Pathogenesis Of Cleft Palate Research Articles

Research progress in molecular mechanism of palatal development

Cleft palate is one of the most common maxillofacial birth defects, which can occur alone or accompany with many known deformities. Palatal selves need to complete the process of vertical growth, elevation, adhesion and fusion in a specific time window of embryo development. Any abnormality in this process will lead to cleft palate. Although previous studies have identified many molecular networks that regulate the growth, location and fusion of palatal selves, there are still many unknown mechanisms for palatal development. The pathogenesis of cleft palate has not been clarified so far. In recent years, the molecular research on palate development has been deepened continuously. Here we summarize major recent advances and integrate the genes and molecular pathways with the cellular and morphogenetic processes of palatal shelf growth, patterning, elevation, adhesion, and fusion, in order to comprehensively understand the genotype-phenotype functional relationship and provide assistance in formulating effective prevention strategies for cleft palate disease.

Novel investigations in retinoic-acid-induced cleft palate about the gut microbiome of pregnant mice.

Cleft palate (CP) is one of the most common congenital birth defects in the craniofacial region, retinoic acid (RA) gavage is the most common method for inducing cleft palate model. Although several mechanisms have been proposed to illuminate RA-induced cleft palate during embryonic development, these findings are far from enough. Many efforts remain to be devoted to studying the etiology and pathogenesis of cleft palate. Recent research is gradually shifting the focus to the effect of retinoic acid on gut microbiota. However, few reports focus on the relationship between the occurrence of CP in embryos and gut microbiota. In our research, we used RA to induce cleft palate model for E10.5 the feces of 5 RA-treated pregnant mice and 5 control pregnant mice were respectively metagenomics analysis. Compared with the control group, Lactobacillus in the gut microbiome the RA group was significantly increased. GO, KEGG and CAZy analysis of differentially unigenes demonstrated the most abundant metabolic pathway in different groups, lipopolysaccharide biosynthesis, and histidine metabolism. Our findings indicated that changes in the maternal gut microbiome palatal development, which might be related to changes in Lactobacillus and These results provide a new direction in the pathogenesis of CP induced by RA.

Comprehensive analysis of plasma miRNA and related ceRNA network in non-syndromic cleft lip and/or palate.

Non-syndromic cleft lip and/or palate (NSCL/P) is a common maxillofacial birth defect, and the etiology of which is complex and still unclear. Accumulating studies indicate that long non-coding RNAs(lncRNAs) and microRNAs(miRNAs) play important roles in NSCL/P. However, the potential regulatory associations remain largely unknown. In this study, we screened differentially expressed miRNAs and constructed competing endogenous RNA (ceRNA) networks to lay a foundation for further research on the regulatory mechanism of ncRNAs in NSCL/P. NSCL/P plasma RNA was analyzed by miRNA sequencing. The bioinformatics database, GEO and STRING database, GO and KEGG enrichment analysis and Cytoscape software were used to analyze and screen lncRNAs and mRNAs potentially related to differential miRNAs. The expression levels of lncRNA, miRNA and mRNA in ceRNA network were detected by RT-qPCR. In NSCL/P plasma samples, there were 47 differentially expressed miRNAs in CPO group and 36 differentially expressed miRNAs in CL/P group. GO and KEGG enrichment analysis showed that cell cycle, cell response to DNA damage stimulation, and the TGF-βsignaling pathway were relevant to the formation of NSCL/P. The RT-qPCR results showed that the expression levels of lncRNA NEAT1, hsa-miR-130b-3p, hsa-miR-212-3p, hsa-miR-200b-3p and SMAD2 were different in NSCL/P. We found that differentially expressed miR-212-3p, miR-200b-3p and miR-130b-3p may be involved in the pathogenesis of cleft palate by regulating related target genes.

