Novel WISP3 mutations causing progressive pseudorheumatoid dysplasia in two Chinese families

Unique mutation spectrum of progressive pseudorheumatoid dysplasia in the Chinese population: a retrospective genotype-phenotype analysis of 105 patients

BACKGROUND

Progressive pseudorheumatoid dysplasia (PPRD) is a rare genetic disease with autosomal recessive inheritance. There was a lack of genotype-phenotype correlation data from the Chinese population. This study aimed to identify the genotype and phenotype characteristics of Chinese PPRD patients and to conduct a genotype-phenotype analysis of Chinese PPRD patients.

METHODS

Genetic analysis was performed for suspected PPRD patients from Peking Union Medical College Hospital. Medical records were collected from the electronic medical record system and patient-held portable health records. Published Chinese PPRD cases were gathered from both international and Chinese local databases. We collected demographic information, genetic variants, clinical manifestations, and imaging characteristics for further analysis.

RESULTS

We included 105 Chinese PPRD patients in the current study. Thirty-three variants, including nine novels and five hotspot variants, were identified, with 26/33 (79%) variants exclusively seen in the Chinese population. Chinese PPRD patients share a phenotype similar to that in international reports. Joint involvement may progress with age (R2 = 0.2541). Long bone shortening and severe deformities occur in three patients with biallelic null variants, of which at least one variant is located in exon 2. Among hotspot variants, c.624dupA (p.C209Mfs*21) were associated with later onset and more involved joints. Elbow joints were more likely to be affected in patients carrying c.624dupA (p.C209Mfs*21) and c.866dupA (p.S209Efs*13). Shoulder joints are more likely to be involved in patients with biallelic null variants (P = 0.027).

CONCLUSIONS

Chinese PPRD patients share a unique mutation spectrum. Among the five hotspot variants, c.624dupA is associated with later onset of disease, more extensive joint involvement, and a tendency to affect elbow joints. Biallelic null variants with at least one variant in exon 2 could be a likely cause of long bone shortening and severe deformities.

CCN6 influences transcription and controls mitochondrial mass and muscle organization

Mutations in Cellular Communication Network Factor 6 (CCN6) are linked to the debilitating musculoskeletal disease Progressive Pseudo Rheumatoid Dysplasia (PPRD), which disrupts mobility. Yet, much remains unknown about CCN6 function at the molecular level. In this study, we revealed a new function of CCN6 in transcriptional regulation. We demonstrated that CCN6 localizes to chromatin and associates with RNA Polymerase II in human chondrocyte lines. Using zebrafish as a model organism we validated the nuclear presence of CCN6 and its association with RNA Polymerase II in different developmental stages from 10 hpf embryo to adult fish muscle. In concurrence with these findings, we confirmed the requirement of CCN6 in the transcription of several genes encoding mitochondrial electron transport complex proteins in the zebrafish, both in the embryonic stages and in the adult muscle. Reduction in the expression of these genes upon morpholino-mediated knockdown of CCN6 protein expression led to reduced mitochondrial mass, which correlated with defective myotome organization during zebrafish muscle development. Overall, this study suggests that the developmental musculoskeletal abnormalities linked with PPRD could be contributed at least partly by impaired expression of genes encoding mitochondrial electron transport complexes due to defects in CCN6 associated transcriptional regulation.

Specific early signs and long-term follow-up findings of Progressive Pseudorheumatoid Dysplasia (PPRD) in the Turkish cohort

OBJECTIVES

Progressive pseudorheumatoid dysplasia (PPRD) is a spondyloepiphyseal dysplasia caused by biallelic variants in CCN6. This study aimed to describe the early signs and follow-up findings in forty-four Turkish PPRD patients.

METHODS

The patients with progressive stiffness of multiple joints, characteristic wide metaphysis of interphalangeal (IP) joints, and platyspondyly were clinically diagnosed with PPRD. Fifteen patients who had first symptoms under 3 years of age were grouped as early-onset, while others were grouped as classical. CCN6 sequencing was performed in 43 patients.

RESULTS

Thirteen pathogenic/likely pathogenic variants were identified, five were novel. c.156C>A(p.Cys52*) variant was found in 53.3% of the families. The initial symptom in the early-onset group was genu varum deformity, while it was widening of IP joints in the classical group. The median age of onset of symptoms and of diagnosis was 4 and 9.7 years, respectively. The mean follow-up duration was 5.6 years. The median age of onset of IP, elbow, knee, and hip stiffness, which became progressive with growth was 5, 9, 9, and 12.2 years, respectively. Waddling gait occurred in 97.7% of the patients. 47.7% lost independent walking ability at the median age of 12 years. In the early-onset group, waddling gait occurred earlier than in classical group (p< 0.001). Two patients had atypical presentation with late-onset and mild or lack of IP involvement.

