Postnatal Skull Development Reveals a Conservative Pattern in Living and Fossil Vizcachas Genus Lagostomus (Rodentia, Chinchillidae).

The plains vizcacha, Lagostomus maximus, is the only living species in the genus, being notably larger than fossil congeneric species, such as Lagostomus incisus, from the Pliocene of Argentina and Uruguay. Here, we compare the skull growth allometric pattern and sexual dimorphism of L. maximus and L. incisus, relating shape and size changes with skull function. We also test whether the ontogenetic trajectories and allometric trends between both sexes of L. maximus follow the same pattern. A common allometric pattern between both species was the elongation of the skull, a product of the lengthening of rostrum, and chondrogenesis on the spheno-occipitalis synchondrosis and coronalis suture. We also detected a low proportion of skull suture fusion. In some variables, older male specimens did not represent a simple linear extension of female trajectory, and all dimorphic traits were related to the development of the masticatory muscles. Sexual dimorphism previously attributed to L. incisus would indicate that this phenomenon was present in the genus since the early Pliocene and suggests social behaviors such as polygyny and male-male competition. Ontogenetic changes in L. incisus were similar to L. maximus, showing a conservative condition of the genus. Only two changes were different in the ontogeny of both species, which appeared earlier in L. incisus compared to L. maximus: the development of the frontal process of the nasals in a square shape, and the straight shape of the occipital bone in lateral view. Juveniles of L. maximus were close to adult L. incisus in the morphospace, suggesting a peramorphic process. The sequence of suture and synchondroses fusion showed minor differences in temporozygomatica and frontonasalis sutures, indicating major mechanical stress in L. maximus related to size. We suggest a generalized growth path in Chinchillidae, but further analyses are necessary at an evolutionary level, including Lagidium and Chinchilla.

Endocranial development in non-avian dinosaurs reveals an ontogenetic brain trajectory distinct from extant archosaurs.

Modern birds possess highly encephalized brains that evolved from non-avian dinosaurs. Evolutionary shifts in developmental timing, namely juvenilization of adult phenotypes, have been proposed as a driver of head evolution along the dinosaur-bird transition, including brain morphology. Testing this hypothesis requires a sufficient developmental sampling of brain morphology in non-avian dinosaurs. In this study, we harness brain endocasts of a postnatal growth series of the ornithischian dinosaur Psittacosaurus and several other immature and mature non-avian dinosaurs to investigate how evolutionary changes to brain development are implicated in the origin of the avian brain. Using three-dimensional characterization of neuroanatomical shape across archosaurian reptiles, we demonstrate that (i) the brain of non-avian dinosaurs underwent a distinct developmental trajectory compared to alligators and crown birds; (ii) ornithischian and non-avialan theropod dinosaurs shared a similar developmental trajectory, suggesting that their derived trajectory evolved in their common ancestor; and (iii) the evolutionary shift in developmental trajectories is partly consistent with paedomorphosis underlying overall brain shape evolution along the dinosaur-bird transition; however, the heterochronic signal is not uniform across time and neuroanatomical region suggesting a highly mosaic acquisition of the avian brain form.

Development of the cranial lateral line system of Brook Trout, Salvelinus fontinalis (Teleostei: Salmonidae): Evolutionary and ecological implications.

The mechanosensory lateral line (LL) system of salmonid fishes has been the focus of comparative morphological studies and behavioral and physiological analyses of flow sensing capabilities, but its morphology and development have not been studied in detail in any one species. Here, we describe the post-embryonic development of the cranial LL system in Brook Trout, Salvelinus fontinalis, using vital fluorescent staining (4-Di-2-ASP), scanning electron microscopy, µCT, and clearing and staining to visualize neuromasts and the process of cranial LL canal morphogenesis. We examined the relationship between the timing of LL development, the prolonged life history of salmonids, and potential ecological implications. The LL system is composed of seven canals containing canal neuromasts (CNs) and four lines of superficial neuromasts (SNs) on the skin. CNs and SNs increase in number and size during the alevin (larval) stage. CN number stabilizes as canal morphogenesis commences, but SN number increases well into the parr (juvenile) stage. CNs become larger and more elongated than SNs, but the relative area occupied by sensory hair cells decreases during ontogeny in both types of neuromasts. Neuromast-centered canal morphogenesis starts in alevins (yolk sac larvae), as they swim up into the water column from their gravel nests (~4 months post-fertilization), after which yolk sac absorption is completed and exogenous feeding begins. Canal morphogenesis proceeds asynchronously within and among canal series and is not complete until ~8 months post-fertilization (the parr stage). Three characters in the LL system and associated dermal bones were used to identify their homologs in other actinopterygians and to consider the evolution of LL canal reduction, thus demonstrating the value of salmonids for the study of LL evolution. The prolonged life history of Brook Trout and the onset of canal morphogenesis at swim-up are predicted to have implications for neuromast function at these critical behavioral and ecological transitions.

