Embryonic requirements for Tcf12 in the development of the mouse coronal suture.

A major feature of Saethre-Chotzen syndrome is coronal craniosynostosis, the fusion of the frontal and parietal bones at the coronal suture. It is caused by heterozygous loss-of-function mutations in either of the bHLH transcription factors TWIST1 and TCF12. Although compound heterozygous Tcf12; Twist1 mice display severe coronal synostosis, the individual role of Tcf12 had remained unexplored. Here, we show that Tcf12 controls several key processes in calvarial development, including the rate of frontal and parietal bone growth, and the boundary between sutural and osteogenic cells. Genetic analysis supports an embryonic requirement for Tcf12 in suture formation, as combined deletion of Tcf12 in embryonic neural crest and mesoderm, but not in postnatal suture mesenchyme, disrupts the coronal suture. We also detected asymmetric distribution of mesenchymal cells on opposing sides of the wild-type frontal and parietal bones, which prefigures later bone overlap at the sutures. In Tcf12 mutants, reduced asymmetry is associated with bones meeting end-on-end, possibly contributing to synostosis. Our results support embryonic requirements of Tcf12 in proper formation of the overlapping coronal suture.

Germline competent embryonic stem cells derived from rat blastocysts.

Rats have important advantages over mice as an experimental system for physiological and pharmacological investigations. The lack of rat embryonic stem (ES) cells has restricted the availability of transgenic technologies to create genetic models in this species. Here, we show that rat ES cells can be efficiently derived, propagated, and genetically manipulated in the presence of small molecules that specifically inhibit GSK3, MEK, and FGF receptor tyrosine kinases. These rat ES cells express pluripotency markers and retain the capacity to differentiate into derivatives of all three germ layers. Most importantly, they can produce high rates of chimerism when reintroduced into early stage embryos and can transmit through the germline. Establishment of authentic rat ES cells will make possible sophisticated genetic manipulation to create models for the study of human diseases.

Hypothermia as an Outcome Predictor Tool in Pediatric Trauma: A Propensity-Matched Analysis.

OBJECTIVE: Hypothermia is an independent risk factor for mortality in adult trauma patients. Two small studies have shown similar results in pediatric trauma patients. Temperature is not included in any pediatric trauma assessment scores. This study sought to compare mortality and various descriptive outcomes between pediatric hypothermic and normothermic trauma patients. METHODS: Data were obtained from the National Trauma Database from 2009 to 2012. Patients meeting inclusion criteria were stratified by presence of isolated head injury, head injury with multiple trauma, and absence of head injury. These groups were then subdivided into hypothermic (temperature ≤36°C) and normothermic groups. We used propensity score matching to 1:1 match hypothermic and normothermic patients. Mortality, neurosurgical interventions, endotracheal intubation, blood transfusion, length of stay, laparotomy, thoracotomy, conversion of cardiac rhythm, and time receiving mechanical ventilation were evaluated. RESULTS: Data from 3,011,482 patients were obtained. There were 414,562 patients who met the inclusion criteria. In all patients meeting inclusion criteria, hypothermia was a significant risk factor in all outcomes measured. Following stratification and 1:1 matching, in all groups, hypothermia was associated with increased mortality (P < 0.0001), increased rate of endotracheal intubation (P < 0.0002), increased need for blood transfusion (P < 0.0025), and conversion of cardiac rhythm (P < 0.0027). CONCLUSION: Hypothermia has been shown to be a significant prognostic indicator in the pediatric trauma patient with further potential application. Future studies are indicated to evaluate the incorporation of hypothermia into the Pediatric Trauma Score not only to help predict injury severity and mortality but also to improve appropriate and expeditious patient transfer to pediatric trauma centers and potentially facilitate earlier intervention.

Negative regulation of endothelin signaling by SIX1 is required for proper maxillary development.

