Neural crest-specific loss of Prkar1a causes perinatal lethality resulting from defects in intramembranous ossification

Correlation of maximal nasal septal deviation with deviation at the maxillary insertion

PURPOSE

It is unclear if septal deviation at the insertion points to the nasal cavity is associated with the overall septal deviation. This study aimed to assess septal deviation at the cribriform plate (CP) and maxillary crest (MC) using CT scans and to see if there was any correlation with overall septal deviation.

METHODS

All consecutive CT sinus scans between January 2020 and December 2021 were retrospectively reviewed. Patients were excluded if they had a history of head, nasal or facial trauma, or any previous nasal surgical procedure. Angles between the septum and MC and the septum and CP as well as maximal angle of septal deviation (MSD) were measured.

RESULTS

A total of 70 scans were included in the final analysis. The mean MSD was 8.14°. The mean septal deviation was 0.89° at the CP and 2.02° at the MC. The correlation coefficient between the deviation at the CP and MSD was 0.025 and between the deviation at the MC and MSD was 0.321.

CONCLUSION

Our data reveal a positive correlation between septal deviation at the floor of the nose and overall septal deviation; this was not observed at the septal deviation at the roof. This could be explained due to the inherent tilt in the cribriform plate or by earlier ossification and fixation of the septum during its development at its insertion to the roof, thereby allowing further growth and potential for deviation of the lower part of the septum and its insertion to the floor.

The advanced concepts for septal l-strut re-designing in septorhinoplasty for better strength and stability by considering of center of gravity

PURPOSE

This study contributes to the multidisciplinary understanding of septal L-strut reshaping and introduces innovative surgical design concepts based on engineering principles of static equilibrium. The objective is to enhance structural strength and stability, ultimately leading to improved surgical outcomes.

METHOD

Finite element analysis is employed to model the three-dimensional septal cartilage in septoplasty. A significant contribution of this work is the introduction of an innovative redesigns for the septal L-strut structure. These redesigns represent the first-ever attempt to incorporate the center of gravity theory into the modeling of the septal L-strut.

RESULTS

Our findings emphasize the significance of attaining a lower center of gravity in the design of the septal L-strut, as it contributes to optimal core strength and stability. To achieve this, we recommend widening the caudal septum and shaping the interior fillet corner to its maximum size, taking into account its specific shape. Notably, the utilization of a standard 20x20 mm septal L-strut, the C-shaped technique, and the septal support graft technique provide superior strength due to enhanced basement support.

CONCLUSION

To enhance surgical outcomes in septal L-strut procedures, design modifications are proposed to improve strength and stability, resulting in optimized performance. Recommendations include widening the caudal septum and incorporating fillet shapes in the geometry to lower the center of gravity.

Bone mineral density loci specific to the skull portray potential pleiotropic effects on craniosynostosis

Skull bone mineral density (SK-BMD) provides a suitable trait for the discovery of key genes in bone biology, particularly to intramembranous ossification, not captured at other skeletal sites. We perform a genome-wide association meta-analysis (n ~ 43,800) of SK-BMD, identifying 59 loci, collectively explaining 12.5% of the trait variance. Association signals cluster within gene-sets involved in skeletal development and osteoporosis. Among the four novel loci (ZIC1, PRKAR1A, AZIN1/ATP6V1C1, GLRX3), there are factors implicated in intramembranous ossification and as we show, inherent to craniosynostosis processes. Functional follow-up in zebrafish confirms the importance of ZIC1 on cranial suture patterning. Likewise, we observe abnormal cranial bone initiation that culminates in ectopic sutures and reduced BMD in mosaic atp6v1c1 knockouts. Mosaic prkar1a knockouts present asymmetric bone growth and, conversely, elevated BMD. In light of this evidence linking SK-BMD loci to craniofacial abnormalities, our study provides new insight into the pathophysiology, diagnosis and treatment of skeletal diseases.