Estimating infant age from skull X-ray images using deep learning.

This study constructed deep learning models using plain skull radiograph images to predict the accurate postnatal age of infants under 12 months. Utilizing the results of the trained deep learning models, it aimed to evaluate the feasibility of employing major changes visible in skull X-ray images for assessing postnatal cranial development through gradient-weighted class activation mapping. We developed DenseNet-121 and EfficientNet-v2-M convolutional neural network models to analyze 4933 skull X-ray images collected from 1343 infants. Notably, allowing for a ± 1 month error margin, DenseNet-121 reached a maximum corrected accuracy of 79.4% for anteroposterior (AP) views (average: 78.0 ± 1.5%) and 84.2% for lateral views (average: 81.1 ± 2.9%). EfficientNet-v2-M reached a maximum corrected accuracy 79.1% for AP views (average: 77.0 ± 2.3%) and 87.3% for lateral views (average: 85.1 ± 2.5%). Saliency maps identified critical discriminative areas in skull radiographs, including the coronal, sagittal, and metopic sutures in AP skull X-ray images, and the lambdoid suture and cortical bone density in lateral images, marking them as indicators for evaluating cranial development. These findings highlight the precision of deep learning in estimating infant age through non-invasive methods, offering the progress for clinical diagnostics and developmental assessment tools.

Bioinformatics Study on Mechanism of Postnatal Development of Craniofacial Bone.

OBJECTIVE: The postnatal development of craniofacial bone plays a crucial role in shaping the overall structure and functionality of the skull and face. Understanding the underlying mechanisms of this intricate process is essential for both clinical and research purposes. In this study, the authors conducted a bioinformatics analysis using the Gene Expression Omnibus database to investigate the molecular pathways and regulatory networks involved in the postnatal development of craniofacial bone. METHODS: In this study, the online Gene Expression Omnibus microarray expression profiling data set GSE27976 was used to identify differentially expressed genes (DEGs) in different age groups. Protein-Protein Interaction network analyses, functional enrichment, and hub genes analysis were performed. The differences in immune infiltration and microenvironment among different types of cells were also analyzed. RESULTS: In total, 523 DEGs, including 287 upregulated and 236 downregulated genes, were identified. GO and KEGG analysis showed that the DEGs were significantly enriched in multiple signaling pathways, such as skeletal system morphogenesis, osteoblast differentiation, and stem cell differentiation. Immune infiltration and microenvironment characteristics analysis showed that there were significant differences in fibroblasts, mesenchymal stem cell, osteoblast, stroma score, and microenvironment score between the two groups. Five hub genes, including IGF1, IL1B, ICAM1, MMP2 , and brain-derived neurotrophic factor, were filled out. CONCLUSION: The findings of this study showed a significant shift in gene expression towards osteogenesis during the first 12 months after birth. These findings emphasize the critical role of the postnatal period in craniofacial bone development and provide valuable insights into the molecular mechanisms underlying this process.

Evaluation and 3D imaging of mineral structure changes of the rabbit (New Zealand) skull during developmental periods.