The role of MEG3 in the proliferation of palatal mesenchymal cells is related to the TGFβ/Smad pathway in TCDD inducing cleft palate

Cleft palate (CP) is a common birth defect with a high incidence of occurrence in humans. The 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic halogenated aromatic hydrocarbon, with a strong CP effect on mice. Increasing recent evidences have shown that long-noncoding RNAs (lncRNAs) play an important role in several diseases, including CP. However, there is a paucity of studies on the role of lncRNA MEG3 in the occurrence and development of TCDD-induced CP. In this study, the relationship between MEG3 and the proliferation of palatal mesenchymal cells and the underlying molecular mechanism were studied by establishing fetal CP with TCDD (64 μg/kg) in C57BL/6N mice. The results revealed that MEG3 was highly expressed during the critical period of CP formation and that the fetal mesenchymal proliferation was significantly inhibited at certain critical periods in the mice receiving TCDD. In addition, we noted a possibility of a crosstalk between MEG3 and the TGF-β/Smad pathway, such that the inhibition of the TGF-β/Smad pathway was induced by TCDD. Cumulatively, our study suggests that TCDD-induced CP may be caused by MEG3 inhibition of the proliferation of palatal mesenchymal cells involving the TGFβ/Smad pathway, which may provide a novel perspective to understand the pathogenesis of CP.

Genome-wide Analyses Identify a Novel Risk Locus for Nonsyndromic Cleft Palate

The 3 major subphenotypes observed in patients with nonsyndromic orofacial clefts (NSOFCs) are nonsyndromic cleft lip only (NSCLO), nonsyndromic cleft lip with palate (NSCLP), and nonsyndromic cleft palate only (NSCPO). However, the genetic architecture underlying NSCPO is largely unknown. Here we performed a 2-stage genome-wide association study (GWAS) on NSCPO and replication analyses of selected variants in other NSOFCs from the Chinese Han population. We identified a novel locus (15q24.3) and a known locus (1q32.2) where variants in or near the gene reached genome-wide significance (2.80 × 10−13 < P < 1.72 × 10−08) in a test for association with NSCPO in a case-control design. Although a variant from 15q24.3 was found to be significantly associated with both NSCPO and NSCLP, the direction of estimated effects on risk were opposite. Our functional annotation of the risk alleles within 15q24.3 coupled with previously established roles of the candidate genes within identified risk loci in periderm development, embryonic patterning, and/or regulation of cellular processes supports their involvement in palate development and the pathogenesis of cleft palate. Our study advances the understanding of the genetic basis of NSOFCs and provides novel insights into the pathogenesis of NSCPO.

Mouse embryonic palatal mesenchymal cells maintain stemness through the PTEN-Akt-mTOR autophagic pathway

BackgroundBoth genetic and environmental factors are implicated in the pathogenesis of cleft palate. However, the molecular and cellular mechanisms that regulate the development of palatal shelves, which are composed of mesenchymal cells, have not yet been fully elucidated. This study aimed to determine the stemness and multilineage differentiation potential of mouse embryonic palatal mesenchyme (MEPM) cells in palatal shelves and to explore the underlying regulatory mechanism associated with cleft palate formation.MethodsPalatal shelves excised from mice models were cultured in vitro to ascertain whether MEPM are stem cells through immunofluorescence and flow cytometry. The osteogenic, adipogenic, and chondrogenic differentiation potential of MEPM cells were also determined to characterize MEPM stemness. In addition, the role of the PTEN-Akt-mTOR autophagic pathway was investigated using quantitative RT-PCR, Western blotting, and transmission electron microscopy.ResultsMEPM cells in culture exhibited cell surface marker expression profiles similar to that of mouse bone marrow stem cells and exhibited positive staining for vimentin (mesodermal marker), nestin (ectodermal marker), PDGFRα, Efnb1, Osr2, and Meox2 (MEPM cells markers). In addition, exposure to PDGFA stimulated chemotaxis of MEPM cells. MEPM cells exhibited stronger potential for osteogenic differentiation as compared to that for adipogenic and chondrogenic differentiation. Undifferentiated MEPM cells displayed a high concentration of autophagosomes, which disappeared after differentiation (at passage four), indicating the involvement of PTEN-Akt-mTOR signaling.ConclusionsOur findings suggest that MEPM cells are ectomesenchymal stem cells with a strong osteogenic differentiation potential and that maintenance of their stemness via PTEN/AKT/mTOR autophagic signaling prevents cleft palate development.