Mouse embryo phenotyping using X-ray microCT

Microscopic X-ray computed tomography (microCT) is a structural ex vivo imaging technique providing genuine isotropic 3D images from biological samples at micron resolution. MicroCT imaging is non-destructive and combines well with other modalities such as light and electron microscopy in correlative imaging workflows. Protocols for staining embryos with X-ray dense contrast agents enable the acquisition of high-contrast and high-resolution datasets of whole embryos and specific organ systems. High sample throughput is achieved with dedicated setups. Consequently, microCT has gained enormous importance for both qualitative and quantitative phenotyping of mouse development. We here summarize state-of-the-art protocols of sample preparation and imaging procedures, showcase contemporary applications, and discuss possible pitfalls and sources for artefacts. In addition, we give an outlook on phenotyping workflows using microscopic dual energy CT (microDECT) and tissue-specific contrast agents.

Integrated analysis identifying long non-coding RNAs (lncRNAs) for competing endogenous RNAs (ceRNAs) network-regulated palatal shelf fusion in the development of mouse cleft palate

BACKGROUND

Cleft palate results from the defective palatal fusion of the medial-edge epithelium after cells undergo epithelial-mesenchymal transition, a process that involves regulation by microRNAs (miRNAs). However, in palatal shelf fusion, miRNA regulation by long non-coding RNAs (lncRNAs) when acting as competing endogenous RNAs (ceRNAs) or miRNA sponges, remains unclear.

METHODS

We systematically analyzed the correlation between lncRNAs, miRNAs, and mRNAs from RNA sequencing profiling in embryonic gestation day 14.5 (E14.5) mouse embryos from control (n=3) and all-trans retinoic acid (ATRA)-treated (n=3) mice. We then constructed a lncRNA-associated ceRNA network. The expression profiles of mRNA, lncRNA, and miRNA were verified by quantitative polymerase chain reaction (qPCR).

RESULTS

In total, 18 aberrantly expressed miRNAs, 861 mRNAs, and 583 lncRNAs were identified from palate samples of control and ATRA-treated samples. Bioinformatics data and integrative analysis identified 69 lncRNAs, 18 miRNAs, and 78 mRNAs that were aberrantly expressed, and a ceRNA network was then constructed. Finally, we identified a NONMMUT004850.2/NONMMUT024276.2-miR-741-3p/miR-465b-5p-Prkar1α ceRNA network associated with palatal shelf fusion at E14.5. The qPCR results showed that NONMMUT004850.2 (P=5E-05), NONMMUT024276.2 (P=0.0012), and Prkar1α (P=3E-05) were up-regulated, whereas miR-741-3p (P=0.006) and miR-465b-5p (P=1E-04) were down-regulated in ATRA-treated mice compared to the control samples. The qPCR results were in concordance with the RNA sequencing profiling.

CONCLUSIONS

Our study demonstrated that NONMMUT004850.2/NONMMUT024276.2-miR-741-3p/miR-465b-5p-Prkar1α could potentially serve as an important regulatory mechanism of palatal fusion in the development of the cleft palate.

Identification of circular RNA-associated competing endogenous RNA network in the development of cleft palate

Circular RNAs (circRNAs) serve as competing endogenous RNAs (ceRNAs) and indirectly regulate gene expression through shared microRNAs (miRNAs). However, the regulatory mechanisms of circRNA as ceRNA associated with the fusion of palatal shelves in palatogenesis are yet unclear. This study aimed to explore the potential mechanism underlying the role of circRNA as ceRNA in cleft palate (CP). First, we systematically analyzed RNA-seq and miRNA-seq data after high-throughput sequencing for embryonic palatal shelf tissues from a mouse CP model induced by maternal exposure to all-trans retinoic acid on embryonic gestation day 14.5 (E14.5). Thirty-nine circRNAs, 18 miRNAs, and 936 messenger RNAs (mRNAs) were significantly dysregulated (log₂ [fold change {FC}] > 1; P < 0.05). Thereafter, we constructed a circRNA-associated ceRNA network. Finally, we determined the circRNA_0954-miRNA-881-3p-PRKAR1α ceRNA network as a hub involved in palatogenesis. Gene Ontology analysis revealed that ceRNA-related genes were associated with facial morphogenesis and developmental gene silencing. Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that ceRNA-related genes are involved in apoptosis (P < 0.05, fold enrichment >1). Quantitative reverse transcription polymerase chain reaction was performed to verify the results of ceRNA analysis. We found that the circRNA-miRNA-mRNA ceRNA network is involved in palatogenesis. The present results imply that circRNA_0954-miRNA-881-3p-PRKAR1α ceRNA network may cause dysfunctional palatal fusion and might facilitate the development of novel epigenetic biomarkers to treat CP in the future.

