Effects of thiourea on the skull of Triturus newts during ontogeny

Background In amphibians, thyroid hormone (TH) has a profound role in cranial development, especially in ossification of the late-appearing bones and remodeling of the skull. In the present study, we explored the influence of TH deficiency on bone ossification and resulting skull shape during the ontogeny of Triturus newt hybrid larvae obtained from interspecific crosses between T. ivanbureschi and T. macedonicus. Methods Larvae were treated with two concentrations of thiourea (an endocrine disruptor that chemically inhibits synthesis of TH) during the midlarval and late larval periods. Morphological differences of the cranium were assessed at the end of the midlarval period (ontogenetic stage 62) and the metamorphic stage after treatment during the late larval period. Results There was no difference in the ossification level and shape of the skull between the experimental groups (control and two treatment concentrations) at stage 62. During the late larval period and metamorphosis, TH deficit had a significant impact on the level of bone ossification and skull shape with no differences between the two treatment concentrations of thiourea. The most pronounced differences in bone development were: the palatopterygoid failed to disintegrate into the palatal and pterygoid portions, retardation was observed in development of the maxilla, nasal and prefrontal bones and larval organization of the vomer was retained in thiourea-treated larvae. Conclusions This implies that deficiency of TH caused retardation in development and arrested metamorphic cranium skeletal reorganization, which resulted in divergent cranial shape compared to the control group. Our results confirmed that skull remodeling and ossification of late-appearing bones is TH–dependent, as in other studied Urodela species. Also, our results indicate that TH plays an important role in the establishment of skull shape during the ontogeny of Triturus newts, especially during the late larval period and metamorphosis, when TH concentrations reach their maximum.

Ontology of Variants of Cranial Structure and Malformations. Part I

Annually severe congenital abnormalities occur in 1 of 33 newborns or about 125.000 live births in the United States and are the leading cause of infant mortality. Craniofacial anomalies account for about one-third of all abnormalities. The prevalence of human congenital malformations is an important characteristic of public health. According to the World Health Organization, the birth rate of children with cleft lip and palate is on average 1:750 newborns, which is 20-30% of all human malformations and 86% of maxillofacial malformations. They contribute significantly to infant morbidity and disability as well as millions of dollars in health care costs each year. Development of the human skull begins about 23-26 days after fertilization, when a multipotent population of cranial neural crest cells migrates from the dorsal part of the neuraxis to the embryonic head region, giving rise to the frontal bone and interparietal part of the occipital bone, while the rest of the cranial arch comes mainly from the mesoderm. A malformation is a deviation from the normal development of an organ or tissue. Among the causes are chromosomal abnormalities, single gene defects, teratogenic or multi-factor agents, that is, a combination of genetic and external factors; the smallest number of cases are idiopathic. Exogenous causes of human congenital abnormalities include: physical (mechanical, thermal, radiation); chemical (hypoxia, malnutrition, hormonal discordance, teratogenic poisons); biological (viruses, bacteria and their toxins, protozoa); mental factors. Endogenous causes are heredity (changes in hereditary structures, mutations); biological inadequacy of germ cells (endocrine disorders, “over-ripening” of germ cells); parents’ age. Congenital craniofacial abnormalities are caused by improper growth and/or development of the brain and facial parts of the skull and soft tissue. Craniofacial abnormalities affecting the skull include macrocephaly, microcephaly and unilateral deformities. Sometimes cranial sutures fuse too early and craniosynostosis occurs, which is accompanied by various cranial deformities. This leads to abnormal cranial development, which can cause dysmorphia, and in the most severe cases catastrophically affect brain development. Conclusion. Based on the analysis of the literature sources, an attempt has been made to summarize the existing information and classifications of congenital cranial abnormalities, as well as the interpretation of various anomalies of the brain and facial skull in alphabetic order. The most common stigmas and malformations of the skull bones are briefly characterized

