Anteroposterior Patterning Research Articles

Evaluation of Size of the Condyle in Vertical and Anteroposterior Skeletal Conditions with the Help of Cone-beam Computed Tomography

Evaluation of size of the condyle in various vertical and anteroposterior skeletal conditions with the help of cone-beam computed tomography (CBCT). In this study, 266 study participants were included consisting of 112 males and 144 females. The study participants were categorized as class I when -1° ≤ A point-nasion-B point angle (ANB) < 4°, class II when ANB ≥ 4°, and class III when ANB < -1°. The study participants were categorized as hypodivergent when the mandibular plane (MP) ≤ 23°, normodivergent when 23° < MP < 30°, and hyperdivergent when MP ≥ 30°. CBCT images were obtained for each subject and measurement of length, width, and height of the condyle was carried out. The data were collected and analysis of covariance test (ANCOVA) was used for statistical analysis. Statistical significance was adjusted at p ≤ 0.05. The size of the condyle was smaller in females. The length of the condyle was similar in different anteroposterior and vertical positions with no significant difference. The width of the condyle and the height of the condyle were greatest in class III anteroposterior condition while they were lowest in class I condition. The width and height of the condyle were greatest in hypodivergent condition while they were lowest in hyperdivergent condition. It was concluded that the height and width of the condyle vary considerably in different vertical and anteroposterior skeletal patterns and the size of the condyle was smaller in women as compared with men. The position of the condyle and its morphology are important features that constitute an important part of orthodontic treatment planning. The skeletal pattern of the patient has also an important effect on the diagnosis, planning of treatment, and prognosis in the orthodontic treatment.

The influence of antero-posterior dentoskeletal pattern on the value of nasal soft tissue angles: a cephalometric study.

The aim of this study was to examine the influence of sagittal dentoskeletal pattern on the value of profile nasal soft tissue angles and estimate the significance of examined differences for each angle. Lateral cephalograms were used to examine the nasofrontal angle, nasofacial angle, nasal tip angle, and nasolabial angle of 120 adult Caucasian subjects (60 male and 60 female) from the central Balkan area. Subjects were divided into four groups according to the ANB angle and incisors inclination: class I as the control group, class II division 1, class II division 2 and class III. By evaluating the influence of sagittal dentoskeletal relationships on the values of examined angles, significant differences were found among subjects with class I and class II/2 (p = 0.028), so as class III (p = 0.002) for nasal tip angle. The nasofacial angle was found to differ among subjects with class I and class II/1 (p = 0.002), so as class III (p = 0.001). Different dentoskeletal patterns have significant influence on values of the nasal tip angle and nasofacial angle, and don't have influence on the values of the nasofrontal and nasolabial angle.

Position of the Hyoid Bone in Anteroposterior Skeletal Patterns.

Introduction Hyoid bone plays a vital role in the craniofacial dynamics. From the maintenance of pharyngeal airway to phonation, deglutition, and mandibular movements, it has multifactorial roles to fulfill. The hyoid bone has a spatial relationship with cranial base, mandible, and cervical vertebrae. This study was performed to determine the position of the hyoid bone in different anteroposterior growth patterns. Materials and Methods 75 lateral cephalograms belonging to all three sagittal skeletal patterns were evaluated in the study. The angular and linear measurements using 10 variables were made to determine the relationship of the hyoid bone with different craniofacial structures. SPSS was used to calculate the descriptive statistics, mean, and standard deviation of all the linear and angular variables. The analysis of variance (ANOVA) and post hoc test were used to compare the means of linear and angular measurement and multiple comparisons, respectively, at p < 0.05 significance level. Results There was no significant difference in the mean angular measurements (NSH and MPH) between the 3 groups (p > 0.05). Also, the multiple comparisons showed no significant difference between the linear measurements (H-FH, H-MP, H-H′, and H-N). However, there was a significant difference in three linear measurements: H-Rgn, RGN-C3, and C3-H. The values were more in class III subjects, compared to class I and class II. Conclusion The linear millimetric distance between points H-RGN, RGN-C3, and C3-H which determine the relationship and spatial position of the hyoid bone with the mandible and third cervical vertebrae was statistically significant among groups. The values were more in class III subjects inferring the anterior position of the hyoid bone.

Can anteroposterior skeletal pattern be determined from a silhouetted profile photograph? A cross-sectional study.

