Secondary Palate Research Articles

Cleft Palate with or without Cleft Lip: The Role of Retronasal Triangle View and Maxillary Gap at 11–14 Weeks

Objective: To evaluate the presence of maxillary gap (MG) and abnormal retronasal triangle (RT) as markers of cleft palate (CP) with and without cleft lip in the first trimester and to assess their association with the type of orofacial cleft (OC). Methods: The RT and the mid-sagittal view of the face were evaluated retrospectively by two operators in 26 fetuses with OC and in 80 normal controls to detect abnormal RT and/or MG. The agreement between operators was calculated. Results: Amongst the 26 fetuses, there were 15 cases of bilateral, 6 cases of unilateral, and 4 cases of median cleft lip and palate, and 1 case of CP alone. The MG was observed in 18 cases by operator 1 and in 17 cases by operator 2; an abnormal RT was detected in 21 cases by operator 1 and in 22 cases by operator 2. Great agreement between operators was obtained. In controls, MG or abnormal RT was suspected in 6 and 2–4% of cases, respectively. Conclusions: RT seems to be more sensitive compared to MG; however, the latter showed an additional diagnostic ability when the secondary palate was involved. Both approaches in combination could be useful in detecting OC in the first trimester.

In Vitro Analysis of Palatal Shelf Elevation During Secondary Palate Formation.

Palatal shelf elevation is an essential morphogenetic process during secondary palate formation. It has been proposed that shelf elevation results from an intrinsic elevating force and is regulated by extrinsic factors that are associated with development of other orofacial structures. Although dynamic palate culture is a common in vitro approach for studying shelf elevation, it requires the tongue or the tongue and mandible to be removed before culture, which prevents any determination of the role of the extrinsic factors in regulating shelf elevation. We showed that ex vivo removal of the tongue and mandible from unfixed embryonic heads led to spontaneous shelf movements that were more pronounced at late E13.5 and early E14.5 than those of E12.5 and early E13.5, suggesting that the strength of the elevating force increases over time during palate development. We further used a suspension culture technique to analyze palatal shelf movement in an intact oral cavity by culturing the orofacial portion of embryonic heads that include the maxilla, palatal shelves, mandible, and tongue (MPMT). MPMT explants were cultured in the serum-free medium with slow rotation for 24-48 hr. The palatal shelves successfully elevated during culture and displayed intermediate morphologies that closely resemble those of in vivo shelf elevation. We demonstrate that the tongue and mandible facilitate shelf medial movement/growth during shelf elevation and further suggest that the interaction of the palatal shelves and tongue could be one of the extrinsic factors that regulate the elevation process. Anat Rec, 302:1594-1604, 2019. © 2019 American Association for Anatomy.

Runx2 function in cells of neural crest origin during intramembranous ossification

Runt-related transcription factor 2 (Runx2), also known as core binding factor 1 (Cbfa1), is a multifunctional transcription factor and an essential master gene controlling osteoblast differentiation. We previously demonstrated the in vivo functions of Runx2 in mesoderm-derived cells. However, no studies have been conducted on Runx2 function during the differentiation of neural crest (NC)-derived cells in vivo. Wingless-type MMTV integration site family member 1 (Wnt1) is expressed in the NC, and Wnt1-Cre efficiently targets craniofacial NC-derived cells. Runx2 deficiency in cells of the Wnt1 lineage (referred henceforth as Runx2wnt1−/− within mice) resulted in defective ossification in certain regions, primarily in the anterior half of the craniofacial bones, including the frontal bone, jugal bone, squamous temporal bone, mandible, maxilla, and nasal bone. The skeletal analysis also revealed that heterozygous Runx2wnt1+/− embryos had an impaired closure of the frontal bone at the metopic suture and lacked the secondary palate in spite of otherwise normal ossification. This result suggests that ossification at the central part of the frontal bone is more dependent on Runx2 expression in comparison to other areas. These results indicate that Runx2 is indispensable not only for mesoderm-derived cells but also for NC-derived cells to differentiate during intramembranous ossification after migration to their destination from the neural plate border. Moreover, this implies that there are different levels of dependency on Runx2 expression for successful ossification between NC-derived cells that have migrated to different locations.

