organization, angiogenesis, biomineralization, and epithelial cell proliferation appeared to be activated in ERS gingiva, genes related to keratinocyte differentiation, epithelial development, and keratinization were of decreased expression. FAM20A immunohistochemistry revealed a strong

Research paper thumbnail of The Enamel Phenotype in Homozygous Fam83h Truncation Mice

Molecular Genetics & Genomic Medicine

Research paper thumbnail of Fam83h null mice support a neomorphic mechanism for human ADHCAI

Molecular Genetics & Genomic Medicine, 2015

Truncation mutations in FAM83H (family with sequence similarity 83, member H) cause autosomal dom... more Truncation mutations in FAM83H (family with sequence similarity 83, member H) cause autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI), but little is known about FAM83H function and the pathogenesis of ADHCAI. We recruited three ADHCAI families and identified two novel (p.Gln457*; p.Lys639*) and one previously documented (p.Q452*) disease-causing FAM83H mutations. We generated and characterized Fam83h-knockout/lacZ-knockin mice. Surprisingly, enamel thickness, density, Knoop hardness, morphology, and prism patterns were similar in Fam83h +/+ , Fam83h +/À , and Fam83h À/À mice. The histology of ameloblasts in all stages of development, in both molars and incisors, was virtually identical in all three genotypes and showed no signs of pathology, although the Fam83h À/À mice usually died after 2 weeks and rarely survived to 7 weeks. LacZ expression in the knockin mice was used to report Fam83h expression in the epithelial tissues of many organs, notably in skin and hair follicles, which manifested a disease phenotype. Pull-down studies determined that FAM83H dimerizes through its N-terminal phospholipase D-like (PLD-like) domain and identified potential FAM83H interacting proteins. Casein kinase 1 (CK1) interacts with the FAM83H PLD-like domain via an F 270-X-X-X-F 274-X-X-X-F 278 motif. CK1 can phosphorylate FAM83H in vitro, and many phosphorylation sites were identified in the FAM83H C-terminus. Truncation of FAM83H alters its subcellular localization and that of CK1. Our results support the conclusion that FAM83H is not necessary for proper dental enamel formation in mice, but may act as a scaffold protein that localizes CK1. ADHCAI is likely caused by gain-of-function effects mediated by truncated FAM83H, which potentially mislocalizes CK1 as part of its pathological mechanism.

Research paper thumbnail of Root anomalies and dentin dysplasia in autosomal recessive hyperphosphatemic familial tumoral calcinosis (HFTC)

Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, 2015

Hyperphosphatemic familial tumoral calcinosis (HFTC, OMIM #211900) is an autosomal recessive meta... more Hyperphosphatemic familial tumoral calcinosis (HFTC, OMIM #211900) is an autosomal recessive metabolic disorder characterized by hyperphosphatemia, tooth root defects, and the progressive deposition of calcium phosphate crystals in periarticular spaces, soft tissues, and sometimes bone. 1 In this HFTC case report, we document the dental phenotype associated with a homozygous missense mutation (g.29077 C>T; c.484 C>T; p.Arg162*) in GALNT3 (OMIM 6017563), a gene encoding UDP-GalNAc transferase 3 that catalyzes the first step of O-linked oligosaccharide biosynthesis in the Golgi. The medical and dental pathology is believed to be caused primarily by high serum phosphate levels (hyperphosphatemia), which, in turn, is caused by failure of GALNT3 to glycosylate the phosphate regulator protein FGF23, impairing its ability inhibit reabsorption of filtered phosphate in the kidneys. Dentists are increasingly called upon to diagnose rare inherited conditions affecting tooth development. Until recently, the genetic etiologies of most dental anomalies were unknown. Although it was appreciated that a tooth phenotype might be one feature of a broader syndrome, no diagnostic tests were available. The revolution in genetics has changed this and offers dentists both the opportunity and the responsibility to contribute to the diagnosis

Research paper thumbnail of Critical roles for WDR72 in calcium transport and matrix protein removal during enamel maturation

Molecular Genetics & Genomic Medicine, 2015

Research paper thumbnail of Ameloblast transcriptome changes from secretory to maturation stages

