Little information is available on the prevalence, geographic distribution and mutation spectrum of genetic skeletal disorders (GSDs) in China. This study systematically reviewed GSDs as defined in “Nosology and Classification of genetic skeletal disorders (2010 version)” using Chinese biomedical literature published over the past 34 years from 1978 to 2012. In total, 16,099 GSDs have been reported. The most frequently reported disorders were Marfan syndrome, osteogenesis imperfecta, fibrous dysplasia, mucopolysaccharidosis, multiple cartilaginous exostoses, neurofibromatosis type 1 (NF1), osteopetrosis, achondroplasia, enchondromatosis (Ollier), and osteopoikilosis, accounting for 76.5% (12,312 cases) of the total cases. Five groups (group 8, 12, 14, 18, 21) defined by “Nosology and Classification of genetic skeletal disorders” have not been reported in the Chinese biomedical literature. Gene mutation testing was performed in only a minor portion of the 16,099 cases of GSDs (187 cases, 1.16%). In total, 37 genes for 41 different GSDs were reported in Chinese biomedical literature, including 43 novel mutations. This review revealed a significant imbalance in rare disease identification in terms of geographic regions and hospital levels, suggesting the need to create a national multi-level network to meet the specific challenge of care for rare diseases in China.

Introduction

Ankylosing spondylitis (AS) is characterized by abnormal bone formation in the spine and the sacroiliac joints. In vitro assays demonstrate that carbonic anhydrase I (CA1) promotes calcium precipitation. This study investigated the function of CA1 for bio-mineralization and determined if common polymorphisms in the CA1 gene might contribute to AS risk.

Methods

Calcification was induced in Saos-2 cells, a human osteosarcoma cell line, with ascorbic acid and β-glycerophosphate. Calcification was determined by Alizarin Red-S (AR-S) staining. Expressions of CA1, alkaline phosphatase (ALP), bone sialoprotein (BSP), osteocalcin (OCN), osterix (OSX) and runt-related transcription factor-2 (Runx2) were determined by real-time PCR and western blotting. The cells were also treated with acetazolamide, an anti-carbonic anhydrase drug. Genotyping was performed using Illumina VeraCode microarray in a case-control study including 51 AS patients, 267 rheumatoid arthritis (RA) patients and 160 healthy controls. The result was confirmed by Taqman assay, including 258 AS patients, 288 RA patients and 288 healthy controls.

Results

Following the induction of calcification, Saos-2 cells produced large amounts of calcium-rich deposits. Increased transcriptions of CA1, ALP, BSP, OCN, OSX and Runx2, essential genes for ossification, were detected in the cultured cells. Following treatmen with acetazolamide, the expression of CA1 obviously declined and mineralized nodule formation was also decreased. Illumina microarray indicates that SNP at rs7841425 also showed significant differences in allelic frequency (P = 0.01396) and genotypic frequency (P = 0.005902) between AS cases and controls. In addition, SNP at rs7827474 showed significant differences in allelic frequency (P = 5.83E-04) and genotypic frequency (P = 0.000186) between RA cases and controls (P values were adjusted to multiple comparisons). The Taqman assay revealed that rs725605 demonstrated statistically significant evidence of allele frequency (P = 0.022307) and gene frequency (P = 0.007731) for association with AS. This SNP did not show significant differences in allelic frequencies and gene frequencies between RA patients and controls.

Conclusions

CA1 may play an essential role in bio-mineralization and new bone formation. The gene encoding CA1 is susceptible to AS.

During the process of matrix vesicle (MV)-mediated initiation of mineralisation, chondrocytes and osteoblasts mineralise the extracellular matrix by promoting the seeding of basic calcium phosphate crystals of hydroxyapatite (HA) along the collagen fibrils. This orchestrated process is carefully regulated by the balanced action of propagators and inhibitors of calcification. The primary antagonistic regulators of extracellular matrix mineralisation are phosphate (Pi) and inorganic pyrophosphate (PPi). Studies in mouse models and in humans have established critical roles for Pi/PPi homeostasis in biomineralisation. In this review, we present the regulators of Pi/PPi, as derived from animal models, and discuss their clinical relevance to physiological and pathological mineralisation.

PADI4 post-translationally converts peptidylarginine to citrulline. PADI4 can disrupt the apoptotic process via the citrullination of histone H3 in the promoter of p53-target genes. The current study focused on PADI4 expression in various subtypes of oesophageal carcinoma (EC) by immunohistochemistry, western blotting and real time PCR. The study also investigated the effect of bile acid deoxycholate (DCA) on PADI4 expression in Eca-109 cells that originated from EC. Apoptosis and DCA-induced toxicity were analyzed by TUNEL, MTT assay and flow cytometry. Additionally, the present study investigated the correlation between single nucleotide polymorphism (SNP) in PADI4 gene and EC risk in Chinese population using Illumina GoldenGate assay. Compared with paraneoplastic tissues, the transcriptional and translational levels of PADI4 were significantly elevated in oesophageal squamous cell carcinoma (ESCC, n=9) and oesophageal adenocarcinoma (EAC, n=5) tissues. Immunolabeling detected expression of PADI4 in ESCC tissues (98.56%, n=139), EAC samples (87.5%, n=16) and oesophageal small cell undifferentiated carcinoma (91.7%, n=12) but not in normal tissues (0%, n=16). Furthermore, PADI4 levels is positively correlated with the pathological classification of ESCC (p=0.009). PADI4 expression levels were consistent with the number of apoptotic cells in the induced Eca-109 cells. rs10437048 [OR= 0.012831; 95% CI, 0.001746~0.094278; p=1.556×10-12] were significantly associated with decreased risk of EC, whereas rs41265997 [OR=12.7; 95% CI, 0.857077~33.207214; p=3.896×10-8] were significantly associated with increased risk of EC. rs41265997 in exon 3 of PADI4 gene is non-synonymous and converts ACG to ATG resulting in a threonine /methionine conversion at position 274 of the protein. Haplotypes GC that carries the variant alleles for rs2501796 and rs2477134 was significantly associated with increased risk of EC (frequency=0.085, p=0.0256, OR=2.7). The results suggest that PADI4 expression is related to the tumorigenic process of EC and the DCA-induced apoptosis. The PADI4 gene may be a valid EC susceptibility gene.

