Introduction of a Cys360Tyr Mutation in ANO5 Creates a Mouse Model for Gnathodiaphyseal Dysplasia

Genetic disruption of Ano5 leads to impaired osteoclastogenesis for gnathodiaphyseal dysplasia

OBJECTIVES

Gnathodiaphyseal dysplasia (GDD; OMIM#166260) is a rare skeletal genetic disorder characterized by sclerosis of tubular bones and cemento-osseous lesions in mandibles. TMEM16E/ANO5 gene mutations have been identified in patients with GDD. Here, Ano5 knockout (Ano5-/-) mice with enhanced osteoblastogenesis were used to investigate whether Ano5 disruption affects osteoclastogenesis.

SUBJECTS AND METHODS

The maturation of osteoclasts, formation of F-actin ring and bone resorption were detected by immunohistochemistry, TRAP, phalloidin staining and Coming Osteo assays. The expression of osteoclast-related factors was measured by qRT-PCR. Early signaling pathways were verified by western blot.

RESULTS

Ano5-/- mice exhibited inhibitory formation of multinucleated osteoclasts with a reduction of TRAP activity. The expression of Nfatc1, c-Fos, Trap, Ctsk, Mmp9, Rank and Dc-stamp was significantly decreased in bone tissues and bone marrow-derived macrophages (BMMs) of Ano5-/- mice. Ano5-/- osteoclasts manifested disrupted actin ring and less mineral resorption. RANKL-induced early signaling pathways were suppressed in Ano5-/- osteoclasts and Ano5 knockdown RAW264.7 cells. Moreover, the inhibitory effects of NF-κB signalling pathway on osteoclastogenesis were partially attenuated with NF-κB signalling activator.

CONCLUSIONS

Ano5 deficiency impairs osteoclastogenesis, which leads to enhanced osteogenic phenotypes mediated by bone homeostasis dysregulation.

Familial gigantiform cementoma with recurrent ANO5 p.Cys356Tyr mutations: Clinicopathological and genetic study with literature review

BACKGROUND

Familial gigantiform cementoma (FGC) is a rare tumor characterized by the early onset of multi-quadrant fibro-osseous lesions in the jaws, causing severe maxillofacial deformities. Its clinicopathological features overlap with those of other benign fibro-osseous lesions. FGC eventually exhibits progressively rapid growth, but no suspected causative gene has been identified.

METHODS

In this study, three patients with FGC were recruited, and genomic DNA from the tumor tissue and peripheral blood was extracted for whole-exome sequencing.

RESULTS

Results showed that all three patients harbored the heterozygous mutation c.1067G > A (p.Cys356Tyr) in the ANO5 gene. Furthermore, autosomal dominant mutations in ANO5 at this locus have been identified in patients with gnathodiaphyseal dysplasia (GDD) and are considered a potential causative agent, suggesting a genetic association between FGC and GDD. In addition, multifocal fibrous bone lesions with similar clinical presentations were detected, including five cases of florid cemento-osseous dysplasia, five cases of polyostotic fibrous dysplasia, and eight cases of juvenile ossifying fibromas; however, none of them harbored mutations in the ANO5 gene.

CONCLUSION

Our findings indicate that FGC may be an atypical variant of GDD, providing evidence for the feasibility of ANO5 gene testing as an auxiliary diagnostic method for complex cases with multiple quadrants.

Integration of metabolomics and transcriptomics provides insights into enhanced osteogenesis in Ano5Cys360Tyr knock-in mouse model

INTRODUCTION

Gnathodiaphyseal dysplasia (GDD; OMIM#166260) is a rare autosomal dominant disorder characterized by diaphyseal sclerosis of tubular bones and cemento-osseous lesions in mandibles. GDD is caused by point mutations in the ANO5 gene. However, the mechanisms underlying GDD have not been disclosed. We previously generated the first knock-in mouse model for GDD expressing a human mutation (p.Cys360Tyr) in ANO5 and homozygous Ano5 knock-in (Ano5^KI/KI ) mice exhibited representative traits of human GDD especially including enhanced osteogenesis.

METHODS

Metabolomics and transcriptomics analyses were conducted for wildtype (Ano5^+/+ ) and Ano5^KI/KI mature mouse calvarial osteoblasts (mCOBs) grown in osteogenic cultures for 14 days to identify differential intracellular metabolites and genes involved in GDD. Subsequently, related differential genes were validated by qRT-PCR. Cell proliferation was confirmed by CCK8 assay and calcium content in mineral nodules was detected using SEM-EDS.