Connective tissue research, 2014

The purpose of this study was to identify the major molecular components in the secretory and mat... more The purpose of this study was to identify the major molecular components in the secretory and maturation stages of amelogenesis through transcriptome analyses. Ameloblasts (40 sections per age group) were laser micro-dissected from Day 5 (secretory stage) and Days 11-12 (maturation stage) first molars. PolyA+ RNA was isolated from the lysed cells, converted to cDNA, and amplified to generate a cDNA library. DNA sequences were obtained using next generation sequencing and analyzed to identify genes whose expression had increased or decreased at least 1.5-fold in maturation stage relative to secretory stage ameloblasts. Among the 9198 genes that surpassed the quality threshold, 373 showed higher expression in secretory stage, while 614 genes increased in maturation stage ameloblasts. The results were cross-checked against a previously published transcriptome generated from tissues overlying secretory and maturation stage mouse incisor enamel and 34 increasing and 26 decreasing express...

Research paper thumbnail of Taurodontism, variations in tooth number, and misshapened crowns in Wnt10a null mice and human kindreds

Molecular genetics & genomic medicine, 2015

WNT10A is a signaling molecule involved in tooth development, and WNT10A defects are associated w... more WNT10A is a signaling molecule involved in tooth development, and WNT10A defects are associated with tooth agenesis. We characterized Wnt10a null mice generated by the knockout mouse project (KOMP) and six families with WNT10A mutations, including a novel p.Arg104Cys defect, in the absence of EDA,EDAR, or EDARADD variations. Wnt10a null mice exhibited supernumerary mandibular fourth molars, and smaller molars with abnormal cusp patterning and root taurodontism. Wnt10a (-/-) incisors showed distinctive apical-lingual wedge-shaped defects. These findings spurred us to closely examine the dental phenotypes of our WNT10A families. WNT10A heterozygotes exhibited molar root taurodontism and mild tooth agenesis (with incomplete penetrance) in their permanent dentitions. Individuals with two defective WNT10A alleles showed severe tooth agenesis and had fewer cusps on their molars. The misshapened molar crowns and roots were consistent with the Wnt10a null phenotype and were not previously a...

Research paper thumbnail of Ectodermal Dysplasia - A Family Study

Annual Research & Review in Biology, 2014

Ectodermal dysplasias (ED) are group of genetically heterogenous conditions that are characterize... more Ectodermal dysplasias (ED) are group of genetically heterogenous conditions that are characterized by abnormal development of ectodermal structures. The most affected structures are teeth, skin and its derivatives (hair, sweat glands) along with other ectodermal structures. The purpose of this work was to present the family with four boys affected with ED. We described the clinical report of male infant (affected twin) aged two months and his older brothers with absence of eyebrows and eyelashes, saddle nose, dry flaky skin, rare thin blond hair, and large number of dental anomalies with pathohistological-skin positive analysis for ectodermal dysplasia. Only a few abnormally formed teeth erupted (microdontia and conical teeth) and at the later then average age. Radiographic examination confirmed previous clinical findings and determined taurodontism of the molar teeth. They also presented pseudoprognathism of the mandible due to micrognathism of the maxilla. Based on the positive family history (two older brothers), clinical picture and pathohistological findings of the skin we concluded that the child (and his twin brother) were also affected. EDA gene missense mutation, Ala349Thr (GCA --> ACA), was responsible for the condition of observed family. Hair hypotriyhosis, brittle, scanty hair, absent or scanty eyelashes and eyebrows, blonde, fine scalp hair, as minor clinical signs at grandmother and only scanty eyelashes at mother were observed. Mutation analysis in families with X-linked ED help in genetic counseling, prenatal diagnosis, and confirmation of carrier status.

Research paper thumbnail of Secreted protein kinases?

Trends in Biochemical Sciences, 2013

Research paper thumbnail of FAM20A Mutations Can Cause Enamel-Renal Syndrome (ERS)

Research paper thumbnail of Altered Enamelin Phosphorylation Site Causes Amelogenesis Imperfecta

Journal of Dental Research, 2010

Defects in the enamelin gene ( ENAM) cause amelogenesis imperfecta (AI). Our objective was to ide... more Defects in the enamelin gene ( ENAM) cause amelogenesis imperfecta (AI). Our objective was to identify the genetic etiology of enamel hypoplasia in a Caucasian proband. Our hypothesis was that ENAM was defective. The proband and his father have an AG insertion (g.13185_13186insAG; p.422FsX448) in ENAM previously identified in AI kindreds from Slovenia and Turkey. The proband, his brother, and his mother have a novel missense mutation (g.12573C>T) that substitutes leucine for a phosphorylated serine (p.S216L) in the 32-kDa enamelin cleavage product. In this family, a defect in one ENAM allele caused minor pitting or localized enamel hypoplasia, whereas defects in both alleles caused severe enamel malformations, with little or no mineral covering dentin. Ser216 is one of two serines on the 32-kDa enamelin that is phosphorylated by Golgi casein kinase and is thought to mediate calcium binding. We propose that phosphorylation of enamelin is critical for its function.