Defects of the Carney complex gene (PRKAR1A) in odontogenic tumors

The surgical treatment of some odontogenic tumors often leads to tooth and maxillary bone loss as well as to facial deformity. Therefore, the identification of genes involved in the pathogenesis of odontogenic tumors may result in alternative molecular therapies. The PRKAR1A gene displays a loss of protein expression as well as somatic mutations in odontogenic myxomas, an odontogenic ectomesenchymal neoplasm. We used a combination of quantitative RT-PCR (qRT-PCR), immunohistochemistry, loss of heterozygosity (LOH) analysis, and direct sequencing of all PRKAR1A exons to assess if this gene is altered in mixed odontogenic tumors. Thirteen tumors were included in the study: six ameloblastic fibromas, four ameloblastic fibro-odontomas, one ameloblastic fibrodentinoma, and two ameloblastic fibrosarcomas. The epithelial components of the tumors were separated from the mesenchymal by laser microdissection in most of the cases. We also searched for odontogenic pathology in Prkar1a(+) (/) (-) mice. PRKAR1A mRNA/protein expression was decreased in the benign mixed odontogenic tumors in association with LOH at markers around the PRKAR1A gene. We also detected a missense and two synonymous mutations along with two 5'-UTR and four intronic mutations in mixed odontogenic tumors. Prkar1a(+) (/) (-) mice did not show evidence of odontogenic tumor formation, which indicates that additional genes may be involved in the pathogenesis of such tumors, at least in rodents. We conclude that the PRKAR1A gene and its locus are altered in mixed odontogenic tumors. PRKAR1A expression is decreased in a subset of tumors but not in all, and Prkar1a(+) (/) (-) mice do not show abnormalities, which indicates that additional genes play a role in this tumor's pathogenesis.

Chondrogenic potential of stem cells from human exfoliated deciduous teeth in vitro and in vivo

OBJECTIVE

The aim of this study was to investigate the chondrogenic potential of stem cells from human exfoliated teeth (SHED).

MATERIALS AND METHODS

SHED cultures were isolated from human exfoliated deciduous teeth. Colony-forming capacity, odonto/osteogenic and adipogenic potential were measured. SHED were cultured for 2 weeks in chondrogenic differentiation medium containing dexamethasone, insulin, ascorbate phosphate, TGF-β3 and bFGF. Toluidine blue staining and safranin O staining were used for chondrogenesis analysis. The related markers, type II collagen and aggrecan, were also investigated using immunohistochemistry. SHED were seeded onto the β-TCP scaffolds and transplanted into the subcutaneous space on the back of nude mice. The transplants were recovered at 2, 4 and 8 weeks post-transplantation for analysis.

RESULTS

SHED showed colony-forming capacity, odonto/osteogenic and adipogenic differentiation capacity. Chondrogenic differentiation was confirmed by toluidine blue staining, safranin O staining, type II collagen and aggrecan immunostaining. After in vivo transplantation, SHED recombined with β-TCP scaffolds were able to generate new cartilage-like tissues.

CONCLUSIONS

The findings demonstrate the chondrogenic differentiation capacity of SHED both in vitro and in vivo models, suggesting the potential of SHED in cartilage tissue engineering.

