Craniofacial growth of fetal Macaca nemestrina: A cephalometric roentgenographic study

The prenatal growth of the macaque craniofacial skeleton is described using lateral radiographs of 82 fetal and 25 neonatal Macaca nemestrina whose known gestational ages range from 50 to 186 days. The ossification sequence of the craniofacial bones resembles that in the human fetus. During gestation, the macaque neurocranium loses its round, globular shape, becoming flattened and elongated in an anteroposterior direction. In contrast, the morphologic pattern of the face is established early in fetal life, and little change takes place during the remaining prenatal period. The macaque craniofacial dimensions develop along the general skeletal growth pattern, unlike the human craniofacial dimensions, which follow an intermediate pattern between the neural and general skeletal patterns. However, despite minor differences, the macaque and human fetal faces follow the same basic patterns of growth.     

Developmental differences between singletons and twins in distributions of dental diameter asymmetries

Craniofacial development and behavioral development differs between human twins and singletons in several ways which are related to symmetry development and detectable in adults. In most of those ways, twin zygosity groups do not differ. Here we use distributions of dental diameters, as a model subsystem of craniofacial development, to show that twins, of both zygosities and both sexes, are substantially more symmetrical than singletons. The observed differences are consistent with previous related observations, none of which can readily be explained by any consequence of twin gestation. They seem instead to represent peculiarities of developmental biology familially associated with twinning.     

Hawaiian craniofacial morphometrics: Average Mokapuan skull,artificial cranial deformation,and the “rocker” mandible

Craniofacial morphology and cultural cranial deformation were analyzed by the computer morphometric system in 79 adult Hawaiian skulls from Mokapu, Oahu. The average Hawaiian male was large, but similar in shape to the female. Both were larger than the present Caucasian, showed a greater dental protrusion, and possessed a larger ANB angle, flatter cranial base, and larger facial heights. Correlations in Hawaiian craniofacial structure were found between an increasing mandibular plane angle and (1) shorter posterior facial height, (2) larger gonial angle, (3) larger cranial base angle, and (4) smaller SNA and SNB angles. Of the 79 skulls studied, 8. 9% were found to have severe head molding or intentional cranial deformation. Significant statistical differences between the molded group and the nonmolded group are, in decreasing significance: (1) larger upper face height, (2) smaller glabella to occiput distance, and (3) increased lower face height with deformation. The morphometric differences were readily seen by graphic comparison between groups. It is postulated that external forces to the neurocranium result in redirection of the growth vectors in the neurocranial functional matrix, including the cranial base, and secondarily, to the orofacial functional matrix. There is a possibility that the cranial deformation is a retention of the normal birth molding changes. The Polynesian “rocker jaw” was found in 81% to 95% of this populace. This mandibular form occurs only with attainment of adult stature and craniofacial form. This data agrees with the hypothesis that mandibular form is modified by the physical forces present and their direction in the orofacial functional matrix.     

The canonical Wnt signaling activator, R-spondin2, regulates craniofacial patterning and morphogenesis within the branchial arch through ectodermal-mesenchymal interaction

R-spondins are a recently characterized family of secreted proteins that activate Wnt/β-catenin signaling. Herein, we determine R-spondin2 (Rspo2) function in craniofacial development in mice. Mice lacking a functional Rspo2 gene exhibit craniofacial abnormalities such as mandibular hypoplasia, maxillary and mandibular skeletal deformation, and cleft palate. We found that loss of the mouse Rspo2 gene significantly disrupted Wnt/β-catenin signaling and gene expression within the first branchial arch (BA1). Rspo2, which is normally expressed in BA1 mesenchymal cells, regulates gene expression through a unique ectoderm–mesenchyme interaction loop. The Rspo2 protein, potentially in combination with ectoderm-derived Wnt ligands, up-regulates Msx1 and Msx2 expression within mesenchymal cells. In contrast, Rspo2 regulates expression of the Dlx5, Dlx6, and Hand2 genes in mesenchymal cells via inducing expression of their upstream activator, Endothelin1 (Edn1), within ectodermal cells. Loss of Rspo2 also causes increased cell apoptosis, especially within the aboral (or caudal) domain of the BA1, resulting in hypoplasia of the BA1. Severely reduced expression of Fgf8, a survival factor for mesenchymal cells, in the ectoderm of Rspo2^−/− embryos is likely responsible for increased cell apoptosis. Additionally, we found that the cleft palate in Rspo2^−/− mice is not associated with defects intrinsic to the palatal shelves. A possible cause of cleft palate is a delay of proper palatal shelf elevation that may result from the small mandible and a failure of lowering the tongue. Thus, our study identifies Rspo2 as a mesenchyme-derived factor that plays critical roles in regulating BA1 patterning and morphogenesis through ectodermal–mesenchymal interaction and a novel genetic factor for cleft palate.     

