Early-Onset Osteoporosis: Molecular Analysis in Large Cohort and Focus on the PLS3 Gene.

Osteoporosis is a skeletal disorder characterized by abnormal bone microarchitecture and low bone mineral density (BMD), responsible for an increased risk of fractures and skeletal fragility. It is a common pathology of the aging population. However, when osteoporosis occurs in children or young adults, it strongly suggests an underlying genetic etiology. Over the past two decades, several genes have been identified as responsible for this particular kind of considered monogenic early-onset osteoporosis (EOOP) or juvenile osteoporosis, the main ones being COL1A1, COL1A2, LRP5, LRP6, WNT1, and more recently PLS3. In this study, the objective was to characterize a large cohort of patients diagnosed with primary osteoporosis and to establish its diagnosis yield. The study included 577 patients diagnosed with primary osteoporosis and its diagnosis yield was established. To this end, next-generation sequencing (NGS) of a panel of 21 genes known to play a role in bone fragility was carried out. A genetic etiology was explained in about 18% of cases, while the others remain unexplained. The most frequently identified gene associated with EOOP is LRP5, which was responsible for 8.2% of the positive results (47 patients). As unexpected, 17 patients (2.9%) had a variant in PLS3 which encodes plastin 3. Alterations of PLS3 are associated with dominant X-linked osteoporosis, an extremely rare disease. Given the rarity of this disease, we focused on it. It was observed that males were more affected than females, but it is noteworthy that three females with a particularly severe phenotype were identified. Of these three, two had a variant in an additional gene involved in EOP, illustrating the probable existence of digenism. We significantly increase the number of variants potentially associated with EOOP, especially in PLS3. The results of our study demonstrate that molecular analysis in EOOP is beneficial and useful.

AI-based diagnosis and phenotype - Genotype correlations in syndromic craniosynostoses.

Apert (AS), Crouzon (CS), Muenke (MS), Pfeiffer (PS), and Saethre Chotzen (SCS) are among the most frequently diagnosed syndromic craniosynostoses. The aims of this study were (1) to train an innovative model using artificial intelligence (AI)-based methods on two-dimensional facial frontal, lateral, and external ear photographs to assist diagnosis for syndromic craniosynostoses vs controls, and (2) to screen for genotype/phenotype correlations in AS, CS, and PS. We included retrospectively and prospectively, from 1979 to 2023, all frontal and lateral pictures of patients genetically diagnosed with AS, CS, MS, PS and SCS syndromes. After a deep learning-based preprocessing, we extracted geometric and textural features and used XGboost (eXtreme Gradient Boosting) to classify patients. The model was tested on an independent international validation set of genetically confirmed patients and non-syndromic controls. Between 1979 and 2023, we included 2228 frontal and lateral facial photographs corresponding to 541 patients. In all, 70.2% [0.593-0.797] (p < 0.001) of patients in the validation set were correctly diagnosed. Genotypes linked to a splice donor site of FGFR2 in Crouzon-Pfeiffer syndrome (CPS) caused a milder phenotype in CPS. Here we report a new method for the automatic detection of syndromic craniosynostoses using AI.

Optic nerve elongation during fronto-facial surgery for Crouzon syndrome: 3D quantification and clinical implications.

OBJECTIVE: Fronto-facial monobloc advancement with internal distraction (FFMBA) is a key procedure in the management of syndromic craniosynostoses. FFMBA involves circumferential dissection and linear enlargement of the orbit, potentially leading to mechanical stress on the optic nerve (ON). Several reports of transient vision loss during the distraction process led us to investigate ON shape modifications during facial advancement, with the aim to potentially refine current clinical guidelines on postoperative management and the distraction schedule. METHODS: Twenty-six patients with Crouzon syndrome were included in this study. ONs were segmented on pre- and postoperative CT scans. Distraction amplitudes, linear and curved lengths, and cross-section diameters of the ON were assessed along the main axis of the nerve. A two-level hierarchical multivariate linear model was used to screen for factors associated with ON morphology. RESULTS: The mean age at FFMBA was 4.4 ± 3.8 years. Two patients presented with transient impaired vision during distraction. The final mean fronto-orbital and temporo-zygomatic distraction amplitudes were 18 ± 4 mm and 18 ± 6 mm, respectively. At the end of distraction, ONs were elongated (+1.8 mm for curved lengths, p = 0.013), and their mean cross-section was reduced (-1.9 mm2, p < 0.001) in the proximal intraorbital portion (first 15 mm). In the 2 patients with visual symptoms, functional impairment was associated with ON area reduction (OR 0.487, p < 0.001) and increased temporo-zygomatic distraction amplitude (OR 2.240, p < 0.001). CONCLUSIONS: ON was elongated during FFMBA, with proximal diameter reduction. Transient visual impairment with normal fundus examination during distraction seemed to have a morphological basis, based on 2 cases. These results suggest the importance of vision monitoring associated with fundus examination during distraction, and advocate for early extubation after FFMBA to allow clinical follow-up.

