Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI1
Molecular analysis of oral pathogens and
saliva, dental caries
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI2
Lecture topics
̶ Factors involved in development of dental caries:
̶ Oral microbiome
Dental plaque (bacterial biofilm)
̶ Saliva
Saliva composition and its functions
̶ Behavioral and environmental factors
̶ Genetic factors
tissue susceptibility to caries
̶ Molecular analysis of saliva
̶ Molecular analysis of oral microbiome
̶ Genetic basis of dental caries
̶ Genetic association studies related to dental caries
3
Dental caries
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI
Dental Health Services Victoria
(www.betterhealth.vic.gov.au)
and factors affecting
their development
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI4
Dental caries
̶ the most common disease
̶ 32 % of the world population
̶ non-communicable disease (according to FDI World Dental Federation)
̶ shares risk factors with many other non-communicable diseases
̶ however → Streptococcus mutans transmission from parents to infants (Early childhood caries)
̶ complex disease
̶ multifactorial (endogenous and exogenous factors), multiple genes are involved in
̶ interaction of several factors contributes to formation of caries
̶ genetic predispositions
̶ composition of oral microflora
̶ composition and physical action of saliva
̶ overall health condition (immune system disorders, systemic diseases affecting immune system)
̶ behavioral and environmental factors
̶ time for which the factors act / interact
Puwadol Jaturawutthichai
(www.shutterstock.com)
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI5
Dental caries
̶ caries dentium
̶ enamel → 95 – 98 % of inorganic matter (apatites - the most important mineral component)
apatite – cationic complexes = ligands Ca2+ and (PO4)2–
counter-ions → Ca10(PO4)6CO3 (carbonate apatite), Ca10(PO4)6(OH)2 (hydroxyapatite), Ca10(PO4)6F2 (fluoroapatite)
dynamic process characterized by alternating periods of demineralization and remineralization of the enamel
→ ↑ demineralization →→ carious lesions progression
̶ caries formation → organic acids (bacteria, diet) dissolve the mineral part of the enamel by
neutralizing apatite counter-ions (crystal structure disintegration)
→ proteolytic enzymes→ degradation of organic matrix (collagens and proteoglycans)
̶ carious lesion → dentin → dentinal tubules → pulp → pulpitis, periodontitis
Puwadol Jaturawutthichai
(www.shutterstock.com)
Color Atlas of Biochemistry
(3rd edition, 2013)
diet
medicaments
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI6
Factors involved in development of caries
̶ Saliva:
̶ complex carioprotective factor
̶ maintaining homeostasis
̶ physical effect
saliva flow (washing and lubrication of tissues
of oral cavity),
oral cavity clearance (washing of harmful substances, not adhered microorganisms)
̶ components
gustin (Carbonic anhydrase VI→ buffering capacity), calcium, phosphate, fluoride ions, proteins of specific (IgA, IgG)
and non-specific immunity (lysozyme, defensins), other components of immune system
̶ ↓ food remnants, ↓ microorganisms, ↓ acidity (dilution, buffer systems - bicarbonate, hydrogen
phosphate, proteins), ↑ substances with antibacterial, antifungal and antiviral properties, ↑
balance between re- and demineralization
̶ reduced saliva flow  dehydration, obstruction / hypofunction of salivary glands (complex
diseases), medicaments (beta blockers, antidepressants, antihistamines),
drugs (methamphetamine, THC)
→ promotion of carious lesions formation
www.dentalcare.com/en-us/professional-education/ce-
courses/ce410/fluoride-s-mechanism-of-action
Demineralization (F- ion presence) Remineralization (F- ion presence)
Acid
(pH < 5,5)
Saliva
pH
6 – 7
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI7
Factors involved in development of caries
̶ Oral microbiome:
̶ second largest and diverse (over 700 species of bacteria)
homeostasis maintenance (competition and displacement of
exogenous pathogens → maintaining ecosystem stability),
immunomodulation
̶ dental plaque = biofilm =
matrix of extracellular polymeric substances (EPS)
+ aerobic bacteria (Streptococcus sanguinis), facultative anaerobes (S. mutans, S. sobrinus, Lactobacillus sp.),
anaerobes (Actinomyces sp., Veillonella sp.), fungi (Candida sp.)