DNA hypermethylation of Fgf16 and Tbx22 associated with cleft palate during palatal fusion.

Objective:Cleft palate (CP) is a congenital birth defect caused by the failure of palatal fusion. Little is known about the potential role of DNA methylation in the pathogenesis of CP. This study aimed to explore the potential role of DNA methylation in the mechanism of CP.Methodology:We established an all-trans retinoic acid (ATRA)-induced CP model in C57BL/6J mice and used methylation-dependent restriction enzymes (MethylRAD, FspEI) combined with high-throughput sequencing (HiSeq X Ten) to compare genome-wide DNA methylation profiles of embryonic mouse palatal tissues, between embryos from ATRA-treated vs. untreated mice, at embryonic gestation day 14.5 (E14.5) (n=3 per group). To confirm differentially methylated levels of susceptible genes, real-time quantitative PCR (qPCR) was used to correlate expression of differentially methylated genes related to CP.Results:We identified 196 differentially methylated genes, including 17,298 differentially methylated CCGG sites between ATRA-treated vs. untreated embryonic mouse palatal tissues (P<0.05, log2FC>1). The CP-related genes Fgf16 (P=0.008, log2FC=1.13) and Tbx22 (P=0.011, log2FC=1.64,) were hypermethylated. Analysis of Fgf16 and Tbx22, using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), identified 3 GO terms and 1 KEGG pathway functionally related to palatal fusion. The qPCR showed that changes in expression level negatively correlated with methylation levels.Conclusions:Taken together, these results suggest that hypermethylation of Fgf16 and Tbx22 is associated with decreased gene expression, which might be responsible for developmental failure of palatal fusion, eventually resulting in the formation of CP.

Pathogenesis of Cleft Palate in Robin Sequence: Observations From Prenatal Magnetic Resonance Imaging

The etiology of the palatal cleft in Robin sequence (RS) is unknown. The purpose of this study was to assess the position of the fetal tongue at prenatal magnetic resonance imaging (MRI) and to suggest a potential relation between tongue position and development of the cleft palate seen in most patients with RS. This is a retrospective case-and-control study including fetuses with prenatal MRIs performed in the authors' center from 2002 to 2017. Inclusion criteria were 1) prenatal MRI of adequate quality, 2) liveborn infant, and 3) postnatal diagnosis of RS (Robin group) or cleft lip and palate (CLP group). Patients with postnatal RS without a palatal cleft were excluded. A control group with normal facial morphology was matched by gestational age. The outcome variable was tongue position at fetal MRI, described as within the cleft, along the floor of the mouth (normal), other, or indeterminate. One hundred twenty-two patients with mean gestational age at MRI of 25.8±4.9weeks were included (Robin, n=21 [17%]; CLP, n=47 [39%]; control, n=54 [44%]). The tongue was visualized within the palatal cleft in 76.2% of the Robin group and 4.3% of the CLP group. The tongue was found along the floor of the mouth (normal) in the remainder of the Robin and CLP groups and in 100% of the control group. These findings suggest a relation between in utero tongue position and the development of cleft palate in RS.

Differences in Oral Structure and Tissue Interactions during Mouse vs. Human Palatogenesis: Implications for the Translation of Findings from Mice.