Jaw morphogenesis is a complex event mediated by inductive signals that establish and maintain the distinct developmental domains required for formation of hinged jaws, the defining feature of gnathostomes. The mandibular portion of pharyngeal arch 1 is patterned dorsally by Jagged-Notch signaling and ventrally by endothelin receptor A (EDNRA) signaling. Loss of EDNRA signaling disrupts normal ventral gene expression, the result of which is homeotic transformation of the mandible into a maxilla-like structure. However, loss of Jagged-Notch signaling does not result in significant changes in maxillary development. Here we show in mouse that the transcription factor SIX1 regulates dorsal arch development not only by inducing dorsal Jag1 expression but also by inhibiting endothelin 1 (Edn1) expression in the pharyngeal endoderm of the dorsal arch, thus preventing dorsal EDNRA signaling. In the absence of SIX1, but not JAG1, aberrant EDNRA signaling in the dorsal domain results in partial duplication of the mandible. Together, our results illustrate that SIX1 is the central mediator of dorsal mandibular arch identity, thus ensuring separation of bone development between the upper and lower jaws.

Yap and Taz play a crucial role in neural crest-derived craniofacial development.

The role of the Hippo signaling pathway in cranial neural crest (CNC) development is poorly understood. We used the Wnt1(Cre) and Wnt1(Cre2SOR) drivers to conditionally ablate both Yap and Taz in the CNC of mice. When using either Cre driver, Yap and Taz deficiency in the CNC resulted in enlarged, hemorrhaging branchial arch blood vessels and hydrocephalus. However, Wnt1(Cre2SOR) mutants had an open cranial neural tube phenotype that was not evident in Wnt1(Cre) mutants. In O9-1 CNC cells, the loss of Yap impaired smooth muscle cell differentiation. RNA-sequencing data indicated that Yap and Taz regulate genes encoding Fox transcription factors, specifically Foxc1. Proliferation was reduced in the branchial arch mesenchyme of Yap and Taz CNC conditional knockout (CKO) embryos. Moreover, Yap and Taz CKO embryos had cerebellar aplasia similar to Dandy-Walker spectrum malformations observed in human patients and mouse embryos with mutations in Foxc1. In embryos and O9-1 cells deficient for Yap and Taz, Foxc1 expression was significantly reduced. Analysis of Foxc1 regulatory regions revealed a conserved recognition element for the Yap and Taz DNA binding co-factor Tead. ChIP-PCR experiments supported the conclusion that Foxc1 is directly regulated by the Yap-Tead complex. Our findings uncover important roles for Yap and Taz in CNC diversification and development.

Msx1 and Msx2 function together in the regulation of primordial germ cell migration in the mouse.

Primordial germ cells (PGCs) are a highly migratory cell population that gives rise to eggs and sperm. Much is known about PGC specification, but less about the processes that control PGC migration. In this study, we document a deficiency in PGC development in embryos carrying global homozygous null mutations in Msx1 and Msx2, both immediate downstream effectors of Bmp signaling pathway. We show that Msx1(-/-);Msx2(-/-) mutant embryos have defects in PGC migration as well as a reduced number of PGCs. These phenotypes are also evident in a Mesp1-Cre-mediated mesoderm-specific mutant line of Msx1 and Msx2. Since PGCs are not marked in Mesp1-lineage tracing, our results suggest that Msx1 and Msx2 function cell non-autonomously in directing PGC migration. Consistent with this hypothesis, we noted an upregulation of fibronectin, well known as a mediator of cell migration, in tissues through which PGCs migrate. We also noted a reduction in the expression of Wnt5a and an increase in the expression in Bmp4 in such tissues in Msx1(-/-);Msx2(-/-) mutants, both known effectors of PGC development.

Foxc1 controls the growth of the murine frontal bone rudiment by direct regulation of a Bmp response threshold of Msx2.

The mammalian skull vault consists of several intricately patterned bones that grow in close coordination. The growth of these bones depends on the precise regulation of the migration and differentiation of osteogenic cells from undifferentiated precursor cells located above the eye. Here, we demonstrate a role for Foxc1 in modulating the influence of Bmp signaling on the expression of Msx2 and the specification of these cells. Inactivation of Foxc1 results in a dramatic reduction in skull vault growth and causes an expansion of Msx2 expression and Bmp signaling into the area occupied by undifferentiated precursor cells. Foxc1 interacts directly with a Bmp responsive element in an enhancer upstream of Msx2, and acts to reduce the occupancy of P-Smad1/5/8. We propose that Foxc1 sets a threshold for the Bmp-dependent activation of Msx2, thus controlling the differentiation of osteogenic precursor cells and the rate and pattern of calvarial bone development.

TGF-ß-activated kinase 1 (Tak1) mediates agonist-induced Smad activation and linker region phosphorylation in embryonic craniofacial neural crest-derived cells.