̶ saliva → proteins with charged surfaces (acidic PRPs, statherin, histatins) → electrostatic interaction with
phosphate and calcium ions of apatite
̶ → (acquired) pellicle formation (mucins, cystatins, albumin, IgA, IgG, lysozyme, alpha-amylase, carbohydrates,
neutral lipids, phospho- and glycolipids, glucosyltransferase)
→ protection against demineralization, partial reduction of microbial adhesion
→ substrate for bacteria→ biofilm formation → dental plaque
https://periobasics.com/dental-plaque/
̶ Dental plaque:
̶ problem: dysbiosis of oral microbiome
disruption of homeostasis
̶ → ↑ cariogenic species (ferment carbohydrates to organic acids + tolerate low pH environment)
→ prevailing Streptococcus mutans a Streptococcus sobrinus, Lactobacillus sp., Candida sp.
̶ factors promoting cariogenic species
↓ saliva, ↓ oral hygiene → ↑ plaque thickness; ↑ intake of sugars / acids → acidification; ↓ immunity, inflammation,…
↑ dental plaque → lack of oxygen → ↑ anaerobic metabolism→ metabolism of fermentable carbohydrates → organic
acids → ↓ pH → demineralization → →→ caries
S. mutans → dextran (α-1,6-D-glucan) → extracellular insoluble polysaccharide → ↑ protection of bacteria against
adverse environment (low pH, antimicrobial factors), ↑ co-adhesion of other species, ↑ plaque adhesion
8
Factors involved in development of caries
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI
https://doi.org/10.3389/fmicb.2018.03323
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI9
Factors involved in development of caries
̶ External factors:
poor oral hygiene
poor eating habits (excessive intake of fermentable carbohydrates)
smoking
alcohol consumption
medicaments (salivary glands function impairment, acidification of oral cavity, antibiotics)
poor access to quality food, drinking water, hygiene supplies, medical care
̶ Time
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI10
Factors involved in development of caries
̶ Genetic predisposition:
̶ complex disease (genetic, epigenetic and exogenous factors)
• multiple genes
• genetic heterogeneity – locus heterogeneity (mutations in genes at different loci), allelic heterogeneity (different
mutations at the same locus)
• incomplete penetrance – pathological phenotype is not manifested in all individuals carrying disease-causing gene
(positive effects of other alleles or exogenous factors)
• phenocopy – pathological phenotype is manifested by individuals who are not carrying disease-causing gene
• high frequency of risk alleles in population
• ethnic variability (disease-causing genes can vary among populations, variant alleles can have different impact on
phenotype in different populations)
→ it is possible to determine only genes (alleles) which act as risk factors → predisposition (predisposing genotype can
increase probability of disease development, but does not determine the disease)
11
Molecular analysis
of saliva
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI
Saliva as a Diagnostic Fluid
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI12
Molecular analysis of saliva
̶ Saliva as a diagnostic fluid
̶ saliva collection: non-invasive, easy, painless,
repeatable (available material), can be used for all age
categories
̶ markers of diseases of the oral cavity, systemic
diseases (disease diagnostics, monitoring of disease
development depending on therapy)
̶ salivaomics – uses high-throughput technologies
(genomics, transcriptomics, proteomics, metabolomics,
lipidomics and microbiomics) to study saliva
components and identify biomarkers
Table describing examples of commonly analyzed biomarkers in whole mouth saliva;
CRP – C-reactive protein; HPLC – high performance liquid chromatography; IC – ion
chromatography; LC-MS – liquid chromatography mass spectrometry; MALDI-TOF MS matrix
assisted laser desorption ionization-time of flight mass spectrometry; RT-LAMP –
reverse transcriptase loop-mediated isothermal amplification; AOPP – Advanced
Oxidation Protein Products; TBARS – Thiobarbituric Acid Reactive Substances; TAC –
Total Antioxidant Capacity; FRAS – Free Radical Analytical Systém.
