Cleidocranial dysplasia (CCD) is an autosomal dominant skeletal dysplasia characterized by persistent open skull sutures whit bulging calvaria, hypoplasia or aplasia of clavicles permitting abnormal opposition of the shoulders, wide public symphysis, short middle phalanx of the fifth fingers and vertebral, craniofacial and dental anomalies. It is a rare disease, with a prevalence of 1-9/1,000,000, high penetrance, and variable expression. The responsible gene of CCD is the runt-related transcription factor 2 gene (RUNX2). We characterize the clinical, genetic and bioinformatic results of four CCD cases. Two Mexican familial with 6 affected members, 9 asymptomatic individuals, and two sporadic cases with CCD, as well as 100 healthy controls. Genomic DNA analyses of the RUNX2 gene was performed for Sanger sequencing. Bioinformatics tools, used to predict the function, stability, and structural changes of the mutated RUNX2 proteins. Three novel heterozygous mutations (c.651_652del; c.538_539delinsCA; c.662T>A) and a previously reported mutation (c.674G>A) were detected. In silico analysis showed that all mutations had functional, stability, and structural alterations in RUNX2 protein. Our results show novel mutations that enrich the pool of RUNX2 gene mutations with CCD. In addition, one patient presented clinical data not previously reported that could represent an expanded phenotype of sever expression.

Sterile alpha motif domain-containing protein 9 (SAMD9) is a regulatory protein centrally involved in cell proliferation and apoptosis. Mapped to 7p21.1, variants in SAMD9 have been reported in <50 pediatric cases worldwide, typically with early lethality. Germline gain-of-function SAMD9 variants are associated with MIRAGE Syndrome (myelodysplasia, infection, restricted growth, adrenal hypoplasia, genital anomalies, and enteropathy). Spalt like transcription factor 1 (SALL1) is a zinc finger transcriptional repressor located at 16q12.1 where only two transcript variants in SALL1 are known. RUNX2 (6p21.1) encodes a nuclear protein with a Runt DNA-binding domain critical for osteoblastic differentiation, skeletal morphogenesis, and serves as a scaffold for nucleic acids and regulatory factors involved in skeletal gene expression. RUNX2 and SALL1 are thus both ‘master regulators’ of tissue organization and embryo development. Here, we describe exome sequencing and copy number variants in two previously unknown mutations—R824Q in SAMD9, and Q253H in SALL1. A new multiexon 3’ terminal duplication in RUNX2 is also reported. This is the first known phenotype characterization for the intersection of all three variants in a healthy 46,XX adult. Focusing on developmental progress, ultrastructural renal anatomy, and selected reproductive aspects, we describe this unique genotype diagnosed incidentally during Covid-19 illness. Individual disruption in SAMD9, RUNX2, or SALL1 would be expected to give a bleak prognosis. However, the convergence discovered here appears to dampen severe pathology, perhaps by cross-gene silencing of effects normally deleterious when such changes occur alone.

Vascular calcification (VC), is a common complication in patients with chronic kidney disease and increases mortality. Although oxidative stress is involved in the onset and progression of this disorder, the specific role of some main redox regulators such as catalase, the main scavenger of H2O2, remains unclear. In the present study, epigastric arteries of kidney transplant recipients, an in vivo model of VC and an in vitro model of VC exhibiting catalase overexpression (Cts) were analyzed. Peri-calcification areas of human epigastric arteries have increased levels of catalase and cytoplasmic rather than nuclear RUNX2. In the in vivo model, advanced aortic VC concurs with lower levels of the H2O2 scavenger, glutathione peroxidase 3 compared to controls. In an early model of calcification using vascular smooth muscle cells (VSMCs), Cts VSMCs showed the expected increase in RUNX2 total levels. However, Cts VMSC also exhibited lower percentage of the nucleus stained for RUNX2 in response to calcifying media. At this early model of VC we did not observe dysregulation of mitochondrial redox state, an increase in general redox state was observed in the cytoplasm. These in vivo and in vitro results highlight the complex role of antioxidant enzymes as catalase in the process of VC by regulation of RUNX2 location.

Humans are often exposed to various environmental contaminants, among which phthalates are prevalent due to their extensive use as plasticizers in various consumer goods. Di(2-ethylhexyl) phthalate (DEHP), a widely used phthalate, is recognized as an endocrine disruptor chemical (EDC). DEHP is reported to affect various organs. Few studies have addressed the effects of phthalates on bone. However, the effects of DEHP on the bone forming cells (osteoblasts) are obscure. The present study was peformed to determine the cytotoxic effects of DEHP on human osteoblasts in vitro and to delineate the mechansims. In this study, we exposed the human osteo-blastic cell line MG-63 to various concentrations of DEHP (1, 25, 50 and 100 µM) for 24, 48 and 72 h. Cell viability was assessed by MTT assay. Total RNA and protein were collected after 48 h treatment with 1 and 100 µM DEHP and determined for the mRNA and/or protein expression of alkaline phosphatase (ALP), sex steroid receptors (androgen and estrogen receptors), receptor activator of nuclear factor kappa-Β ligand (RANKL), runt-related transcription factor 2 (RUNX2) and peroxisome proliferator-activated receptor alpha (PPARα). The mRNA expression was stud-ied by real-time RT-PCR analysis and the protein expression was determined by western blot analysis. Statistical analyses were done by one-way analysis of variance (ANOVA) followed by the Students–Newman–Keuls (SNK) test. The exposure of MG-63 cells to DEHP caused a signifi-cant decrease in osteoblast viability in all the treatment groups and at all the time points stud-ied. Interestingly, DEHP exposure decreased the mRNA expression of ALP, a bone formation marker. DEHP had differential effects on estrogen receptor alpha (ERα) mRNA and protein ex-pression. However, DEHP treatment downregulated the mRNA and protein expression of ERβ, and androgen receptor (AR). Surprisingly, DEHP downregulated the RANKL mRNA expression. DEHP decreased the protein expression of RUNX2, the key transcription factor and master regu-lator of bone formation. Furthermore, DEHP increased the PPARα protein expression in the os-teoblasts. Importantly, DEHP increased the reactive oxygen species (ROS) molecules and thus oxidative stress in osteoblasts, as observed by increased hydrogen peroxide, hydroxyl radical levels and lipid peroxidation. On the other hand, it decreased the enzymatic and non-enzymatic antioxidant levels namely catalase, superoxide dismutase, glutathione peroxidase activity and reduced glutathione. Our study demonstrated that in vitro exposure to DEHP reduces the osteo-blast viability possibly through alterations in the oxidant-antioxidant system and modulation of the key genes involved in bone formation, highlighting the cytotoxic effects of DEHP on bone forming cells.