BACKGROUND: The role of Smad-independent TGF-ß signaling in craniofacial development is poorly elucidated. RESULTS: In craniofacial mesenchymal cells, Tak1 regulates both R-Smad C-terminal and linker region phosphorylation in TGF-ß signaling. CONCLUSION: Tak1 plays an irreplaceable role in craniofacial ecto-mesenchyme during embryogenesis. SIGNIFICANCE: Understanding the mechanisms of TGF-ß signaling contributes to knowledge of pathogenetic mechanisms underlying common craniofacial birth defects. Although the importance of TGF-ß superfamily signaling in craniofacial growth and patterning is well established, the precise details of its signaling mechanisms are still poorly understood. This is in part because of the concentration of studies on the role of the Smad-dependent (so-called "canonical") signaling pathways relative to the Smad-independent ones in many biological processes. Here, we have addressed the role of TGF-ß-activated kinase 1 (Tak1, Map3k7), one of the key mediators of Smad-independent (noncanonical) TGF-ß superfamily signaling in craniofacial development, by deleting Tak1 specifically in the neural crest lineage. Tak1-deficient mutants display a round skull, hypoplastic maxilla and mandible, and cleft palate resulting from a failure of palatal shelves to appropriately elevate and fuse. Our studies show that in neural crest-derived craniofacial ecto-mesenchymal cells, Tak1 is not only required for TGF-ß- and bone morphogenetic protein-induced p38 Mapk activation but also plays a role in agonist-induced C-terminal and linker region phosphorylation of the receptor-mediated R-Smads. Specifically, we demonstrate that the agonist-induced linker region phosphorylation of Smad2 at Thr-220, which has been shown to be critical for full transcriptional activity of Smad2, is dependent on Tak1 activity and that in palatal mesenchymal cells TGFßRI and Tak1 kinases mediate both overlapping and distinct TGF-ß2-induced transcriptional responses. To summarize, our results suggest that in neural crest-derived ecto-mesenchymal cells, Tak1 provides a critical point of intersection in a complex dialogue between the canonical and noncanonical arms of TGF-ß superfamily signaling required for normal craniofacial development.

Cyclic dermal BMP signalling regulates stem cell activation during hair regeneration.

In the age of stem cell engineering it is critical to understand how stem cell activity is regulated during regeneration. Hairs are mini-organs that undergo cyclic regeneration throughout adult life, and are an important model for organ regeneration. Hair stem cells located in the follicle bulge are regulated by the surrounding microenvironment, or niche. The activation of such stem cells is cyclic, involving periodic beta-catenin activity. In the adult mouse, regeneration occurs in waves in a follicle population, implying coordination among adjacent follicles and the extrafollicular environment. Here we show that unexpected periodic expression of bone morphogenetic protein 2 (Bmp2) and Bmp4 in the dermis regulates this process. This BMP cycle is out of phase with the WNT/beta-catenin cycle, thus dividing the conventional telogen into new functional phases: one refractory and the other competent for hair regeneration, characterized by high and low BMP signalling, respectively. Overexpression of noggin, a BMP antagonist, in mouse skin resulted in a markedly shortened refractory phase and faster propagation of the regenerative wave. Transplantation of skin from this mutant onto a wild-type host showed that follicles in donor and host can affect their cycling behaviours mutually, with the outcome depending on the equilibrium of BMP activity in the dermis. Administration of BMP4 protein caused the competent region to become refractory. These results show that BMPs may be the long-sought 'chalone' inhibitors of hair growth postulated by classical experiments. Taken together, results presented in this study provide an example of hierarchical regulation of local organ stem cell homeostasis by the inter-organ macroenvironment. The expression of Bmp2 in subcutaneous adipocytes indicates physiological integration between these two thermo-regulatory organs. Our findings have practical importance for studies using mouse skin as a model for carcinogenesis, intra-cutaneous drug delivery and stem cell engineering studies, because they highlight the acute need to differentiate supportive versus inhibitory regions in the host skin.

Reverse shock index multiplied by the motor component of the Glasgow Coma Scale predicts mortality and need for intervention in pediatric trauma patients.