This study aimed to determine the morphometric measurements anatomically and CT images of skulls of healthy male and female rabbits during postnatal development, to analyse the data statistically and to demonstrate the structural changes in bone. A total of 40 rabbits (20 females and 20 males) were divided into four groups including prepubertal period (group I (0-1 month)), period between adolescence and adulthood (group II (3-5 month)) and later (young adult period as group III (1-3 years) and old adult period as group IV (3-5 years)), with five animals in each group. After the morphometric measurements, the surface area and volume values of the skull were calculated. The skulls were reconstructed using a 3D Slicer (5.0.2), which is used for 3D modelling. The cranial bones in each group were then crushed using a grinder so that the powdered samples were obtained for XRF (X-ray fluorescence technique). The p-value was statistically highly significant between group and gender (p < 0.001). In morphometric measurements, males were generally higher than females. Only PL, GBOC and GNB measurements were higher in females. The p-value between groups (in all measurements), between genders (in TL, GLN, FL, VL, OZB and GBN parameters) and between groups and genders (in TL, DL and VL parameters) was statistically highly significant (p < 0.001). The p-value between the groups, p-value between sexes and p-value between group and sex in Si, P, K, Ca, Ni, Zn, Sr, Sr and Ca/P elements were statistically significant (p < 0.001). Consequently, metric, volume and surface area measurements were taken through 3D modelling of skull bone in prepubertal period (group I), period between adolescence and adulthood (group II) and later (young adult period as group III and old adult period as group IV) of rabbits and the change in the mineral structure during postnatal development and effect of sex on this change were investigated. This might be the first study to assess both metric and mineral changes at four age intervals taken during the life span of rabbits.

Does cranial bone ossification differ in children with developmental dysplasia of the hip?

OBJECTIVES: This study aims to compare cranial bone ossification between patients with developmental dysplasia of the hip (DDH) and healthy individuals. PATIENTS AND METHODS: Between September 2021 and April 2022, a total of 60 healthy female individuals (median age: 24.5 months; range, 18 to 36 months) and 56 female DDH patients (median age: 23 months; range, 18 to 35 months) were included. Age, head circumference, weight, height, and patency of the anterior fontanel were measured in groups. Percentiles were classified as very low, low, normal, high and very high. All patients were female and those with abnormal thyroid function test, vitamin D, calcium, phosphate and alkaline phosphatase values were not included in the study. For those diagnosed with DDH, they were included in the group regardless of the type of treatment. RESULTS: No statistically significant difference was found between the groups in terms of age and weight (p>0.05). The very low and very high head circumferences were more frequent, and the normal head circumferences were less frequent in the DDH group (p<0.05). There was no significant difference between groups in terms of fontanel closure (p>0.05). In open fontanels, no significant difference was found in both groups in terms of age (p>0.05). CONCLUSION: Our study results showed no significant difference between the fontanel ossifications of children with and without DDH; however, we found that the ossification of the skull bones of children with DDH was different compared to healthy children.

Ontogenetic changes in jaw leverage and skull shape in tufted and untufted capuchins.

The ontogeny of feeding is characterized by shifting functional demands concurrent with changes in craniofacial anatomy; relationships between these factors will look different in primates with disparate feeding behaviors during development. This study examines the ontogeny of skull morphology and jaw leverage in tufted (Sapajus) and untufted (Cebus) capuchin monkeys. Unlike Cebus, Sapajus have a mechanically challenging diet and behavioral observations of juvenile Sapajus suggest these foods are exploited early in development. Landmarks were placed on three-dimensional surface models of an ontogenetic series of Sapajus and Cebus skulls (n = 53) and used to generate shape data and jaw-leverage estimates across the tooth row for three jaw-closing muscles (temporalis, masseter, medial pterygoid) as well as a weighted combined estimate. Using geometric morphometric methods, we found that skull shape diverges early and shape is significantly different between Sapajus and Cebus throughout ontogeny. Additionally, jaw leverage varies with age and position on the tooth row and is greater in Sapajus compared to Cebus when calculated at the permanent dentition. We used two-block partial least squares analyses to identify covariance between skull shape and each of our jaw muscle leverage estimates. Sapajus, but not Cebus, has significant covariance between all leverage estimates at the anterior dentition. Our findings show that Sapajus and Cebus exhibit distinct craniofacial morphologies early in ontogeny and strong covariance between leverage estimates and craniofacial shape in Sapajus. These results are consistent with prior behavioral and comparative work suggesting these differences are a function of selection for exploiting mechanically challenging foods in Sapajus, and further emphasize that these differences appear quite early in ontogeny. This research builds on prior work that has highlighted the importance of understanding ontogeny for interpreting adult morphology.

Apical expansion of calvarial osteoblasts and suture patency is dependent on fibronectin cues.

