Fetal Tongue Research Articles

Olfactory-like receptor cDNAs are present in human lingual cDNA libraries

Olfactory and pheromone receptors (ORs) constitute a large family of G-protein-coupled receptors involved in the detection and transduction of odorant signals. Using degenerated primers complementary to the highly conserved transmembrane domains II, III, VI, and VII within this protein family, Gaudin et al. have recently described the expression of several OR genes in foetal human tongue. Among the nine genes identified in human foetal tongue ( HTPCR06, HGMP07I, JCG6, TPCR85, JCGI1, JCG2, JCG3, JCG5, and JCG9), only four ( HTPCR06, HGMP07I, JCG3, and JCG5) were found to be expressed in adult tongue, suggesting that ORs might perform developmental functions in this organ. The objective of our work was to obtain additional information about the expression of olfactory-like genes in human tongue. In the present study, the synthesis and the screening of a cDNA library from epithelial cells of human adult tongue is reported. Two kinds of PCR analysis were performed. First, partial olfactory-like receptor cDNAs amplified with the degenerated primers used by Gaudin et al. were cloned and described. Second, a comparison of the expression profiles of the olfactory-like receptor genes previously identified before was carried out using specific primers. Among the genes studied we found that four genes ( HTPCR06, JCG3, JCG5, and JCG6) are expressed in epithelial cells of the surface of the adult tongue. Additionally, we show that three olfactory-like receptor genes OR7A5/ HTPCR2, OR6Q1, and OR7C1/ TPCR86 are also expressed in these cells.

Isolation and developmental expression analysis of Tbx22, the mouse homolog of the human X-linked cleft palate gene.

Mutations in the TBX22 gene have been identified recently in patients with the X-linked cleft palate and ankyloglossia syndrome, suggesting that the TBX22 transcription factor plays an important role in palate development. However, because ankyloglossia has been reported in the majority of patients with TBX22 mutations, it has been speculated that the cleft palate phenotype is secondary to defective fetal tongue movement. To understand the role of TBX22 in disease pathogenesis and in normal development, it is necessary to carry out a detailed temporal and spatial gene expression analysis. We report here the isolation and developmental expression analysis of the mouse homolog Tbx22. The mouse Tbx22 gene encodes a putative protein of 517 amino acid residues, which shares 72% overall amino acid sequence identity with the human TBX22 protein. By using interspecific backcross analysis, we have localized the Tbx22 gene to mouse chromosome X, in a region syntenic to human chromosome Xq21, where the TBX22 gene resides, indicating that Tbx22 is the ortholog of human TBX22. Our in situ hybridization analysis shows that Tbx22 is expressed in a temporally and spatially highly restricted pattern during mouse palate and tongue development. Together with the mutant phenotypes in human patients, our data indicate a primary role for Tbx22 in both palate and tongue development.

New GPCRs from a human lingual cDNA library.

Sweet and bitter taste perception involve G protein coupled receptors (GPCRs) present at the taste receptor cell surface. It is likely that various mechanisms are active and various families of GPCRs are involved in the perception of these tastes. The expression of GPCRs in human tongue was studied using degenerated primers corresponding to transmembrane domains 2 or 3 (for 5' primer), 6 or 7 (for 3' primer) of olfactory-like receptors in reverse transcription-polymerase chain reaction experiments. It was demonstrated that four previously identified, eight new olfactory-like receptor genes, three previously known and eight new olfactory-like receptor pseudogenes, mostly located on chromosome 11, are expressed in adult tongue and/or in fetal tongue. Previously identified genes include HGMP071, HTPCR06, TPCR120 and TPCR85 whose cDNAs were originally isolated from male germinal cells. New genes were named JCG1, JCG2, JCG3, JCG4, JCG5, JCG6, JCG9 and JCG10. HGMP071, HTPCR06, TPCR120, JCG3 and JCG5 are also expressed in the epithelium of adult tongue, whereas all these genes are expressed in fetal tongue. Although functional studies are needed before definitive conclusions are made, the obtained results imply that lingual olfactory-like receptors could be involved in taste perception.