DEVELOPMENT OF THE INNER NASAL CAVITY IN ANIMALS IN PHYLO- AND ONTOGENESIS: FUNCTIONAL ANATOMIC SIGNIFICANCE IN THE DEVELOPMENT PERIOD

Іntroduction: Main functions of the inner nose in humans are respiration and olfaction. Therefore, human needs a large surface of inhalable and exhalable air contact, warming and moistening. Importance of these organs in animals in phylogenesis before and after the secondary palate development can explain their anatomic and functional designation. The aim is to find out the functional significance of some anatomic formations of the inner nose and their development peculiarities in phylo-and ontogenesis. Materials and methods: We used a comparative anatomy method where we compared well-known facts of different animals’ development before and after secondary palate formation in phylo- and ontogenesis. Review: Olfactory organ in lower vertebrates develops as canal with two openings through which as a result of water penetration the olfactory ability increases. Sinuses formation in animals happens after secondary palate formation. Secondary palate in embryo develops by second month of development, and sinuses’ development begins on the 3-4 month. As a result, upper jaws and facial skull became stronger. Importance of mucous and lacrimal glands of the nose cavity and mucous glands of mouth received new functions of animal and vegetable food digestion. Conclusions: development of the secondary palate in warm-blooded vertebrates changed (limited) functional applicability of the lacrimal gland and nasolacrimal canal, mucous glands of nose and vegetative innervation. Groups of lacrimal, mucous glands of nose and mouth are unified system of primary, neurosecretory reaction to environment.

Embryonic Midfacial Palatal Organ Culture Methods in Developmental Toxicology.

The morphogenesis of the secondary palate provides an interesting model for many of the processes involved in embryonic development. A number of in vitro models have been used to study craniofacial development, including whole embryo culture, palatal mesenchymal and micromass cell cultures, and Trowell-like palatal cultures in which dissected palates are cultured individually or as pairs in contact on a support above medium. This chapter presents a detailed protocol for the culture of maxillary midfacial tissues, including the palatal shelves, in suspension culture. This method involves isolation of the midfacial tissues (maxillary arch and palatal shelves) and suspension of the tissues in medium in flasks. On a rocker in an incubator, the palatal shelves elevate, grow, make contact, and fuse in a time span analogous to that occurring in the intact embryo in utero.

A statistical analysis of incidence, etiology, and management of palatal fistula.

Objective:The purpose of this study was to retrospectively review the incidence, profile, and the management of palatal fistula occurring in patients operated for cleft palate in our institute.Materials and Methods:A retrospective analysis was performed on all cleft palatal fistula patients who presented during the period from August 2007 to October 2017, to classify their site, age of presentation, surgery performed, and outcome. A record of the type of cleft palate and previous palatoplasty was also obtained. The outcome in terms of incidence and fistula formation depending on Veau's classification was analyzed.Results:Twenty-two patients reported with palatal fistula during this period. The incidence of fistula formation of our institute was 9.6%. Incisive foramen (13/22) was the most common site of fistula formation. Among various techniques used, local and buccal flaps were found to be useful in a maximum number of cases (14/22). The rate of fistula recurrence was 18.2% (4/22). On retrospective analysis of our institutional data, it was found that the incidence of cleft palate fistula was significantly higher in clefts with Veau Types III and IV (13/18) as compared to Veau Types I and II (5/18).Conclusion:This study shows that the fistula rate of our institution was 9.6%. Complete clefts (unilateral or bilateral) involving both primary and secondary palates predispose more to fistula formation.

Ultrasound imaging of the fetal secondary palate: Methodological description of a two-dimensional approach and a case series.