Janšáková et at.,
Klin. Biochem. Metab., 26 (47), 2018, No. 1, p. 21–26
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI13
Molecular analysis of saliva
̶ Saliva as a diagnostic fluid
̶ worse reproducibility of results  high variability
▪ technical (sampling, processing, method used)
▪ interindividual
▪ biological (influence of the condition of the oral cavity, systemic
diseases (Sjögren's syndrome), xerostomia (medicaments),
▪ ↓↓↓ analyte concentration in comparison with serum → ↑ saliva
sample volume, detection limit, depletion of abundant proteins
→ standardization
→ correlation of protein markers to saliva total protein concentration
→ standardization of used methods
Table describing examples of commonly analyzed biomarkers in whole mouth saliva;
CRP – C-reactive protein; HPLC – high performance liquid chromatography; IC – ion
chromatography; LC-MS – liquid chromatography mass spectrometry; MALDI-TOF MS matrix
assisted laser desorption ionization-time of flight mass spectrometry; RT-LAMP –
reverse transcriptase loop-mediated isothermal amplification; AOPP – Advanced
Oxidation Protein Products; TBARS – Thiobarbituric Acid Reactive Substances; TAC –
Total Antioxidant Capacity; FRAS – Free Radical Analytical System.
Janšáková et at.,
Klin. Biochem. Metab., 26 (47), 2018, No. 1, p. 21–26
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI14
Molecular analysis of saliva
̶ Saliva as a diagnostic fluid – dental caries susceptibility
̶ point-of-care testing (chair-side diagnostic kits):
̶ physical properties: volume, flow rate, viscosity, consistency
̶ pH and buffering capacity of saliva
̶ lactate
̶ determination of cariogenic bacteria S. mutans and Lactobacillus sp.
commercial kits (visual or
colorimetric detection)
commercial kits
(immunochromatographic detection
of antigen, cultivation kit)
commercial kits
(colorimetric detection)
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI15
Molecular analysis of saliva
̶ Saliva as a diagnostic fluid – dental caries susceptibility
̶ saliva protein biomarkers associated with caries susceptibility:
↑ saliva total protein, total antioxidant capacity (TAC)
↑ alpha-amylase, mucins (MUC1 a MUC5B)
↓ arginine deiminase system, albumin, proteinase 3, PRP1/3, statherin, histatin 1
↓ concentrations of calcium and bicarbonate ions
↓ urease activity
̶ saliva protein biomarkers associated with susceptibility to early childhood caries:
↑ PRPs, histatins, IgA, IgG
↓ statherin
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI16
Molecular analysis of saliva
̶ Saliva as a diagnostic fluid – examples of disease biomarkers
̶ autoimmune diseases
Sjögren's syndrome - α-amylase, carbonic anhydrase VI, lactoferrin, β2-microglobulin
̶ neurodegenerative diseases
Alzheimer's disease - total tau protein, phosphorylated tau protein, amyloid-β and alpha-synuclein
̶ genetic diseases
cystic fibrosis – Ca, PO4
2-, Na, K, Cl, ↓ saliva volume, urea, uric acid, prostaglandin E2
̶ cancer
squamous cell carcinoma – IL-8, IL-6, IL-1β, IL-4, IL-1, VEGF, HER2, tissue polypeptide antigen (TPA) and EGFR,
LDH, N-α-acetyltransferase 10 protein (Naa10p), carcinoembryonic antigen (CEA) protein, serum basic fibroblast
growth factor (bFGF), transferrin, cyclin D, Maspin, specific mRNAs ………….