To determine the degree to which the anteroposterior (AP) skeletal jaw relation can accurately be determined from a silhouetted clinical profile photograph and whether the level of agreement is influenced by patient vertical proportions. Cross-sectional study. University Dental Hospital of Manchester, United Kingdom. Specialist orthodontists. Eight specialist orthodontists assessed 37 silhouetted profile photographs of individuals aged 11-19 years and determined the class and severity of AP skeletal pattern. These assessments were compared to corresponding lateral cephalometric radiographs, where ANB values, supplemented by an Eastman Correction and a Wits Appraisal, where appropriate, were used for sagittal skeletal classification. The agreement between silhouette and cephalometric AP determination yielded a weighted kappa score of 0.207 (95% confidence interval [CI] 0.135-0.278), which indicates only a fair level of agreement. The silhouetted sagittal skeletal pattern classification, along with severity, agreed with the lateral cephalometric radiograph in 29% of instances. Class III individuals were identified correctly 19.2% of the time. There was a statistically significant difference in kappa scores between the high angle (K= 0.439; 95% CI 0.310-0.568) and low angle (K = 0.068; 95% CI 0.007-0.130) patients (P < 0.001), as well as the high and average angle (K= 0.151; 95% CI 0.031-0.270) patients (P < 0.05). AP skeletal pattern, as determined from a lateral cephalometric radiograph, has only a fair level of agreement to that from a silhouetted profile photograph. Vertical proportions were shown to have a significant effect on the determination of the sagittal skeletal pattern and class III skeletal patterns were shown to be the most difficult to identify from profile silhouettes.

Control of mouse limb initiation and antero-posterior patterning by Meis transcription factors

Meis1 and Meis2 are homeodomain transcription factors that regulate organogenesis through cooperation with Hox proteins. Elimination of Meis genes after limb induction has shown their role in limb proximo-distal patterning; however, limb development in the complete absence of Meis function has not been studied. Here, we report that Meis1/2 inactivation in the lateral plate mesoderm of mouse embryos leads to limb agenesis. Meis and Tbx factors converge in this function, extensively co-binding with Tbx to genomic sites and co-regulating enhancers of Fgf10, a critical factor in limb initiation. Limbs with three deleted Meis alleles show proximal-specific skeletal hypoplasia and agenesis of posterior skeletal elements. This failure in posterior specification results from an early role of Meis factors in establishing the limb antero-posterior prepattern required for Shh activation. Our results demonstrate roles for Meis transcription factors in early limb development and identify their involvement in previously undescribed interaction networks that regulate organogenesis.

Vangl2 promotes the formation of long cytonemes to enable distant Wnt/\u03b2-catenin signaling

Wnt signaling regulates cell proliferation and cell differentiation as well as migration and polarity during development. However, it is still unclear how the Wnt ligand distribution is precisely controlled to fulfil these functions. Here, we show that the planar cell polarity protein Vangl2 regulates the distribution of Wnt by cytonemes. In zebrafish epiblast cells, mouse intestinal telocytes and human gastric cancer cells, Vangl2 activation generates extremely long cytonemes, which branch and deliver Wnt protein to multiple cells. The Vangl2-activated cytonemes increase Wnt/β-catenin signaling in the surrounding cells. Concordantly, Vangl2 inhibition causes fewer and shorter cytonemes to be formed and reduces paracrine Wnt/β-catenin signaling. A mathematical model simulating these Vangl2 functions on cytonemes in zebrafish gastrulation predicts a shift of the signaling gradient, altered tissue patterning, and a loss of tissue domain sharpness. We confirmed these predictions during anteroposterior patterning in the zebrafish neural plate. In summary, we demonstrate that Vangl2 is fundamental to paracrine Wnt/β-catenin signaling by controlling cytoneme behaviour.

Correlation between the transverse dimension of the maxilla, upper airway obstructive site, and OSA severity.