The study aims to describe our two-dimensional (2D) ultrasound approach to visualize the fetal secondary palate and plot its growth curve and to describe and demonstrate its clinical implementation. This is a two parts retrospective study. First, we measured the antero-posterior length of the bony secondary palate, from the soft to hard palate interface (SHPI) line to the alveolar ridge, blindly by two operators during routine scans of low-risk fetuses, and plot a longitudinal growth curve. In the second part, we describe four cases of prenatal diagnosis of secondary palate cleft. Sixty-eight fetuses were included: 14 to 15weeks (n=20), 21 to 24weeks (n=32), and 29 to 35weeks (n=16). The bony secondary palate elongates along gestation from a mean of 5.3mm (+/-0.46mm) at 14 to 15weeks to 15.9mm (+/-1.7mm) at 29 to 35weeks. We found high intraobserver and interobserver correlation between measurements. All four cases diagnosed by this approach were confirmed postnatally. The SHPI, representing the normally developed secondary bony palate, can be imaged in the fetus by direct 2D ultrasound as early as 14weeks. A gap within or nonvisualization of the SHPI is highly suggestive for a secondary palate cleft.

Spatio-Temporal Expression and Functional Analysis of miR-206 in Developing Orofacial Tissue.

Development of the mammalian palate is dependent on precise, spatiotemporal expression of a panoply of genes. MicroRNAs (miRNAs), the largest family of noncoding RNAs, function as crucial modulators of cell and tissue differentiation, regulating expression of key downstream genes. Our laboratory has previously identified several developmentally regulated miRNAs, including miR-206, during critical stages of palatal morphogenesis. The current study reports spatiotemporal distribution of miR-206 during development of the murine secondary palate (gestational days 12.5-14.5). Potential cellular functions and downstream gene targets of miR-206 were investigated using functional assays and expression profiling, respectively. Functional analyses highlighted potential roles of miR-206 in governing TGFß- and Wnt signaling in mesenchymal cells of the developing secondary palate. In addition, altered expression of miR-206 within developing palatal tissue of TGFß3-/- fetuses reinforced the premise that crosstalk between this miRNA and TGFß3 is crucial for secondary palate development.

Prionochelys matutina Zangerl, 1953 (Testudines: Pan-Cheloniidae) from the Late Cretaceous of the United States and the evolution of epithecal ossifications in marine turtles.

BackgroundMany neritic to nearshore species of marine adapted turtle from the Late Cretaceous of North America are thought to represent the stem lineage of Cheloniidae but due to fragmentary holotypes, low total specimen counts, and resultantly incomplete morphological character suites, are routinely placed either within or outside of crown group Chelonioidea leaving their precise cladistic affinities uncertain. Despite this systematic ambiguity, the referral of these species to either the stem of Cheloniidae or Chelonioidea belies the critical importance of these taxa in any investigation into the origins of extant marine turtles. The adequate incorporation of these species into phylogenetic studies requires the formal description of relatively complete specimens, particularly those possessing associated cranial and post-cranial material.MethodsRemarkably complete fossil specimens of several adult and juvenile marine turtles from the Mooreville Chalk and Eutaw Formations (Alabama, USA) are formally described and assigned to Prionochelys matutina. This material provides new information into the anatomy, ontogeny, and cladistic affinities of the species. A phylogenetic hypothesis for Late Cretaceous marine turtles is then generated through the consilience of stratigraphic, morphological, and molecular data.ResultsPhylogenetic analysis places Prionochelys matutina on the stem of Cheloniidae as a member of a monophyletic clade with other putative pan-cheloniids, including Ctenochelys stenoporus, Ctenochelys acris, Peritresius martini, and Peritresius ornatus. The members of this clade possess incipient secondary palates, pronounced carapacial and plastral fontanelles at all stages of development, and are characterized by the presence of superficial ossifications at the apices of the neural keel elevations along the dorsal midline of the carapace.DiscussionThe epithecal osteoderms dorsal to the neural series (epineurals) found in Ctenochelyidae are unique among turtles. The presence of epineurals in ctenochelyid turtles shows that epithecal ossifications arose independently in both leatherback (Dermochelyidae) and hard-shelled (Cheloniidae) marine turtles. Whether or not the epineurals of Ctenochelyidae are homologous with the dermal ossicles comprising the carapace of Dermochelys coriacea remains untested however, histological thin sectioning of dermochelyid and ctenochelyd epithecal elements may reveal meaningful information in future studies.

