ATP2B2 de novo variants as a cause of variable neurodevelopmental disorders that feature dystonia, ataxia, intellectual disability, behavioral symptoms, and seizures

PURPOSE

ATP2B2 encodes the variant-constrained plasma-membrane calcium-transporting ATPase-2, expressed in sensory ear cells and specialized neurons. ATP2B2/Atp2b2 variants were previously linked to isolated hearing loss in patients and neurodevelopmental deficits with ataxia in mice. We aimed to establish the association between ATP2B2 and human neurological disorders.

METHODS

Multinational case recruitment, scrutiny of trio-based genomics data, in silico analyses, and functional variant characterization were performed.

RESULTS

We assembled 7 individuals harboring rare, predicted deleterious heterozygous ATP2B2 variants. The alleles comprised 5 missense substitutions that affected evolutionarily conserved sites and 2 frameshift variants in the penultimate exon. For 6 variants, a de novo status was confirmed. Unlike described patients with hearing loss, the individuals displayed a spectrum of neurological abnormalities, ranging from ataxia with dystonic features to complex neurodevelopmental manifestations with intellectual disability, autism, and seizures. Two cases with recurrent amino-acid variation showed distinctive overlap with cerebellar atrophy-associated ataxia and epilepsy. In cell-based studies, all variants caused significant alterations in cytosolic calcium handling with both loss- and gain-of-function effects.

CONCLUSION

Presentations in our series recapitulate key phenotypic aspects of Atp2b2-mouse models and underline the importance of precise calcium regulation for neurodevelopment and cerebellar function. Our study documents a role for ATP2B2 variants in causing heterogeneous neurodevelopmental and movement-disorder syndromes.

CaMKII inhibition due to TRIC-B loss-of-function dysregulates SMAD signalling in osteogenesis imperfecta

Ca²⁺ is a second messenger that regulates a variety of cellular responses in bone, including osteoblast differentiation. Mutations in trimeric intracellular cation channel B (TRIC-B), an endoplasmic reticulum channel specific for K⁺, a counter ion for Ca²⁺ flux, affect bone and cause a recessive form of osteogenesis imperfecta (OI) with a still puzzling mechanism. Using a conditional Tmem38b knock out mouse, we demonstrated that lack of TRIC-B in osteoblasts strongly impairs skeleton growth and structure, leading to bone fractures. At the cellular level, delayed osteoblast differentiation and decreased collagen synthesis were found consequent to the Ca²⁺ imbalance and associated with reduced collagen incorporation in the extracellular matrix and poor mineralization. The impaired SMAD signalling detected in mutant mice, and validated in OI patient osteoblasts, explained the osteoblast malfunction. The reduced SMAD phosphorylation and nuclear translocation were mainly caused by alteration in Ca²⁺ calmodulin kinase II (CaMKII)-mediated signalling and to a less extend by a lower TGF-β reservoir. SMAD signalling, osteoblast differentiation and matrix mineralization were only partially rescued by TGF-β treatment, strengthening the impact of CaMKII-SMAD axes on osteoblast function. Our data established the TRIC-B role in osteoblasts and deepened the contribution of the CaMKII-SMAD signalling in bone.

The PLEKHA7-PDZD11 complex regulates the localization of the calcium pump PMCA and calcium handling in cultured cells

The plasma membrane calcium ATPase (PMCA) extrudes calcium from the cytosol to the extracellular space to terminate calcium-dependent signaling. Although the distribution of PMCA is crucial for its function, the molecular mechanisms that regulate the localization of PMCA isoforms are not well understood. PLEKHA7 is implicated by genetic studies in hypertension and the regulation of calcium handling. PLEKHA7 recruits the small adapter protein PDZD11 to adherens junctions, and together they control the trafficking and localization of plasma membrane associated proteins, including the Menkes copper ATPase. Since PDZD11 binds to the C-terminal domain of b-isoforms of PMCA, PDZD11 and its interactor PLEKHA7 could control the localization and activity of PMCA. Here, we test this hypothesis using cultured cell model systems. We show using immunofluorescence microscopy and a surface biotinylation assay that KO of either PLEKHA7 or PDZD11 in mouse kidney collecting duct epithelial cells results in increased accumulation of endogenous PMCA at lateral cell–cell contacts and PDZ-dependent ectopic apical localization of exogenous PMCA4x/b isoform. In HeLa cells, coexpression of PDZD11 reduces membrane accumulation of overexpressed PMCA4x/b, and analysis of cytosolic calcium transients shows that PDZD11 counteracts calcium extrusion activity of overexpressed PMCA4x/b, but not PMCA4x/a, which lacks the PDZ-binding motif. Moreover, KO of PDZD11 in either endothelial (bEnd.3) or epithelial (mouse kidney collecting duct) cells increases the rate of calcium extrusion. Collectively, these results suggest that the PLEKHA7–PDZD11 complex modulates calcium homeostasis by regulating the localization of PMCA.