Acquiring a better comprehension of obstructive sleep apnea physiopathology can contribute to improving patient selection for surgical treatments. We hypothesize that maxillary transverse deficiency restricts the space available for the tongue, leading to upper airway obstruction during sleep. Our primary hypothesis was that maxillary transverse deficiency increases the prevalence of tongue collapse during drug-induced sleep endoscopy (DISE). The secondary hypothesis was that maxillary transverse deficiency will also increase the prevalence of circumferential collapse at the velopharynx. The exploratory hypothesis was that maxillary transverse deficiency is associated with increased obstructive sleep apnea severity. The objectives of this study were to correlate maxillary morphometric measurements with (1) the anatomic level of obstruction during DISE and (2) the apnea-hypopnea index on polysomnography. We made a cross-sectional analysis of patients with obstructive sleep apnea undergoing DISE in search of positive airway pressure alternative treatment. Maxillary measurements were collected from a computed tomography scan (interpremolar distance, intermolar distance [IMD] and sella-nasion A point angle), findings from DISE, and sleep study variables from polysomnography. Correlation between computed tomography, DISE, and polysomnography data was assessed using Pearson's correlation, and receiver operating characteristic curves were determined for each facial measurement. Sixty-nine patients were included in the study. The group with velopharyngeal circumferential collapse had mean IMD = 26.30 mm (25.5-31.45), and the group with anteroposterior collapse had mean IMD = 29.20 mm (26.8-33.10; P = .040). The group with complete tongue-base obstruction had mean interpremolar distance = 26.40 mm (25.1-28) and IMD = 26.30 mm (25.6-28.4), and the group without obstruction had mean interpremolar distance = 28.7 mm (27.2-30; P = .003) and IMD = 34.06 mm (32.1-37; P < .001). The receiver operating characteristic curve determined an IMD cutoff of 29.8 mm for predicting tongue-base obstruction. The maxillary transverse deficiency, identified by reduction in interpremolar distance and IMD, predicted the occurrence of complete tongue-base obstruction, complete concentric collapse at the velopharynx, and multilevel obstruction during DISE. We did not find an association between the maxillary measurements and obstructive sleep apnea severity. These associations hold some promise in ultimately supplanting insights previously available only through DISE.

Aberrant Gcm1 expression mediates Wnt/\u03b2-catenin pathway activation in folate deficiency involved in neural tube defects

Wnt signaling plays a major role in early neural development. An aberrant activation in Wnt/β-catenin pathway causes defective anteroposterior patterning, which results in neural tube closure defects (NTDs). Changes in folate metabolism may participate in early embryo fate determination. We have identified that folate deficiency activated Wnt/β-catenin pathway by upregulating a chorion-specific transcription factor Gcm1. Specifically, folate deficiency promoted formation of the Gcm1/β-catenin/T-cell factor (TCF4) complex formation to regulate the Wnt targeted gene transactivation through Wnt-responsive elements. Moreover, the transcription factor Nanog upregulated Gcm1 transcription in mESCs under folate deficiency. Lastly, in NTDs mouse models and low-folate NTDs human brain samples, Gcm1 and Wnt/β-catenin targeted genes related to neural tube closure are specifically overexpressed. These results indicated that low-folate level promoted Wnt/β-catenin signaling via activating Gcm1, and thus leaded into aberrant vertebrate neural development.

Analysis of symmetricity in the three different (sagittal, transverse and frontal) planes in generalized nonsegmental vitiligo.

Nonsegmental vitiligo is defined as being "often symmetrical", however, no work has tackled the point as to how valid it is to depend upon the concept of symmetricity in generalized nonsegmental vitiligo. To investigate vitiligo symmetry, taking into account sites of predilection, the clinical characteristics of patients were studied. This multicentric study included 712 nonsegmental vitiligo patients with 2876 examined lesions. Three models were drawn for each patient. Sagittal, transverse and frontal planes were drawn to divide the body into right/left, upper/lower and anterior/posterior halves respectively. Patients were examined by Wood's light and analyzed for symmetry. Bilateral involvement was present in 78% (P < 0.001). Studying the similarity of clinical involvement in the upper and lower body parts revealed that such similarity was present in 38%, with a significant positive association in some areas. Studying clinical similarity in the anteroposterior distribution pattern revealed a significant positive association in 11%. Relatively low number of patients. We found significant bilateral symmetry in the lesions of 78% of vitiligo patients. Our work could aid in drawing the anticipated vitiligo map in patients with active disease, helping in increasing our understanding of the clinical behaviour of this disease.

Assessment of Site, Degree and Pattern of Airway Obstruction in Patients with Moderate to Severe Obstructive Sleep Apnoea (OSA) Using Drug Induced Sleep Endoscopy (DISE)and Its Association with Awake Fibreoptic Evaluation and Polysomnography Parameters.