BACKGROUND: Timely identification of high-risk pediatric trauma patients and appropriate resource mobilization may lead to improved outcomes. We hypothesized that reverse shock index times the motor component of the Glasgow Coma Scale (rSIM) would perform equivalently to reverse shock index times the total Glasgow Coma Scale (rSIG) in the prediction of mortality and the need for intervention following pediatric trauma. METHODS: The 2017-2020 National Trauma Data Bank datasets were used. We included all patients <16 years of age that had a documented prehospital and trauma bay systolic blood pressure, heart rate, and total GCS. We excluded all patients who arrived at the trauma center without vital signs and interfacility transport patients. Receiver operating characteristic (ROC) curves were used to model the performance of each metric as a classifier with respect to our primary and secondary outcomes, and the area under the ROC curve (AUC) was used for comparison. Our primary outcome was mortality prior to hospital discharge. Secondary outcomes included blood product administration or hemorrhage control intervention (surgery or angiography) < 4 hours following hospital arrival and ICU admission. RESULTS: After application of exclusion criteria, 77,996 patients were included in our analysis. rSIM and rSIG performed equivalently as predictors of mortality in the 1-2 (p = 0.05) and 3-5 (p = 0.28) year categories, but rSIM was statistically outperformed by rSIG in the 6-12 (AUC: 0.96 vs. 0.95, p = 0.04) and 13-16 (AUC: 0.96 vs. 0.95, p < 0.01) year-old age categories. rSIM and rSIG also performed similarly with respect to prediction of secondary outcomes. CONCLUSION: rSIG and rSIM are both outstanding predictors of mortality following pediatric trauma. Statistically significant differences in favor of rSIG were noted in some age groups. Because of the simplicity of calculation, rSIM may be a useful tool for pediatric trauma triage. LEVEL OF EVIDENCE: III, Diagnostic Tests or Criteria.

Augmentation of BMP Signaling in Cranial Neural Crest Cells Leads to Premature Cranial Sutures Fusion through Endochondral Ossification in Mice.

Craniosynostosis is a congenital anomaly characterized by the premature fusion of cranial sutures. Sutures are a critical connective tissue that regulates bone growth; their aberrant fusion results in abnormal shapes of the head and face. The molecular and cellular mechanisms have been investigated for a long time, but knowledge gaps remain between genetic mutations and mechanisms of pathogenesis for craniosynostosis. We previously demonstrated that the augmentation of bone morphogenetic protein (BMP) signaling through constitutively active BMP type 1A receptor (caBmpr1a) in neural crest cells (NCCs) caused the development of premature fusion of the anterior frontal suture, leading to craniosynostosis in mice. In this study, we demonstrated that ectopic cartilage forms in sutures prior to premature fusion in caBmpr1a mice. The ectopic cartilage is subsequently replaced by bone nodules leading to premature fusion with similar but unique fusion patterns between two neural crest-specific transgenic Cre mouse lines, P0-Cre and Wnt1-Cre mice, which coincides with patterns of premature fusion in each line. Histologic and molecular analyses suggest that endochondral ossification in the affected sutures. Both in vitro and in vivo observations suggest a greater chondrogenic capacity and reduced osteogenic capability of neural crest progenitor cells in mutant lines. These results suggest that the augmentation of BMP signaling alters the cell fate of cranial NCCs toward a chondrogenic lineage to prompt endochondral ossification to prematurely fuse cranial sutures. By comparing P0-Cre;caBmpr1a and Wnt1-Cre;caBmpr1a mice at the stage of neural crest formation, we found more cell death of cranial NCCs in P0-Cre;caBmpr1a than Wnt1-Cre;caBmpr1a mice at the developing facial primordia. These findings may provide a platform for understanding why mutations of broadly expressed genes result in the premature fusion of limited sutures. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Lower incidence of blunt cerebrovascular injury among young, properly restrained children: An ATOMAC multicenter study.