Evaluation of bone density and microarchitecture in adult patients with X-linked hypophosphatemic rickets: A pilot longitudinal study.

X-linked Hypophosphatemia (XLH) is the most common type of inherited rickets. Although the clinical features are well characterized, bone structure, mineralization, and biomechanical properties are poorly known. Our aim was to analyze bone properties in the appendicular and axial skeleton of adults with XLH. In this observational case-control study, each affected patient (N = 14; 9 females; age 50 ± 15 years) was matched by sex, age and body mass index to a minimum of two healthy controls (N = 34). Dual-energy X-ray Absorptiometry (DXA) analyses revealed that areal bone mineral density (aBMD) was higher in XLH patients at the lumbar spine (Z score mean difference = +2.47 SD, P value = 1.4 × 10-3). Trabecular Bone Score was also higher at the lumbar spine (P value = 1.0 × 10-4). High Resolution peripheral Quantitative Computed Tomography (HRpQCT) demonstrated that bone cross-sectional area was larger at the distal radius (P value = 6 × 10-3). Total and trabecular volumetric BMD were lower at both sites. Trabecular bone volume fraction was also lower with fewer trabecular numbers at both sites. However, bone strength evaluated by micro-finite element analyzes revealed unaffected bone stiffness and maximum failure load. Evaluation of bone mineralization with aBMD by DXA at the distal radius correlated with vBMD by HRpQCT measurements at both sites. PTH levels were inversely correlated with trabecular vBMD and BV/TV at the tibia. We then followed a subset of nine patients (median follow-up of 4 years) and reassessed HRpQCT. At the tibia, we observed a greater decrease than expected from an age and sex standardized normal population in total and cortical vBMD as well as a trabecularization of the cortical compartment. In conclusion, in adult patients with XLH, bone mineral density is high at the axial skeleton but low at the appendicular skeleton. With time, microarchitectural alterations worsen. We propose that noninvasive evaluation methods of bone mineralization such as DXA including the radius should be part of the management of XLH patients. Larger studies are needed to evaluate the clinical significance of BMD changes in XLH patients under conventional or targeted therapies.

Novel variant in LRP6 associated with unusual and severe clinical presentation: Case report.

Low-density lipoprotein receptor-related protein 6 (LRP6) is a co-receptor of the Wnt signaling pathway, which plays an essential role in various biological activities during embryonic and postnatal development. LRP6 is exceptionally associated with rare diseases and always with autosomal dominant inheritance. Here we report a familial phenotype of high bone mass associated with skeletal anomalies and oligodontia but also persistent left superior vena cava, inguinal hernia, hepatic cysts, abnormal posterior fossa and genital malformations. Molecular analysis revealed a novel heterozygous variant, NM_002336.2: c.724T>C, p.(Trp242Arg), in affected individuals. This variant is located in the first ß-propellant motif of LRP6, to which sclerostin (SOST) and dickkopf1 (DKK1), two LRP6 co-receptor inhibitors and various Wnt ligands bind. According to the literature and integrating data from structural analysis, this variant distorts the binding of SOST and DKK1, thus leading to overactivation of Wnt signaling pathways involved in osteoblast differentiation. This novel heterozygous variant in LRP6 underlies the role of LRP6 in skeletal and dental disorders as well as, probably, cardiac, cerebral and genital developments.

