The dorsal lingual epithelium, which is composed of taste buds and keratinocytes differentiated from K14⁺ basal cells, discriminates taste compounds and maintains the epithelial barrier. N6-methyladenosine (m⁶A) is the most abundant mRNA modification in eukaryotic cells. How METTL3-mediated m⁶A modification regulates K14⁺ basal cell fate during dorsal lingual epithelium formation and regeneration remains unclear. Here we show knockout of Mettl3 in K14⁺ cells reduced the taste buds and enhanced keratinocytes. Deletion of Mettl3 led to increased basal cell proliferation and decreased cell division in taste buds. Conditional Mettl3 knock-in mice showed little impact on taste buds or keratinization, but displayed increased proliferation of cells around taste buds in a protective manner during post-irradiation recovery. Mechanically, we revealed that the most frequent m⁶A modifications were enriched in Hippo and Wnt signaling, and specific peaks were observed near the stop codons of Lats1 and FZD7. Our study elucidates that METTL3 is essential for taste bud formation and could promote the quantity recovery of taste bud after radiation.
Animals ; Epithelium/metabolism* ; Homeostasis ; Methylation ; Methyltransferases/metabolism* ; Mice ; RNA ; Taste Buds/metabolism*

OBJECTIVES: To identify the alternative splicing isoform of mouse sweet taste receptor T1R2, and investigate the effect of lipopolysaccharide (LPS) local injection on T1R2 alternative splicing and the function of sweet taste receptor as one of the bacterial virulence factors. METHODS: After mouse taste bud tissue isolation was conducted, RNA extraction and reverse transcription polymerase chain reaction (PCR) were performed to identify the splicing isoform of T1R2. Heterologous expression experiments RESULTS: T1R2 splicing isoform T1R2_Δe3p formed sweet taste receptors with T1R3, which could not be activated by sweet taste stimuli and significantly downregulated the function of canonical T1R2/T1R3. Local LPS injection significantly increased the expression ratio of T1R2_Δe3p in mouse taste buds. CONCLUSIONS LPS stimulation affects the alternative splicing of mouse sweet taste receptor T1R2 and significantly upregulates the expression of non-functional isoform T1R2_Δe3p, suggesting that T1R2 alternative splicing regulation may be one of the mechanisms by which microbial infection affects host taste perception.
Alternative Splicing ; Animals ; Lipopolysaccharides ; Mice ; Receptors, G-Protein-Coupled/metabolism* ; Taste ; Taste Buds

The nutritional and metabolic status alters the peripheral taste perception and food intake by participating in the modulation of taste information integration. The taste receptors and neuropeptides in the taste buds are the important targets of this modulation process. To explore the effects of nutritional status on the expressions of galanin and its receptors in the taste buds, we compared the mRNA levels of galanin and its specific receptor GalR2 in the taste buds among the high-fat diet induced obese rats (HF), chronically restricted diet rats (CR) and control rats. The high-fat diet, half of chow diet, and normal chow diet were given to HF, CR and control groups for 6 weeks, respectively. The body weight and some metabolic indexes, including blood glucose, triglyceride and cholesterol levels were detected. The mRNA expressions of galanin and its receptors in taste buds were determined using real-time PCR. Results showed that compared with control rats, the body weights, levels of blood glucose and triglyceride were significantly elevated in HF rats; while the mRNA expressions of galanin and GalR2 were dramatically decreased. However, galanin mRNA expression in CR rats was increased to 2.3 times of that in control group. Considering the results obtained from our previous studies, we conclude that the behavioral changes in tasting choice of HF rats may be related to the expressions of galanin and GalR2 in the taste buds. The changes of galanin and GalR2 in taste buds are involved in the peripheral mechanism of nutritional status regulating taste perception and feeding behavior in rats.
Animals ; Body Weight ; Galanin ; metabolism ; Nutritional Status ; RNA, Messenger ; metabolism ; Rats ; Receptor, Galanin, Type 2 ; metabolism ; Taste Buds ; metabolism

Taste is mediated by multicellular taste buds distributed throughout the oral and pharyngeal cavities. The taste buds can detect five basic tastes: sour, sweet, bitter, salty and umami, allowing mammals to select nutritious foods and avoid the ingestion of toxic and rotten foods. Once developed, the taste buds undergo continuous renewal throughout the adult life. In the past decade, significant progress has been achived in delineating the cellular and molecular mechanisms governing taste buds development and homeostasis. With this knowledges and in-depth investigations in the future, we can achieve the precise management of taste dysfunctions such as dysgeusia and ageusia.
Animals ; Food ; Homeostasis ; Mammals ; Taste ; Taste Buds ; growth & development

OBJECTIVETo compare characterization of microRNAs (miRNAs) expression profiles of induced pluripotent stem cells (iPSCs) reprogrammed from human dental pulp stem cells (DPSCs) and stem cells from apical papilla (SCAP) and screen-specific microRNA.