BACKGROUND: Motor vehicle collision (MVC) remains a leading cause of injury and death among children, but the proper use of child safety seats and restraints has lowered the risks associated with motor vehicle travel. Blunt cerebrovascular injury (BCVI) is rare but significant among children involved in MVC. This study reviewed the incidence of BCVI after MVC causing blunt injury to the head, face, or neck, comparing those that were properly restrained with those that were not. METHODS: A prospective, multi-institutional observational study of children younger than 15 years who sustained blunt trauma to the head, face, or neck (Abbreviated Injury Scale score >0) and presented at one of six level I pediatric trauma centers from 2017 to 2020 was conducted. Diagnosis of BCVI was made either by imaging or neurological symptoms at 2-week follow-up. Restraint status among those involved in MVC was compared for each age group. RESULTS: A total of 2,284 patients were enrolled at the 6 trauma centers. Of these, 521 (22.8%) were involved in an MVC. In this cohort, after excluding patients with missing data, 10 of 371 (2.7%) were diagnosed with a BCVI. For children younger than 12 years, none who were properly restrained suffered a BCVI (0 of 75 children), while 7 of 221 (3.2%) improperly restrained children suffered a BCVI. For children between 12 and 15 years of age, the incidence of BCVI was 2 of 36 (5.5%) for children in seat belts compared with 1 of 36 (2.8%) for unrestrained children. CONCLUSION: In this large multicenter prospectively screened pediatric cohort, the incidence of BCVI among properly restrained children under 12 years after MVC was infrequent, while the incidence was 3.2% among those without proper restraint. This effect was not seen among children older than 12 years. Restraint status in young children may be an important factor in BCVI screening. LEVEL OF EVIDENCE: Prognostic and Epidemiological; Level IV.

Diagnostic accuracy of screening tools for pediatric blunt cerebrovascular injury: An ATOMAC multicenter study.

BACKGROUND: Blunt cerebrovascular injury (BCVI) is rare but significant among children. There are three sets of BCVI screening criteria validated for adults (Denver, Memphis, and Eastern Association for the Surgery of Trauma criteria) and two that have been validated for use in pediatrics (Utah score and McGovern score), all of which were developed using retrospective, single-center data sets. The purpose of this study was to determine the diagnostic accuracy of each set of screening criteria in children using a prospective, multicenter pediatric data set. METHODS: A prospective, multi-institutional observational study of children younger than 15 years who sustained blunt trauma to the head, face, or neck and presented at one of six level I pediatric trauma centers from 2017 to 2020 was conducted. All patients were screened for BCVI using the Memphis criteria, but criteria for all five were collected for analysis. Patients underwent computed tomography angiography of the head or neck if the Memphis criteria were met at presentation or neurological abnormalities were detected at 2-week follow-up. RESULTS: A total of 2,284 patients at the 6 trauma centers met the inclusion criteria. After excluding cases with incomplete data, 1,461 cases had computed tomography angiography and/or 2-week clinical follow-up and were analyzed, including 24 cases (1.6%) with BCVI. Sensitivity, specificity, positive predictive value, and negative predictive value for each set of criteria were respectively 75.0, 87.5, 9.1, and 99.5 for Denver; 91.7, 71.1, 5.0, and 99.8 for Memphis; 79.2, 82.7, 7.1, and 99.6 for Eastern Association for the Surgery of Trauma; 45.8, 95.8, 15.5, and 99.1 for Utah; and 75.0, 89.5, 10.7, and 99.5 for McGovern. CONCLUSION: In this large multicenter pediatric cohort, the Memphis criteria demonstrated the highest sensitivity at 91.7% and would have missed the fewest BCVI, while the Utah score had the highest specificity at 95.8% but would have missed more than half of the injuries. Development of a tool, which narrows the Memphis criteria while maintaining its sensitivity, is needed for application in pediatric patients. LEVEL OF EVIDENCE: Diagnostic Test/Criteria; Level II.

Alterations in Brca1 expression in mouse ovarian granulosa cells have short-term and long-term consequences on estrogen-responsive organs.