The skull roof, or calvaria, is comprised of interlocking plates of bones that encase the brain. Separating these bones are fibrous sutures that permit growth. Currently, we do not understand the instructions for directional growth of the calvaria, a process which is error-prone and can lead to skeletal deficiencies or premature suture fusion (craniosynostosis, CS). Here, we identify graded expression of fibronectin (FN1) in the mouse embryonic cranial mesenchyme (CM) that precedes the apical expansion of calvaria. Conditional deletion of Fn1 or Wasl leads to diminished frontal bone expansion by altering cell shape and focal actin enrichment, respectively, suggesting defective migration of calvarial progenitors. Interestingly, Fn1 mutants have premature fusion of coronal sutures. Consistently, syndromic forms of CS in humans exhibit dysregulated FN1 expression, and we also find FN1 expression altered in a mouse CS model of Apert syndrome. These data support a model of FN1 as a directional substrate for calvarial osteoblast migration that may be a common mechanism underlying many cranial disorders of disparate genetic etiologies.

Key Roles of Gli1 and Ihh Signaling in Craniofacial Development.

The Hedgehog (Hh) signaling pathway orchestrates its influence through a dynamic interplay of Hh proteins, the cell surface receptor Ptch1, Smo, and Gli transcription factors, contributing to a myriad of developmental events. Indian Hedgehog (Ihh) and Gli zinc finger transcription factor 1 (Gli1) play crucial roles in developmental regulation within the Hh signaling pathway. Ihh regulates chondrocyte proliferation, differentiation, and bone formation, impacting the development of cranial bones, cartilage, and the temporomandibular joint (TMJ). Losing Ihh results in cranial bone malformation and decreased ossification and affects the formation of cranial base cartilage unions, TMJ condyles, and joint discs. Gli1 is predominantly expressed during early craniofacial development, and Gli1+ cells are identified as the primary mesenchymal stem cells (MSCs) for craniofacial bones, crucial for cell differentiation and morphogenesis. In addition, a complex mutual regulatory mechanism exists between Gli1 and Ihh, ensuring the normal function of the Hh signaling pathway by directly or indirectly regulating each other's expression levels. And the interaction between Ihh and Gli1 significantly impacts the normal development of craniofacial tissues. This review summarizes the pivotal roles of Gli1 and Ihh in the intricate landscape of mammalian craniofacial development and outlines the molecular regulatory mechanisms and intricate interactions governing the growth of bone and cartilage exhibited by Gli1 and Ihh, which provides new insights into potential therapeutic strategies for related diseases or researches of tissue regeneration.

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Craniomaxillofacial development involves a series of highly ordered temporal-spatial cellular differentiation processes in which a variety of cell signaling factors, such as fibroblast growth factors, play important regulatory roles. As a classic fibroblast growth factor, fibroblast growth factor 7 (FGF7) serves a wide range of regulatory functions. Previous studies have demonstrated that FGF7 regulates the proliferation and migration of epithelial cells, protects them, and promotes their repair. Furthermore, recent findings indicate that epithelial cells are not the only ones subjected to the broad and powerful regulatory capacity of FGF7. It has potential effects on skeletal system development as well. In addition, FGF7 plays an important role in the development of craniomaxillofacial organs, such as the palate, the eyes, and the teeth. Nonetheless, the role of FGF7 in oral craniomaxillofacial development needs to be further elucidated. In this paper, we summarized the published research on the role of FGF7 in oral craniomaxillofacial development to demonstrate the overall understanding of FGF7 and its potential functions in oral craniomaxillofacial development.

Changes in the Craniomaxillofacial Growth and Development of Sprague Dawley Rats Subjected to Permanent Experimental Unilateral Nasal Obstruction / Cambios en el Crecimiento y Desarrollo Cráneo Maxilo Facial de Ratas Sprague Dawley Sometidas a Obstrucción Nasal Unilateral Experimental Permanente