Clefting of the secondary palate is one of the most common human birth defects and results from failure of the palatal shelves to fuse during embryonic development. Palatogenesis is traditionally considered to be a highly conserved developmental process among mammalian species. However, cleft palate phenotypes in humans are considerably more variable than those seen in mice, the most common animal model for studying palatal development and pathogenesis of cleft palate. In this investigation, we utilized macroscopic observations, histology and 3D imaging techniques to directly compare palate morphology and the oral-nasal cavity during palate closure in mouse embryos and human conceptuses. We showed that mouse and human palates display distinct morphologies attributable to the structural differences of the oral-nasal cavity. We further showed that the palatal shelves interact differently with the primary palate and nasal septum in the hard palate region and with pharyngeal walls in the soft palate region during palate closure in mice and humans. Knowledge of these morphological differences is important for improved translation of findings in mouse models of human cleft lip/palate and, as such, should ultimately enhance our understanding of human palatal morphogenesis and the pathogenesis of cleft lip/palate in humans.

MSX1 and TGF- 3 are novel target genes functionally regulated by FOXE1

FOXE1 mutations cause the Bamforth-Lazarus syndrome characterized by thyroid and craniofacial defects. Although a pioneer activity of FOXE1 in thyroid development has been reported, FOXE1 regulation in other contexts remains unexplored. We pointed to: (i) a role of FOXE1 in controlling the expression of MSX1 and TGF-β3 relevant in craniofacial development and (ii) a causative part of FOXE1 mutations or mice Foxe1(-/-) genotype in the pathogenesis of cleft palate in the Bamforth-Lazarus syndrome. The MSX1 and TGF-β3 up-regulation in response to FOXE1 at both transcriptional and translational levels and the recruitment of FOXE1 to specific binding motifs, together with the transactivation of the promoters of these genes, indicate that MSX1 and TGF-β3 are direct FOXE1 targets. Moreover, we showed that all the known forkhead-domain mutations, but not the polyalanine-stretch polymorphisms, affect the FOXE1 ability to bind to and transactivate MSX1 and TGF-β3 promoters. In 14-day Foxe1(-/-) mice embryos, Tgf-β3 and Msx1 mRNAs were almost absent in palatal shelves compared with Foxe1(+/-) embryos. Our findings give new insights into the genetic mechanisms underlying the Bamforth-Lazarus syndrome-associated facial defects.

Cell cycle proteins in normal and chemically induced abnormal secondary palate development: a review

Cell cycle progression and thus proper cell number is essential for normal development of organs and organisms. Craniofacial tissues including the secondary palate are vulnerable to disruption of cell cycle progression and proliferation by many chemicals including mycotoxin, secalonic acid D (SAD), glucocorticoids, retinoic acid and 2,3,7,8-tetrachlorodibenzodioxin. Induction of cleft palate (CP) by SAD in mice occurs from a reduction in the size of developing palatal shelves. This is associated with an inhibition of proliferation of murine and human embryonic palatal mesenchymal (MEPM and HEPM) cells as well as a G1/S block of cell cycle. In murine embryonic palates and HEPM cells, SAD inhibited G1/S-phase-specific cyclin-dependent kinase (CDK)2 activity, reduced the level of cyclin E and increased the level of the CDK2 inhibitor, p21. These results, together with those from other laboratories, suggest that common cell cycle protein targets (biomarkers), relevant to the pathogenesis of CP by multiple chemical exposures, that can form the basis for the diagnosis and the development of preventive strategies, are likely to exist.

Effect of 2,3,7,8-Tetrachlorodibenzo-p-dioxin on Cleft Palate-related Genes in Mouse Embryonic Palatal Mesenchymal Cells