Intrauterine growth and ultrasound findings in fetuses with Beckwith-Wiedemann syndrome

To assess intrauterine growth in a series of nine fetuses diagnosed with Beckwith-Wiedemann syndrome. Infants confirmed postnatally to have Beckwith-Wiedemann syndrome were identified from records maintained in the Division of Clinical Genetics. Antenatal ultrasound and birth records were evaluated. Head circumference (HC), abdominal circumference (AC), and estimated fetal weight (EFW) were assigned percentiles based on gestational age. Newborn HC and birth weight were also assigned percentiles. Polyhydramnios was diagnosed using either amniotic fluid index or documented subjective assessment. Nine infants with Beckwith-Wiedemann syndrome had antenatal ultrasound examinations. Seven of these had more than one examination. Two infants were suspected to have Beckwith-Wiedemann syndrome in utero. Important ultrasound findings included omphalocele (four), enlarged liver and kidneys (one), and enlarged liver (one). Fetal tongue protrusion on ultrasound was not identified in any fetus. Six of nine fetuses (66%) with ultrasound examinations after 25 weeks' gestation had polyhydramnios. Evaluation of the fetal HC, AC, and EFW percentiles demonstrated that fetuses with Beckwith-Wiedemann syndrome may exhibit accelerated growth as early as 25-30 weeks' gestation, but may exceed the 90th percentile only after 36 weeks' gestation. Fetuses with omphalocele, polyhydramnios, and an AC less than the 90th percentile may have Beckwith-Wiedemann syndrome. Polyhydramnios and accelerated growth beginning between 25 and 36 weeks' gestation, even without omphalocele, should alert the physician to the possibility of Beckwith-Wiedemann syndrome.

Development of the fetal tongue between 14 and 26 weeks of gestation: in utero ultrasonographic measurements

Our objective was to establish nomograms for fetal tongue measurements from 14 weeks until mid-gestation by using transvaginal and transabdominal high-resolution ultrasound techniques. A prospective, cross-sectional study was performed on 120 normal singleton pregnancies between 14 and 26 weeks of gestation. Tongue circumference was measured by transvaginal ultrasonography between 14 and 17 weeks, and by abdominal ultrasound between 18 and 26 weeks of gestation. Fetal tongue circumference, as a function of gestational age, was expressed by the regression equation: tongue circumference (mm) = -23.9 + 3.75 x gestational age (weeks). The correlation, r2 = 0.95, was found to be highly statistically significant (p < 0.0001). The normal mean of tongue circumference per week and the 95% prediction limits were defined. During the study period we evaluated two cases with tongue circumference outside these 95% confidence limits: one had microglossia, the other macroglossia, and both were found to be associated with abnormal fetal karyotype. The presented normative data may be helpful in the prenatal diagnosis of suspected congenital syndromes that include, among their manifestations, tongue growth disturbances.

A type I ovine interferon with limited similarity to IFN-α, IFN-ω and IFN-τ: gene structure, biological properties and unusual species specificity

A gene encoding a 195 amino-acid (a.a.) polypeptide with a putative 23 a.a. signal sequence that had about 60% a.a. sequence identity to ovine interferon-ω (OvIFN-ω) and 55% or less identity to BoIFN-τ, OvIFN-τ and all known IFN-α and -β has been identified from an ovine genomic DNA library. Surprisingly, it shared almost complete identity to genes for rabbit IFN-ω within its coding sequence and proximal promoter region, although the two were different in their 3′-ends. This IFN (tentatively termed ovine IFN-ω variant, OvIFN-ωv), purified in recombinant form from E. coli, had normal antiviral activity when tested on sheep fetal tongue and brain cells and rabbit kidney cells, but very low activity towards bovine, goat and human cells. It competed with 125I-labeled BiIFN-τ for binding to IFN receptors on ovine cells. Expression of OvIFN-ω v was not detected by reverse transcription-PCR either in ovine peripheral blood leukocytes infected with Sendai virus, or in any other tissues examined. OvIFN-ω v may represent a previously unrecognized, non-virally inducible type I subtype distinct from IFN-α, -β, -ω and -τ. The presence of a conserved gene in rabbit and sheep could reflect a recent interspecies transfer.