The Osteoblast Transcriptome in Developing Zebrafish Reveals Key Roles for Extracellular Matrix Proteins Col10a1a and Fbln1 in Skeletal Development and Homeostasis.

Zebrafish are now widely used to study skeletal development and bone-related diseases. To that end, understanding osteoblast differentiation and function, the expression of essential transcription factors, signaling molecules, and extracellular matrix proteins is crucial. We isolated Sp7-expressing osteoblasts from 4-day-old larvae using a fluorescent reporter. We identified two distinct subpopulations and characterized their specific transcriptome as well as their structural, regulatory, and signaling profile. Based on their differential expression in these subpopulations, we generated mutants for the extracellular matrix protein genes col10a1a and fbln1 to study their functions. The col10a1a-/- mutant larvae display reduced chondrocranium size and decreased bone mineralization, while in adults a reduced vertebral thickness and tissue mineral density, and fusion of the caudal fin vertebrae were observed. In contrast, fbln1-/- mutants showed an increased mineralization of cranial elements and a reduced ceratohyal angle in larvae, while in adults a significantly increased vertebral centra thickness, length, volume, surface area, and tissue mineral density was observed. In addition, absence of the opercle specifically on the right side was observed. Transcriptomic analysis reveals up-regulation of genes involved in collagen biosynthesis and down-regulation of Fgf8 signaling in fbln1-/- mutants. Taken together, our results highlight the importance of bone extracellular matrix protein genes col10a1a and fbln1 in skeletal development and homeostasis.

Long-term follow-up of severe autosomal recessive SP7-related bone disorder.

The SP7 gene encodes a zinc finger transcription factor (Osterix), which is a member of the Sp subfamily of sequence-specific DNA-binding proteins, playing an important role in osteoblast differentiation and maturation. SP7 pathogenic variants have been described in association with different allelic disorders. Monoallelic or biallelic SP7 variants cause Osteogenesis imperfecta type XII (OI12), a very rare condition characterized by recurrent fractures, skeletal deformities, undertubulation of long bones, hearing loss, no dentinogenesis imperfecta, and white sclerae. Monoallelic or biallelic SP7 variants may also cause sclerotic skeletal dysplasias (SSD), partially overlapping with Juvenile Paget's disease and craniodiaphyseal dysplasia, characterized by skull hyperostosis, long bones sclerosis, large ribs and clavicles, and possible recurrent fractures. Here, we report the long-term follow-up of an 85-year-old woman presenting with a complex bone disorder including features of either OI12 (bone fragility with multiple fractures, severe deformities and short stature) or SSD (striking skull hyperostosis with optic atrophy, very large ribs and clavicles and long bones sclerosis). Exome sequencing showed previously undescribed biallelic loss of function variants in the SP7 gene: NM_001173467.2(SP7): c.359_362del, p.(Asp120Valfs*11); NM_001173467.2(SP7): c.1163_1174delinsT, p.(Pro388Leufs*33). RT-qPCR confirmed a severely reduced SP7 transcription compared to controls. Our report provides new insights into the clinical and molecular features and long-term outcome of SP7-related bone disorders (SP7-BD), suggesting a continuum phenotypic spectrum characterized by bone fragility, undertubulation of long bones, scoliosis, and very heterogeneous bone mineral density ranging from osteoporosis to osteosclerosis.

Clinico-biological refinement of BCL11B-related disorder and identification of an episignature: A series of 20 unreported individuals.

