No abstract

De novo variants in the gene encoding cyclin-dependent kinase 13 (CDK13) have been associated with congenital heart defects and intellectual disability (ID). Here, we present the clinical assessment of 15 individuals and report novel de novo missense variants within the kinase domain of CDK13. Furthermore, we describe 2 nonsense variants and a recurrent frame-shift variant. We demonstrate the synthesis of 2 aberrant CDK13 transcripts in lymphoblastoid cells from an individual with a splice-site variant. Clinical characteristics of the individuals include mild to severe ID, developmental delay, behavioral problems, (neonatal) hypotonia and a variety of facial dysmorphism. Congenital heart defects were present in 2 individuals of the current cohort, but in at least 42% of all known individuals. An overview of all published cases is provided and does not demonstrate an obvious genotype-phenotype correlation, although 2 individuals harboring a stop codons at the end of the kinase domain might have a milder phenotype. Overall, there seems not to be a clinically recognizable facial appearance. The variability in the phenotypes impedes an à vue diagnosis of this syndrome and therefore genome-wide or gene-panel driven genetic testing is needed. Based on this overview, we provide suggestions for clinical work-up and management of this recently described ID syndrome.

Objective: We performed a 1-year evaluation of a novel strategy of simultaneously analyzing single nucleotide variants (SNVs), copy number variants (CNVs) and copynumber-neutral Absence-of-Heterozygosity from Whole Exome Sequencing (WES) data for prenatal diagnosis of fetuses with ultrasound (US) anomalies and a noncausative QF-PCR result.Methods: After invasive diagnostics, whole exome parent-offspring trio-sequencing with exome-wide CNV analysis was performed in pregnancies with fetal US anomalies and a non-causative QF-PCR result (WES-CNV). On request, additional SNV-analysis, restricted to (the) requested gene panel(s) only (with the option of whole exome SNV-analysis afterward) was performed simultaneously (WES-CNV/ SNV) or as rapid SNV-re-analysis, following a normal CNV analysis. Results:In total, 415 prenatal samples were included. Following a non-causative QF-PCR result, WES-CNV analysis was initially requested for 74.3% of the chorionic villus (CV) samples and 45% of the amniotic fluid (AF) samples. In case WES-CNV analysis did not reveal a causative aberration, SNV-re-analysis was requested in 41.7% of the CV samples and 17.5% of the AF samples. All initial analyses could be finished within 2 weeks after sampling. For SNV-re-analysis during pregnancy, turn-around-times (TATs) varied between one and 8 days.The data described in this paper were presented orally at the ISPD meeting in Montreal in June 2022, and won the "Best presenter" prize. Genetics and Genomics.

Results: Inhibition of PKR increased mineralization (p<0.001; fig.1). TNF-a þ IL-17A induced PKR-dependent NFkB translocation to the nucleus in MC3T3-E1 cells after 1 hour ( fig.2). Treatment of MC3T3-E1 cells with 1mM PKRi for 7-days resulted in an increase in the mRNA expression of Phospho1 (2.2-fold; p<0.05), ALP (3.9-fold; p<0.01), and BGLAP (2.2-fold; p<0.01). Treatment with 2.4mM PKRi resulted in an enhanced effect with increases in mRNA expression of Phospho1 (5.5fold; p<0.05), ALP (3.7-fold; p<0.01), and BGLAP (8.32-fold; p<0.01). In contrast, treatment with 1mM PKRi decreased OPG (1.9-fold; p<0.01) and RUNX2 (2-fold; p<0.01) mRNA expression. Interestingly, DMSO (0.005%) also reduced OPG and RUNX2 expression. I.A injection of DMSO (0.5%) caused an increase in OARSI bone scores (6.4-fold; p<0.01) and extensive joint damage compared to contralateral knees or 1% ethanol controls (4-fold; p¼0.05). PKRi (223mM in DMSO) reduced bone changes (5-fold; p<0.05). I.A injection of DMSO altered several gait parameters indicative of pain (days 1-7, the maximum contact (maximum intensity) (p<0.01), print width (P<0.05) and mean print intensity (p<0.05) were reduced compared to baseline values) whereas treatment with PKRi alleviated this, showing increased maximum contact (maximum intensity) (p<0.05 vs DMSO).Conclusions: This study reveals that PKR signaling is induced in osteoblasts by inflammatory cytokine treatment, and that inhibition of this pathway increases the initialization and progression of mineralization in vitro. By day 7, inhibition of PKR resulted in a mature osteoblast phenotype with increased BGLAP and reduced RUNX2 expression. In vivo, PKRi reduced DMSO-induced bone remodeling, inflammation and degeneration and reduced abnormal gait indicative of pain. Since PKRi is dissolved in DMSO, careful consideration of vehicle effects is required since DMSO has a clear negative impact on joint health; importantly PKRi abrogates this effect. Collectively, this data shows a clear role for PKR in bone homeostasis. Therefore, targeted inhibition of PKR activity may provide novel therapies for the treatment of musculoskeletal diseases, such as osteoarthritis, where bone changes drive the pathology. UNRAVELING THE ROLE OF WWP2 IN OSTEOARTHRITIS PATHOPHYSIOLOGY