Development of an organotypic stem cell model for the study of human embryonic palatal fusion.

Cleft palate (CP) is a common birth defect, occurring in an estimated 1 in 1,000 births worldwide. The secondary palate is formed by paired palatal shelves, consisting of a mesenchymal core with an outer layer of epithelial cells that grow toward each other, attach, and fuse. One of the mechanisms that can cause CP is failure of fusion, that is, failure to remove the epithelial seam between the palatal shelves to allow the mesenchyme confluence. Epidermal growth factor (EGF) plays an important role in palate growth and differentiation, while it may impede fusion. We developed a 3D organotypic model using human mesenchymal and epithelial stem cells to mimic human embryonic palatal shelves, and tested the effects of human EGF (hEGF) on proliferation and fusion. Spheroids were generated from human umbilical-derived mesenchymal stem cells (hMSCs) directed down an osteogenic lineage. Heterotypic spheroids, or organoids, were constructed by coating hMSC spheroids with extracellular matrix solution followed by a layer of human progenitor epithelial keratinocytes (hPEKs). Organoids were incubated in co-culture medium with or without hEGF and assessed for cell proliferation and time to fusion. Osteogenic differentiation in hMSC spheroids was highest by Day 13. hEGF delayed fusion of organoids after 12 and 18 hr of contact. hEGF increased proliferation in organoids at 4 ng/ml, and proliferation was detected in hPEKs alone. Our results show that this model of human palatal fusion appropriately mimics the morphology of the developing human palate and responds to hEGF as expected.

OC23.04: The “superimposed line sign”: a novel marker in early diagnosis of secondary cleft palate

OC23.04: The “superimposed line sign”: a novel marker in early diagnosis of secondary cleft palate

Five-Fold Variation Among Surgeons and Hospitals in the Use of Secondary Palate Surgery.

To identify child-, surgeon- and hospital-specific factors at the time of primary cleft palate repair that are associated with the use of secondary palate surgery. Retrospective cohort study. Forty-nine pediatric hospitals. Children who underwent cleft palate repair between 1998 and 2015. Time from primary cleft palate repair to secondary palate surgery. By 5 years after the primary palate repair, 27.5% of children had undergone secondary palate surgery. In multivariable analysis, cleft type and age at primary palate repair were both associated with secondary surgery ( P < .01). Children with unilateral cleft lip and palate had a 1.69-fold increased hazard of secondary surgery (95% confidence interval [CI]: 1.54-1.85) compared to children with cleft palate alone. Primary palate repair before 9 months had a 3.99-fold increased hazard of secondary surgery (95% CI: 3.39-4.07) compared to repair at 16 to 24 months of age. After adjusting for cleft type, age at repair, and procedure volume, there remained substantial variation in secondary surgery use among surgeons and hospitals ( P < .01). For children with isolated cleft palate, the predicted proportion of children undergoing secondary surgery within 5 years of primary repair ranged from 8.5% to 46.0% across surgeons and 9.1% to 49.4% across hospitals. There are substantial differences among surgeons and hospitals in the rates of secondary palate surgery. Further work is needed to identify causes for this variation among providers and develop interventions to reduce the need for secondary surgery.

SPINA classification of cleft lip and palate: A suggestion for a complement

Spina's classification uses the incisive foramen as an anatomic reference to define groups I, II, and III. In some cases, the morphological manifestation of the cleft arises simultaneously pre- and postforamen, but without communicating. Considering that group I refers to isolated clefts of the primary palate and group III includes isolated clefts of the secondary palate, the authors suggest the classification group IIa for the association of these two occurrences in the same patient, thus associating two classifications. The original structure proposed by Spina is maintained and simply complemented and updated to Spina-A classification.