Accurate assessment of site of obstruction in Obstructive Sleep Apnoea (OSA) is key to its effective management, especially the surgical intervention. Currently, Drug induced sleep endoscopy (DISE) is widely used to assess the obstruction during sleep as assessing during physiologic sleep is impractical and cumbersome. To assess the site, pattern and degree of airway obstruction in patients with moderate to severe obstructive sleep apnoea using DISE and to find a co-relation of DISE findings with awake fibreoptic assessment and severity of OSA. 41 adult patients (29 males, 12 females, mean AHI 40.58 ± 16.94, mean age 54 ± 9.15years underwent awake fibreoptic nasal endoscopy in the outpatient department and propofol induced DISE in the main operation theatre. The site/s, degree and pattern of obstruction were recorded as per VOTE and Fujita classification. Velum was the commonest site of collapse followed by oropharynx, base of tongue and epiglottis. All had multilevel collapse with velum, oropharynx and base of tongue being the most common combination. At velum, base of tongue and epiglottis, antero-posterior pattern of collapse was commonest and at oropharynx lateral pattern of collapse was the commonest. We found no difference in the site, pattern or severity of collapse between the moderate and severe group though there was a tendency of epiglottis collapse being present more frequently in severe OSA. Awake fibreoptic endoscopic evaluation was able to assess the collapse at level of velum with higher sensitivity but with poor specificity. There was high chances of missing a hypopharyngeal collapse with fibreoptic endoscopic evaluation.

Purified Bighead protein efficiently promotes head development in the South African clawed frog, Xenopus laevis.

Vertebrate embryonic development is regulated by a few families of extracellular signaling molecules. Xenopus laevis embryos offer an excellent system to study the cell-cell communication signals that govern embryonic patterning. In the frog embryos, Wnt/β-catenin plays a pivotal role in regulating embryonic axis development, and modulation of the Wnt pathway is required for proper antero-posterior patterning. Recently, a novel secreted, organizer-specific Wnt inhibitor, Bighead, was identified that acts by downregulating Lrp6 plasma membrane levels. Here, I describe a method to purify biologically active Bighead protein and confirm that Bighead promotes Xenopus head development.

Positional awake nasoendoscopic pattern-based surgical decision for correction of retropalatal obstruction in OSA.

To evaluate differential surgical interventions for obstructive sleep apnea (OSA) patients with single-level retropalatal based on the preoperative topographical diagnosis using nasoendoscopy with Müller's maneuver during supine position (MM-P). This case series included adult patients with OSA who showed a predominant single-level retropalatal collapse on MM-P. An anteroposterior pattern of collapse was managed by an anterior advancement procedure, while a transverse pattern of collapse was managed by lateral/anterolateral advancement procedures (double suspension sutures). A combined procedure was provided to the concentric type of collapse. All patients underwent evaluation of the polysomnography, Epworth Sleepiness Scale (ESS) values and snoring scores both preoperatively and 6-8months after surgery. Among 102 patients, the most commonly reported pattern of collapse at the retropalatal level was the concentric pattern (48.04%) followed by the transverse pattern (27.45%). The AP-pattern of collapse was reported in 24.51%. In the postoperative follow-up visits, no early or late complications were reported. All included groups showed significant improvement in polysomnographic data (mean AHI and lowest O2 saturation level). Significant improvement of VAS of snoring was reported. The overall success rate was ˃90%. Preoperative differential diagnosis of OSA with MM-P allows for tailored surgical management. Tailored procedures could yield good surgical outcomes when patients are properly selected and the technique is chosen according to preoperative topographical diagnostic assessment. This study might provide an available less-costly and effective preoperative planning for OSA intervention. 4.

Evaluation of the maxillary sinus volume and dimensions in different skeletal classes using cone beam computed tomography