PURPOSE: BCL11B-related disorder (BCL11B-RD) arises from rare genetic variants within the BCL11B gene, resulting in a distinctive clinical spectrum encompassing syndromic neurodevelopmental disorder, with or without intellectual disability, associated with facial features and impaired immune function. This study presents an in-depth clinico-biological analysis of 20 newly reported individuals with BCL11B-RD, coupled with a characterization of genome-wide DNA methylation patterns of this genetic condition. METHODS: Through an international collaboration, clinical and molecular data from 20 individuals were systematically gathered, and a comparative analysis was conducted between this series and existing literature. We further scrutinized peripheral blood DNA methylation profile of individuals with BCL11B-RD, contrasting them with healthy controls and other neurodevelopmental disorders marked by established episignature. RESULTS: Our findings unveil rarely documented clinical manifestations, notably including Rubinstein-Taybi-like facial features, craniosynostosis, and autoimmune disorders, all manifesting within the realm of BCL11B-RD. We refine the intricacies of T cell compartment alterations of BCL11B-RD, revealing decreased levels naive CD4+ T cells and recent thymic emigrants while concurrently observing an elevated proportion of effector-memory expressing CD45RA CD8+ T cells (TEMRA). Finally, a distinct DNA methylation episignature exclusive to BCL11B-RD is unveiled. CONCLUSION: This study serves to enrich our comprehension of the clinico-biological landscape of BCL11B-RD, potentially furnishing a more precise framework for diagnosis and follow-up of individuals carrying pathogenic BCL11B variant. Moreover, the identification of a unique DNA methylation episignature offers a valuable diagnosis tool for BCL11B-RD, thereby facilitating routine clinical practice by empowering physicians to reevaluate variants of uncertain significance within the BCL11B gene.

Dysregulation of MicroRNAs in Adult Osteogenesis Imperfecta: The miROI Study.

As epigenetic regulators of gene expression, circulating micro-RiboNucleic Acids (miRNAs) have been described in several bone diseases as potential prognostic markers. The aim of our study was to identify circulating miRNAs potentially associated with the severity of osteogenesis imperfecta (OI) in three steps. We have screened by RNA sequencing for the miRNAs that were differentially expressed in sera of a small group of OI patients versus controls and then conducted a validation phase by RT-qPCR analysis of sera of a larger patient population. In the first phase of miROI, we found 79 miRNAs that were significantly differentially expressed. We therefore selected 19 of them as the most relevant. In the second phase, we were able to validate the significant overexpression of 8 miRNAs in the larger OI group. Finally, we looked for a relationship between the level of variation of the validated miRNAs and the clinical characteristics of OI. We found a significant difference in the expression of two microRNAs in those patients with dentinogenesis imperfecta. After reviewing the literature, we found 6 of the 8 miRNAs already known to have a direct action on bone homeostasis. Furthermore, the use of a miRNA-gene interaction prediction model revealed a 100% probability of interaction between 2 of the 8 confirmed miRNAs and COL1A1 and/or COL1A2. This is the first study to establish the miRNA signature in OI, showing a significant modification of miRNA expression potentially involved in the regulation of genes involved in the physiopathology of OI. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Lrp5 p.Val667Met Variant Compromises Bone Mineral Density and Matrix Properties in Osteoporosis.

Early-onset osteoporosis (EOOP) has been associated with several genes, including LRP5, coding for a coreceptor in the Wnt pathway. Variants in LRP5 were also described in osteoporosis pseudoglioma syndrome, combining severe osteoporosis and eye abnormalities. Genomewide-association studies (GWAS) showed that LRP5 p.Val667Met (V667M) variant is associated with low bone mineral density (BMD) and increased fractures. However, despite association with a bone phenotype in humans and knockout mice, the impact of the variant in bone and eye remains to be investigated. Here, we aimed to evaluate the bone and ocular impact of the V667M variant. We recruited 11 patients carrying the V667M variant or other loss-of-function variants of LRP5 and generated an Lrp5 V667M mutated mice. Patients had low lumbar and hip BMD Z-score and altered bone microarchitecture evaluated by HR-pQCT compared with an age-matched reference population. Murine primary osteoblasts from Lrp5 V667M mice showed lower differentiation capacity, alkaline phosphatase activity, and mineralization capacity in vitro. Ex vivo, mRNA expression of Osx, Col1, and osteocalcin was lower in Lrp5 V667M bones than controls (all p < 0.01). Lrp5 V667M 3-month-old mice, compared with control (CTL) mice, had decreased BMD at the femur (p < 0.01) and lumbar spine (p < 0.01) with normal microarchitecture and bone biomarkers. However, Lrp5 V667M mice revealed a trend toward a lower femoral and vertebral stiffness (p = 0.14) and had a lower hydroxyproline/proline ratio compared with CTL, (p = 0.01), showing altered composition and quality of the bone matrix. Finally, higher tortuosity of retinal vessels was found in the Lrp5 V667M mice and unspecific vascular tortuosity in two patients only. In conclusion, Lrp5 V667M variant is associated with low BMD and impaired bone matrix quality. Retinal vascularization abnormalities were observed in mice. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Pathogenic variants in the paired-related homeobox 1 gene (PRRX1) cause craniosynostosis with incomplete penetrance.