Abstract: Prophylactic Use of Buccal Fat Flaps to Improve Oral Mucosal Healing Following Furlow Palatoplasty

BACKGROUND: Furlow palatoplasty (FP) is increasingly used both for primary palatoplasty and secondary correction of VPI. While FP offers the advantage of lengthening the palate, the most tenuous component of the oral mucosal repair is anterior transposition of the oral mucosal z-plasty flap. When a secondary FP was done to correct VPI following primary FP, the senior author found oral mucosal separation in 53% of cases. To mitigate this problem, we prophylactically placed pedicled buccal fat pad flaps to provide an additional vascular layer to promote healing of the overlying oral mucosal z-plasty flap. METHODS: A retrospective chart review identified patients who underwent pedicled buccal fat pad flaps with FP performed by the senior author (A.G.). Cleft palate diagnosis, Veau classification, primary and secondary palate repair surgeries, surgical technique and post-operative complications were extracted. The need for buccal fat flap augmentation was determined if the oral mucosal z-plasty flap showed duskiness during transposition or was under tension at the time of closure. Unilateral versus bilateral buccal fat flaps were chosen based on expected areas of tension in the final repair. On the buccal mucosa, a longitudinal incision just lateral to the most posterior aspect of the alveolar ridge was made, from which buccal fat was gently teased out. This was tunneled submucosally to the palatal repair site, where it was secured just posterior to the hard palate and anterior to the transposed levator veli palatine muscle. The oral side of the Furlow palatoplasty was then brought together over these pedicled buccal fat flaps. RESULTS: We identified six patients who underwent FP with buccal fat flap augmentation. Two patients (33%) were primary FP while four patients (67%) were secondary FP. Three patients had unilateral cleft lip and palate, two had submucosal cleft palate and one had cleft palate only. The youngest patient was 11 months old, and the oldest was 7 years and 9 months. Half of the procedures used bilateral buccal fat pad flaps while the remainder were unilateral. All patients were seen at two weeks postoperatively and followed up regularly, with average follow-up time of 21 months (range 8–41 months). Post-operatively, one patient demonstrated a 1 cm area of mucosal dehiscence at the tip of the posterior triangular flap, which healed uneventfully. There were no other post-operative complications observed, including donor-site complications, complications relating to the buccal fat pad flap. No patient developed an oronasal fistula. DISCUSSION: Our experience suggests that the buccal fat pad flap may minimize vascular compromise and dehiscence of the oral mucosal z-plasty following FP. This separation rate decreased from 8/15 (53%) patients in our prior series of secondary FP procedures to 1/4 (25%) patients undergoing secondary FP with buccal fat flaps. Cleft palate surgeons should consider adding this low-risk technique to their repertoire, as it provides an additional vascular layer beneath the most tenuous part of the oral mucosal closure in a FP, and may improve vascularity to the overlying oral mucosa so as to minimize dehiscence at this closure.

Audiological Alterations in Patients With Cleft Palate.

Chronic otitis media with effusion (OME) is a recurrent complication, usually found in cleft palate patients.Conductive hearing loss is the result of the Eustachian tube dysfunction caused by the absence of fusion and the altered insertion of the muscles of the secondary palate. It is also the consequence of an ineffective muscular reconstruction after primary cleft palate repair. This is a cohort study to compare 4 groups of patients born with isolated cleft lip (ICL), unilateral cleft lip/palate (UCLP), bilateral cleft lip/palate (BCLP), and isolated cleft palate (ICP), received in our hospital between June 2015 to September 2017, operated by the same surgeon, using the same surgical technique and protocol.Complete cleft palate repair was performed, in average, at 10 months, and placement of ventilation tubes, if necessary, was made in the same operatory act.After palate repair, primary or secondary hearing loss was checked, joint to the connection with the type of used ventilation tubes, recurrences and complications also were considered. The study sample was integrated by 69 patients, 2 of 11 patients with ICL (18.18%), 30 of 34 patients with UCLP (88.23%), 17 of 19 patients with BCLP (89.47%), and 4 of 5 patients with ICP (80.00%) were diagnosed with OME requiring ventilation tubes at the time of surgery. It can be established that the average hearing loss in patients with diabolos in the postoperative period is 19.4 db and in those patients with T tubes it is 14.2 db, the difference being statistically significant (P < 0.05). Hearing improvement prior to language acquisition is essential for a proper speech development. Early trans tympanic tubes implantation during cleft palate repair contributes to a correct short-term ventilation of the middle ear, being the T tubes the best option.