Aim: The extension of the maxillary sinus is an important issue for fixed orthodontic treatments and maxillofacial surgery. The aim of this study is to investigate the dimensions and volume of the maxillary sinus in different skeletal classes and, also the effect on the anteroposterior growth pattern of the maxilla.Materials and Methods: The cone-beam computed tomography (CBCT) images of 48 patients were obtained from the archive of the Department of Oral and Maxillofacial Radiology. The CBCT images were taken prior to orthognathic surgery for the surgical planning of all patients. According to the sagittal skeletal position of the maxilla, the patients were divided into three groups: normal maxilla group, retrognathic maxilla group and, prognathic maxilla group. Dimensional and volumetric measurements of the maxillary sinus were performed by the same oral and maxillofacial radiologist.Results: Although no statistical difference was observed between different skeletal groups regarding the maxillary sinus dimensions and volume, the results did show that there was an inverse and statistically significant correlation between the left maxillary sinus width and age (p0.05). There was a statistically significant difference between males and females for the width, height, and depth of right maxillary sinus, the right maxillary sinus volume, the height and depth of left maxillary sinus.Conclusion: In conclusion, for orthodontists and maxillofacial surgeons, the dimensional and volumetric measurements performed by CBCT act as a pathfinder role in the insertion of miniscrews, orthodontic tooth movement through the maxillary sinus, and the orthognathic surgeries such as Le Fort osteotomies.

ASSESSMENT OFPHARYNGEAL WIDTH AND LENGTH, POSITION OF HYOID BONE, IT’S SIZE ANDINCLINATION OF SOFT PALATE IN DIFFERENT SKELETAL MALOCCLUSIONS IN UTTRAKHAND POPULATION

Background: Uvulo-glosso-pharyngeal dimensions and size and position of associated structures are integral part of Orthodontic treatment planning. Since decades various authors have assessed airway dimensions by different methods and implied the results in diagnosis and treatment planning.Aims & Objectives: The aim of this study was to investigate the uvulo-pharyngeal dimensions and position of hyoid bone in subjects with different anteroposterior jaw relationships.Method: Cephalometric radiographs of 30 subjects (age 15-25 years of Uttrakhand ethnic origin) were divided into three Groups accorging to ANB and Wits appraisal. Group 1, Skeletal Class I (ANB 1-4 and Wits Appraisal -1 to 0) Group 2, Skeletal Class II (ANB >4 and Wits Appraisal >1) & Group 3, Skeletal Class III (ANB <1 and Wits Appraisal < -1.5). Statistical analysis was undertaken using one-way ANOVA to evaluate the mean and standard deviation in the three Groups and Post hoc Tukey test was done to compare the variables between the three Groups.Results: On an average, upper airway width was decreased in Group 2 and increased in Group 3 (p=0.028). Lower airway was increased in Group 3 (p=o.005). Velopharyngeal airway was decreased in Group 2 and increased in Group 3(p=0.042).Thickness of soft palate was increased in Group 3(p= 0.0.13). Hyoid bone was positioned poaterioinferiorly in Group 2 and Anterosuperiorly in Group 3(p=0.002). In conclusion, uvulo-pharyngeal airway and position of hyoid bone are affected by anteroposterior skeletal patterns in Uttrakhand population despite of its multiethenicity.

Apical ectodermal ridge regulates three principal axes of the developing limb.

Understanding limb development not only gives insights into the outgrowth and differentiation of the limb, but also has clinical relevance. Limb development begins with two paired limb buds (forelimb and hindlimb buds), which are initially undifferentiated mesenchymal cells tipped with a thickening of the ectoderm, termed the apical ectodermal ridge (AER). As a transitional embryonic structure, the AER undergoes four stages and contributes to multiple axes of limb development through the coordination of signalling centres, feedback loops, and other cell activities by secretory signalling and the activation of gene expression. Within the scope of proximodistal patterning, it is understood that while fibroblast growth factors (FGFs) function sequentially over time as primary components of the AER signalling process, there is still no consensus on models that would explain proximodistal patterning itself. In anteroposterior patterning, the AER has a dual-direction regulation by which it promotes the sonic hedgehog (Shh) gene expression in the zone of polarizing activity (ZPA) for proliferation, and inhibits Shh expression in the anterior mesenchyme. In dorsoventral patterning, the AER activates Engrailed-1 (En1) expression, and thus represses Wnt family member 7a (Wnt7a) expression in the ventral ectoderm by the expression of Fgfs, Sp6/8, and bone morphogenetic protein (Bmp) genes. The AER also plays a vital role in shaping the individual digits, since levels of Fgf4/8 and Bmps expressed in the AER affect digit patterning by controlling apoptosis. In summary, the knowledge of crosstalk within AER among the three main axes is essential to understand limb growth and pattern formation, as the development of its areas proceeds simultaneously.