Objective: To investigate the possible involvement of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the pathogenesis of cleft palate in mouse palatal cells.Materials and Methods: Palatal shelves of gestation day 12.5 ICR mouse foetuses were removed and cultured with serum. One day after the second passage, the medium was changed to serum free and 2,3,7,8-tetrachlorodibenzo-p-dioxin was added at 1 ng/mL, 10 ng/mL, and 100 ng/mL. After culture for 1 and 3 hours, all cellular RNA was isolated from the cells. Expression of some cleft palate-related genes was analysed semiquantitatively using reverse transcriptase-polymerase chain reaction. Five genes (Tgfb3, Msx1, Lhx8, Fgfrl, and Fgfr2) were selected on the basis that functional disturbance of these genes causes cleft palate with high frequency. The data were compared with GAPDH.Results: In the first passage, many mouse embryonic palatal mesenchymal cells had spread out, and a number of monolayer spindle-shaped cells were identified. The cells were stable in the second passage and also in the serum free medium. One hour after addition of 2,3,7,8-tetrachlorodibenzo-p-dioxin, Tgfb3 mRNA expression was reduced at a concentration of 100 ng/mL. After 3 hours, Tgfb3, Msxl, and Lhx8 mRNA expression were also reduced. However, there was no effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the gene expression for Fgfr1 and Fgfr2 mRNA.Conclusion: 2,3,7,8-Tetrachlorodibenzo-p-dioxin may contribute to the induction of cleftpalate by suppressing Tgfb3, Msx1, and Lhx8 gene expression.

Selective inhibition of murine palatal mesenchymal cell proliferation in vitro by secalonic acid D.

Secalonic acid D (SAD), a teratogenic mycotoxin, induces cleft palate (CP) in the offspring of exposed mice by inhibiting palatal shelf growth. Since reduced proliferation, increased apoptosis, and/or decreased extracellular matrix (ECM) synthesis of palatal mesenchymal cells (PMC) can all contribute to smaller shelf size, the hypothesis that teratogenically relevant concentrations (0 to 120 microg/ml) of SAD will have adverse effects on one or more of these cellular processes was tested, using primary murine PMC cultures. Exposure to SAD resulted in significant and dose-dependent decreases in mesenchymal cell number, uptake of (3)H-thymidine, and expression of proliferating cell nuclear antigen (PCNA). Trypan blue dye exclusion assay, however, revealed significant cell death only at higher doses, suggesting that the decrease in cell number at lower (more realistic) doses is likely a consequence of reduced cell proliferation and not cell death. Further, negative results in the DNA fragmentation analysis following SAD exposure suggested that cell death caused by higher levels of SAD was unrelated to apoptosis. Similarly, results of (3)H-glucosamine uptake assay indicated inhibitory effect of SAD on accumulation of hyaluronic acid (HA) or sulfated glycosaminoglycans (sGAG) only at the highest dose tested. Also, SAD affected neither extracellular nor cell-associated fibronectin expression at any dose tested. Taken together, these data suggest that the pathogenesis of CP by SAD is likely a result of a reduction in the size of the palatal shelf caused by SAD-induced inhibition of mesenchymal cell proliferation.

Alteration in the expression of bone morphogenetic protein-2,3,4,5 mRNA during pathogenesis of cleft palate in BALB/c mice

To identify the function of these bone morphogenetic proteins (BMP) during pathogenesis of cleft palate, an experimental model was established in BALB/c mice. Cleft palate was induced by exposure to retinoic acid on embryonic day (E)12. The expression of BMP-2,3,4,5 mRNA in normal and abnormal embryonic palatal shelves was then examined from E13 to E16 by in situ hybridization. The results showed that BMP-4 mRNA was expressed strongly and uniformly in normal epithelial cells and dispersed mesenchymal cells on E13. BMP-2,5 mRNA expression appeared only in dispersed mesenchymal cells. With the development of shelves, the staining density of BMP-2,4,5 decreased gradually in mesenchymal cells outside of the condensation and increased inside the condensation. After shelves had fused on E16, no positive signals for BMP-2,4,5 were detected in dispersed mesenchymal cells, but their expression persisted in the condensation. Exposure to retinoic acid delayed the formation of the condensation and decreased BMP-2,4,5 mRNA dramatically in mesenchyme from E13 to E15. BMP-3 mRNA expression were almost negative in either control or retinoic acid-treated groups during all stages. It was concluded that spatial and temporal expression of BMP-2,4,5 was required during normal palatogenesis, and that a deficiency of their mRNA expression may contribute to the pathogenesis of cleft palate.