breast cancer - HER2/neu (C-erbB-2), VEGF, EGF, specific mRNAs, autoantibodies against HER2 and MUC-1
pankreas cancer – transcriptomic markers of mRNAs (KRAS, MBD3L2, ACRV1 a DPM1), specific miRNA,
lactoperoxidase, Cyclophilin B, Cytokeratins (14, 16 a 17)
̶ endocrine diseases
Cushing's syndrome and Addison's disease - cortisol
sex hormones - polycystic ovary syndrome, menopause / andropause, anovulation, hypogonadism,
hyperestrogenism
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI17
Molecular analysis of saliva
̶ Saliva as a diagnostic fluid – examples of disease biomarkers
̶ cardiovascular diseases
CK-MB, myoglobin, troponin I, myeloperoxidase, inflammation markers (CRP, TNF-α, MMP-9), cellular adhesion
molecules (soluble CD40 and ICAM-1)
̶ metabolism
diabetes mellitus type 2 - 1,5-anhydroglucitol, CRP, leptin, IL-6, TNF-α
̶ infectious diseases
HIV - antibodies against HIV
viruses - IgM / IgA antibodies, viral RNA
Candidiasis, amebiasis - Candida sp., Entamoeba histolytica (antibodies)
Hepatitis - DNA of HBV virus
Peptic ulcer disease, gastritis - Helicobacter pylori (IgG antibodies, H. pylori DNA)
̶ allergy
food allergies - IgE and IgG1
̶ periodontitis
bacteria of ‚red complex‘ (Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola), Aggregatibacter
actinomycetemcomitans
biomarkers - MMP-8, MMP-9, osteoprotegerin, ALT, α-amylase
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI18
Molecular analysis of saliva
̶ Saliva as a diagnostic fluid
– diseases biomarkers
https://www.oraldna.com/trends-in-salivary-testing/
https://www.ada.org/en/member-center/oral-health-topics/salivary-diagnostics
19
Molecular analysis of
oral microbiome
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI
https://www.jorthodsci.org/viewimage.asp?img=
JOrthodontSci_2014_3_4_125_143233_f6.jpg
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI20
Molecular analysis of OM
̶ Oral microbiome
– biomarker of dental caries and periodontitis
̶ polymicrobial infection → microbiological profile of patients
→ disease susceptibiity
→ early diagnosis of disease (before onset of symptoms)
→ monitoring the course of disease and effectiveness of treatment (shift of microbiota from dysbiosis to eubiosis),
targeted treatment
→ an effective tool for disease prevention (evidence of patient dental care)
→ development of new therapeutic approaches, personalized dental treatment
→ research - an effort to fully characterize a "healthy" microbiome (Which components of the microbiome should be
monitored to evaluate the return of the microbiome from dysbiosis to a state compatible with health? Is it sufficient to
monitor only selected key species or is it necessary to use multispecies assays?)
https://doi.org/10.1038/s41579-018-0089-x
Microbial colonization occurs on all available surfaces, and microorganisms can also penetrate epithelial
tissues and cells. The microbiota assembles into biofilm communities on the abiotic and biotic surfaces.
In health (left), eubiotic biofilms maintain a homeostatic balance with the host. In disease (right), caries
and periodontitis ensue when biofilms become dysbiotic, resulting in increased levels and duration of
low pH challenge and the induction of destructive inflammatory responses, respectively. EPS,
extracellular polymeric substance; GCF, gingival crevicular fluid.