METHODSHuman DPSCs and SCAP were reprogrammed into iPSCs using a Sendai virus vector. Total RNA of human DPSCs-iPSCs and SCAP-iPSCs were extracted. miRNAs were labeled and hybridized. Slides were scanned, and images were imported into GenePix Pro 6.0 for grid alignment and data extraction. Significant differentially expressed miRNAs between the two groups were identified using fold change and P-value and were analyzed.

RESULTSBoth human DPSCs and SCAP were successfully reprogrammed into iPSCs. Among miRNA genes analyzed by miRNA microarray, 68 were differentially expressed by more than 10-fold in DPSCs-iPSCs; 37 of these genes were up-regulated, and 31 were down-regulated. In SCAP-iPSCs, 107 genes were differentially expressed by more than 10-fold; 68 were up-regulated, and 39 were down-regulated. In both cells, only miR-302e was up-regulated, whereas 9 miRNAs were down-regulated: miR-29b-3p, miR-181b-5p, miR-4328, miR-22-5p, miR-145-5p, miR-4324, let-7b-5p, miR-181a-5p, and miR-27b-3p.

CONCLUSIONSMultiple miRNAs participated in reprogramming of human DPSCs and SCAP into iPSCs. Most miRNAs are related to cell cycle, transforming growth factor-β signaling pathways and epithelial-mesenchymal transition.

Cell Cycle ; Cell Division ; Dental Pulp ; Down-Regulation ; Electrodes ; Epithelial Cells ; Humans ; Induced Pluripotent Stem Cells ; MicroRNAs ; Taste Buds ; Up-Regulation

The tongue has 4 kinds of papillae, which are filiform, fungiform (FU), foliate (FO) and circumvallate papilla (CV). Tongue papillae except filiform papilla include taste buds. The papillae differ in taste sensitivities, likely due to differential expression of taste receptors. In this study, we evaluated differences in the expression levels of taste receptors in FU, FO and CV. Male DBA2 mice, 42-60 days old, were used in the study. Messenger RNAs were extracted from the murine epithelial tissues including FU, FO and CV. Cloned DNAs were synthesized by reverse transcription. Quantitative PCRs (qPCRs) were performed to determine mRNA expression levels of taste receptors. Results of qPCR revealed that the relative expression levels and patterns were different among FU, FO and CV. All three type 1 taste receptors were expressed FU, FO and CV at varying relative expression levels. All 35 kinds of type 2 taste receptors showed higher expression in FO and CV than in FU. Tas2r108 and Tas2r137 showed the two highest expression levels in all tested papillae. The differential expression levels and patterns of taste receptors among the three papillae could contribute to the different physiological sensitivities by tongue areas. Additional studies such as in situ hybridization or taste receptor cell activity recording is necessary to elucidate the functional relationship between expression levels of taste receptors and taste sensitivity.
Animals ; Clone Cells ; DNA ; Humans ; In Situ Hybridization ; Male ; Mice ; Mice, Inbred DBA* ; Polymerase Chain Reaction ; Reverse Transcription ; RNA, Messenger ; Taste Buds ; Tongue*

The sweet taste receptors present in the taste buds are heterodimers comprised of T1R2 and T1R3. This receptor is also expressed in pancreatic beta-cells. When the expression of receptor subunits is determined in beta-cells by quantitative reverse transcription polymerase chain reaction, the mRNA expression level of T1R2 is extremely low compared to that of T1R3. In fact, the expression of T1R2 is undetectable at the protein level. Furthermore, knockdown of T1R2 does not affect the effect of sweet molecules, whereas knockdown of T1R3 markedly attenuates the effect of sweet molecules. Consequently, a homodimer of T1R3 functions as a receptor sensing sweet molecules in beta-cells, which we designate as sweet taste-sensing receptors (STSRs). Various sweet molecules activate STSR in beta-cells and augment insulin secretion. With regard to intracellular signals, sweet molecules act on STSRs and increase cytoplasmic Ca2+ and/or cyclic AMP (cAMP). Specifically, when an STSR is stimulated by one of four different sweet molecules (sucralose, acesulfame potassium, sodium saccharin, or glycyrrhizin), distinct signaling pathways are activated. Patterns of changes in cytoplasmic Ca2+ and/or cAMP induced by these sweet molecules are all different from each other. Hence, sweet molecules activate STSRs by acting as biased agonists.
Bias (Epidemiology)* ; Calcium ; Cyclic AMP ; Cytoplasm ; Insulin ; Polymerase Chain Reaction ; Potassium ; Reverse Transcription ; RNA, Messenger ; Saccharin ; Sodium ; Taste Buds

