An osteosclerotic form of Robinow syndrome

Chondrocyte Polarity During Endochondral Ossification Requires Protein-Protein Interactions Between Prickle1 and Dishevelled2/3

The expansion and growth of the endochondral skeleton requires organized cell behaviors that control chondrocyte maturation and oriented division. In other organs, these processes are accomplished through Wnt/planar cell polarity (Wnt/PCP) signaling pathway and require the protein-protein interactions of core components including Prickle1 (PK1) and Dishevelled (DVL). To determine the function of Wnt/PCP signaling in endochondral ossification of the cranial base and limb, we utilized the Prickle1^Beetlejuice (Pk1^Bj ) mouse line. The Pk1^Bj allele has a missense mutation in the PK1 LIM1 domain that results in a hypomorphic protein. Similar to human patients with Robinow syndrome, the Prickle1^Bj/Bj mouse mutants lack growth plate expansion resulting in shorter limbs and midfacial hypoplasia. Within the Prickle1^Bj/Bj limb and cranial base growth plates we observe precocious maturation of chondrocytes and stalling of terminal differentiation. Intriguingly, we observed that the growth plate chondrocytes have randomized polarity based on the location of the primary cilia and the location of PRICKLE1, DVL2, and DVL3 localization. Importantly, mutant PK1^Bj protein has decreased protein-protein interactions with both DVL2 and DVL3 in chondrocytes as revealed by in vivo co-immunoprecipitation and proximity ligation assays. Finally, we propose a model where the interaction between the Prickle1 LIM1 domain and DVL2 and DVL3 contributes to chondrocyte polarity and contributes to proximal-distal outgrowth of endochondral elements. © 2021 American Society for Bone and Mineral Research (ASBMR).

Clinical and molecular characterization of four patients with Robinow syndrome from different families

Robinow syndrome (RS) is a rare heterogeneous disorder characterized by short stature, short-limbs, craniofacial, oro-dental abnormalities, vertebral segmentation defects, and frequently genital hypoplasia. Both autosomal dominant and recessive patterns of inheritance are observed with many causative genes. Here, we present the phenotypes and genotypes of four children with RS from different Indian families. Sequence variants were identified in genes ROR2, DVL1, and DVL3. Our results expand the mutational spectrum of RS and we also highlight the radiological changes in the radius and ulna in patients with ROR2 sequence variants which are primarily characteristic for ROR2 related RS but have been reported in WNT5A related RS.

Craniofacial phenotypes associated with Robinow syndrome

Robinow syndrome is characterized by mesomelic limb shortening, hemivertebrae, and genital hypoplasia. Due to low prevalence and considerable phenotypic variability, it has been challenging to definitively characterize features of Robinow syndrome. While craniofacial abnormalities associated with Robinow syndrome have been broadly described, there is a lack of detailed descriptions of genotype-specific phenotypic craniofacial features. Patients with Robinow syndrome were invited for a multidisciplinary evaluation conducted by specialist physicians at our institution. A focused assessment of the craniofacial manifestations was performed by a single expert examiner using clinical examination and standard photographic images. A total of 13 patients with clinical and molecular diagnoses consistent with either dominant Robinow syndrome (DRS) or recessive Robinow syndrome (RRS) were evaluated. On craniofacial examination, gingival hyperplasia was nearly ubiquitous in all patients. Orbital hypertelorism, a short nose with anteverted and flared nares, a triangular mouth with a long philtrum, cleft palate, macrocephaly, and frontal bossing were not observed in all individuals but affected individuals with both DRS and RRS. Other anomalies were more selective in their distribution in this patient cohort. We present a comprehensive analysis of the craniofacial findings in patients with Robinow Syndrome, describing associated morphological features and correlating phenotypic manifestations to underlying genotype in a manner relevant for early recognition and focused evaluation of these patients.