CONCLUSION

We observed that genu varum deformity before the age of 3 years was an early sign for PPRD and almost half of the patients lost walking ability at the median age of 12 years.

CCN6 mutation detection in Chinese patients with progressive pseudo-rheumatoid dysplasia and identification of four novel mutations

Background

No formal diagnostic criteria for progressive pseudo‐rheumatoid dysplasia (PPD) are available because of insufficient clinical data, which results in that PPD is often misdiagnosed with other diseases. Whole exome sequencing (WES) and Sanger sequencing were employed to reveal the novel mutations on CCN6 of five patients with PPD from China in order to increase the clinical data of PPD.

Methods

Four suspected PPD pedigrees containing five patients in total were collected from 1998 to 2018 in our medical center. The phenotypes of each suspected PPD case were recorded in detail, and peripheral blood samples were collected for subsequent sequencing. Genomic DNA was extracted from peripheral blood samples, and Agilent liquid phase chip capture system was utilized for efficient enrichment of whole exome region DNA. After acquiring raw sequenced reads of whole exome region, bioinformatics analysis was completed in conjunction with reference or genome sequence (GRCh37/hg19). Sanger sequencing was performed to identify the results of WES.

Results

In total, four novel PPD‐related mutation sites in CCN6 gene were identified including (CCN6):c.643 + 2T>C, (CCN6):c.1064_1065dupGT(p.Gln356ValfsTer33), (CCN6):c.1064G > A), and exon4:c.670dupA:p.W223fs.

Conclusion

Our findings increase the clinical data of PPD including the CCN6 mutation spectrum, the clinical symptoms and signs. Moreover, the study highlights the utility of WES in reaching definitive diagnoses for PPD.

A genome-wide association study identifies new genes associated with developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is one of the most common congenital malformations and covers a spectrum of hip disorders from mild dysplasia to irreducible dislocation. The pathological mechanisms of DDH are poorly understood, which hampers the development of diagnostic tools and treatments. To gain insight into its disease mechanism, we explored the potential biological processes that underlie DDH by integrating pathway analysis tools and performing a genome-wide association study (GWAS). A total of 406 DDH-associated genes (P < 0.001) were identified by our GWAS using a Chinese Han cohort consisting of 386 DDH cases and 500 healthy controls (Set A). We verified the significant loci (P < 10^-5 ) in another Chinese Han cohort consisting of 574 DDH patients and 569 healthy controls (Set B). An intronic Single Nucleotide Polymorphism (SNP) (rs61930502) showed significant association in Set A and Set B (P = 2.65 × 10^-7 and 2.0 × 10^-4 , respectively). The minor allele, rs61930502-A, which tended to prevent DDH showed a dominant effect. Heat shock 70 kDa protein 8 (HSPA8) showed the most direct interactions with other proteins which were coded by DDH-associated genes in the protein-protein interaction analysis. Interestingly, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis suggested a relation between DDH and the genes involved in type II diabetes mellitus pathway (P = 0.0067). Our genetic and protein interaction evidence could open avenues for future studies of DDH.

A Novel Homozygous Frameshift Mutation in CCN6 Causing Progressive Pseudorheumatoid Dysplasia (PPRD) in a Consanguineous Yemeni Family

Background: Progressive pseudorheumatoid dysplasia (PPRD) inherited in an autosomal recessive fashion, is a disabling disease, characterized by platyspondyly, irregularities of the vertebral bodies, narrowing of the intervertebral discs and intraarticular spaces, widening of the epiphysis-metaphysis, polyarthralgia, multiple joint contractures, and disproportionate short stature. A number of studies have been performed on this deformity in various populations around the globe, including the Arab population. Mutations in CCN6, located on 6q22, are reported to cause this anomaly. Case Presentation: The present study describes the investigation of a consanguineous family of Yemeni origin. Clinical examination of the patient revealed short stature with progressive skeletal abnormalities, stiffness and enlargement of small joints of the hands along with restriction of movements of proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints with weakness and gait disturbance. Sanger sequencing revealed a novel homozygous frameshift deletion mutation (c.746delT; p.Val249Glyfs^*10) in CCN6 which may lead to NMD (Nonsense mediated decay). This mutation expands the spectrum of pathogenic variants in CCN6 causing PPRD.