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI21
Molecular analysis of OM
̶ Oral microbiome – methods of analysis
̶ point-of-care testing (chair-side diagnostics) :
dental caries risk – device CariScreen Susceptibility Testing Meter (Oral
BioTech LLC) – after wiping the plaque off the tooth surface by special brush
a reaction of ATP occurs nad bioluminescence is measured by the device
→ bacterial activity S. mutans
̶ analysis in laboratory
commercial kits – an example
periodontitis – kit MyPerioPath® (OralDNA Lab), saliva test, testing presence
and amount of 11 bacteria species that promote periodontitis onset and
development (quantitative real-time PCR analysis)
https://www.creative-bioarray.com/support/atp-
cell-viability-assay.htm
https://carifree.com/product/pro-cariscreen-
testing-meter/
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI22
Molecular analysis of OM
̶ Oral microbiome – methods of analysis
̶ sampling
→ microbial communities present on different parts of the oral cavity (saliva, tongue, palate, buccal mucosa,
tooth surfaces, gums, supra- / subgingival plaque, tonsils, throat) show an overall similarity, but with small
differences
→ sample collecting from a specific site / rinsing of the whole mouth
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI23
Molecular analysis of OM
̶ Oral microbiome – methods of analysis
̶ microbiological cultivations
→ OM is one of the most complex microbial communities in the human body → some species have not yet been
cultivated
̶ 16S rRNA sequencing
→ sequencing of the conserved gene for 16S rRNA, the most common method, taxonomic data only
̶ whole genome shotgun sequencing (WGS)
→ DNA is randomly cut and then subjected to Sanger sequencing or NGS; a tool for metagenomic analysis; not only
taxonomic data but also biological functional profiles of the microbial community
̶ qPCR
→ not only the gene for 16S rRNA, but also other genes; also allows quantification
̶ ELISA test
→ antigens, P. gingivalis
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI24
Molecular analysis of OM
̶ Oral microbiome
̶ database
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI25
Molecular analysis of OM
̶ Oral microbiome
– a potential biomarker of
systemic diseases
dysbiosis as a noninvasive
biomarker
Oral and systemic diseases associated with the oral microbiome. A representation of the associations found between diseases with increases
or decreases of the abundances of organisms in the oral cavity. Organisms listed in blue have been shown to be increased in abundance in
the oral cavity in individuals presenting with the noted disease, and organisms listed in red have been shown to be decreased. Those in
purple may be either increased or decreased depending on the conditions or progression of the disease.
doi:10.3390/microorganisms8020308
26
Genetic association
studies - candidate
gene approach
(case-control studies)
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI
http://www.discoveryandinnovation.com/BIOL20
2/notes/lecture25.html
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI27
Genetic association studies
̶ Candidate genes
̶ Selection of suitable candidate genes
in general, based of known biological, physiological and/or functional relevance to the disease
search for new potential genes (alleles) in the whole genome (GWAS, QTL - quantitative trait locus)
̶ Suitable candidate genes for caries association studies
genes participating in tooth development and affecting its morphology
genes related to immune response
genes related to production and composition of saliva
genes related to taste preferences
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI28
Genetic association studies
̶ Candidate genes
̶ Selection of alleles (polymorphisms)
SNP, CNV, VNTR
based on studies already performed in other populations, GWAS, QTL
minor allele frequency is sufficient in a given population
(↓ frequency of allele in the population  ↑ number of cases / controls)
linkage disequilibrium among SNPs → tagSNP
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI29
Genetic association studies
̶ Methods of genotyping
̶ selection of an appropriate methodical approach
number of polymorphisms to be determined
total number of samples to be genotyped
quality of DNA sample (genomic DNA - blood, saliva, buccal swab)
costs - equipment, chemicals, consumables
availability of commercial genotyping services
Genetika v zubním lékařství, Jaro/2021 – Zubní lékařství, Ústav patologické fyziologie LF MU30
Genetic association studies
̶ Metody genotypizace
̶ výběr vhodného metodického přístupu – podle čeho vybírat
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI31
Genetic association studies
̶ Genotyping methods
̶ PCR+RFLP (restriction fragment lenght polymorphism)
→ PCR amplification followed by specific restriction digestion
polymorphism is part of a palindromic sequence
Hinf I
5´… G A N T C … 3´
3´… C T N A G … 5´
II. alela → 5´… G A G T C … 3´
I. alela → 5´… G A G C C … 3´
Huang, BCM Cancer (2008)
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI32
Genetic association studies
̶ Genotyping methods
̶ allele-specific PCR