Pathogenesis of cleft palate in TGF-beta3 knockout mice.

We previously reported that mutation of the transforming growth factor-beta3 (TGF-beta3) gene caused cleft palate in homozygous null (-/-) mice. TGF-beta3 is normally expressed in the medial edge epithelial (MEE) cells of the palatal shelf. In the present study, we investigated the mechanisms by which TGF-beta3 deletions caused cleft palate in 129 x CF-1 mice. For organ culture, palatal shelves were dissected from embryonic day 13.5 (E13.5) mouse embryos. Palatal shelves were placed singly or in pairs on Millipore filters and cultured in DMEM/F12 medium. Shelves were placed in homologous (+/+ vs +/+, -/- vs -/-, +/- vs +/-) or heterologous (+/+ vs -/-, +/- vs -/-, +/+ vs +/-) paired combinations and examined by macroscopy and histology. Pairs of -/- and -/- shelves failed to fuse over 72 hours of culture whereas pairs of +/+ (wild-type) and +/+ or +/- (heterozygote) and +/-, as well as +/+ and -/- shelves, fused within the first 48 hour period. Histological examination of the fused +/+ and +/+ shelves showed complete disappearance of the midline epithelial seam whereas -/- and +/+ shelves still had some seam remnants. In order to investigate the ability of TGF-beta family members to rescue the fusion between -/- and -/- palatal shelves in vitro, either recombinant human (rh) TGF-beta1, porcine (p) TGF-beta2, rh TGF-beta3, rh activin, or p inhibin was added to the medium in different concentrations at specific times and for various periods during the culture. In untreated organ culture -/- palate pairs completely failed to fuse, treatment with TGF-beta3 induced complete palatal fusion, TGF-beta1 or TGF-beta2 near normal fusion, but activin and inhibin had no effect. We investigated ultrastructural features of the surface of the MEE cells using SEM to compare TGF-beta3-null embryos (E 12. 5-E 16.5) with +/+ and +/- embryos in vivo and in vitro. Up to E13.5 and after E15.5, structures resembling short rods were observed in both +/+ and -/- embryos. Just before fusion, at E14.5, a lot of filopodia-like structures appeared on the surface of the MEE cells in +/+ embryos, however, none were observed in -/- embryos, either in vivo or in vitro. With TEM these filopodia are coated with material resembling proteoglycan. Interestingly, addition of TGF-beta3 to the culture medium which caused fusion between the -/- palatal shelves also induced the appearance of these filopodia on their MEE surfaces. TGF-beta1 and TGF-beta2 also induced filopodia on the -/- MEE but to a lesser extent than TGF-beta3 and additionally induced lamellipodia on their cell surfaces. These results suggest that TGF-beta3 may regulate palatal fusion by inducing filopodia on the outer cell membrane of the palatal medial edge epithelia prior to shelf contact. Exogenous recombinant TGF-beta3 can rescue fusion in -/- palatal shelves by inducing such filopodia, illustrating that the effects of TGF-beta3 are transduced by cell surface receptors which raises interesting potential therapeutic strategies to prevent and treat embryonic cleft palate.

Developmental stage specificity and dose response of secalonic acid D-induced cleft palate and the absence of cytotoxicity in developing mouse palate