Progressive pseudorheumatoid dysplasia: a rare childhood disease

Progressive pseudorheumatoid dysplasia (PPRD) is a genetic bone disorder characterised by the progressive degeneration of articular cartilage that leads to pain, stiffness and joint enlargement. As PPRD is a rare disease, available literature is mainly represented by single case reports and only a few larger case series. Our aim is to review the literature concerning clinical, laboratory and radiological features of PPRD. PPRD is due to a mutation in Wnt1-inducible signalling protein 3 (WISP3) gene, which encodes a signalling factor involved in cartilage homeostasis. The disease onset in childhood and skeletal changes progresses over time leading to significant disability. PPRD is a rare condition that should be suspected if a child develops symmetrical polyarticular involvement without systemic inflammation, knobbly interphalangeal joints of the hands, and gait abnormalities. A full skeletal survey, or at least a lateral radiograph of the spine, can direct towards a correct diagnosis that can be confirmed molecularly. More than 70 WISP3 mutations have so far been reported. Genetic testing should start with the study of genomic DNA extracted from blood leucocytes, but intronic mutations in WISP3 causing splicing aberrations can only be detected by analysing WISP3 mRNA, which can be extracted from cultured skin fibroblasts. A skin biopsy is, therefore, indicated in patients with typical PPRD findings and negative mutation screening of genomic DNA.

Progressive pseudorheumatoid dysplasia with new-found gene mutation of Wntl inducible signaling pathway protein 3

BACKGROUND

As one kind of osteochondrodysplasia, progressive pseudorheumatoid dysplasia (PPD) is also known as spondyloepiphyseal dysplasia tarda with progressive arthropathy or arthropathy progressive pseudorheumatoid of childhood. PPD is a very rare disease, especially in China, and has an estimated prevalence of 1/1000000 due to lacking definite prevalence survey. It is an autosomal recessive disorder caused by gene mutation of Wntl inducible signaling pathway protein 3 (WISP3). Its basic pathological change is persistent degeneration and loss of articular cartilage in multiple joints. Its clinical appearances include bone enlargement, platyspondyly, irregular endplate, secondary osteoarthritis, extensive osteoporosis, joint rigidity and function loss. Clinical diagnosis of PPD is made based on clinical appearance and imaging examinations, whereas its definite diagnosis depends on gene sequencing. PPD has no severe effect on life span, but causes high disability rate and very poor prognosis. There are only case reports with limited information in China.

CASE PRESENTATION

One female patient was diagnosed as PPD and secondary osteoarthritis. She had typical clinical appearance and imaging examinations, and received individualized therapeutic regimens. She had a gene mutation (c.72delT, p.T24TfsX4) of WISP3. This gene mutation has not been reported by previous literatures and included in Single Nucleotide Polymorphism Database.

CONCLUSIONS

As the first time, this paper reported a patient with PPD caused by new-found gene mutation (c.72delT, p.T24TfsX4) of WISP3.

WISP3 mutation associated with pseudorheumatoid dysplasia

Progressive pseudorheumatoid dysplasia (PPD) is a skeletal dysplasia characterized by predominant involvement of articular cartilage with progressive joint stiffness. Here we report genetic characterization of a consanguineous family segregating an uncharacterized from of skeletal dysplasia. Whole-exome sequencing of four affected siblings and their parents identified a loss-of-function homozygous mutation in the WISP3 gene, leading to diagnosis of PPD in the affected individuals. The identified variant (Chr6: 112382301; WISP3:c.156C>A p.Cys52*) is rare and predicted to cause premature termination of the WISP3 protein.

Delayed-onset of progressive pseudorheumatoid dysplasia in a Chinese adult with a novel compound WISP3 mutation: a case report

BACKGROUND

Progressive pseudorheumatoid dysplasia (PPD) is a rare autosomal recessive genetic disease that is characterized by pain, stiffness and enlargement of multiple joints with an age of onset between 3 and 8 years old. Mutations in the WISP3 (Wnt1-inducible signal pathway) gene are known to be the cause of PPD.

CASE PRESENTATION

We present a case of delayed-onset PPD in a Chinese man. The 35-year-old proband presented with an almost 20-year history of pain and limitations in mobility in multiple joints. Based on the clinical manifestations, the patient was diagnosed with PPD; however, there was no specific evidence to confirm this diagnosis. Through mutational analyses, two WIPS3 mutations in exon 4, including a novel frameshift mutation (c.670dupA) in the paternal allele and an already described nonsense mutation (c.756C > A, p.Cys252*) in the maternal allele, were identified in the proband. Thus, the patient was diagnosed with PPD. Furthermore, we found that the proband's son only carried one of the mutations (c.670dupA) and therefore determined that he would not be affected by PPD in the future.

CONCLUSIONS

In this case, we successfully diagnosed the disease that the proband was affected precisely after the reunion of clinical diagnosis and genetic analysis. These findings demonstrate the clinical utility of genetic analysis to diagnose skeletal dysplasia and guide genetic counseling.