Ridge Preservation Using a Novel Freeze-dried Enzyme-deantigenic Bone Paste: A Histomorphometric-retrospective Pilot Case Series

AIM AND OBJECTIVE

The aim of this study is to provide preliminary retrospective evidence concerning the histologic and histomorphometric outcome of a novel freeze-dried equine-derived bone paste (EDEBEX) for ridge preservation of sockets following tooth extraction.

MATERIALS AND METHODS

This pilot retrospective case series describes the histologic and histomorphometric outcome of three patients who received the equine-derived bone paste in post-extractive sockets to allow the preservation of the alveolar ridge. Patients were later rehabilitated with monolithic-zirconia, implant-supported prostheses.

RESULTS

All patients healed uneventfully. The collected biopsies showed a prevalence of bone formation at 4 months, compact lamellar bone, with well-defined lamellae surrounding Haversian and Volkmann's canals at 6 months, and an intermediate degree of maturation in active anabolic phase at 7 months after grafting. The amount of mineralized matrix was 63.3-70.7%, whereas medullar spaces were 26.0-30.7%.

CONCLUSION

Histologic examination showed that the bone paste was fully biocompatible. Bone regeneration occurred within the first 4 months from grafting, with 63.3-70.7% mineralized bone matrix. The residual biomaterial, when present, did not exceed, on average, 2%.

CLINICAL SIGNIFICANCE

Ridge preservation using bone substitutes as an alternative to autogenous bone is known to be effective. However, available clinical evidence still does not indicate the biomaterial, if any, that should be preferred to carry it out. The equine bone paste used in the present study appears to be a good candidate for further investigation because it is easy to handle in the clinical setting and it displays a good bone formation rate.

Browning Effects of a Chronic Pterostilbene Supplementation in Mice Fed a High-Fat Diet

Obesity and related comorbidities are a major health concern. The drugs used to treat these conditions are largely inadequate or dangerous, and a well-researched approach based on nutraceuticals would be highly useful. Pterostilbene (Pt), i.e., 3,5-dimethylresveratrol, has been reported to be effective in animal models of obesity, acting on different metabolic pathways. We investigate here its ability to induce browning of white adipose tissue. Pt (5 µM) was first tested on 3T3-L1 mature adipocytes, and then it was administered (352 µmol/kg/day) to mice fed an obesogenic high-fat diet (HFD) for 30 weeks, starting at weaning. In the cultured adipocytes, the treatment elicited a significant increase of the levels of Uncoupling Protein 1 (UCP1) protein—a key component of thermogenic, energy-dissipating beige/brown adipocytes. In vivo administration antagonized weight increase, more so in males than in females. Analysis of inguinal White Adipose Tissue (WAT) revealed a trend towards browning, with significantly increased transcription of several marker genes (Cidea, Ebf2, Pgc1α, PPARγ, Sirt1, and Tbx1) and an increase in UCP1 protein levels, which, however, did not achieve significance. Given the lack of known side effects of Pt, this study strengthens the candidacy of this natural phenol as an anti-obesity nutraceutical.

[Skeletal mineralization in a prepubertal female population affected by juvenile idiopathic arthritis]

BACKGROUND

Puberty is an essential step in bone mass accrual. Growth failure and impairment of sexual maturation are frequent manifestations of chronic illnesses in the paediatric population, and chronic rheumatologic disorders such as juvenile idiopathic arthritis (JIA) are no exception to this.

METHODS

The aim of our study was to prospectively evaluate bone density in adolescent females with JIA, and to correlate the results with clinical variables, in particular with age at menarche. Lumbar spine (L2-L4) area bone mineral density (aBMD) (assessed by Dual X-ray Absorbiometry, DXA) was monitored every 6-12 months in a group of 38 girls with JIA. The evaluated bone density accrual during the peripubertal time as well as absolute and relative (Z-score) aBMD in relationship with age at menarche, JIA subset, disease activity (as evaluated by ESR and Hgb), corticosteroid and methotrexate treatment (mean pro kg daily dose, cumulative dose) was assessed. Height, body mass index (BMI), bone mass content (BMC) values were also collected. Volumetric BMD (vBMD) evaluated with a geometric correction formula has been calculated and compared to aBMD.