Research paper thumbnail of STIM1 and SLC24A4 Are Critical for Enamel Maturation

Journal of Dental Research, 2014

Dental enamel formation depends upon the transcellular transport of Ca2+ by ameloblasts, but litt... more Dental enamel formation depends upon the transcellular transport of Ca2+ by ameloblasts, but little is known about the molecular mechanism, or even if the same process is operative during the secretory and maturation stages of amelogenesis. Identifying mutations in genes involved in Ca2+ homeostasis that cause inherited enamel defects can provide insights into the molecular participants and potential mechanisms of Ca2+ handling by ameloblasts. Stromal Interaction Molecule 1 (STIM1) is an ER transmembrane protein that activates membrane-specific Ca2+ influx in response to the depletion of ER Ca2+ stores. Solute carrier family 24, member 4 (SLC24A4), is a Na+/K+/Ca2+ transporter that exchanges intracellular Ca2+ and K+ for extracellular Na+. We identified a proband with syndromic hypomaturation enamel defects caused by a homozygous C to T transition (g.232598C>T c.1276C>T p.Arg426Cys) in STIM1, and a proband with isolated hypomaturation enamel defects caused by a homozygous C to...

Research paper thumbnail of Institute of Dental and Craniofacial Research

This work was supported by National

Research paper thumbnail of Tooth Development: Learn from "The Normal" and "The Abnormal

Research paper thumbnail of A Genetic Model for the Secretory Stage of Dental Enamel Formation

Journal of Structural Biology

The revolution in genetics has rapidly increased our knowledge of human and mouse genes that are ... more The revolution in genetics has rapidly increased our knowledge of human and mouse genes that are critical for the formation of dental enamel and helps us understand how enamel evolved. In this graphical review we focus on the roles of 41 genes that are essential for the secretory stage of amelogenesis when characteristic enamel mineral ribbons initiate on dentin and elongate to expand the enamel layer to the future surface of the tooth. Based upon ultrastructural analyses of genetically modified mice, we propose a molecular model explaining how a cell attachment apparatus including collagen 17, α6ß4 and αvß6 integrins, laminin 332, and secreted enamel proteins could attach to individual enamel mineral ribbons and mold their cross-sectional dimensions as they simultaneously elongate and orient them in the direction of the retrograde movement of the ameloblast membrane.

Research paper thumbnail of Mouse Dspp frameshift model of human dentinogenesis imperfecta

Scientific Reports

Non-syndromic inherited defects of tooth dentin are caused by two classes of dominant negative/ga... more Non-syndromic inherited defects of tooth dentin are caused by two classes of dominant negative/gain-of-function mutations in dentin sialophosphoprotein (DSPP): 5′ mutations affecting an N-terminal targeting sequence and 3′ mutations that shift translation into the − 1 reading frame. DSPP defects cause an overlapping spectrum of phenotypes classified as dentin dysplasia type II and dentinogenesis imperfecta types II and III. Using CRISPR/Cas9, we generated a Dspp−1fs mouse model by introducing a FLAG-tag followed by a single nucleotide deletion that translated 493 extraneous amino acids before termination. Developing incisors and/or molars from this mouse and a DsppP19L mouse were characterized by morphological assessment, bSEM, nanohardness testing, histological analysis, in situ hybridization and immunohistochemistry. DsppP19L dentin contained dentinal tubules but grew slowly and was softer and less mineralized than the wild-type. DsppP19L incisor enamel was softer than normal, whi...