Extremity anomalies associated with Robinow syndrome

Robinow syndrome, a rare genetic disorder, is characterized by skeletal dysplasia with, among other anomalies, extremity and hand anomalies. There is locus heterogeneity and both dominant and recessive inheritance. A detailed description of associated extremity and hand anomalies does not currently exist due to the rarity of this syndrome. This study seeks to document the hand anomalies present in Robinow syndrome to allow for improved rates of timely and accurate diagnosis. A focused assessment of the extremities and stature was performed using clinical examination and standard photographic images. A total of 13 patients with clinical and molecular diagnosis consistent with dominant Robinow syndrome or recessive Robinow syndrome were evaluated. All patients had limb shortening, the most common of which was mesomelia; however, rhizomelia and micromelia were also seen. These findings are relevant to clinical characterization, particularly as Robinow syndrome has classically been defined as a "mesomelic disorder." A total of eight distinct hand anomalies were identified in 12 patients with both autosomal recessive and dominant forms of Robinow syndrome. One patient did not present with any hand differences. The most common hand findings included brachydactyly, broad thumbs, and clinodactyly. A thorough understanding of the breadth of Robinow syndrome-associated extremity and hand anomalies can aid in early patient identification, improving rates of timely diagnosis and allowing for proactive management of sequelae.

Characterization of the Robinow syndrome skeletal phenotype, bone micro-architecture, and genotype-phenotype correlations with the osteosclerotic form

Robinow syndrome (RS) is a genetically heterogeneous skeletal dysplasia with recent reports suggesting an osteosclerotic form of the disease. We endeavored to investigate the full spectrum of skeletal anomalies in a genetically diverse cohort of RS patients with a focus on the bone micro-architecture. Seven individuals with molecularly confirmed RS, including four with DVL1 variants and single individuals with variants in WNT5A, ROR2, and GPC4 underwent a musculoskeletal focused physical examination, dual-energy X-ray absorptiometry (DEXA) scan, and high-resolution peripheral quantitative computed tomography (HR-pQCT). Skeletal examination revealed variability in limb shortening anomalies consistent with recent reports. DEXA scan measures revealed increased total body bone mineral density (BMD) (3/7), cranial BMD (5/7), and non-cranial BMD (1/7). Cranial osteosclerosis was only observed in DVL1-RS (4/4) and GPC4-RS (1/1) subjects and in one case was complicated by choanal atresia, bilateral conductive hearing loss, and cranial nerve III, VI, and VII palsy. HR-pQCT revealed a unique pattern of low cortical BMD, increased trabecular BMD, decreased number of trabeculations, and increased thickness of the trabeculations for the DVL1-RS subjects. The spectrum of skeletal anomalies including the micro-architecture of the bones observed in RS has considerable variability with some osteosclerosis genotype-phenotype correlations more frequent with DVL1 variants.

Decompressive Cranial Vault Remodeling in Osteosclerotic Robinow Syndrome

We present a novel application of endocranial burr contouring for cranial vault expansion as a surgical adjunct during decompressive craniectomy in patients with cranial osteosclerosis. A 16-year-old female with osteosclerotic Robinow syndrome complicated by slit ventricle syndrome presented with refractory intracranial hypertension following external ventricular drain placement. Symptoms included severe headaches and altered mental status. Given the severe intracranial volume restriction secondary to massive calvarial thickening (2.5 cm), the patient was taken to the operating room for urgent surgical decompression. After frontal and parietal craniectomy, burr and osteotome contouring were used to remove two-thirds of the endocranial calvarial bone flap thickness resulting in a 9% cranial vault expansion while preserving an overall normal head size. There were no immediate postoperative complications. At over 3 years postoperatively, the patient had reduced headaches, maintained adequate shunt function, and has not required further vault reconstruction.