PURPOSE: Studies have previously implicated PRRX1 in craniofacial development, including demonstration of murine Prrx1 expression in the preosteogenic cells of the cranial sutures. We investigated the role of heterozygous missense and loss-of-function (LoF) variants in PRRX1 associated with craniosynostosis. METHODS: Trio-based genome, exome, or targeted sequencing were used to screen PRRX1 in patients with craniosynostosis; immunofluorescence analyses were used to assess nuclear localization of wild-type and mutant proteins. RESULTS: Genome sequencing identified 2 of 9 sporadically affected individuals with syndromic/multisuture craniosynostosis, who were heterozygous for rare/undescribed variants in PRRX1. Exome or targeted sequencing of PRRX1 revealed a further 9 of 1449 patients with craniosynostosis harboring deletions or rare heterozygous variants within the homeodomain. By collaboration, 7 additional individuals (4 families) were identified with putatively pathogenic PRRX1 variants. Immunofluorescence analyses showed that missense variants within the PRRX1 homeodomain cause abnormal nuclear localization. Of patients with variants considered likely pathogenic, bicoronal or other multisuture synostosis was present in 11 of 17 cases (65%). Pathogenic variants were inherited from unaffected relatives in many instances, yielding a 12.5% penetrance estimate for craniosynostosis. CONCLUSION: This work supports a key role for PRRX1 in cranial suture development and shows that haploinsufficiency of PRRX1 is a relatively frequent cause of craniosynostosis.

Early-onset gout and rare deficient variants of the lactate dehydrogenase D gene.

OBJECTIVES: To investigate whether the lactate dehydrogenase D (LDHD) gene deficiency causes juvenile-onset gout. METHODS: We used whole-exome sequencing for two families and a targeted gene-sequencing panel for an isolated patient. d-lactate dosages were analysed using ELISA. RESULTS: We demonstrated linkage of juvenile-onset gout to homozygous carriage of three rare distinct LDHD variants in three different ethnicities. In a Melanesian family, the variant was (NM_153486.3: c.206C>T; rs1035398551) and, as compared with non-homozygotes, homozygotes had higher hyperuricaemia (P = 0.02), lower fractional clearance of urate (P = 0.002), and higher levels of d-lactate in blood (P = 0.04) and urine (P = 0.06). In a second, Vietnamese, family, very severe juvenile-onset gout was linked to homozygote carriage of an undescribed LDHD variant (NM_153486.3: c.1363dupG) leading to a frameshift followed by a stop codon, p.(AlaGly432fsTer58). Finally, a Moroccan man, with early-onset and high d-lactaturia, whose family was unavailable for testing, was homozygous for another rare LDHD variant [NM_153486.3: c.752C>T, p.(Thr251Met)]. CONCLUSION: Rare, damaging LDHD variants can cause autosomal recessive early-onset gout, the diagnosis of which can be suspected by measuring high d-lactate levels in the blood and/or urine.

Clinical interest of molecular study in cases of isolated midline craniosynostosis.