Research paper thumbnail of Novel REST Truncation Mutations Causing Hereditary Gingival Fibromatosis

Journal of Dental Research

Hereditary gingival fibromatosis (HGF) is a rare genetic disorder featured by nonsyndromic pathol... more Hereditary gingival fibromatosis (HGF) is a rare genetic disorder featured by nonsyndromic pathological overgrowth of gingiva. The excessive gingival tissues can cause dental, masticatory, and phonetic problems, which impose severe functional and esthetic burdens on affected individuals. Due to its high recurrent rate, patients with HGF have to undergo repeated surgical procedures of gingival resection, from childhood to adulthood, which significantly compromises their quality of life. Unraveling the genetic etiology and molecular pathogenesis of HGF not only gains insight into gingival physiology and homeostasis but also opens avenues for developing potential therapeutic strategies for this disorder. Recently, mutations in REST (OMIM *600571), encoding a transcription repressor, were reported to cause HGF (GINGF5; OMIM #617626) in 3 Turkish families. However, the functions of REST in gingival homeostasis and pathogenesis of REST-associated HGF remain largely unknown. In this study,...

Research paper thumbnail of Dental malformations associated with biallelic MMP20 mutations

Molecular Genetics & Genomic Medicine

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial ... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Research paper thumbnail of ENAM mutations and digenic inheritance

Molecular Genetics & Genomic Medicine

Research paper thumbnail of AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout‐NLS‐lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue‐specificity

Molecular Genetics & Genomic Medicine

Research paper thumbnail of Transcriptome analysis of gingival tissues of enamel‐renal syndrome

Journal of Periodontal Research

Background and objective: Biallelic loss-of-function mutations of human FAM20A have been known to... more Background and objective: Biallelic loss-of-function mutations of human FAM20A have been known to cause enamel-renal syndrome (ERS), featured by agenesis of dental enamel, nephrocalcinosis, and other orodental abnormalities, including gingival hyperplasia. However, while the histopathology of this gingival anomaly has been analyzed, its underlying molecular mechanism remains largely unknown. This study aimed to unravel the pathogenesis of gingival hyperplasia in ERS. Methods: Whole exome sequencing was conducted for an ERS case. Transcriptome analyses, using RNA sequencing, of the patient's gingiva were performed to unravel dysregulated molecules and aberrant biological processes underlying the gingival pathology of ERS, which was further confirmed by histology and immunohistochemistry. Results: Two novel frameshift FAM20A mutations in Exon 1 (g.5417delG; c.129delG; p.Cys44Alafs*101) and Exon 5 (g.62248_62249delAG; c.734_735delAG; p.Glu245Glyfs*11) were identified. Transcriptional profiling of patient's gingival tissue revealed a total of 1683 genes whose expression had increased (1129 genes) or decreased (554 genes) at least 2-fold compared to control gingival tissues. There were 951 Gene Ontology (GO) terms of biological process being significantly over-represented or under-represented. While GOs involved in extracellular matrix organization, angiogenesis, biomineralization, and epithelial cell proliferation appeared to be activated in ERS gingiva, genes related to keratinocyte differentiation, epithelial development, and keratinization were of decreased expression. FAM20A immunohistochemistry revealed a strong

Research paper thumbnail of The Enamel Phenotype in Homozygous Fam83h Truncation Mice

Molecular Genetics & Genomic Medicine

Research paper thumbnail of Fam83h null mice support a neomorphic mechanism for human ADHCAI

Molecular Genetics & Genomic Medicine, 2015

Truncation mutations in FAM83H (family with sequence similarity 83, member H) cause autosomal dom... more Truncation mutations in FAM83H (family with sequence similarity 83, member H) cause autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI), but little is known about FAM83H function and the pathogenesis of ADHCAI. We recruited three ADHCAI families and identified two novel (p.Gln457*; p.Lys639*) and one previously documented (p.Q452*) disease-causing FAM83H mutations. We generated and characterized Fam83h-knockout/lacZ-knockin mice. Surprisingly, enamel thickness, density, Knoop hardness, morphology, and prism patterns were similar in Fam83h +/+ , Fam83h +/À , and Fam83h À/À mice. The histology of ameloblasts in all stages of development, in both molars and incisors, was virtually identical in all three genotypes and showed no signs of pathology, although the Fam83h À/À mice usually died after 2 weeks and rarely survived to 7 weeks. LacZ expression in the knockin mice was used to report Fam83h expression in the epithelial tissues of many organs, notably in skin and hair follicles, which manifested a disease phenotype. Pull-down studies determined that FAM83H dimerizes through its N-terminal phospholipase D-like (PLD-like) domain and identified potential FAM83H interacting proteins. Casein kinase 1 (CK1) interacts with the FAM83H PLD-like domain via an F 270-X-X-X-F 274-X-X-X-F 278 motif. CK1 can phosphorylate FAM83H in vitro, and many phosphorylation sites were identified in the FAM83H C-terminus. Truncation of FAM83H alters its subcellular localization and that of CK1. Our results support the conclusion that FAM83H is not necessary for proper dental enamel formation in mice, but may act as a scaffold protein that localizes CK1. ADHCAI is likely caused by gain-of-function effects mediated by truncated FAM83H, which potentially mislocalizes CK1 as part of its pathological mechanism.