Deletion of the T-box transcription factor gene, Tbx1, in mice induces differential expression of genes associated with cleft palate in humans

ObjectiveWe examined the function of the T-box transcription factor 1 (TBX1) in palatogenesis. DesignTbx1-knockout mice were histologically examined by hematoxylin and eosin staining. Next, secondary palatal shelves dissected from wild type or Tbx1-knockout mice embryos at embryonic day 13.5 were investigated with microarray analysis, gene ontology analysis, and real-time quantitative polymerase chain reaction. We performed gene profiling of developing palatal shelves from wild type and Tbx1-knockout embryos. We also analyzed the association of mouse genes linked to cleft palate with biological processes and compared the results with those of our ontology analysis of dysregulated genes in Tbx1-knockout palatal shelves. ResultsHistological analysis of Tbx1-knockout palate with complete cleft palate at postnatal day 1 showed aplasia of secondary palates associated with a small mandible and a small tongue compared to wild type littermates. Gene ontology analysis indicated that genes associated with development of the nervous system, muscle, and biomineral tissue were dysregulated in Tbx1-knockout palatal shelves. Furthermore, in Tbx1-knockout palatal shelves, genes associated with human cleft palate, specifically, myosin heavy chain 3 (Myh3) and nebulin (Neb), were downregulated and gamma-aminobutyric acid type A receptor beta 3 subunit (Gabrb3) was upregulated. ConclusionsOur findings demonstrate that TBX1 maintains normal growth and development of palatal shelves, mediated through the regulation of genes involved in muscle cell differentiation, nervous system development, and biomineral tissue development. Multiple factors in Tbx1-knockout mice may lead to various subtypes of cleft palate.

Runx1-Stat3-Tgfb3 signaling network regulating the anterior palatal development

Runx1 deficiency results in an anteriorly specific cleft palate at the boundary between the primary and secondary palates and in the first rugae area of the secondary palate in mice. However, the cellular and molecular pathogenesis underlying such regional specificity remain unknown. In this study, Runx1 epithelial-specific deletion led to the failed disintegration of the contacting palatal epithelium and markedly downregulated Tgfb3 expression in the primary palate and nasal septum. In culture, TGFB3 protein rescued the clefting of the mutant. Furthermore, Stat3 phosphorylation was disturbed in the corresponding cleft regions in Runx1 mutants. The Stat3 function was manifested by palatal fusion defects in culture following Stat3 inhibitor treatment with significant downregulation of Tgfb3. Tgfb3 is therefore a critical target of Runx1 signaling, and this signaling axis could be mediated by Stat3 activation. Interestingly, the expression of Socs3, an inhibitor of Stat3, was specific in the primary palate and upregulated by Runx1 deficiency. Thus, the involvement of Socs3 in Runx1-Tgfb3 signaling might explain, at least in part, the anteriorly specific downregulation of Tgfb3 expression and Stat3 activity in Runx1 mutants. This is the first study to show that the novel Runx1-Stat3-Tgfb3 axis is essential in anterior palatogenesis.