→ primers that are specific for particular allele
→ if the allele is present → amplification product is generated → detection
https://doi.org/10.1016/j.jim.2004.10.007
Genetika v zubním lékařství, Jaro/2021 – Zubní lékařství, Ústav patologické fyziologie LF MU33
Genetic association studies
̶ Genotyping methods
̶ real-time PCR → fluorescently labeled hybridization probes
→commercial TaqMan probes
heterozygote
homozygote
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI34
Genetic association studies
̶ Genotyping methods
̶ Sanger sequencing → sequence of a part of DNA with polymorphism
heterozygote
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI35
Genetic association studies
̶ Genotyping methods
̶ Single Nucleotide Polymorphism
Detection with the iPLEX® Assay
and the MassARRAY® System
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI36
Genetic association studies
̶ Genes that have been associated
with increased risk of dental carries
̶ Proteins involved in development of enamel
AMELX – Amelogenin gene
ENAM – Enamelin gene
TUFT1 – Tuftelin gene
KLK4 – gene encoding Kallikrein-related peptidase 4
AMBN – Ameloblastin gene
TFIP11 – gene encoding Tuftelin-interacting protein 11
MMPs (MMP20) – genes encoding Matrix Metalloproteinases
Schematic diagram of histological changes in amelogenesis. The histological development of enamel crystals goes hand in hand
with changes in ameloblast morphology. Undifferentiated epithelial cells receive signals to transform into secretory ameloblast
cells of some 75 μm tall and ∼5 μm in diameter with a specialized distal cell process (Tomes’ process) which plays an important
role in matrix exocytosis. These same cells will retransform into shorter cells (∼35 μm tall) during maturation devoid of the
Tomes’ process. In maturation stage, ameloblasts undergo cyclical changes from a cell with a distal ruffled border, the
ruffled‐ameloblast (RA), to a cell with a smooth distal border, the smooth‐ameloblast (SA). Tight junctions are found at the basal
and apical pole of secretory ameloblasts. The apical or distal pole is closest to the enamel crystals. In RA cells, tight junctions
are found only at the apical pole but in SA cells they are located at the basal pole. Organellar distribution differs in cells at each
stage (see text for details). SI = stratum intermedium, PL = papillary layer, EMPs = enamel matrix proteins. MMP20 and KLK4
are the main proteases in AMEL processing. See also organellar distribution at each stage.
https://doi.org/10.1016/j.sjbs.2020.11.071
https://doi.org/10.1113/JP272775
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI37
Genetic association studies
̶ Genes that have been associated
with increased risk of dental carries
̶ Taste receptors → associated with heightened preference for sweet taste → ↑ sugar intake
TAS2R38 – gene encoding Taste receptor 2 member 38 → G protein-coupled receptor, responsible for sensitivity to bitter
taste
TAS1R2 / TAS1R3 – genes encoding Taste receptor 1 member 2 and 3 → G protein-coupled heterodimeric receptor,
responsible for sensitivity to sweet taste
https://doi.org/10.3390/s100403411
https://doi.org/10.1080/00016357.2020.1832253
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI38
Genetic association studies
̶ Genes that have been associated
with increased risk of dental carries
̶ Glucose transporter → associated with heightened preference for sweet taste → ↑ sugar intake
GLUT2 – gene encoding Glucose transporter 2 – required for glucose-stimulated insulin secretion (pancreatic β-cells),
controls perception of glucose (nervous system) → control of food intake
- expression is required for the physiological control of glucose-sensitive genes, its inactivation in the liver leads
to impaired glucose-stimulated insulin secretion
https://doi.org/10.1080/00016357.2020.1832253
https://doi.org/10.3390/s100403411
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI39
Genetic association studies
̶ Genes that have been associated
with increased risk of dental carries
̶ Proteins of immune system
MBL2 – gene encoding Mannose-binding lectin (AKA Mannose-binding protein, Mannan-binding protein/lectin, Collectin 1,
MBP1, or Mannose-binding protein C)
– soluble serum lectin recognizing specific carbohydrates on bacterial surfaces → ↓ complement activation
Schematic representation of the lectin pathway of the complement system. The lectin pathway (LP) is
triggered by five pattern recognition receptors (PRR): mannose-binding lectin (MBL), ficolin-1, -2, and -3,
and collectin 11 (CL11 or CL-K1). The LP is initiated when these PRRs bind to pathogen-associated
molecular patterns (PAMPs) on the surface of pathogens or to apoptotic or necrotic cells (damageassociates
molecular patterns, DMAPs). Circulating MBL, CL11, and ficolins form complexes with MASP-1
and MASP-2. After the binding of MBL, ficolins, and CL-11 to their targets, MASP-1 auto-activates and
triggers MASP-2. Activated MASP-2 cleaves C4 and C2 allowing the assembly of the C3 (C4bC2a) and C5
(C4bC2a(C3)n)convertases and the subsequent activation of the terminal pathway. Activated MASP-1 also
cleaves C2. MAC = membrane attack complex.