Microvasculature of the dorsal mucosa of human fetal tongue: A SEM study of corrosion casts

The vasculature of the dorsal mucosa of the tongue was investigated in 18-21 week human fetuses by corrosion casting and scanning electron microscopy. Microvascular systems of the fungiform, foliate and circumvallate papillae, albeit less complex, showed similarity to those described in children, while the capillary networks of the filiform papillae were not yet fully developed, having either a knot-like or cone-like form instead of the corolla-like pattern typical of the postnatal period. Morphological features suggesting angiogenesis included both capillary outgrowths characteristic of vascular sprouting and tiny holes in the vascular walls regarded as evidence of intussusceptive capillary growth. The subpapillary vascular network supplying and draining the papillary vessels was composed of the more superficial capillary bed and the deeper plexus of larger arterioles and venules.

Effects of insulin-like growth factors on organotypic cocultures of embryonic rat brainstem slices and skeletal muscle fibres

Embryonic rat brainstem slices including the facial and hypoglossal motor nuclei were maintained in organotypic cocultures with explants of embryonic tongue or post-natal skeletal muscle for periods up to 3 weeks. Survival and differentiation of motoneurones were dependent both on the type of muscle explant and its position relative to the brainstem. Tongue explants induced a more important glial outgrowth, a motoneurone migration towards the muscle, earlier muscular contractions and a more complete neuronal and muscular differentiation. Since the foetal tongue contains IGF levels as high as foetal liver, these effects might be due in part to diffussion of IGF from the explanted muscle. Indeed, foetal liver explants or crude foetal liver extracts induced effects similar to those of tongue explants. These effects can be reproduced by addition of IGF-1 or IGF-2, or both, into the culture medium. Although IGF-1 and IGF-2 had similar effects, IGF-1 induced a more pronounced muscular differentiation and IGF-2 promoted neuronal differentiation. Our results suggest that IGFs are good candidates as muscle-derived neurotrophic factors promoting survival and differentiation of rat cranial motoneurones. These results also stress the importance of neuroglial trophic interactions and target development.

Prenatal diagnosis of cleft palate: contribution of color Doppler ultrasound.

The antenatal diagnosis of cleft palate by ultrasound can sometimes be difficult by conventional B-mode imaging, especially when the tongue is in its normal position. We describe two cases which illustrate the value of color Doppler in the antenatal diagnosis of cleft palate. In the first case, at 32 weeks' gestation, there was a large defect with a massive passage of flow extending from the buccal cavity into one of the nasal fossae. In the second case, at 22 weeks' gestation, a parasagittal view demonstrated the fetal tongue to be in the normal position, but there was an abnormal trajectory off low from the buccal cavity into one of the nasal fossae followed by an exit at the level of the cleft. Although a cleft lip was demonstrated on B-mode imaging, we would not have been able to make the diagnosis of cleft palate without color Doppler. This is the first report describing the contribution of color Doppler to the antenatal diagnosis of cleft palate.

Characterization of cytokeratin patterns in the developing human tongue.

The characterization of cytokeratin (CK) in adult oral mucosa and developing teeth have been well documented in human. Cytokeratin distribution in developing oral mucosa has not yet been described. The aim of this study was to identify the expression of CK in human fetal tongue (week 10 to week 23) and to correlate the results with morphological maturation. Simple epithelial CK are expressed in all cell layers during the early stages, essentially in peridermal cells. From the 14th week, CK 18 is present only in the taste buds, making this polypeptide a reliable marker for this sensory organ. CK 4 and 13 are expressed from the 10th to the 23rd week by both ventral and dorsal lingual epithelia. Terminal differentiation keratins (CK 1, 2 and 10-11) can only be detected immunohistochemically at the 14th week in some cells on the external surface of some papillae. The number of these papillae and positive cells increase at the 19th and 23rd weeks. The terminal differentiation markers are expressed several weeks earlier than the formation of a well-distinguished keratinized layer.