Micro-computed tomography imaging and analysis in developmental biology and toxicology

Micro-computed tomography (micro-CT) is a high resolution imaging technique that has expanded and strengthened in use since it was last reviewed in this journal in 2004. The technology has expanded to include more detailed analysis of bone, as well as soft tissues, by use of various contrast agents. It is increasingly applied to questions in developmental biology and developmental toxicology. Relatively high-throughput protocols now provide a powerful and efficient means to evaluate embryos and fetuses subjected to genetic manipulations or chemical exposures. This review provides an overview of the technology, including scanning, reconstruction, visualization, segmentation, and analysis of micro-CT generated images. This is followed by a review of more recent applications of the technology in some common laboratory species that highlight the diverse issues that can be addressed.

Knockdown of PRKAR1A, the gene responsible for Carney complex, interferes with differentiation in osteoblastic cells

PRKAR1A is the gene encoding the type 1A regulatory subunit of protein kinase A, and it is the cause of the inherited human tumor syndrome Carney complex. Data from our laboratory has demonstrated that Prkar1a loss causes tumors in multiple cell lineages, including neural crest cells and osteoblasts. We have proposed that one mechanism by which tumorigenesis occurs is through the failure of terminal differentiation. In the present study, we directly test the effects of Prkar1a reduction on osteogenic differentiation in mouse and human cells in vitro. We found that Prkar1a levels noticeably increased during osteoblastic differentiation, indicating a positive correlation between the expression of Prkar1a and osteogenic potential. To validate this hypothesis, we generated stable Prkar1a knockdown in both mouse and human cells. These cells displayed significantly suppressed bone nodule formation and decreased expression of osteoblast markers such as osteocalcin and osteopontin. These observations imply that the antiosteogenic effect of Prkar1a ablation is not species or cell line specific. Furthermore, because Runt-related transcription factor-2 (Runx2) is a key mediator of osteoblast differentiation, we reasoned that the function of this transcription factor may be inhibited by Prkar1a knockdown. Chromatin immunoprecipitation and luciferase assays demonstrated that Prkar1a ablation repressed DNA binding and function of Runx2 at its target genes. Additionally, we determined that this effect is likely due to reductions in the Runx2-cooperating transcription factors forkhead box O1 and activating transcription factor 4. Taken together, this study provides direct evidence that ablation of Prkar1a interferes with signaling pathways necessary for osteoblast differentiation.

cAMP/PKA signaling defects in tumors: genetics and tissue-specific pluripotential cell-derived lesions in human and mouse

In the last few years, bench and clinical studies led to significant new insight into how cyclic adenosine monophosphate (cAMP) signaling, the molecular pathway that had been identified in the early 2000s as the one involved in most benign cortisol-producing adrenal hyperplasias, affects adrenocortical growth and development, as well as tumor formation. A major discovery was the identification of tissue-specific pluripotential cells (TSPCs) as the culprit behind tumor formation not only in the adrenal, but also in bone. Discoveries in animal studies complemented a number of clinical observations in patients. Gene identification continued in parallel with mouse and other studies on the cAMP signaling and other pathways.

Rac1 is required for Prkar1a-mediated Nf2 suppression in Schwann cell tumors

Schwannomas are peripheral nerve sheath tumors that often occur in the setting of an inherited tumor predisposition syndrome, including Neurofibromatosis Types 1 (NF1) and 2 (NF2), Familial Schwannomatosis (FS) and Carney Complex (CNC). Loss of the NF2 tumor suppressor (encoding NF2, or Merlin) is associated with upregulation of the Rac1 small GTPase, which is thought to play a key role in mediating tumor formation. In prior studies, we generated a mouse model of schwannomas by performing tissue-specific knockout of the CNC gene Prkar1a, which encodes the type 1A regulatory subunit of Protein Kinase A. These tumors exhibited down-regulation of Nf2 protein and an increase in activated Rac1. To assess the requirement for Rac1 in schwannoma formation, we generated a double knockout of Prkar1a and Rac1 in Schwann cells and monitored tumor formation. Loss of Rac1 reduced tumor formation by reducing proliferation and enhancing apoptosis. Surprisingly, the reduction of tumor formation was accompanied by re-expression of the Nf2 protein. Furthermore, activated Rac1 was able to downregulate Nf2 in vitro in a Pak-dependent manner. These in vivo data indicate that activation of Rac1 is responsible for suppression of Nf2 protein production; deficiency of Nf2 in Schwann cells leads to loss of cellular growth control and tumor formation.. Further, PKA activation through mutation in Prkar1a is sufficient to initiate Rac1 signaling, with subsequent reduction of Nf2 and schwannomagenesis. Although in vitro evidence has shown that loss of Nf2 activates Rac1, our data indicates that signaling between Nf2 and Rac1 occurs in a bidirectional fashion, and these interactions are modulated by PKA.