SUMMARY: Breathing is considered a vital function dependent on factors such as adequate permeability of the nasal route, which is linked to physiological functions, intellectual processes, and craniofacial growth. The aim of this study was to determine the changes in the craniomaxillofacial growth and bone development of Sprague Dawley rats subjected to permanent experimental unilateral nasal obstruction. Twenty-four newborn rats were used, randomized, and divided into experimental and control groups. The right nostril was obstructed, and weight, length, and Lee's index measurements were recorded at 8 and 16 weeks. Craniomandibular x-rays were taken of each animal, obtaining linear neuro- and viscerocranial measurements. Then, a biochemical analysis was performed to measure the alkaline phosphatase concentration. The results were analyzed in the SPSS software, performing a descriptive analysis, using a t-test for independent samples, comparing basal, cephalometric, and biochemical characteristics between the control and experimental groups, considering a significance range of 5%. When comparing the experimental and control groups, the variables length, weight, and Lee's index presented no significant differences. In the x-ray analysis, at 8 weeks, the Co-L1 and Co-Mn measurements were reduced, whereas the Ba-So increased, with significant differences. At 16 weeks, the L1-O, Po-Ba, and E-Mu measurements decreased; however, Co-Gn registered a greater value with significant differences. The alkaline phosphatase levels fell significantly at week 16 in the experimental group. In conclusion, the reduction of permanent nasal respiratory flow is related to modifications in facial growth at 8 and 16 weeks and to the reduction of alkaline phosphatases at 16 weeks.

La respiración se considera una función vital, dependiente de factores como la permeabilidad adecuada de la vía nasal, vinculada con funciones fisiológicas, procesos intelectuales y crecimiento cráneofacial. El objetivo de este estudio fue determinar los cambios en el crecimiento y desarrollo óseo cráneo maxilo facial de ratas Sprague Dawley sometidas a obstrucción nasal unilateral experimental permanente. Se utilizaron 24 ratas macho neonatas, randomizadas y divididas en grupo control y experimental. Fue realizada obstrucción nasal de la narina derecha y realizadas mediciones de peso, longitud e índice de Lee a las 8 y 16 semanas. Se efectuaron radiografías cráneomandibulares a cada animal, obteniendo medidas lineales de neuro y viscerocráneo. Posteriormente se realizó análisis bioquímico, para medir la concentración de fosfatasa alcalina. Los resultados fueron analizados en el software SPSS, realizándose análisis descriptivo, empleando prueba T para muestras independientes comparando características basales, cefalométricas y bioquímicas entre los grupos control y experimental, considerando un umbral de significancia de 5 %. Al comparar los grupos control y experimental, las variables longitud, peso e índice de Lee no presentaron diferencias significativas. En el análisis radiográfico, a las 8 semanas, las medidas Co-L1 y Co-Mn presentaron reducción, mientras que Ba-So aumentó, con diferencias significativas. A las 16 semanas, las medidas L1-O, Po-Ba y E-Mu disminuyeron, sin embargo, Co-Gn registró un mayor valor, con diferencias significativas. Los niveles de fosfatasa alcalina disminuyeron significativamente en la semana 16 en el grupo experimental. En conclusión, la reducción de flujo respiratorio nasal permanente se relaciona con modificaciones del crecimiento facial a las 8 y 16 semanas y con la reducción de ALK en análisis a las 16 semanas.

The gelatinases, matrix metalloproteinases 2 and 9, play individual roles in skeleton development.

The gelatinases, a subgroup of the matrix metalloproteinases (MMPs) superfamily are composed of two members; MMP2 and MMP9. They are known to degrade gelatin among other components of the extracellular matrix. Recently, the two gelatinases were found to be necessary for neural crest cell migration and to compensate for each other loss in these cells. To characterize their involvement in the skeletal system, and to better reveal their individual or common roles, we have generated double knockout (dKO) mice, lacking both MMP2 and MMP9. Comprehensive analysis of the skeleton morphological and mechanical parameters at postnatal day (P) 0, P21, 3 months (M) and 8M of age, revealed an unexpected distinct role for each gelatinase; MMP2 was found to be involved merely in intramembranous ossification which led to a smaller skull and inferior cortical parameters upon its loss, while MMP9 was found to affect only the endochondral ossification process, which led to shorter long-bones in its absence. Importantly, the dKO mice demonstrated a combination of both the skull and long bone phenotypes as found in the single-KOs, and not a severer additive phenotype. Transcriptome analysis on the cortical bone, the growth plate and the skull frontal bone, found many genes that were differentially expressed as a direct or indirect result of MMP-loss, and reinforced the specific and distinct role of each gelatinase in each bone type. Altogether, these results suggest that although both gelatinases share the same substrates and are highly expressed in flat and long bones, they are indispensable and control separately the development of different bones.