Susceptibility of a Fetal Tongue Cell Line Derived from Bighorn Sheep to Five Serotypes of Bluetongue Virus and its Potential for the Isolation of Viruses

A cell line (BHFTE) was derived from a tongue explant of a bighorn sheep fetus (Ovis canadensis nelsoni). The cells have been maintained through 23 serial passages, and the modal number of chromosomes was calculated to be 55. Monolayer cultures were shown to be susceptible to various viruses, including bluetongue virus (BTV). Of 5 BTV serotypes (2, 10, 11, 13, and 17) tested, each produced a cytopathic effect (CPE) on initial passage at 33 C. A field isolate (serotype 10) of BTV from a black-tailed deer (Odocoileus hemionus columbianus) in its second passage in Vero-M cells also produced CPE when inoculated into BHFTE cells. Antigens of BTV were demonstrated by direct immunofluorescence in the cytoplasm of BHFTE cells inoculated with homogenates of chicken embryos injected with clinical specimens from a domestic sheep and an Arabian oryx (Oryx gazella leucoryx). A suspension of BTV-infected gnats (Culicoides spp.) produced CPE and BTV-specific fluorescence on the first passage in cells inoculated with a suspension of blood from sheep experimentally infected with BTV. Additionally, selected bovine viruses induced CPE in the cells. The cell line, which is free of mycoplasma and bovine viral diarrhea virus contamination, may be useful in diagnostic medicine and research involving the ruminant species.

Healing of specialized tongue epithelium following cryosurgery

Although cryosurgery of oral tissues has been extensively studied, there is little information concerning healing and repapillation of the dorsum of the tongue. Using light, transmission, and scanning electron microscopy, an investigation of the sequence of reformation of papillae was carried out in the hamster. Four days postoperatively there was mitotic activity and cell migration at the periphery of the wound. At the edge of the ulcer there were partially damaged tongue papillae with evidence of recovery. Damaged papillae had regenerated completely within 2 weeks. In the central ulcerated area, epithelium healed by migration and, within this new epithelium, tongue papillae commenced to form by a process similar to that seen in the fetal tongue. Repapillation of the central area of the lesion was complete 6 weeks after operation, leaving minimal scarring. The details of these processes are described.

Genetic aspects of the effects of methylmercury in mice: the incidence of cleft palate and concentrations of adenosine 3':5' cyclic monophosphate in tongue and palatal shelf.

Concentrations of adenosine 3':5' cyclic monophosphate (cAMP) were measured in the tongues and palates of 14.5-day-old fetuses from control and methylmercury-treated mothers of four inbred lines of mice which represent the four possible combinations of two H-2 alleles and two residual genetic backgrounds. The incidence of cleft palate in fetuses from control and methylmercury-treated mothers was also examined. The H-2 alleles significantly affected the degree of reduction of cAMP concentration in palates seen in fetuses from mothers treated with methylmercury. Neither the H-2 allele nor the residual genetic background played a role in the effect of methylmercury on cAMP concentrations in fetal tongues. The magnitude of increase in the incidence of cleft palate with methylmercury treatment was approximately the same for all lines. Thus, methylmercury-induced cleft palate may not be mediated by the reduction of cAMP. Finally, fetuses with cleft lip had increased palatal cAMP levels, whether or not they were from control or methylmercury treated mothers.

Scanning electron microscopy of developing papillae on the tongue of human embryos and fetuses

The appearance and differentiation of papillae on dorsal and lateral surfaces of human embryonic and fetal tongues, at various developmental ages, were studied by scanning electron microscopy. Formaldehyde and phosphate buffer fixation provided satisfactory preservation. At 8–9 weeks, the anterior two-thirds of the tongue showed no obvious signs of papillae. In contrast, just anterior to the sulcus terminalis rounded elevations were seen, suggesting initial signs of circumvallate papillae. At 10–13 weeks, the distribution and shape of elevations on the anterior two-thirds of the tongue indicated the beginning of fungiform papillae. Openings located on the dorsal surface of many of these fungiforms contained an amorphous central structure projecting out of the papilla. First signs of foliate papillae were seen at 10 weeks. At 15–18 weeks, fungiform and filiform papillae were recognized, although sometimes their borders were obscured by scaling epithelial cells. At 23–26 weeks, all papillae exhibited their adult form.