The Neanderthal face is not cold adapted

Many morphological features of the Pleistocene fossil hominin Homo neanderthalensis, including the reputed large size of its paranasal sinuses, have been interpreted as adaptations to extreme cold, as some Neanderthals lived in Europe during glacial periods. This interpretation of sinus evolution rests on two assumptions: that increased craniofacial pneumatization is an adaptation to lower ambient temperatures, and that Neanderthals have relatively large sinuses. Analysis of humans, other primates, and rodents, however, suggests that the first assumption is suspect; at least the maxillary sinus undergoes a significant reduction in volume in extreme cold, in both wild and laboratory conditions. The second assumption, that Neanderthal sinuses are large, extensive, or even ‘hyperpneumatized,’ has held sway since the first specimen was described and has been interpreted as the causal explanation for some of the distinctive aspects of Neanderthal facial form, but has never been evaluated with respect to scaling. To test the latter assumption, previously published measurements from two-dimensional (2D) X-rays and new three-dimensional (3D) data from computed tomography (CT) of Neanderthals and temperate-climate European Homo sapiens are regressed against cranial size to determine the relative size of their sinuses. The 2D data reveal a degree of craniofacial pneumatization in Neanderthals that is both commensurate with the size of the cranium and comparable in scale with that seen in temperate climate H. sapiens. The 3D analysis of CT data from a smaller sample supports this conclusion. These results suggest that the distinctive Neanderthal face cannot be interpreted as a direct result of increased pneumatization, nor is it likely to be an adaptation to resist cold stress; an alternative explanation is thus required.     

Avian Facial Morphogenesis Is Regulated by c-Jun N-terminal Kinase/Planar Cell Polarity (JNK/PCP) Wingless-related (WNT) Signaling

Wingless-related proteins (WNTs) regulate extension of the central axis of the vertebrate embryo (convergent extension) as well as morphogenesis of organs such as limbs and kidneys. Here, we asked whether WNT signaling directs facial morphogenesis using a targeted approach in chicken embryos. WNT11 is thought to mainly act via β-catenin-independent pathways, and little is known about its role in craniofacial development. RCAS::WNT11 retrovirus was injected into the maxillary prominence, and the majority of embryos developed notches in the upper beak or the equivalent of cleft lip. Three-dimensional morphometric analysis revealed that WNT11 prevented lengthening of the maxillary prominence, which was due in part to decreased proliferation. We next determined, using a series of luciferase reporters, that WNT11 strongly induced JNK/planar cell polarity signaling while repressing the β-catenin-mediated pathway. The activation of the JNK-ATF2 reporter was mediated by the DEP domain of Dishevelled. The impacts of altered signaling on the mesenchyme were assessed by implanted Wnt11- or Wnt3a-expressing cells (activates β-catenin pathway) into the maxillary prominence or by knocking down endogenous WNT11 with RNAi. Host cells were attracted to Wnt11 donor cells. In contrast, cells exposed to Wnt3a or the control cells did not migrate. Cells in which endogenous WNT11 was knocked down were more oriented and shorter than those exposed to exogenous WNT11. The data suggest that JNK/planar cell polarity WNT signaling operates in the face to regulate several morphogenetic events leading to lip fusion.     

Neural crest cell signaling pathways critical to cranial bone development and pathology

Neural crest cells appear early during embryogenesis and give rise to many structures in the mature adult. In particular, a specific population of neural crest cells migrates to and populates developing cranial tissues. The ensuing differentiation of these cells via individual complex and often intersecting signaling pathways is indispensible to growth and development of the craniofacial complex. Much research has been devoted to this area of development with particular emphasis on cell signaling events required for physiologic development. Understanding such mechanisms will allow researchers to investigate ways in which they can be exploited in order to treat a multitude of diseases affecting the craniofacial complex. Knowing how these multipotent cells are driven towards distinct fates could, in due course, allow patients to receive regenerative therapies for tissues lost to a variety of pathologies. In order to realize this goal, nucleotide sequencing advances allowing snapshots of entire genomes and exomes are being utilized to identify molecular entities associated with disease states. Once identified, these entities can be validated for biological significance with other methods. A crucial next step is the integration of knowledge gleaned from observations in disease states with normal physiology to generate an explanatory model for craniofacial development. This review seeks to provide a current view of the landscape on cell signaling and fate determination of the neural crest and to provide possible avenues of approach for future research.     

统万城遗址出土人骨颅面测量性状

统万城遗址位于陕西省靖边县,是十六国时期大夏国都城所在,历经北魏、西魏、北周、隋、唐、五代、北宋七个朝代共575年。其所处中国北方农牧交错地带,一直是人群往来、交融之地。本文参照《人体测量手册》所列方法对统万城遗址出土人骨进行颅面形态特征的分析。结果表明,统万城遗址出土颅骨是以亚洲蒙古人种为主体,在形态上既存在古人种类型的差异,又表现出多种古人种类型融合的特点,另外还有个体表现出少量欧罗巴人群的性状。统万城遗址居民颅面特征的多态性与融合性,和古代人群演化的历时性特点相吻合,与统万城历史上频繁的人群往来相关,欧罗巴人种因素可能来自粟特人的影响。男女两性居民的主体构成可能有不同来源,随着政治权力主体变化,农人与牧人所占比重也发生了变化。     

广西玉林地区汉族儿童青少年头面部发育特征

为了了解广西玉林地区汉族儿童青少年头面型,本文采用分层随机抽样方法对广西玉林地区1119名7－16岁城镇汉族儿童青少年的9项头面部指标进行测量,分析和比较儿童青少年容貌特征的发育与年龄增长的关系,按头面部各项指数分型。结果显示：汉族儿童青少年头面部的9项指标除头最大宽外均随年龄的增长而增大,各年龄组的性别间存在显著性差异。头面型以中头型和圆头型、高头型、狭头型及阔面型和中面型为主。