Evaluation of pharyngeal airway volume and nasal septum deviation relation in different sagittal and vertical craniofacial patterns through cone beam computed tomography

ObjectivePharyngeal airway, maxilla, mandible and nasal septum are maxillofacial structures with intimate relationship. The mutual effects of these structures would modify treatment plan and final results of surgical or orthodontic interventions. The objective of this study was to evaluate the association of nasal septum deviation and pharyngeal airway volume in various antero-posterior and vertical facial skeletal patterns. Methods215 cone beam computed tomography scans were assessed to determine four variables; Presence of nasal septum deviation in coronal and axial planes, pharyngeal airway volume, antero-posterior skeletal facial pattern and vertical craniofacial pattern. The relation among these variables was investigated. To determine intra-rater reliability of measurements intra-class correlation coefficient was calculated for 10 % of the sample size. ResultsA significant difference was found between pharyngeal airway volume of men and women (P < 0.05). No significant association between nasal septum deviation and pharyngeal airway volume was detected in different antero-posterior and vertical facial patterns. Nasal septum deviation had no significant correlation with sagittal facial patterns but presented a considerable relation with vertical facial patterns (P < 0.001). No significant association was distinguished between pharyngeal airway volume and facial pattern of growth both anterior-posteriorly and vertically. The reliability of measurements was excellent (0.9). ConclusionsMales have significantly larger pharyngeal volume. Nasal septum deviation has a statistically significant relation with vertical skeletofacial patterns. Although pharyngeal airway volume did not present a significant relation with sagittal and vertical craniofacial patterns, the greatest dimensions were related to horizontal vertical facial pattern and Class I sagittal pattern.

A cross-sectional retrospective study of normal changes in the pharyngeal airway volume in white children with 3 different skeletal patterns from age 9 to 15 years: Part 1

This study investigated correlations between airway size and age, sex, and skeletal patterns; identified airway change trends; and measured volumetric norms in children via cone-beam computed tomography. Four hundred twenty nontreated white patients were stratified by age, sex, and anteroposterior skeletal pattern. The nasopharyngeal airway (NPA), oropharyngeal airway (OPA), and total pharyngeal airway (TPA) volumes were delineated on 3-dimensional digital cephalograms. SPSS (SPSS, Chicago, Ill) was used to run an analysis of variance and post-hoc analyses. The Class III group had significantly larger OPA volumes than Class I and II groups. Male subjects had considerably larger NPA volumes than female subjects. Age was significantly associated with all 3 airway volumes (P<0.05). The young cohort (ages, 9-10years) had a mean TPA of 11,435.34±484.45mm3, the middle cohort (ages, 11-13years) had a mean TPA of 14,152.07±395.46mm3, and the older cohort (ages, 14-15years) had a mean TPA of 18,057.99±484.25mm3. An effect of skeletal classification on OPA and a sex effect on NPA were observed. The annual change in the mean of TPA volume decreased in subjects aged 10-12years, then rebounded until 14years. TPA change peaked in female subjects 1year before male subjects.

Skeletal growth in class II malocclusion from childhood to adolescence: does the profile straighten?

BackgroundThere is relatively little appreciation of the changes in maxillary-mandibular relationships occurring during adolescence among subjects with normal and increased overjet. The aim of this study was to assess differences in changes in maxillo-mandibular relationships during the adolescent growth period based on the presence of a normal (< 4 mm) or increased (> 4 mm) overjet in childhood. Our hypothesis was that there is no difference in the change of the A point, nasion, B point (ANB) angle during growth between these two overjet groups. Lateral cephalograms were obtained from 65 subjects taken from the American Association of Orthodontists Foundation (AAOF) Craniofacial Growth Legacy Collections Project. Cephalograms were obtained at ages 7–10 (T0) and 14–17 (T1) with allocation into two groups based on baseline overjet (> 4 mm: group 1, 2-4 mm: group 2). Random effects linear regression was used to account for multiple within -patient measurements with dependent variables including antero-posterior skeletal pattern (based on sella, nasion, A point (SNA); sella, nasion, B point (SNB); and ANB angles).ResultsWe included a similar number of males (n = 34; 52.3%) and females (n = 31; 47.7%). The mean ANB was higher at baseline in group 1 (5.42, SD 2.16°) than in group 2 (3.08, SD 1.91°). The hypothesis was rejected as the ANB angle reduced by 1.92° more in the larger overjet group with the association being statistically significant after accounting for age and gender (P < 0.001; 95% CI 1.06 to 2.77). No significant gender-related effect (P = 0.624; 95% CI − 0.637 to 1.07) was observed overall. However, there was no significant increase in SNA angle in the > 4 mm overjet group compared to the 2–4 mm group (0.857°, P = 0.271; 95% CI − 0.669 to 2.383). The SNB angle increased by 1.15° more in the higher overjet group but there was only weak evidence of an association (P = 0.086; 95% CI − 2.464 to 0.164).ConclusionsA slight straightening of the facial profile was observed in both groups with a statistically significant greater reduction in ANB arising in the group with larger baseline overjet. This translated into a marginal reduction in the overjet in this group.