X-ray microtomography–based atlas of mouse cranial development

Background X-ray microtomography (μCT) has become an invaluable tool for non-destructive analysis of biological samples in the field of developmental biology. Mouse embryos are a typical model for investigation of human developmental diseases. By obtaining 3D high-resolution scans of the mouse embryo heads, we gain valuable morphological information about the structures prominent in the development of future face, brain, and sensory organs. The development of facial skeleton tracked in these μCT data provides a valuable background for further studies of congenital craniofacial diseases and normal development. Findings In this work, reusable tomographic data from 7 full 3D scans of mouse embryo heads are presented and made publicly available. The ages of these embryos range from E12.5 to E18.5. The samples were stained by phosphotungstic acid prior to scanning, which greatly enhanced the contrast of various tissues in the reconstructed images and enabled precise segmentation. The images were obtained on a laboratory-based μCT system. Furthermore, we provide manually segmented masks of mesenchymal condensations (for E12.5 and E13.5) and cartilage present in the nasal capsule of the scanned embryos. Conclusion We present a comprehensive dataset of X-ray 3D computed tomography images of the developing mouse head with high-quality manual segmentation masks of cartilaginous nasal capsules. The provided μCT images can be used for studying any other major structure within the developing mouse heads. The high quality of the manually segmented models of nasal capsules may be instrumental to understanding the complex process of the development of the face in a mouse model.

Abnormal cranium development in children and adolescents affected by syndromes or diseases associated with neurodysfunction

Microcephaly and macrocephaly can be considered both cranial growth defects and clinical symptoms. There are two assessment criteria: one applied in dysmorphology and another conventionally used in clinical practice. The determination of which definition or under which paradigm the terminology should be applied can vary on a daily basis and from case to case as necessity dictates, as can defining the relationship between microcephaly or macrocephaly and syndromes or diseases associated with neurodysfunction. Thus, there is a need for standardization of the definition of microcephaly and macrocephaly. This study was designed to investigate associations between abnormal cranial development (head size) and diseases or syndromes linked to neurodysfunction based on essential data collected upon admission of patients to the Neurological Rehabilitation Ward for Children and Adolescents in Poland. The retrospective analysis involved 327 children and adolescents with medical conditions associated with neurodysfunction. Two assessment criteria were applied to identify subgroups of patients with microcephaly, normal head size, and macrocephaly: one system commonly used in clinical practice and another applied in dysmorphology. Based on the results, children and adolescents with syndromes or diseases associated with neurodysfunction present abnormal cranial development (head size), and microcephaly rarely co-occurs with neuromuscular disease. Macrocephaly frequently co-occurs with neural tube defects or neuromuscular diseases and rarely with cerebral palsy (p < 0.05); microcephaly frequently co-occurs with epilepsy and hypothyroidism (p < 0.001). Traditional classification facilitates the identification of a greater number of relationships and is therefore recommended for use in daily practice. There is a need to standardize the definition of microcephaly and macrocephaly and to include them in ‘Human Phenotype Ontology’ terms.

Cost comparison of surgical management of nonsagittal synostosis: traditional open versus endoscope-assisted techniques

OBJECTIVEManagement of craniosynostosis at an early age is important for mitigating the risk of abnormal cranial development, but treatment can result in significant expenses. Previous research has shown that endoscope-assisted craniectomy (EAC) is less costly than open cranial vault remodeling (CVR) for patients with sagittal synostosis. The aim of this study was to strengthen the existing body of healthcare cost research by elucidating the charges associated with open and endoscopic treatment for patients with nonsagittal synostosis.METHODSThe authors performed a retrospective analysis of data obtained in 41 patients who underwent open CVR and 38 who underwent EAC with postoperative helmet therapy for nonsagittal, single-suture craniosynostosis (metopic, coronal, and lambdoid) between 2008 and 2018. All patients were < 1 year of age at the time of surgery and had a minimum 1 year of follow-up. Inpatient charges, physician fees, helmet charges, and outpatient clinic visits in the 1st year were analyzed.RESULTSThe mean ages of the children treated with EAC and open CVR were 3.5 months and 8.7 months, respectively. Patients undergoing EAC with postoperative helmet therapy required more outpatient clinic visits in the 1st year than patients undergoing CVR (4 vs 2; p < 0.001). Overall, 13% of patients in the EAC group required 1 helmet, 30% required 2 helmets, 40% required 3 helmets, and 13% required 4 or more helmets; the mean total helmeting charges were $10,072. The total charges of treatment, including inpatient charges, physician fees, outpatient clinic visit costs, and helmet charges, were significantly lower for the EAC group than they were for the open CVR group ($50,840 vs $95,588; p < 0.001).CONCLUSIONSDespite the additional charges for postoperative helmet therapy and the more frequent outpatient visits, EAC is significantly less expensive than open CVR for patients with metopic, coronal, and lambdoid craniosynostosis. In conjunction with the existing literature on clinical outcomes and perioperative resource utilization, these data support EAC as a cost-minimizing treatment for eligible patients with nonsagittal synostosis.