Molecular genetics and targeted therapy of WNT-related human diseases (Review)

Canonical WNT signaling through Frizzled and LRP5/6 receptors is transduced to the WNT/β-catenin and WNT/stabilization of proteins (STOP) signaling cascades to regulate cell fate and proliferation, whereas non-canonical WNT signaling through Frizzled or ROR receptors is transduced to the WNT/planar cell polarity (PCP), WNT/G protein-coupled receptor (GPCR) and WNT/receptor tyrosine kinase (RTK) signaling cascades to regulate cytoskeletal dynamics and directional cell movement. WNT/β-catenin signaling cascade crosstalks with RTK/SRK and GPCR-cAMP-PKA signaling cascades to regulate β-catenin phosphorylation and β-catenin-dependent transcription. Germline mutations in WNT signaling molecules cause hereditary colorectal cancer, bone diseases, exudative vitreoretinopathy, intellectual disability syndrome and PCP-related diseases. APC or CTNNB1 mutations in colorectal, endometrial and prostate cancers activate the WNT/β-catenin signaling cascade. RNF43, ZNRF3, RSPO2 or RSPO3 alterations in breast, colorectal, gastric, pancreatic and other cancers activate the WNT/β-catenin, WNT/STOP and other WNT signaling cascades. ROR1 upregulation in B-cell leukemia and solid tumors and ROR2 upregulation in melanoma induce invasion, metastasis and therapeutic resistance through Rho-ROCK, Rac-JNK, PI3K-AKT and YAP signaling activation. WNT signaling in cancer, stromal and immune cells dynamically orchestrate immune evasion and antitumor immunity in a cell context-dependent manner. Porcupine (PORCN), RSPO3, WNT2B, FZD5, FZD10, ROR1, tankyrase and β-catenin are targets of anti-WNT signaling therapy, and ETC-159, LGK974, OMP-18R5 (vantictumab), OMP-54F28 (ipafricept), OMP-131R10 (rosmantuzumab), PRI-724 and UC-961 (cirmtuzumab) are in clinical trials for cancer patients. Different classes of anti-WNT signaling therapeutics are necessary for the treatment of APC/CTNNB1-, RNF43/ZNRF3/RSPO2/RSPO3- and ROR1-types of human cancers. By contrast, Dickkopf-related protein 1 (DKK1), SOST and glycogen synthase kinase 3β (GSK3β) are targets of pro-WNT signaling therapy, and anti-DKK1 (BHQ880 and DKN-01) and anti-SOST (blosozumab, BPS804 and romosozumab) monoclonal antibodies are being tested in clinical trials for cancer patients and osteoporotic post-menopausal women. WNT-targeting therapeutics have also been applied as reagents for in vitro stem-cell processing in the field of regenerative medicine.

Mutations in DVL1 cause an osteosclerotic form of Robinow syndrome

Robinow syndrome (RS) is a phenotypically and genetically heterogeneous condition that can be caused by mutations in genes encoding components of the non-canonical Wnt signaling pathway. In contrast, germline mutations that act to increase canonical Wnt signaling lead to distinctive osteosclerotic phenotypes. Here, we identified de novo frameshift mutations in DVL1, a mediator of both canonical and non-canonical Wnt signaling, as the cause of RS-OS, an RS subtype involving osteosclerosis, in three unrelated individuals. The mutations all delete the DVL1 C terminus and replace it, in each instance, with a novel, highly basic sequence. We showed the presence of mutant transcript in fibroblasts from one individual with RS-OS and demonstrated unimpaired protein stability with transfected GFP-tagged constructs bearing a frameshift mutation. In vitro TOPFlash assays, in apparent contradiction to the osteosclerotic phenotype, revealed that the mutant allele was less active than the wild-type allele in the canonical Wnt signaling pathway. However, when the mutant and wild-type alleles were co-expressed, canonical Wnt activity was 2-fold higher than that in the wild-type construct alone. This work establishes that DVL1 mutations cause a specific RS subtype, RS-OS, and that the osteosclerosis associated with this subtype might be the result of an interaction between the wild-type and mutant alleles and thus lead to elevated canonical Wnt signaling.