In some cases of infants with apparently isolated single-suture synostosis, an underlying variant can be found. We aimed to determine the molecular substratum in isolated sagittal and metopic craniosynostosis. To this end, we included all infants who presented isolated midline synostosis (sagittal or metopic) and had undergone surgery at the craniosynostosis national reference center of Lyon University Hospital. All infants were examined by a multidisciplinary team including neurosurgeons, clinical geneticists and neuropsychologist. Among 101 infants tested, 13 carried a total of 13 variants; that is, 12.9% of the infants carried a variant in genes known to be involved in craniosynostosis. Seven infants carried SMAD6 variants, 2 in FGFR2, 1 in TWIST1, one in FREM1, one in ALX4 and one in TCF12. All variants were detected at the heterozygous level in genes associated with autosomal dominant craniosynostosis. Also, neurodevelopmental testing showed especially delayed acquisition of language in children with than without variants in SMAD6. In conclusion, a high percentage of young children with isolated midline craniosynostosis, especially in isolated trigonocephaly, carried SMAD6 variants. The interpretation of the pathogenicity of the genes must take into account incomplete penetrance, usually observed in craniosynostosis. Our results highlight the interest of molecular analysis in the context of isolated sagittal and/or metopic craniosynostosis to enhance an understanding of the pathophysiology of midline craniosynostosis.

wnt11f2 Zebrafish, an Animal Model for Development and New Insights in Bone Formation.

Wnt signaling is a key regulator of osteoblast differentiation and mineralization in humans and animals, mediated by the canonical Wnt/ß-catenin and noncanonical signaling pathways. Both pathways are crucial in regulating osteoblastogenesis and bone formation. The zebrafish silberblick (slb) carries a mutation in wnt11f2, a gene that contributes to embryonic morphogenesis; however, its role in bone morphology is unknown. wnt11f2 was originally known as wnt11; it was recently reclassified to avoid confusion in comparative genetics and disease modeling. The goal of this review is to summarize the characterization of the wnt11f2 zebrafish mutant and to deliver some new insights concerning its role in skeletal development. In addition to the previously described defects in early development in this mutant as well as craniofacial dysmorphia, we show an increase in tissue mineral density in the heterozygous mutant that points to a possible role of wnt11f2 in high bone mass phenotypes.

Neurodevelopmental and Epilepsy Phenotypes in Individuals With Missense Variants in the Voltage-Sensing and Pore Domains of KCNH5.

BACKGROUND AND OBJECTIVES: KCNH5 encodes the voltage-gated potassium channel EAG2/Kv10.2. We aimed to delineate the neurodevelopmental and epilepsy phenotypic spectrum associated with de novo KCNH5 variants. METHODS: We screened 893 individuals with developmental and epileptic encephalopathies for KCNH5 variants using targeted or exome sequencing. Additional individuals with KCNH5 variants were identified through an international collaboration. Clinical history, EEG, and imaging data were analyzed; seizure types and epilepsy syndromes were classified. We included 3 previously published individuals including additional phenotypic details. RESULTS: We report a cohort of 17 patients, including 9 with a recurrent de novo missense variant p.Arg327His, 4 with a recurrent missense variant p.Arg333His, and 4 additional novel missense variants. All variants were located in or near the functionally critical voltage-sensing or pore domains, absent in the general population, and classified as pathogenic or likely pathogenic using the American College of Medical Genetics and Genomics criteria. All individuals presented with epilepsy with a median seizure onset at 6 months. They had a wide range of seizure types, including focal and generalized seizures. Cognitive outcomes ranged from normal intellect to profound impairment. Individuals with the recurrent p.Arg333His variant had a self-limited drug-responsive focal or generalized epilepsy and normal intellect, whereas the recurrent p.Arg327His variant was associated with infantile-onset DEE. Two individuals with variants in the pore domain were more severely affected, with a neonatal-onset movement disorder, early-infantile DEE, profound disability, and childhood death. DISCUSSION: We describe a cohort of 17 individuals with pathogenic or likely pathogenic missense variants in the voltage-sensing and pore domains of Kv10.2, including 14 previously unreported individuals. We present evidence for a putative emerging genotype-phenotype correlation with a spectrum of epilepsy and cognitive outcomes. Overall, we expand the role of EAG proteins in human disease and establish KCNH5 as implicated in a spectrum of neurodevelopmental disorders and epilepsy.

Diagnosis and Outcomes of Late-Onset Wilson's Disease: A National Registry-Based Study.