Research paper thumbnail of Root anomalies and dentin dysplasia in autosomal recessive hyperphosphatemic familial tumoral calcinosis (HFTC)

Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, 2015

Hyperphosphatemic familial tumoral calcinosis (HFTC, OMIM #211900) is an autosomal recessive meta... more Hyperphosphatemic familial tumoral calcinosis (HFTC, OMIM #211900) is an autosomal recessive metabolic disorder characterized by hyperphosphatemia, tooth root defects, and the progressive deposition of calcium phosphate crystals in periarticular spaces, soft tissues, and sometimes bone. 1 In this HFTC case report, we document the dental phenotype associated with a homozygous missense mutation (g.29077 C>T; c.484 C>T; p.Arg162*) in GALNT3 (OMIM 6017563), a gene encoding UDP-GalNAc transferase 3 that catalyzes the first step of O-linked oligosaccharide biosynthesis in the Golgi. The medical and dental pathology is believed to be caused primarily by high serum phosphate levels (hyperphosphatemia), which, in turn, is caused by failure of GALNT3 to glycosylate the phosphate regulator protein FGF23, impairing its ability inhibit reabsorption of filtered phosphate in the kidneys. Dentists are increasingly called upon to diagnose rare inherited conditions affecting tooth development. Until recently, the genetic etiologies of most dental anomalies were unknown. Although it was appreciated that a tooth phenotype might be one feature of a broader syndrome, no diagnostic tests were available. The revolution in genetics has changed this and offers dentists both the opportunity and the responsibility to contribute to the diagnosis

Research paper thumbnail of Critical roles for WDR72 in calcium transport and matrix protein removal during enamel maturation

Molecular Genetics & Genomic Medicine, 2015

Research paper thumbnail of Ameloblast transcriptome changes from secretory to maturation stages

Connective tissue research, 2014

The purpose of this study was to identify the major molecular components in the secretory and mat... more The purpose of this study was to identify the major molecular components in the secretory and maturation stages of amelogenesis through transcriptome analyses. Ameloblasts (40 sections per age group) were laser micro-dissected from Day 5 (secretory stage) and Days 11-12 (maturation stage) first molars. PolyA+ RNA was isolated from the lysed cells, converted to cDNA, and amplified to generate a cDNA library. DNA sequences were obtained using next generation sequencing and analyzed to identify genes whose expression had increased or decreased at least 1.5-fold in maturation stage relative to secretory stage ameloblasts. Among the 9198 genes that surpassed the quality threshold, 373 showed higher expression in secretory stage, while 614 genes increased in maturation stage ameloblasts. The results were cross-checked against a previously published transcriptome generated from tissues overlying secretory and maturation stage mouse incisor enamel and 34 increasing and 26 decreasing express...

Research paper thumbnail of Taurodontism, variations in tooth number, and misshapened crowns in Wnt10a null mice and human kindreds

Molecular genetics & genomic medicine, 2015

WNT10A is a signaling molecule involved in tooth development, and WNT10A defects are associated w... more WNT10A is a signaling molecule involved in tooth development, and WNT10A defects are associated with tooth agenesis. We characterized Wnt10a null mice generated by the knockout mouse project (KOMP) and six families with WNT10A mutations, including a novel p.Arg104Cys defect, in the absence of EDA,EDAR, or EDARADD variations. Wnt10a null mice exhibited supernumerary mandibular fourth molars, and smaller molars with abnormal cusp patterning and root taurodontism. Wnt10a (-/-) incisors showed distinctive apical-lingual wedge-shaped defects. These findings spurred us to closely examine the dental phenotypes of our WNT10A families. WNT10A heterozygotes exhibited molar root taurodontism and mild tooth agenesis (with incomplete penetrance) in their permanent dentitions. Individuals with two defective WNT10A alleles showed severe tooth agenesis and had fewer cusps on their molars. The misshapened molar crowns and roots were consistent with the Wnt10a null phenotype and were not previously a...