Downregulation of PKD1 by shRNA results in defective osteogenic differentiation via cAMP/PKA pathway in human MG-63 cells

Mutations and/or deletions of Pkd1 in mouse models resulted in attenuation of osteoblast function and defective bone formation; however, the function of PKD1 in human osteoblast and bone remains uncertain. In the current study, we used lentivirus-mediated shRNA technology to stably knock down PKD1 in the human osteoblastic MG-63 cell line and to investigate the role of PKD1 on human osteoblast function and molecular mechanisms. We found that a 53% reduction of PKD1 by PKD1 shRNA in stable, transfected MG-63 cells resulted in increased cell proliferation and impaired osteoblastic differentiation as reflected by increased BrdU incorporation, decreased alkaline phosphatase activity, and calcium deposition and by decreased expression of RUNX2 and OSTERIX compared to control shRNA MG-63 cells. In addition, knockdown of PKD1 mRNA caused enhanced adipogenesis in stable PKD1 shRNA MG-63 cells as evidenced by elevated lipid accumulation and increased expression of adipocyte-related markers such as PPARγ and aP2. The stable PKD1 shRNA MG-63 cells exhibited lower basal intracellular calcium, which led to attenuated cytosolic calcium signaling in response to fluid flow shear stress, as well as increased intracellular cAMP messages in response to forskolin (10 µM) stimulation. Moreover, increased cell proliferation, inhibited osteoblastic differentiation, and osteogenic and adipogenic gene markers were significantly reversed in stable PKD1 shRNA MG-63 cells when treated with H89 (1 µM), an inhibitor of PKA. These findings suggest that downregulation of PKD1 in human MG-63 cells resulted in defective osteoblast function via intracellular calcium-cAMP/PKA signaling pathway.

Thyroid-specific ablation of the Carney complex gene, PRKAR1A, results in hyperthyroidism and follicular thyroid cancer

Thyroid cancer is the most common endocrine malignancy in the population, and the incidence of this cancer is increasing at a rapid rate. Although genetic analysis of papillary thyroid cancer (PTC) has identified mutations in a large percentage of patients, the genetic basis of follicular thyroid cancer (FTC) is less certain. Thyroid cancer, including both PTC and FTC, has been observed in patients with the inherited tumor predisposition Carney complex, caused by mutations in PRKAR1A. In order to investigate the role of loss of PRKAR1A in thyroid cancer, we generated a tissue-specific knockout of Prkar1a in the thyroid. We report that the resulting mice are hyperthyroid and developed follicular thyroid neoplasms by 1 year of age, including FTC in over 40% of animals. These thyroid tumors showed a signature of pathway activation different from that observed in other models of thyroid cancer. In vitro cultures of the tumor cells indicated that Prkar1a-null thyrocytes exhibited growth factor independence and suggested possible new therapeutic targets. Overall, this work represents the first report of a genetic mutation known to cause human FTC that exhibits a similar phenotype when modeled in the mouse. In addition to our knowledge of the mechanisms of human follicular thyroid tumorigenesis, this model is highly reproducible and may provide a viable mechanism for the further clinical development of therapies aimed at FTC.