Incessant menstrual cycle activity, uninterrupted by either pregnancy or oral contraceptive use, is the most important risk factor for sporadic ovarian cancer. Menstrual cycle progression is partly controlled by steroid hormones such as estrogens and others that are secreted by the ovarian granulosa cells. We showed earlier that mice carrying a homozygous granulosa cell-specific knockout of Brca1, the homolog of BRCA1 that is associated with familial ovarian cancer predisposition in humans, develop benign epithelial tumors in their reproductive tract. These tumors are driven, at least in part, by a prolongation of the proestrus phase of the estrus cycle (equivalent to the follicular phase of the menstrual cycle) in Brca1 mutant mice, resulting in prolonged unopposed estrogen stimulation. Mutant mice synchronized in proestrus also showed increased circulating estradiol levels, but the possibility that this change also has a role in tumor predisposition was not investigated. We sought to determine whether these changes in hormonal stimulation result in measurable changes in tissues targeted by estrogen outside the ovary. Here we show that mice carrying a Brca1 mutation in their ovarian granulosa cells show increased endometrial proliferation during proestrus, implying that the effects of Brca1 inactivation on estrogen stimulation have short-term consequences, at least on this target organ. We further show that mutant mice develop increased femoral trabecular thickness and femoral length, which are well-known consequences of chronic estrogen stimulation. Estrogen biosynthesis by granulosa cells was increased not only in mice carrying a homozygous Brca1 mutation, but also in heterozygous mutants mimicking the mutational status in granulosa cells of human BRCA1 mutation carriers. The results suggest that human germline BRCA1 mutations, although associated with increased cancer risk, may also have beneficial consequences, such as increased bone strength, that may have contributed to the maintenance of mutated BRCA1 alleles in the human gene pool.

Jagged1 functions downstream of Twist1 in the specification of the coronal suture and the formation of a boundary between osteogenic and non-osteogenic cells.

The Notch pathway is crucial for a wide variety of developmental processes including the formation of tissue boundaries. That it may function in calvarial suture development and figure in the pathophysiology of craniosynostosis was suggested by the demonstration that heterozygous loss of function of JAGGED1 in humans can cause Alagille syndrome, which has craniosynostosis as a feature. We used conditional gene targeting to examine the role of Jagged1 in the development of the skull vault. We demonstrate that Jagged1 is expressed in a layer of mesoderm-derived sutural cells that lie along the osteogenic-non-osteogenic boundary. We show that inactivation of Jagged1 in the mesodermal compartment of the coronal suture, but not in the neural crest compartment, results in craniosynostosis. Mesodermal inactivation of Jagged1 also results in changes in the identity of sutural cells prior to overt osteogenic differentiation, as well as defects in the boundary between osteogenic and non-osteogenic compartments at the coronal suture. These changes, surprisingly, are associated with increased expression of Notch2 and the Notch effector, Hes1, in the sutural mesenchyme. They are also associated with an increase in nuclear ß-catenin. In Twist1 mutants, Jagged1 expression in the suture is reduced substantially, suggesting an epistatic relationship between Twist1 and Jagged1. Consistent with such a relationship, Twist1-Jagged1 double heterozygotes exhibit a substantial increase in the severity of craniosynostosis over individual heterozygotes. Our results thus suggest that Jagged1 is an effector of Twist1 in coronal suture development.

Inactivation of Msx1 and Msx2 in neural crest reveals an unexpected role in suppressing heterotopic bone formation in the head.

In an effort to understand the morphogenetic forces that shape the bones of the skull, we inactivated Msx1 and Msx2 conditionally in neural crest. We show that Wnt1-Cre inactivation of up to three Msx1/2 alleles results in a progressively larger defect in the neural crest-derived frontal bone. Unexpectedly, in embryos lacking all four Msx1/2 alleles, the large defect is filled in with mispatterned bone consisting of ectopic islands of bone between the reduced frontal bones, just anterior to the parietal bones. The bone is derived from neural crest, not mesoderm, and, from DiI cell marking experiments, originates in a normally non-osteogenic layer of cells through which the rudiment elongates apically. Associated with the heterotopic osteogenesis is an upregulation of Bmp signaling in this cell layer. Prevention of this upregulation by implantation of noggin-soaked beads in head explants also prevented heterotopic bone formation. These results suggest that Msx genes have a dual role in calvarial development: They are required for the differentiation and proliferation of osteogenic cells within rudiments, and they are also required to suppress an osteogenic program in a cell layer within which the rudiments grow. We suggest that the inactivation of this repressive activity may be one cause of Wormian bones, ectopic bones that are a feature of a variety of pathological conditions in which calvarial bone development is compromised.

The developing mouse coronal suture at single-cell resolution.