Loss of HAND2 and HOXD13 Binding Sites in the ZPA Regulatory Sequence (ZRS) is not Sufficient to Disrupt Activity in the Limb

The ZPA regulatory sequence (ZRS) is a limb‐specific enhancer that localizes Sonic Hedgehog (SHH) expression to the zone of polarizing activity (ZPA), which consequently regulates anteroposterior patterning in the developing limb. ZRS deletion lacks SHH expression in the limb resulting in loss of posterior limb structures, while ZRS single nucleotide variants (SNVs) can lead to ectopic SHH expression causing preaxial polydactyly (PPD). However, the ZRS mechanism of action is not well characterized. HAND2 and HOXD13 are key transcription factors in SHH regulation that bind to the ZRS, potentially modulating SHH transcription. The present study’s objective was to determine the role of HAND2 and HOXD13 binding sites in ZRS function. To evaluate ZRS enhancer activity, ZRS was cloned into an enhancer‐GFP reporter construct. HAND2 and HOXD13 binding sites were altered using site‐directed mutagenesis, and contructs were electroporated into presumptive limb buds in Hamburger‐Hamilton stage 14 chicken embryos. GFP expression was evaluated 48 hours post‐electroporation. ZRS with mutated HAND2 and HOXD13 binding sites retained activity in the limb bud in a pattern that overlapped ZRS activity. This is unexpected since HAND2 and HOXD13 are known to be critical for SHH expression. Future work is needed to clarify the binding site(s) critical to activity and to characterize the factors involved in ZRS function.Support or Funding InformationSupported in part by a grant from the Department of Pathology, Loma Linda University.

Wnt signaling regulates neural plate patterning in distinct temporal phases with dynamic transcriptional outputs

The process that partitions the nascent vertebrate central nervous system into forebrain, midbrain, hindbrain, and spinal cord after neural induction is of fundamental interest in developmental biology, and is known to be dependent on Wnt/β-catenin signaling at multiple steps. Neural induction specifies neural ectoderm with forebrain character that is subsequently posteriorized by graded Wnt signaling: embryological and mutant analyses have shown that progressively higher levels of Wnt signaling induce progressively more posterior fates. However, the mechanistic link between Wnt signaling and the molecular subdivision of the neural ectoderm into distinct domains in the anteroposterior (AP) axis is still not clear. To better understand how Wnt mediates neural AP patterning, we performed a temporal dissection of neural patterning in response to manipulations of Wnt signaling in zebrafish. We show that Wnt-mediated neural patterning in zebrafish can be divided into three phases: (I) a primary AP patterning phase, which occurs during gastrulation, (II) a mes/r1 (mesencephalon-rhombomere 1) specification and refinement phase, which occurs immediately after gastrulation, and (III) a midbrain-hindbrain boundary (MHB) morphogenesis phase, which occurs during segmentation stages. A major outcome of these Wnt signaling phases is the specification of the major compartment divisions of the developing brain: first the MHB, then the diencephalic-mesencephalic boundary (DMB). The specification of these lineage divisions depends upon the dynamic changes of gene transcription in response to Wnt signaling, which we show primarily involves transcriptional repression or indirect activation. We show that otx2b is directly repressed by Wnt signaling during primary AP patterning, but becomes resistant to Wnt-mediated repression during late gastrulation. Also during late gastrulation, Wnt signaling becomes both necessary and sufficient for expression of wnt8b, en2a, and her5 in mes/r1. We suggest that the change in otx2b response to Wnt regulation enables a transition to the mes/r1 phase of Wnt-mediated patterning, as it ensures that Wnts expressed in the midbrain and MHB do not suppress midbrain identity, and consequently reinforce formation of the DMB. These findings integrate important temporal elements into our spatial understanding of Wnt-mediated neural patterning and may serve as an important basis for a better understanding of neural patterning defects that have implications in human health.