BACKGROUND: Wilson's disease (WD) is usually diagnosed in children and young adults; limited data exist on late-onset forms. OBJECTIVE: The aim was to characterize the clinical and paraclinical presentations, therapeutic management, and outcomes in patients with late-onset WD. METHODS: Patients diagnosed with WD after age 40 years were identified from the French Wilson's Disease Registry (FWDR). Clinical, laboratory, and imaging findings and treatment were reported at diagnosis and last follow-up. RESULTS: Forty-five patients were identified (median age: 49, range: 40-64) and placed in three groups according to their clinical presentation: neurological (n = 20, median diagnostic delay: 20 months), hepatic (n = 13, diagnostic delay: 12 months), and family screening (n = 12), all confirmed genetically. Six neurological patients had an atypical presentation (1 torticollis, 2 writer's cramps, 2 functional movement disorders, and 1 isolated dysarthria), without T2/fluid-attenuated inversion recovery brain magnetic resonance imaging (MRI) hyperintensities; 5 of 6 had no Kayser-Fleischer ring (KFR); 5 of 6 had liver involvement. In the neurological group, 84% of patients improved clinically, and 1 developed copper deficiency. In the hepatic group, 77% had cirrhosis; 6 patients required liver transplantation. In the screened group, 43% had mild liver involvement; 3 were not treated and remained stable; 24-h urinary copper excretion was normal in 33% of patients at diagnosis. CONCLUSIONS: In the FWDR, late-onset forms of WD affect 8% of patients, mostly with neurological presentations. Thirty percent of the neurological forms were atypical (isolated long-lasting symptoms, inconspicuous brain MRI, no KFR). With personalized treatment, prognosis was good. This study emphasized that WD should be suspected at any age and even in cases of atypical presentation. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Novel pathogenic variants in SLCO2A1 causing autosomal dominant primary hypertrophic osteoarthropathy.

Primary hypertrophic osteoarthropathy (PHO), or pachydermoperiostosis, is characterized by a clinical association including digital clubbing, periostosis and pachydermia. SLCO2A1 and HPGD genes are both responsible for PHO. The pathology is classically defined as an autosomal recessive disorder with clinical variability ranging from a mild to more severe phenotype. However, the hypothesis for an autosomal dominant form suggested for a long time was only demonstrated for the first time in 2021 for SLCO2A1. We aimed to detect a second pathogenic variant by a deep sequencing of the entire SLCO2A1 and HPGD genes, associated with functional transcription analysis in PHO patients harboring only one heterozygous variant. Among 10 PHO patients, 4 presented a single pathogenic or probably pathogenic novel variant in SLCO2A1 in heterozygous status (NM_005630.3: c.234+1G > A, c.1523_1524delCT, c.1625G > A and c.31delC), and the others carried homozygous pathogenic variants. For heterozygous forms, we found no additional pathogenic variant in HPGD or SLCO2A1. PHO can be a dominant form with age at disease onset later than that for the recessive form. This dominant form is not exceptional in young adults. In conclusion, both modes of inheritance of PHO explain the clinical variability and the difference in age at disease onset. Molecular analysis is especially required in the incomplete form to distinguish it from secondary hypertrophic osteoarthropathy.

A Zebrafish Mutant in the Extracellular Matrix Protein Gene efemp1 as a Model for Spinal Osteoarthritis.

Osteoarthritis is a degenerative articular disease affecting mainly aging animals and people. The extracellular matrix protein Efemp1 was previously shown to have higher turn-over and increased secretion in the blood serum, urine, and subchondral bone of knee joints in osteoarthritic patients. Here, we use the zebrafish as a model system to investigate the function of Efemp1 in vertebrate skeletal development and homeostasis. Using in situ hybridization, we show that the efemp1 gene is expressed in the brain, the pharyngeal arches, and in the chordoblasts surrounding the notochord at 48 hours post-fertilization. We generated an efemp1 mutant line, using the CRISPR/Cas9 method, that produces a severely truncated Efemp1 protein. These mutant larvae presented a medially narrower chondrocranium at 5 days, which normalized later at day 10. At age 1.5 years, µCT analysis revealed an increased tissue mineral density and thickness of the vertebral bodies, as well as a decreased distance between individual vertebrae and ruffled borders of the vertebral centra. This novel defect, which has, to our knowledge, never been described before, suggests that the efemp1 mutant represents the first zebrafish model for spinal osteoarthritis.