Sutures separate the flat bones of the skull and enable coordinated growth of the brain and overlying cranium. The coronal suture is most commonly fused in monogenic craniosynostosis, yet the unique aspects of its development remain incompletely understood. To uncover the cellular diversity within the murine embryonic coronal suture, we generated single-cell transcriptomes and performed extensive expression validation. We find distinct pre-osteoblast signatures between the bone fronts and periosteum, a ligament-like population above the suture that persists into adulthood, and a chondrogenic-like population in the dura mater underlying the suture. Lineage tracing reveals an embryonic Six2+ osteoprogenitor population that contributes to the postnatal suture mesenchyme, with these progenitors being preferentially affected in a Twist1+/-; Tcf12+/- mouse model of Saethre-Chotzen Syndrome. This single-cell atlas provides a resource for understanding the development of the coronal suture and the mechanisms for its loss in craniosynostosis.

Mesenchymal origin of hepatic stellate cells, submesothelial cells, and perivascular mesenchymal cells during mouse liver development.

UNLABELLED: The knowledge concerning fetal hepatic stellate cells (HSCs) is scarce, and their cell lineage and functions are largely unknown. The current study isolated fetal liver mesenchymal cells from a mouse expressing beta-galactosidase under the control of Msx2 promoter by fluorescence-activated cell sorting (FACS) and surveyed marker genes by microarray analysis. Based on the location and immunostaining with conventional and newly disclosed markers, we have identified three distinct populations of fetal liver mesenchymal cells expressing both desmin and p75 neurotrophin receptor (p75NTR): HSCs in the liver parenchyma; perivascular mesenchymal cells expressing alpha-smooth muscle actin (alpha-SMA); and submesothelial cells associated with the basal lamina beneath mesothelial cells and expressing activated leukocyte cell adhesion molecule (ALCAM) and platelet-derived growth factor receptor alpha. A transitional cell type from the submesothelial cell phenotype to fetal HSCs was also identified near the liver surface. Mesothelial cells expressed podoplanin and ALCAM. Ki-67 staining showed that proliferative activity of the submesothelial cells is higher than that of mesothelial cells and transitional cells. Using anti-ALCAM antibodies, submesothelial and mesothelial cells were isolated by FACS. The ALCAM(+) cells expressed hepatocyte growth factor and pleiotrophin. In culture, the ALCAM(+) cells rapidly acquired myofibroblastic morphology and alpha-SMA expression. The ALCAM(+) cells formed intracellular lipid droplets when embedded in collagen gel and treated with retinol, suggesting the potential for ALCAM(+) cells to differentiate to HSCs. Finally, we demonstrated that fetal HSCs, submesothelial cells, and perivascular mesenchymal cells are all derived from mesoderm by using MesP1-Cre and ROSA26 reporter mice. CONCLUSION: Fetal HSCs, submesothelial cells, and perivascular mesenchymal cells are mesodermal in origin, and ALCAM(+) submesothelial cells may be a precursor for HSCs in developing liver.

Resolving homology in the face of shifting germ layer origins: Lessons from a major skull vault boundary.

The vertebrate skull varies widely in shape, accommodating diverse strategies of feeding and predation. The braincase is composed of several flat bones that meet at flexible joints called sutures. Nearly all vertebrates have a prominent 'coronal' suture that separates the front and back of the skull. This suture can develop entirely within mesoderm-derived tissue, neural crest-derived tissue, or at the boundary of the two. Recent paleontological findings and genetic insights in non-mammalian model organisms serve to revise fundamental knowledge on the development and evolution of this suture. Growing evidence supports a decoupling of the germ layer origins of the mesenchyme that forms the calvarial bones from inductive signaling that establishes discrete bone centers. Changes in these relationships facilitate skull evolution and may create susceptibility to disease. These concepts provide a general framework for approaching issues of homology in cases where germ layer origins have shifted during evolution.

Development and Validation of a Controlled Vocabulary: An OWL Representation of Organizational Structures of Trauma Centers and Trauma Systems.

In trauma care and trauma care research there exists an implementation gap regarding a consistent controlled vocabulary to describe organizational aspects of trauma centers and trauma systems. This paper describes the development and evaluation of a controlled vocabulary for trauma care organizations. We give a detailed description of the involvement of domain experts in the domain analysis workflow and the authoring of definitions and additional term descriptions. Finally, the paper details the evaluation methodology to assess the initial version of the controlled vocabulary. The results of the evaluation show that our development process yields terms most of which find approval from domain experts not involved in the development. In addition, our evaluation tools resulted in valuable domain expert input to optimize the controlled vocabulary.