Palate development after fetal tongue removal in cortisone-treated mice.

Morphological studies of cortisone-induced cleft palate have shown retardation in the rotation of palatine shelves from a sagittal to a transverse plane. Cortisone also reduces fetal muscular movements, which may explain why displacement of the tongue from between the palatine shelves is delayed. Previous work with extrauterine development of control fetuses demonstrated that fetal membranes and tongue were major obstacles to shelf rotation. Thus, removal of these obstacles might permit rotation and fusion of palatine shelves in cortisone-treated fetuses. In the present experiment, fetuses from cortisone-treated strain CD-1 mice were released from uterus and membranes and allowed to develop for eight hours in a fluid medium with the umbilical cord left intact. Compared to 4% fusion in utero, there was palatal fusion in 20% of fetuses released from membranes. When the fetal tongue was removed during extrauterine development, the frequency of fusions increased to 61%. Fusion appeared normal by the criteria applicable through light microscopy. Thus, cortisone induces cleft palate primarily through interference with shelf rotation. The palatine shelves of treated fetuses retain their ability to fuse when they can come in contact during the normal time for palate closure.

Serodiagnosis of nosematosis by immunofluorescence using cell-culture-grown organisms.

This simple procedure for the detection of serum antibodies to Nosema cuniculi in rabbits and other host species incorporates indirect immunofluorescence and uses as antigen N. cuniculi isolated from urine and cultured in a human fibroblast-like cell line derived from foetal tongue. Examination of rabbit sera from 8 institutions indicated that no institution was free from Nosema infection. The prevalence of infection in 4 separate Australian rabbit colonies varied from 25 to 75%.

Differentiation of lingual filiform papillae of the rat in organ culture

Explants of 14-day rat foetal tongue were grown in organ culture for periods up to 6 days. Filiform papillae similar to those that develop in vivo developed in the cultures. It is concluded that development of these complex structures can occur in the absence of nervous or vascular influences and is probably dependent on interaction between epithelium and mesenchyme.

Myoneural maturation and function of the foetal rat tongue at the time of secondary palate closure

Most authors consider the tongue active in secondary palate closure; some consider it passive; but specific information is wanting. We therefore studied the Holtzman rat foetal tongue by direct observation, histologically, under direct and neural stimulation, and when curarized. The tongue has differentiated into myoblasts (longitudinalis and verticalis) and young fibres (transversus, hyoglossus, genioglossus) four hours prior to closure. At this age it responds to both direct electrical and XII nerve nucleus stimulation. Curarization at high levels neither prevents closure nor abolishes foetal reflexes. The tongue myoneural apparatus is functional at palate closure.

Electron microscope study of the developing taste bud in rat fungiform papilla

An electron microscope study of the morphological sequence of events occurring in the development of the fungiform papilla and taste bud on the rat tongue has been performed. For convenience of description, five stages of development have been defined: 1. Stage 1: Formation of epithelial eminences associated with connective tissue papillae on the dorsal surface of the embryonic tongue. Connective tissue cells are seen in close apposition to the basement membrane underlying the epithelial eminences. These eminences have a distribution on the fetal tongue similar to that of fungiform papillae on the adult tongue. 2. Stage 2: Growth of nerve fibers into the connective tissue core of the forming fungiform papilla. Small, dense granules are seen in the proximal cytoplasm of the basal layer of epithelial cells at the top of the fungiform papilla. 3. Stage 3: Invasion of epithelium at the top of the fungiform papilla by nerve processes. Associated with this is the appearance of clusters of vesicles in the epithelial cells near their area of contact with nerve processes. These vesicles have been interpreted as morphological evidence of an interaction between epithelial cells and nerve processes, an interaction which precedes differentiation of the cells into taste bud cells. 4. Stage 4: Differentiation of cells which assume the configurations arbitrarily designated as peripheral, basal, and type I cells, the latter possessing apical microvilli. The designation of cell types is employed for convenience to describe stages of cellular differentiation. The surface of the fungiform papilla is keratinized. 5. Stage 5: The appearance of type II cells and the taste pore. The type II cells are thought to play an active role in the formation and maintenance of the taste pore.