Background

One of the most distinctive features of ankylosing spondylitis (AS) is new bone formation and bone resorption at sites of chronic inflammation. Previous studies have indicated that the hyperplasia and inflammation of synovial tissues are significantly related to the pathogenic process of AS. The present study used a proteomic approach to identify novel AS-specific proteins by simultaneously comparing the expression profiles of synovial membranes from patients with AS, rheumatoid arthritis (RA) and osteoarthritis (OA).

Methods

Synovial tissues were collected from the hip joints of patients with AS and knee joints of patients with RA or OA (n = 10 for each disease) during joint replacement surgery. Proteins extracted from the synovial tissues were separated by 2-D electrophoresis (2-DE), and the proteins with significantly increased expression in the AS samples were subjected to MALDI-TOF/TOF-MS analysis. The results were verified using western blotting and immunohistochemistry. Levels of the candidate proteins in synovial fluids from knee joints (n = 40 for each disease) were measured using ELISA.

Results

The proteomic approach revealed significantly increased expression of carbonic anhydrase I (CA1) in the synovial membrane of patients with AS as compared with the RA and OA tissue samples. Immunohistochemistry and western blotting analysis confirmed the findings described above. The ELISA detected a higher level of CA1 in synovial fluids from patients with AS than those with OA. The mean value of the CA1 level was also higher in AS patients as compared with RA patients. This study also detected increased expression of alpha-1-antitrypsin in the synovial tissues from AS patients, which is in agreement with other reports.

Conclusion

In vitro experiments by other groups indicated that CA1 catalyzes the generation of HCO3- through the hydration of CO2, which then combines with Ca2+ to form a CaCO3 precipitate. Calcification is an essential step of bone formation. Substantial evidence indicates that carbonic anhydrase also stimulates bone resorption. Hence, overexpression of CA1 in the synovial tissues of AS patients may promote improper calcification and bone resorption in AS.

Background

Peptidylarginine deiminase type 4 (PAD4/PADI4) post-translationally converts peptidylarginine to citrulline. Recent studies suggest that PADI4 represses expression of p53-regulated genes via citrullination of histones at gene promoters.

Methods

Expression of PADI4 was investigated in various tumors and non-tumor tissues (n = 1673) as well as in A549, SKOV3 and U937 tumor cell lines by immunohistochemistry, real-time PCR, and western blot. Levels of PADI4 and citrullinated antithrombin (cAT) were investigated in the blood of patients with various tumors by ELISA (n = 1121).

Results

Immunohistochemistry detected significant PADI4 expression in various malignancies including breast carcinomas, lung adenocarcinomas, hepatocellular carcinomas, esophageal squamous cancer cells, colorectal adenocarcinomas, renal cancer cells, ovarian adenocarcinomas, endometrial carcinomas, uterine adenocarcinomas, bladder carcinomas, chondromas, as well as other metastatic carcinomas. However, PADI4 expression was not observed in benign leiomyomas of stomach, uterine myomas, endometrial hyperplasias, cervical polyps, teratomas, hydatidiform moles, trophoblastic cell hyperplasias, hyroid adenomas, hemangiomas, lymph hyperplasias, schwannomas, neurofibromas, lipomas, and cavernous hemangiomas of the liver. Additionally, PADI4 expression was not detected in non-tumor tissues including cholecystitis, cervicitis and synovitis of osteoarthritis, except in certain acutely inflamed tissues such as in gastritis and appendicitis. Quantitative PCR and western blot analysis showed higher PADI4 expression in gastric adenocarcinomas, lung adenocarcinomas, hepatocellular carcinomas, esophageal squamous cell cancers and breast cancers (n = 5 for each disease) than in the surrounding healthy tissues. Furthermore, western blot analysis detected PADI4 expression in cultured tumor cell lines. ELISA detected increased PADI4 and cAT levels in the blood of patients with various malignant tumors compared to those in patients with chronic inflammation and benign tumors. This was consistent with immunohistochemical results. Additionally, PADI4 and cAT levels were significantly associated with higher levels of known tumor markers.

Conclusion

Our results suggest that PADI4 expression is increased in the blood and tissues of many malignant tumors, a finding useful for further understanding of tumorigenesis.