Development of Normal and Cleft Palate: A Central Role for Connective Tissue Growth Factor (CTGF)/CCN2

Development of the palate is the result of an organized series of events that require exquisite spatial and temporal regulation at the cellular level. There are a myriad of growth factors, receptors and signaling pathways that have been shown to play an important role in growth, elevation and/or fusion of the palatal shelves. Altered expression or activation of a number of these factors, receptors and signaling pathways have been shown to cause cleft palate in humans or mice with varying degrees of penetrance. This review will focus on connective tissue growth factor (CTGF) or CCN2, which was recently shown to play an essential role in formation of the secondary palate. Specifically, the absence of CCN2 in KO mice results in defective cellular processes that contribute to failure of palatal shelf growth, elevation and/or fusion. CCN2 is unique in that it has been shown to interact with a number of other factors important for palate development, including bone morphogenetic proteins (BMPs), fibroblast growth factors (FGFs), epidermal growth factor (EGF), Wnt proteins and transforming growth factor-βs (TGF-βs), thereby influencing their ability to bind to their receptors and mediate intracellular signaling. The role that these factors play in palate development and their specific interactions with CCN2 will also be reviewed. Future studies to elucidate the precise mechanisms of action for CCN2 and its interactions with other regulatory proteins during palatogenesis are expected to provide novel information with the potential for development of new pharmacologic or genetic treatment strategies for clinical intervention of cleft palate during development.

Ectopic Hedgehog Signaling Causes Cleft Palate and Defective Osteogenesis

Cleft palate is a common birth defect that frequently occurs in human congenital malformations caused by mutations in components of the Sonic Hedgehog (SHH) signaling cascade. Shh is expressed in dynamic, spatiotemporal domains within epithelial rugae and plays a key role in driving epithelial-mesenchymal interactions that are central to development of the secondary palate. However, the gene regulatory networks downstream of Hedgehog (Hh) signaling are incompletely characterized. Here, we show that ectopic Hh signaling in the palatal mesenchyme disrupts oral-nasal patterning of the neural crest cell–derived ectomesenchyme of the palatal shelves, leading to defective palatine bone formation and fully penetrant cleft palate. We show that a series of Fox transcription factors, including the novel direct target Foxl1, function downstream of Hh signaling in the secondary palate. Furthermore, we demonstrate that Wnt/bone morphogenetic protein (BMP) antagonists, in particular Sostdc1, are positively regulated by Hh signaling, concomitant with downregulation of key regulators of osteogenesis and BMP signaling effectors. Our data demonstrate that ectopic Hh-Smo signaling downregulates Wnt/BMP pathways, at least in part by upregulating Sostdc1, resulting in cleft palate and defective osteogenesis.

Convergent Evolution of a Eusuchian-Type Secondary Palate within Shartegosuchidae

Shartegosuchids are a poorly known, early-branching group of Asian and North American crocodylomorphs. Shartegosuchids have been hypothesized to have eusuchian-type secondary palates, but a paucity of described material makes assessing this difficult. Our fieldwork in western Mongolia recovered cranial material of a new Shartegosuchus specimen from the Ulan Malgait Formation, which we CT-scanned and digitally reconstructed to investigate its palatal morphology. We then incorporated this new anatomical information into a revised phylogenetic dataset to assess its affinities. Our study confirms that Shartegosuchus has a posteriorly placed choana that is fully enclosed by the pterygoids, but differs from Eusuchia in possessing a secondary palatal fenestra and reduced palatine bones. Shartegosuchus, together with Adzhosuchus, Fruitachampsa, and Nominosuchus, forms the monophyletic group Shartegosuchidae. Shartegosuchidae is nested within a larger clade Shartegosuchoidea, and this clade is an earlier-diverging lineage than Eusuchia, showing that a eusuchian-type secondary palate evolved multiple times in crocodylomorphs, including very early in the group's evolutionary history. The co-occurrence of Nominosuchus in the Ulan Malgait Formation and the Shishigou Formation allows us to assign an early Oxfordian age to Shartegosuchus. The independent evolution of a eusuchian-type secondary palate in an oreinorostral group suggests that the link between platyrostry and a closed secondary palate has been overstated.