Morphological evolution of the skull roof in extinct temnospondyl amphibians mirrors conservative ontogenetic patterns

Understanding the evolution of development is essential to unravel how morphological evolution proceeds in phenotypic space and how the resulting morphological disparity originates. In particular, the study of ontogenetic allometric patterns and their evolution is relevant because allometry is thought to constrain morphological evolution to specific directions and to promote morphological change by producing pronounced phenotypic differences along phenotypic lines of least evolutionary resistance. The extinct clade of temnospondyl amphibians enables a unique opportunity to investigate the interplay between developmental and morphological evolution in deep time because individuals of different growth stages are known for numerous species. Temnospondyls lived during the Paleozoic and Mesozoic in a wide range of habitats and had different life cycles (e.g., metamorphosing, neotenic). In spite of this, cranial morphology is markedly conserved within the clade. Herein, we investigate whether the ontogenetic allometric patterns of the skull roof in temnospondyls are also conserved or reflect the variety of their ecological adaptations and life-cycles and examine the extent to which the ontogenetic allometry may account for the adult cranial morphology. Using geometric morphometric techniques, we computed the ontogenetic allometries of 13 temnospondyl species and the evolutionary allometry of the clade. A conserved pattern of morphological change during ontogeny not associated to phylogeny or life-style is recovered across the clade. Furthermore, the evolutionary allometry strongly resembles the conserved ontogenetic changes of shape. These results suggest strong ancestral constraints in cranial development, which, in turn, may explain the low morphological disparity in the group.

Mutations in Kinesin Family Member 6 Reveal Specific Role in Ependymal Cell Function and Human Neuro-Cranial Development

ABSTRACTCerebrospinal fluid flow is crucial for neurodevelopment and homeostasis of the ventricular system of the brain, with localized flow being established by the polarized beating of the ependymal cell (EC) cilia. Here, we report a homozygous one base-pair deletion, c.1193delT (p.Leu398Glnfs*2), in the Kinesin Family Member 6 (KIF6) gene in a child displaying neurocranial defects and intellectual disability. To test the pathogenicity of this novel human KIF6 mutation we engineered an analogous C-terminal truncating mutation in mouse. These mutant mice display severe, postnatal-onset hydrocephalus. We generated a Kif6-LacZ transgenic mouse strain and report expression specifically and uniquely within the ependymal cell (EC) layer of the brain, without labeling other multiciliated mouse tissues. Analysis of Kif6 mutant mice with scanning electron microscopy (SEM) and immunofluorescence (IF) revealed a reduction in EC cilia, without effect on other multiciliated tissues. Consistent with our findings in mice, defects of the ventricular system and EC cilia were observed in kif6 mutant zebrafish. Overall, this work describes the first clinically-defined KIF6 homozygous null mutation in human and defines KIF6 as a conserved mediator of neuro-cranial morphogenesis with a specific role in the maintenance of EC cilia in vertebrates.AUTHOR SUMMARYCerebrospinal fluid flow is crucial for neurodevelopment and homeostasis of the ventricular system of the brain. Localized flows of cerebrospinal fluid throughout the ventricular system of the brain are established from the polarized beating of the ependymal cell (EC) cilia. Here, we identified a homozygous truncating mutation in KIF6 in a child displaying neuro-cranial defects and intellectual disability. To test the function of KIF6 in vivo, we engineered mutations of Kif6 in mouse. These Kif6 mutant mice display severe hydrocephalus, coupled with a loss of EC cilia. Similarly, we observed hydrocephalus and a reduction in EC cilia in kif6 mutant zebrafish. Overall, this work describes the first clinically-defined KIF6 mutation in human, while our animal studies demonstrate the pathogenicity of mutations in KIF6 and establish KIF6 as a conserved mediator of neuro-cranial development and EC cilia maintenance in vertebrates.