https://doi.org/10.1007/978-1-4614-9209-2_7-1
https://doi.org/10.1080/08927014.2020.1856821
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI40
Genetic association studies
̶ Genes that have been associated
with increased risk of dental carries
̶ Proteins in saliva
DEFB1 – gene encoding β-Defensin 1 – an antimicrobial peptide from family of Defensins (alpha, beta), which includes
cysteine-rich cyclic cationic peptides. They are part of innate immunity, create channels in the cytoplasmic
membrane of bacteria, stimulate the immune system incl. complement (classical pathway), act as chemoattractants.
LTF – Lactoferrin gene – transport globular glycoprotein, binds free iron. Part of innate immunity, antibacterial (peroxides are
formed when interacting with bacterial membranes), antiviral (competition of adhesion of viral particles to host cells,
binding to particles of certain types of viruses), antifungal (against C. albicans) activity, stimulation of phagocytosis.
LYZL2 – gene encoding Lysozyme-like protein 2 – part of C-type Lysozyme family.
Hydrolyzes glycosidic bonds in peptidoglycans (breaking down the cell wall of G+ bacteria).
https://doi.org/10.1590/1807-3107bor-2017.vol31.0041
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI41
̶ Genes that have been associated
with increased risk of dental carries
̶ Proteins in saliva
CA6 – gene encoding Carbonic anhydrase VI – enzyme also called ‚gustin‘, catalyzes the hydratation of carbon dioxide to form
bicarbonate ions and protons. Saliva pH maintenance (bicarbonate buffer system)
MUC7 – gene encoding Mucin 7 – low molecular weight glycoprotein (MG2), participates in the formation of acquired pellicle and
thus in bacterial adhesion and biofilm formation
MUC5B – gene encoding Mucin 5B – glycoprotein (MG2), participates in the formation of acquired pellicle and thus in bacterial
adhesion and biofilm formation
PRH1 – gene encoding salivary acidic proline-rich phosphoprotein 1, participates in the formation of acquired pellicle and thus in
bacterial adhesion and biofilm formation
Genetic association studies
https://doi.org/10.1590/1807-3107bor-2017.vol31.0041
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI42
Genetic association studies
̶ Pitfalls of genetic association studies of dental caries
̶ too many factors play a role in etiopathogenesis → set of patients (cases) can never be perfectly categorized → perfectly
defined set of cases cannot be created → maximally defined set of cases as far as possible
̶ most studies do not confirm the association, only suggests (some studies even give conflicting results)
→ further association studies (more samples) - studies of individual polymorphisms (but their effect may be small), but also
genes and loci (gene-based and gene-cluster analysis) → further strengthening of results
→ meta-analysis – a combination of data obtained by an exhaustive search of published and unpublished data worldwide →
increasing the consistency of the results (by increasing the strength of the result). Many primary studies are too small to
demonstrate an important clinical effect (not strong enough). A combination of all studies that answer the same clinical
question → increase in statistical power or significance level
̶ detailed questionnaires for evaluating the influence of psychological, sociological, economic and behavioral factors →
fragmentation of set of cases to too many groups of too few patients
Genetics in Dentistry, Spring/2021 – Dentistry, Department of Pathophysiology MED MUNI43
https://doi.org/10.1111/adj.12262