Endocranial ontogeny and evolution in early Homo sapiens: The evidence from Herto, Ethiopia.

Fossils and artifacts from Herto, Ethiopia, include the most complete child and adult crania of early Homo sapiens. The endocranial cavities of the Herto individuals show that by 160,000 y ago, brain size, inferred from endocranial size, was similar to that seen in modern human populations. However, endocranial shape differed from ours. This gave rise to the hypothesis that the brain itself evolved substantially during the past ∼200,000 y, possibly in tandem with the transition from Middle to Upper Paleolithic techno-cultures. However, it remains unclear whether evolutionary changes in endocranial shape mostly reflect changes in brain morphology rather than changes related to interaction with maxillofacial morphology. To discriminate between these effects, we make use of the ontogenetic fact that brain growth nearly ceases by the time the first permanent molars fully erupt, but the face and cranial base continue to grow until adulthood. Here we use morphometric data derived from digitally restored immature and adult H. sapiens fossils from Herto, Qafzeh, and Skhul (HQS) to track endocranial development in early H. sapiens. Until the completion of brain growth, endocasts of HQS children were similar in shape to those of modern human children. The similarly shaped endocasts of fossil and modern children indicate that our brains did not evolve substantially over the past 200,000 y. Differences between the endocranial shapes of modern and fossil H. sapiens adults developed only with continuing facial and basicranial growth, possibly reflecting substantial differences in masticatory and/or respiratory function.

Ontogenetic variation in the skull of Stenopterygius quadriscissus with an emphasis on prenatal development.

The availability of a large sample size from a range of ontogenetic stages makes Stenopterygius quadriscissus a good model to study ontogenetic variation in a fossil sauropsid. We qualitatively examined pre- and postnatal ontogenetic changes in the cranium of S. quadriscissus. The prenatal ossification sequence is similar to other diapsids, exhibiting delayed chondrocranial ossification compared to the dermatocranium. In the dermatocranium, the circumorbital area is more ossified earlier in development relative to other elements, especially those of the skull roof where ossification is comparatively weaker across prenatal stages. Perinatally all cranial elements are ossified, and many scarf and step joints are already closed. We propose four prenatal and three postnatal stages in S. quadriscissus on the basis of relative ossification, size and qualitative cranial characters pertaining to the jugal, parietal, frontal, pterygoid and surangular. These will provide a basis for determining ontogenetic stages in other ichthyosaurs. Moreover, our postnatal observations aid in refining ontogenetic characters for phylogenetic studies. Lastly, we observed that the antimeric sutures of the midline of the skull roof are open perinatally and that fusion of the midline only appears in the adult stage. We hypothesize that the loose connection of the midline functions as a fontanelle, limiting potential damage during birth.

On the sequence heterochrony of cranial ossification of bats in light of Haeckel's recapitulation theory.

Haeckel's recapitulation theory has been a controversial topic in evolutionary biology. However, we have seen some recent cases applying Haeckel's view to interpret the interspecific variation of prenatal ontogeny. To revisit the validity of Haeckel's recapitulation theory, we take bats that have undergone drastic morphological changes and possess a characteristic ecology as a case study. All members of Rhinolophoidea and Yangochiroptera can generate an ultrasonic pulse from the larynx to interpret surrounding objects (laryngeal echolocation) whereas Pteropodidae lacks such ability. It is known that the petrosal bone is particularly derived in shape and expanded in laryngeal echolocators. If Haeckel's recapitulation theory holds, the formation of this derived trait should occur later than those of other bones. Therefore, we compared the prenatal ossification timing of the petrosal in 15 bat species and five outgroup species. We found that the ossification of the petrosal is accelerated in laryngeal echolocators while it is the last bone to ossify in non-laryngeal echolocating bats and non-volant mammals, which runs counter to the prediction generated by Haeckel's recapitulation theory. We point out the evolutionarily labile nature of trait developmental timing and emphasize that Haeckel's recapitulation theory does not hold in many cases. We caution that generating predictions on ancestral conditions and evolutionary history leading from Haeckel's recapitulation theory is not well supported.

Bone Regeneration of a 3D-Printed Alloplastic and Particulate Xenogenic Graft with rhBMP-2.