RESULTS

Patients were divided into two groups: - group I included girls with menarche age within normal limits for Italian standards; - group II included girls with delayed menarche. The BMD values and Z scores in group I were not significantly different to normal population. The BMD values and Z scores in group II were significantly decreased when compared to the normal population (p<0.001). With a multivariate analysis only age at menarche seemed independently related to peripubertal mineralization (p=0.025, r between -0.65 and -0.75). With a binary logistic analysis only disease activity (ESR and Hgb values) seems independently related to a menarche delay (1.24+/-0.4 for each mm/h).

CONCLUSION

Our data show a critical role for disease activity in determination of a regular pubertal onset and an optimal bone density achievement.

[Long-term evaluation of infliximab in the treatment of persistently active juvenile idiopathic arthritis refractory to conventional therapy]

OBJECTIVES

To evaluate, in long-term open label prospective study, infliximab as therapeutic choice for Juvenile Idiopathic Arthritis (JIA) non responsive to conventional therapy.

METHODS

We enrolled to treat with infliximab 78 JIA patients (66 females, 12 males): the mean age was 20.7+/-7.1 years (median 20.9, range 5.4-34.9); mean JIA duration was 13.6+/-7.6 years (median 13.5, range 0.4-31.4). Infliximab, at dose of 3-10 mg/kg/infusion added to weekly subcutaneous Methotrexate or other previous DMARDs, was administered by intravenous infusions at weeks 0, 2, 6 and every 8 weeks thereafter. Chest X-ray, Mantoux's test, electrocardiogram were performed at baseline; laboratory tests and clinical evaluation were performed at each infusion. Response was evaluated according to ACR improvement criteria.

RESULTS

Mean treatment period was 21.6 months+/-18.8 (median 14.7, range 1.4-72.4). Just after first infusion most of patients reported significant improvement in pain, fatigue, morning stiffness. Infliximab is still successfully administered to 23 patients (29.5%); 55 (70.5%) patients suspended because of: inefficacy (7), infusion reactions (17), adverse events (9), disease flare-up after a period of effectiveness on synovitis, pain, and morning stiffness (19), remission (2), lack of compliance to treatment (1). Infusion reactions, like dyspnea, flushing, chills, headache, hypotension, anxiety, throat oedema, were observed in 29 patients (34.5%). Anti-DNA antibodies were present in 7 patients (none developed Systemic Lupus Erythematous).

CONCLUSIONS

Infliximab showed impressive effectiveness treating refractory JIA, although most of patients had to discontinue treatment because of disease flare-up or adverse events. Infliximab may represent a good therapeutic choice in patients non-responders to Methotrexate.

Dynamic aspects of endometriosis in a mouse model through analysis of implantation and progression

The aim of this study was to use normal immunocompetent mice to set up a model for endometriosis which allowed to study the dynamic aspects involved in initiation and progression of the disease. Thirty mice were surgically transplanted with autologous endometrium and at 3 weeks showed evidence of endometriosis. Diagnosis of endometriotic lesions was histologically confirmed. Visual inspection using a caliper revealed that, after an initial decrease in size (from 33.44+/-2.33 mm2 to 24.24+/-2.37 mm2 (p<0.01)) detected at 3 weeks after transplantation, there was a significant increase of lesion area from 21.30+/-3.15 mm2 to 43.93+/-6.29 mm2 (p<0.05) in the following 4 weeks. When we compared these results to those obtained in mice which underwent bilateral annessiectomy, we observed that, when bilateral annessiectomy was performed simultaneously to endometrial transplantation, lesion surfaces were similar between mice which were or were not subjected to bilateral ovariectomy. On the other hand, when bilateral annessiectomy was performed at second laparotomy and then evaluated after 4 weeks, differently from what observed in control mice, surface values decreased from 21.24+/-2.29 mm2 to 10.58+/-3.40 mm2 (p<0.01). Finally, progression of lesions in estrogen supplemented mice seems less evident than in control mice since only a slight but not significant increase in size (from 21.32+/-3.32 mm2 to 26.18+/-6.98 mm2, p=0.32) was detected. The results presented herein demonstrate that surgically induced endometrial implants in mice are dynamic lesions and that implantation and progression of endometriosis represent different stages in the ethiopathogenesis of the disease. Moreover, we showed that progression, but not implantation, of ectopic endometrium is dependent upon the functionally and structurally integrity of the ovaries. This is a model of endometriosis established in normal immunocompetent mice, and, consequently, may represent a reliable tool for testing new immunological therapeutical approaches and studying the role of different genes using transgenic mice.