Zebrafish as a model to investigate a biallelic gain-of-function variant in MSGN1, associated with a novel skeletal dysplasia syndrome.

BACKGROUND/OBJECTIVES: Rare genetic disorders causing specific congenital developmental abnormalities often manifest in single families. Investigation of disease-causing molecular features are most times lacking, although these investigations may open novel therapeutic options for patients. In this study, we aimed to identify the genetic cause in an Iranian patient with severe skeletal dysplasia and to model its molecular function in zebrafish embryos. RESULTS: The proband displays short stature and multiple skeletal abnormalities, including mesomelic dysplasia of the arms with complete humero-radio-ulna synostosis, arched clavicles, pelvic dysplasia, short and thin fibulae, proportionally short vertebrae, hyperlordosis and mild kyphosis. Exome sequencing of the patient revealed a novel homozygous c.374G > T, p.(Arg125Leu) missense variant in MSGN1 (NM_001105569). MSGN1, a basic-Helix-Loop-Helix transcription factor, plays a crucial role in formation of presomitic mesoderm progenitor cells/mesodermal stem cells during early developmental processes in vertebrates. Initial in vitro experiments show protein stability and correct intracellular localization of the novel variant in the nucleus and imply retained transcription factor function. To test the pathogenicity of the detected variant, we overexpressed wild-type and mutant msgn1 mRNA in zebrafish embryos and analyzed tbxta (T/brachyury/ntl). Overexpression of wild-type or mutant msgn1 mRNA significantly reduces tbxta expression in the tailbud compared to control embryos. Mutant msgn1 mRNA injected embryos depict a more severe effect, implying a gain-of-function mechanism. In vivo analysis on embryonic development was performed by clonal msgn1 overexpression in zebrafish embryos further demonstrated altered cell compartments in the presomitic mesoderm, notochord and pectoral fin buds. Detection of ectopic tbx6 and bmp2 expression in these embryos hint to affected downstream signals due to Msgn1 gain-of-function. CONCLUSION: In contrast to loss-of-function effects described in animal knockdown models, gain-of-function of MSGN1 explains the only mildly affected axial skeleton of the proband and rather normal vertebrae. In this context we observed notochord bending and potentially disruption of pectoral fin buds/upper extremity after overexpression of msgn1 in zebrafish embryos. The latter might result from Msgn1 function on mesenchymal stem cells or on chondrogenesis in these regions. In addition, we detected ectopic tbx6 and bmp2a expression after gain of Msgn1 function in zebrafish, which are interconnected to short stature, congenital scoliosis, limb shortening and prominent skeletal malformations in patients. Our findings highlight a rare, so far undescribed skeletal dysplasia syndrome associated with a gain-of-function mutation in MSGN1 and hint to its molecular downstream effectors.

Risk Factors for Reoperation Following Single-Level Cervical Disc Arthroplasty as Utilized in a Representative Sample of United States Clinical Practice: A Retrospective PearlDiver Study.

STUDY DESIGN: Retrospective Cohort. OBJECTIVES: Most data regarding cervical disc arthroplasty (CDA) outcomes are from highly controlled clinical trials with strict inclusion/exclusion criteria. This study aimed to identify risk factors for CDA reoperation, in "real world" clinical practice using a national insurance claims database. METHODS: The PearlDiver database was queried for patients (2010-2020) who underwent a subsequent cervical procedure following a single-level CDA. Patients with less than 2 years follow-up were excluded. Primary outcome was to evaluate risk factors for reoperation. Secondary outcome was to evaluate the types of reoperations. Risk factors were compared using descriptive statistics. Multivariate regression analyses were used to ascertain the association among risk factors and reoperation. RESULTS: Of 14,202 patients who met inclusion criteria, 916 (6.5%) underwent reoperation. Patients undergoing reoperation were slightly older with higher Elixhauser Comorbidity Index (ECI) scores, however both were not risk factors for reoperation. Patients with diagnoses such as smoking, myelopathy, inflammatory disorders, spinal deformity, trauma, or a history of prior cervical surgery were at greater risk for reoperation. No association was found between the year of index surgery and reoperation risk. The most common reoperation procedure was cervical fusion. CONCLUSIONS: As billed for in the United States since 2010, CDA was associated with a 6.5% reoperation rate over a mean follow-up time of 5.3 years. Smoking, myelopathy, inflammatory disorders, spinal deformity, and a history of prior cervical surgery or trauma are risk factors for reoperation following CDA. Though patients who underwent a reoperation were older, age was not found to be an independent risk factor for a subsequent procedure.