Incidence of cleft palate (CP) in full-term mouse fetuses was evaluated following administration of 25 mg/kg of the mycotoxin, secalonic acid D (SAD), to groups of female mice on each of Days 10, 11, 12, 13, 14, or 15 of pregnancy. Although the highest numerical incidence (45.3%) of cleft palate resulted following SAD exposure on Day 12 of pregnancy, and the response tapered off to 16.9% on Day 10 and 0% on Day 15 of pregnancy, similar responses were produced also following exposures on Days 11 (38.4%) and 13 (39.9%) of pregnancy. Maternal exposure to doses of 0, 15, 20, 25, or 30 mg/kg of SAD, given on Day 12 of pregnancy indicated that although fetuses in the 30-mg/kg group had the highest incidence (51.9%) of CP, the effect was associated with increased resorptions and decreased fetal weights. The 25-mg/kg dose was optimally teratogenic (45.3% cleft palate) and maximally tolerable with neither an increase in resorptions nor a decrease in fetal body weights. Cytotoxicity of the optimally teratogenic dose of SAD (25 mg/kg given ip) on Day 12 of pregnancy was evaluated as a possible mechanism of SAD teratogenicity using indices such as mesenchymal cell density, mitotic index, and the uptake of [ 3H]thymidine in the developing palatal shelves. No evidence of SAD cytotoxicity was obtained in palatal shelves indicating a possible role for nonlethal cellular effects of SAD in the pathogenesis of CP. These studies also suggest the suitability of the maternal 25-mg/kg dose of SAD to study cellular biochemical effects in the developing embryo without the complicating influence of cytotoxic effects.

Cleft palate in diastrophic dysplasia. Morphology, results of treatment and complications.

Forty-one of 95 Finnish patients (43%) with diastrophic dysplasia had open cleft palate (CP). Submucous CP or its microforms were observed in an additional 30 patients (32%). Even though most of the patients have micrognathia, the high frequency of submucous clefts speaks against the role of the interposed tongue in the pathogenesis of CP in the Pierre Robin sequence. There was no hypernasality of speech in 27 of the 30 patients with submucous CP or its microforms, and the spontaneous speech of the other three was good. This is in contrast with observations in isolated submucous CP in general. No operative treatment was indicated in any case. Results after treatment of open CP and speech problems were in good agreement with results from the patients with isolated CP from the same period of time. As newborns 11 of the patients (12%) had severe respiratory difficulties caused by glossoptosis, and a Douglas operation was performed in three patients. Spinal compression due to abnormalities in cervical vertebrae and to dorsiflexion necessitated by intubation and velopharyngeal surgery may be a dangerous operative complication of patients with diastrophic dysplasia.

On the pathogenesis of cleft palate in the Pierre Robin syndrome.

In a series of Pierre Robin syndrome (PRS) and isolated cleft palate patients (ICP) both U- and V-formed clefts were observed with equal frequency, but the PRS clefts were in average slightly wider. There were totally submucous clefts among the PRS patients. There was no statistical difference between the groups in the prevalence of clefts in the relatives of the patients. The incidence of (genetically influenced) conical elevations in the lower lip was lowest in the noncleft subjects, high in ICP and highest in PRS children. The incidence of hypodontia, which acceptedly is genetically influenced, was also highest in the PRS group. Thus the foetal malposition with the tongue between the palatal shelves does not seem to play any decisive role in the pathogenesis of most PRS clefts. The cause for the PRS is more likely a genetically influenced growth disturbance in the maxilla and the mandible, which due to the organogenetic differences leads to diverging end results, micrognathia and cleft.

Pathogenesis of cleft palate in mouse embryos following lead acetate (LA) and triamcinolone acetonide (TA) treatment

Pathogenesis of cleft palate in mouse embryos following lead acetate (LA) and triamcinolone acetonide (TA) treatment

The mechanism of palatal shelf elevation and the pathogenesis of cleft palate.

Both normal Wistar rat fetuses and those with cleft palate induced by 5-Fluoro-2-Desoxyuridine were studied with a view to elucidating the mechanism of palatal shelf elevation and the pathogenesis of cleft palate. It was postulated that normal shelf elevation is brought about rapidly by an intrinsic turgor shelf force generated by binding of water to mucopolysaccharides. Interference with mucopolysaccharide synthesis would seem to be an important factor in the pathogenesis of some types of cleft palate.