This study aimed to evaluate the bone regeneration capacity of a customized alloplastic material and xenograft with recombinant human bone morphogenetic protein-2 (rhBMP-2). We prepared hydroxyapatite (HA)/tricalcium phosphate (TCP) pure ceramic bone blocks made using a 3D printing system and added rhBMP-2 to both materials. In eight beagle dogs, a total of 32 defects were created on the lower jaws. The defective sites of the negative control group were left untreated (N group; 8 defects), and those in the positive control group were filled with particle-type Bio-Oss (P group; 12 defects). The defect sites in the experimental group were filled with 3D-printed synthetic bone blocks (3D group; 12 defects). Radiographic and histological evaluations were performed after healing periods of 6 and 12 weeks and showed no significant difference in new bone formation and total bone between the P and 3D groups. The 3D-printed custom HA/TCP graft with rhBMP-2 showed bone regeneration effects similar to that of particulate Bio-Oss with rhBMP-2. Through further study and development, the application of 3D-printed customized alloplastic grafts will be extended to various fields of bone regeneration.

Generation of a new six1-null line in Xenopus tropicalis for study of development and congenital disease.

The vertebrate Six (Sine oculis homeobox) family of homeodomain transcription factors plays critical roles in the development of several organs. Six1 plays a central role in cranial placode development, including the precursor tissues of the inner ear, as well as other cranial sensory organs and the kidney. In humans, mutations in SIX1 underlie some cases of Branchio-oto-renal (BOR) syndrome, which is characterized by moderate-to-severe hearing loss. We utilized CRISPR/Cas9 technology to establish a six1 mutant line in Xenopus tropicalis that is available to the research community. We demonstrate that at larval stages, the six1-null animals show severe disruptions in gene expression of putative Six1 target genes in the otic vesicle, cranial ganglia, branchial arch, and neural tube. At tadpole stages, six1-null animals display dysmorphic Meckel's, ceratohyal, and otic capsule cartilage morphology. This mutant line will be of value for the study of the development of several organs as well as congenital syndromes that involve these tissues.

Riding the crest to get a head: neural crest evolution in vertebrates.

In their seminal 1983 paper, Gans and Northcutt proposed that evolution of the vertebrate 'new head' was made possible by the advent of the neural crest and cranial placodes. The neural crest is a stem cell population that arises adjacent to the forming CNS and contributes to important cell types, including components of the peripheral nervous system and craniofacial skeleton and elements of the cardiovascular system. In the past few years, the new head hypothesis has been challenged by the discovery in invertebrate chordates of cells with some, but not all, characteristics of vertebrate neural crest cells. Here, we discuss recent findings regarding how neural crest cells may have evolved during the course of deuterostome evolution. The results suggest that there was progressive addition of cell types to the repertoire of neural crest derivatives throughout vertebrate evolution. Novel genomic tools have enabled higher resolution insight into neural crest evolution, from both a cellular and a gene regulatory perspective. Together, these data provide clues regarding the ancestral neural crest state and how the neural crest continues to evolve to contribute to the success of vertebrates as efficient predators.

Age estimation of immature human skeletal remains from mandibular and cranial bone dimensions in the postnatal period.

Age estimation is one of the crucial first steps in the identification of human skeletal remains in both forensic and archeological contexts. In the postnatal period, age is traditionally estimated from dental development or skeletal growth, typically long bone diaphyseal length. However, in many occasions other methods are required. This study provides alternative means of estimating age of juvenile remains from the size of several cranial bones and the mandible. A sample of 185 identified juvenile skeletons between birth and 13 years of age from two European collections were used (Lisbon and Spitalfields). Measurements of the frontal, occipital-lateralis, occipital-basilaris, occipital-squamous, zygomatic, maxilla, and mandible were used to calculate classical calibration regression formulae for the sexes combined. The sample was divided into three age groups birth-2 years, 2-6 years, and 2-12.9 years, depending on bone and its growth trajectory. For all the bones, measurements of the youngest age groups yielded the most precise age estimates. The vault bones on average yielded the best performing models, with the frontal bone having the most precise of all. The mandible performed on par with the best performing cranial bones, particularly in individuals under the age of 2 years. This study provides one of the most comprehensive approaches to juvenile age estimation based on bones of the skull, providing a resource that potentially can help estimate age of juvenile skeletons from a variety of circumstances.