Research paper thumbnail of Ectodermal Dysplasia - A Family Study

Annual Research & Review in Biology, 2014

Ectodermal dysplasias (ED) are group of genetically heterogenous conditions that are characterize... more Ectodermal dysplasias (ED) are group of genetically heterogenous conditions that are characterized by abnormal development of ectodermal structures. The most affected structures are teeth, skin and its derivatives (hair, sweat glands) along with other ectodermal structures. The purpose of this work was to present the family with four boys affected with ED. We described the clinical report of male infant (affected twin) aged two months and his older brothers with absence of eyebrows and eyelashes, saddle nose, dry flaky skin, rare thin blond hair, and large number of dental anomalies with pathohistological-skin positive analysis for ectodermal dysplasia. Only a few abnormally formed teeth erupted (microdontia and conical teeth) and at the later then average age. Radiographic examination confirmed previous clinical findings and determined taurodontism of the molar teeth. They also presented pseudoprognathism of the mandible due to micrognathism of the maxilla. Based on the positive family history (two older brothers), clinical picture and pathohistological findings of the skin we concluded that the child (and his twin brother) were also affected. EDA gene missense mutation, Ala349Thr (GCA --> ACA), was responsible for the condition of observed family. Hair hypotriyhosis, brittle, scanty hair, absent or scanty eyelashes and eyebrows, blonde, fine scalp hair, as minor clinical signs at grandmother and only scanty eyelashes at mother were observed. Mutation analysis in families with X-linked ED help in genetic counseling, prenatal diagnosis, and confirmation of carrier status.

Research paper thumbnail of Secreted protein kinases?

Trends in Biochemical Sciences, 2013

Research paper thumbnail of FAM20A Mutations Can Cause Enamel-Renal Syndrome (ERS)

Research paper thumbnail of Altered Enamelin Phosphorylation Site Causes Amelogenesis Imperfecta

Journal of Dental Research, 2010

Defects in the enamelin gene ( ENAM) cause amelogenesis imperfecta (AI). Our objective was to ide... more Defects in the enamelin gene ( ENAM) cause amelogenesis imperfecta (AI). Our objective was to identify the genetic etiology of enamel hypoplasia in a Caucasian proband. Our hypothesis was that ENAM was defective. The proband and his father have an AG insertion (g.13185_13186insAG; p.422FsX448) in ENAM previously identified in AI kindreds from Slovenia and Turkey. The proband, his brother, and his mother have a novel missense mutation (g.12573C>T) that substitutes leucine for a phosphorylated serine (p.S216L) in the 32-kDa enamelin cleavage product. In this family, a defect in one ENAM allele caused minor pitting or localized enamel hypoplasia, whereas defects in both alleles caused severe enamel malformations, with little or no mineral covering dentin. Ser216 is one of two serines on the 32-kDa enamelin that is phosphorylated by Golgi casein kinase and is thought to mediate calcium binding. We propose that phosphorylation of enamelin is critical for its function.

Research paper thumbnail of STIM1 and SLC24A4 Are Critical for Enamel Maturation

Journal of Dental Research, 2014

Dental enamel formation depends upon the transcellular transport of Ca2+ by ameloblasts, but litt... more Dental enamel formation depends upon the transcellular transport of Ca2+ by ameloblasts, but little is known about the molecular mechanism, or even if the same process is operative during the secretory and maturation stages of amelogenesis. Identifying mutations in genes involved in Ca2+ homeostasis that cause inherited enamel defects can provide insights into the molecular participants and potential mechanisms of Ca2+ handling by ameloblasts. Stromal Interaction Molecule 1 (STIM1) is an ER transmembrane protein that activates membrane-specific Ca2+ influx in response to the depletion of ER Ca2+ stores. Solute carrier family 24, member 4 (SLC24A4), is a Na+/K+/Ca2+ transporter that exchanges intracellular Ca2+ and K+ for extracellular Na+. We identified a proband with syndromic hypomaturation enamel defects caused by a homozygous C to T transition (g.232598C>T c.1276C>T p.Arg426Cys) in STIM1, and a proband with isolated hypomaturation enamel defects caused by a homozygous C to...