3-dimensional imaging modalities for phenotyping genetically engineered mice

A variety of 3-dimensional (3D) digital imaging modalities are available for whole-body assessment of genetically engineered mice: magnetic resonance microscopy (MRM), X-ray microcomputed tomography (microCT), optical projection tomography (OPT), episcopic and cryoimaging, and ultrasound biomicroscopy (UBM). Embryo and adult mouse phenotyping can be accomplished at microscopy or near microscopy spatial resolutions using these modalities. MRM and microCT are particularly well-suited for evaluating structural information at the organ level, whereas episcopic and OPT imaging provide structural and functional information from molecular fluorescence imaging at the cellular level. UBM can be used to monitor embryonic development longitudinally in utero. Specimens are not significantly altered during preparation, and structures can be viewed in their native orientations. Technologies for rapid automated data acquisition and high-throughput phenotyping have been developed and continually improve as this exciting field evolves.

Genes into geometry: imaging for mouse development in 3D

Mammalian development is a sophisticated program coordinated by a complex set of genetic and physiological factors. Alterations in anatomy or morphology provide intrinsic measures of progress in or deviations from this program. Emerging three-dimensional imaging methods now allow for more sophisticated morphological assessment than ever before, enabling comprehensive phenotyping, visualization of anatomical context and patterns, automated and quantitative morphological analysis, as well as improved understanding of the developmental time course. Furthermore, these imaging tools are becoming increasingly available and will consequently play a prominent role in elucidating the factors that direct and influence mammalian development.

Differential role of PKA catalytic subunits in mediating phenotypes caused by knockout of the Carney complex gene Prkar1a

The Carney complex is an inherited tumor predisposition caused by activation of the cAMP-dependent protein kinase [protein kinase A (PKA)] resulting from mutation of the PKA-regulatory subunit gene PRKAR1A. Myxomas and tumors in cAMP-responsive tissues are cardinal features of this syndrome, which is unsurprising given the important role played by PKA in modulating cell growth and function. Previous studies demonstrated that cardiac-specific knockout of Prkar1a causes embryonic heart failure and myxomatous degeneration in the heart, whereas limited Schwann cell-specific knockout of the gene causes schwannoma formation. In this study, we sought to determine the role of PKA activation in this phenotype by using genetic means to reduce PKA enzymatic activity. To accomplish this goal, we introduced null alleles of the PKA catalytic subunits Prkaca (Ca) or Prkacb (Cb) into the Prkar1a-cardiac knockout (R1a-CKO) or limited Schwann cell knockout (R1a-TEC3KO) line. Heterozygosity for Prkaca rescued the embryonic lethality of the R1a-CKO, although mice had a shorter than normal lifespan and died from cardiac failure with atrial thrombosis. In contrast, heterozygosity for Prkacb only enabled the mice to survive 1 extra day during embryogenesis. Biochemical analysis indicated that reduction of Ca markedly reduced PKA activity in embryonic hearts, whereas reduction of Cb had minimal effects. In R1a-TEC3KO mice, tumorigenesis was completely suppressed by a heterozygosity for Prkaca, and by more than 80% by heterozygosity for Prkacb. These data suggest that both developmental and tumor phenotypes caused by Prkar1a mutation result from excess PKA activity due to PKA-Ca.

Nasal septum morphology in human fetuses in computed tomography images

Objectives

Nasal septum deformation (NSD) may cause breathing dysfunction. The reason for a septal deviation is the developmental anomaly in growth of the elastic septum or its skeleton. Such a type of deviation is called physiological. Some deviations can result from the prenatal trauma. The aim of the work was the analysis of the anatomy of the nasal cavity with a special interest focused on the nasal septum and its deviation.

Materials and methods

The nasal cavity with its bones and septum was analyzed in CT images of 105 spontaneously aborted fetuses (57 males and 48 females) aged 12 and 40 weeks of gestation. We attempted to assess the morphometric development of the nasal cavity with tomographic scanning methods and to detect anatomical variations.

Results

In 15 (14.3%) fetuses, NSD were detected on radiological sections. The angle between the virtual line from the sphenoid sinus ostium through limen nasi and the horizontal plane was 33.6 ± 2.3°, on average.

Conclusions

NSD may already be found in fetuses. The observation of the nasal cavity development enables to evaluate the growth and symmetry of the nasal septum and to foretell predispositions for dysfunction in the upper respiratory tract.