RESULTS

Metabolomics identified 42 differential metabolites that are primarily involved in amino acid and pyrimidine metabolism, and endocrine and other factor-regulated calcium reabsorption. Concomitantly, transcriptomic analysis revealed 407 differentially expressed genes in Ano5^KI/KI osteoblasts compared with wildtype. Gene ontology and pathway analysis indicated that Ano5^Cys360Tyr mutation considerably promoted cell cycle progression and perturbed calcium signaling pathway, which were confirmed by validated experiments. qRT-PCR and CCK-8 assays manifested that proliferation of Ano5^KI/KI mCOBs was enhanced and the expression of cell cycle regulating genes (Mki67, Ccnb1, and Ccna2) was increased. In addition, SEM-EDS demonstrated that Ano5^KI/KI mCOBs developed higher calcium contents in mineral nodules than Ano5^+/+ mCOBs, while some calcium-related genes (Cacna1, Slc8a1, and Cyp27b1) were significantly up-regulated. Furthermore, osteocalcin which has been proved to be an osteoblast-derived metabolic hormone was upregulated in Ano5^KI/KI osteoblast cultures.

DISCUSSION

Our data demonstrated that the Ano5^Cys360Tyr mutation could affect the metabolism of osteoblasts, leading to unwonted calcium homeostasis and cellular proliferation that can contribute to the underlying pathogenesis of GDD disorders.

Ano5 modulates calcium signaling during bone homeostasis in gnathodiaphyseal dysplasia

ANO5 encodes transmembrane protein 16E (TMEM16E), an intracellular calcium-activated chloride channel in the endoplasmic reticulum. Mutations in ANO5 are associated with gnathodiaphyseal dysplasia (GDD), a skeletal disorder causing the jaw deformity and long bone fractures. However, the coordinated mechanism by which ANO5 mediates bone homeostasis in GDD remains poorly defined. Here, we show that ablation of Ano5 reduced intracellular calcium transients, leading to defects in osteogenesis and osteoclastogenesis and thus bone dysplasia. We found a causative de novo ANO5 frameshift insertion mutation (p.L370_A371insDYWRLNSTCL) in a GDD family with osteopenia, accompanied by a decrease in TMEM16E expression and impaired RANKL-induced intracellular calcium ([Ca²⁺]_i) oscillations in osteoclasts. Moreover, using Ano5 knockout (KO) mice, we found that they exhibited low bone volume, abnormal calcium deposits, and defective osteoblast and osteoclast differentiation. We also showed that Ano5 deletion in mice significantly diminished [Ca²⁺]_i oscillations in both osteoblasts and osteoclasts, which resulted in reduced WNT/β-Catenin and RANKL-NFATc1 signaling, respectively. Osteoanabolic treatment of parathyroid hormone was effective in enhancing bone strength in Ano5 KO mice. Consequently, these data demonstrate that Ano5 positively modulates bone homeostasis via calcium signaling in GDD.

Gnathodiaphyseal dysplasia with a novel genetic variant in a large family from Iran

Background

Gnathodiaphyseal dysplasia (GDD) is an ultrarare autosomal dominant bone dysplasia characterized by cementoosseous lesions of the jawbones, bone fragility, frequent bone fractures at the young age, bowing of tubular bones, and diaphyseal sclerosis of long bones associated with generalized osteopenia. GDD is caused by point mutations in anoctamin‐5 (ANO5) on chromosome 11p14.3. For the past few years, next generation sequencing (NGS) technology has facilitated the discovery of causative variants in genetically heterogeneous diseases.

Methods

In this study, exome sequencing (ES) was performed using the DNA sample of the proband. Family histories and clinical information were collected through comprehensive medical examination and genetic counseling.

Results

ES results identified a heterozygous variant, NM_213599.3:c.1078T>C(p.Cys360Arg) in the ANO5 gene. Sanger sequencing was performed to confirm the detected pathogenic variant in DNA samples of the entire family (except deceased individuals), which segregated with the disease within the family. Finally, in silico analysis was applied to test the pathogenicity of the variant using various online software.

Conclusion

In summary, our investigation identified a novel pathogenic variant in the ANO5, responsible for gnathodiaphyseal dysplasia in a large Iranian family. Therefore, based on the present study, this variant can be helpful for diagnosis and effective management of GDD patients.

Gnathodiaphyseal dysplasia (GDD) is an ultrarare autosomal dominant bone dysplasia characterized by cementoosseous lesions of the jawbones, bone fragility, frequent bone fractures at the young age. In this study, Exome Sequencing results identified a heterozygous mutation, NM_213599.3:c.1078T>C(p.Cys360Arg) in the ANO5 confirmed by Sanger sequencing.