The sensor of the taste is the taste bud. The signals originated from the taste buds are transmitted to the central nervous system through the gustatory taste nerves. The chorda tympani nerve (innervating the taste buds of the anterior tongue) and glossopharyngeal nerve (innervating the taste buds of the posterior tongue) are the two primary gustatory nerves. The injuries of gustatory nerves cause their innervating taste buds atrophy, degenerate and disappear. The related taste function is also impaired. The impaired taste function can be restored after the gustatory nerves regeneration. The rat model of cross-regeneration of gustatory nerves is an important platform for research in the plasticity of the central nervous system. The animal behavioral responses and the electrophysiological properties of the gustatory nerves have changed a lot after the cross-regeneration of the gustatory nerves. The effects of the injury, regeneration and cross-regeneration of the gustatory nerves on the taste function in the animals will be discussed in this review. The prospective studies on the animal model of cross-regeneration of gustatory nerves are also discussed in this review. The study on the injury, regeneration and cross-regeneration of the gustatory nerves not only benefits the understanding of mechanism for neural plasticity in gustatory nervous system, but also will provide theoretical basis and new ideas for seeking methods and techniques to cure dysgeusia.
Animals ; Chorda Tympani Nerve ; physiology ; Glossopharyngeal Nerve ; physiology ; Nerve Regeneration ; Neuronal Plasticity ; Rats ; Taste ; physiology ; Taste Buds ; physiology ; Tongue ; innervation

Cytokeratin (CK) comprises the intermediate filament cytoskeleton of epithelial cells. Patterns of CK expression can be regarded as a specific marker for epithelial differentiation status. The aim of this study was to identify CK expression on tongues of Korean native goats ranging from 60-day-old fetuses to newborns during prenatal development using immunohistochemistry. The tongues of fetuses were removed from 2- to 4-year-old female Korean native goats by caesarean section performed under general anesthesia. Immunohistochemistry was performed to assess CK expression patterns on developing goat tongues using serial paraffin-embedded sections. Light zones signifying CK immunoreactivity in dorsal lingual epithelia were weakly positive in 60-day-old fetuses. In 90-day-old fetuses, deep areas in dorsal lingual epithelia were strongly positive for CK expression and superficial areas were moderately positive. In 120-day-old fetuses, light zones of lingual epithelia in the vallate papilla were strongly positive for CK expression, whereas ducts of von Ebner's glands were moderately positive. In neonates, taste buds were positive for CK expression, whereas non-taste epithelial cells and von Ebner's glands were negative. These findings indicate that goat tongues have different patterns of CK expression during development and provide a morphological basis for studies on the biological mechanism of epithelial differentiation.
Anesthesia, General ; Cesarean Section ; Child, Preschool ; Cytoskeleton ; Epithelial Cells ; Epithelium ; Female ; Fetus ; Goats* ; Humans ; Immunohistochemistry ; Infant, Newborn ; Intermediate Filaments ; Keratins* ; Pregnancy ; Taste Buds ; Tongue* ; von Ebner Glands

Taste is an important sense in survival and growth of animals. The growth and maintenance of taste buds, the receptor organs of taste sense, are under the regulation of various neurotrophic factors. But the distribution aspect of neurotrophic factors and their receptors in distinct taste cell types are not clearly known. The present research was designed to characterize mRNA expression pattern of neurotrophic factors and their receptors in distinct type of taste cells. In male 45-60 day-old Sprague-Dawley rats, epithelial tissues with and without circumvallate and folliate papillaes were dissected and homogenized, and mRNA expressions for neurotrophic factors and their receptors were determined by RT-PCR. The mRNA expressions of brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), receptor tyrosine kinase B (TrkB), exclusion of nerve growth factor (NGF), neurotrophin-4/5 (NT4/5), receptor tyrosine kinase A (TrkA), receptor tyrosine kinase C (TrkC), and p75NGFR were observed in some population of taste cell. In support of this result and to characterize which types of taste cells express NT3, BDNF, or TrkB, we examined mRNA expressions of NT3, BDNF, or TrkB in the PLCbeta2 (a marker of Type II cell)- and/or SNAP25 (a marker of Type III cell)-positive taste cells by a single taste cell RT-PCR and found that the ratio of positively stained cell numbers were 17.4, 6.5, 84.1, 70.3, and 1.4% for PLCbeta2, SNAP25, NT3, BDNF, and TrkB, respectively. In addition, all of PLCbeta2- and SNAP25-positive taste cells expressed NT3 mRNA, except for one taste bud cell. The ratios of NT3 mRNA expressions were 100% and 91.7% in the SNAP25- and PLCbeta2-positive taste cells, respectively. However, two TrkB-positive taste cells co-expressed neither PLCbeta2 nor SNAP 25. The results suggest that the most of type II or type III cells express BDNF and NT3 mRNA, but the expression is shown to be less in type I taste cells.
Animals ; Brain-Derived Neurotrophic Factor ; Cell Count ; Humans ; Male ; Nerve Growth Factor ; Nerve Growth Factors* ; Protein-Tyrosine Kinases ; Rats* ; Rats, Sprague-Dawley ; RNA, Messenger ; Taste Buds*