Single-Level Anterolateral and Posterior Interbody Fusion Techniques are Associated with Equivalent Long-Term Lumbar Reoperations.

STUDY DESIGN: Retrospective Cohort Study. OBJECTIVE: This study compares reoperation rates and complications following single-level ALIF/LLIF and TLIF/PLIF. SUMMARY OF BACKGROUND DATA: Anterior lumbar interbody fusion (ALIF), lateral lumbar interbody fusion (LLIF), transforaminal lumbar interbody fusion (TLIF), and posterior lumbar interbody fusion (PLIF) are widely used for degenerative disc disease. Lumbar interbody fusions have high rates of reoperation primarily related to adjacent segment pathology and pseudarthrosis. METHODS: The PearlDiver database was queried for patients (2010-2021) who had single-level ALIF/LLIF or TLIF/PLIF with same-day, single-level posterior instrumentation. ALIF/LLIF were combined and similarly, TLIF/PLIF were combined, given how these operations are indistinguishable with Current Procedural Terminology (CPT) coding. All patients were followed for ≥2 years and excluded if they had spinal traumas, fractures, infections, or neoplasms prior to surgery. The two cohorts, ALIF/LLIF and TLIF/PLIF, were matched 1:1 based on age, sex, Elixhauser-Comorbidity Index (ECI), smoking status, and diabetes. The primary outcome was the incidence of all-cause subsequent lumbar operations. Secondary outcomes included 90-day surgical complications. RESULTS: After 1:1 matching, each cohort contained 14,070 patients. All-cause subsequent lumbar operations were nearly identical at 5-year follow-up (9.4% ALIF/LLIF vs. 9.5% TLIF/PLIF, P=0.91) (Table 2). Survival analysis using all-cause subsequent lumbar operations as the endpoint showed an equivalent 10-year survival rate of 86.0% (95%CI: 85.2-86.8) (Figure 1). Within 90 days, TLIF/PLIF had more infections (1.3% vs. 1.7%, P=0.007) and dural injuries (0.2% vs. 0.4%, P=0.001). There was no difference in wound dehiscence, hardware complications, or medical complications (Table 3). CONCLUSION: As utilized in real-world clinical practice, single-level anterolateral versus posterior approaches for interbody fusion have no effect on long term reoperation rates.

Risk of Postoperative Sciatic Nerve Palsy After Posterior Acetabular Fracture Fixation: Does Patient Position Matter?

OBJECTIVES: To determine whether the prone or lateral position is associated with postoperative sciatic nerve palsy in posterior acetabular fracture fixation. DESIGN: Retrospective cohort study. SETTING: Three Level I trauma centers. PATIENTS: Patients with acetabular fractures treated with a posterior approach (n = 1045). INTERVENTION: Posterior acetabular fixation in the prone or lateral positions. OUTCOME MEASUREMENTS: The primary outcome was the prevalence of postoperative sciatic nerve palsy by position. Secondary outcomes were risk factors for nerve palsy, using multiple regression analysis and propensity scoring. RESULTS: The rate of postoperative sciatic nerve palsy was 9.5% (43/455) in the prone position and 1.5% (9/590) in the lateral position ( P < 0.001). Intraoperative blood loss and surgical duration were significantly higher for patients who developed a postoperative sciatic nerve palsy. Subgroup analysis showed that position did not influence palsy prevalence in posterior wall fractures. For other fracture patterns, propensity score analysis demonstrated a significantly increased odds ratio of palsy in the prone position [aOR 7.14 (2.22-23.00); P = 0.001]. CONCLUSIONS: With the exception of posterior wall fracture patterns, the results of this study suggest that factors associated with increased risk for postoperative sciatic nerve palsy after a posterior approach are fractures treated in the prone position, increased blood loss, and prolonged operative duration. These risks should be considered alongside the other goals (eg, reduction quality) of acetabular fracture surgery when choosing surgical positioning. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.