Purpose: Articular cartilage is an intricate and remarkable tissue found within synovial joints. It is essential for providing low-friction and load bearing during movement, resulting in pain-free mobility. Chondrocytes are the sole cell population present within the articular cartilage and play a critical role in tissue homeostasis. As the cellular building blocks of cartilage, they direct the synthesis and maintenance of this tissues proteoglycan-rich collagenous extracellular matrix (ECM), which in turn confers the mechanical properties required for cartilage to withstand shear and compressive loadings generated about 1000's of times per day. The cartilage ECM is enriched for negatively charged proteoglycans, specifically aggrecan. The abundance of these large aggregating proteoglycans results in increased tissue hydration and in the context of a collagen network (mainly type II); confers unique strength and shape to the articular cartilage, providing structural support and load resistance. Interestingly, previous research examining the effect of ablating superficial chondrocytes on the integrity of articular cartilage in mice knee joints surprisingly observed that chondrocyte depletion did not result in cartilage degradation. Expanding on this finding, the current study depleted chondrocytes within all 3 zones of articular cartilage (superficial, transitional, deep) to investigate how its compositional and structural integrity was affected. Furthermore, it was investigated if and how articular chondrocyte depletion relates to changes in cartilage biomechanical properties.Methods: Acan-CreER T2 and Gt(Rosa) DTA mice were bred to obtain Acan-CreER T2þ/-: Gt(Rosa) DTAþ/offspring, hereafter referred to as ACAN mice. Through tamoxifen treatment, diphtheria toxin (DTA) expression was induced in aggrecan expressing cells (chondrocytes) leading to cell death. Knee joints were harvested 5 and 9 weeks post-DTA induction and samples were analyzed histologically and biomechanically. Safranin-O/Fast Green staining was performed, and tissue structure was compared to wild-type (WT) control mice Acan-CreER T2-/-: Gt(Rosa) DTAþ/-. Biomechanical testing using a 3-axis mechanical tester (Biomomentum) was carried out on the articular surface of the femoral condyles to obtain their spatial distribution of stiffness. Using automated mapping and a pre-defined set of standardized positions and boundaries, stiffness and thickness measurements were quantified and compared to the WT controls. Long-term histological assessment of knee joints was also carried out 4 and 7 months post-DTA induction. Results: Histological analysis of ACAN mice knee joints demonstrated a regional lack of proteoglycan staining and decreased chondrocyte numbers when compared to the WT control ( Figure 1). Differences in cartilage structure between the WT and ACAN mice were evident by 5weeks post-DTA induction. By 9 weeks post-DTA induction, the results suggest a partial rescue of phenotype (proteoglycan staining, chondrocyte numbers) within the articular carti...

No abstract

Dysregulation of Wingless and Int‐1 (Wnt) signaling has been strongly associated with development and progression of osteoarthritis (OA). Here, we set out to investigate the independent effects of either mechanical stress (MS) or inflammation on Wnt signaling in human neocartilage pellets, and to relate this Wnt signaling to OA pathophysiology. OA synovium‐conditioned media (OAS‐CM) was collected after incubating synovium from human end‐stage OA joints for 24 h in medium. Cytokine levels in the OAS‐CM were determined with a multiplex immunoassay (Luminex). Human neocartilage pellets were exposed to 20% MS, 2% OAS‐CM or 1 ng/mL Interleukin‐1β (IL‐1β). Effects on expression levels of Wnt signaling members were determined by reverse transcription‐quantitative polymerase chain reaction. Additionally, the expression of these members in articular cartilage from human OA joints was analyzed in association with joint space narrowing (JSN) and osteophyte scores. Protein levels of IL‐1β, IL‐6, IL‐8, IL‐10, tumor necrosis factor α, and granulocyte‐macrophage colony‐stimulating factor positively correlated with each other. MS increased noncanonical WNT5A and FOS expression. In contrast, these genes were downregulated upon stimulation with OAS‐CM or IL‐1β. Furthermore, Wnt inhibitors DKK1 and FRZB decreased in response to OAS‐CM or IL‐1β exposure. Finally, expression of WNT5A in OA articular cartilage was associated with increased JSN scores, but not osteophyte scores. Our results demonstrate that MS and inflammatory stimuli have opposite effects on canonical and noncanonical Wnt signaling in human neocartilage. Considering the extent to which MS and inflammation contribute to OA in individual patients, we hypothesize that targeting specific Wnt pathways offers a more effective, individualized approach.

No abstract