De novo missense variants in exon 9 of SEPHS1 cause a neurodevelopmental condition with developmental delay, poor growth, hypotonia, and dysmorphic features.

Selenophosphate synthetase (SEPHS) plays an essential role in selenium metabolism. Two mammalian SEPHS paralogues, SEPHS1 and SEPHS2, share high sequence identity and structural homology with SEPHS. Here, we report nine individuals from eight families with developmental delay, growth and feeding problems, hypotonia, and dysmorphic features, all with heterozygous missense variants in SEPHS1. Eight of these individuals had a recurrent variant at amino acid position 371 of SEPHS1 (p.Arg371Trp, p.Arg371Gln, and p.Arg371Gly); seven of these variants were known to be de novo. Structural modeling and biochemical assays were used to understand the effect of these variants on SEPHS1 function. We found that a variant at residue Trp352 results in local structural changes of the C-terminal region of SEPHS1 that decrease the overall thermal stability of the enzyme. In contrast, variants of a solvent-exposed residue Arg371 do not impact enzyme stability and folding but could modulate direct protein-protein interactions of SEPSH1 with cellular factors in promoting cell proliferation and development. In neuronal SH-SY5Y cells, we assessed the impact of SEPHS1 variants on cell proliferation and ROS production and investigated the mRNA expression levels of genes encoding stress-related selenoproteins. Our findings provided evidence that the identified SEPHS1 variants enhance cell proliferation by modulating ROS homeostasis. Our study supports the hypothesis that SEPHS1 plays a critical role during human development and provides a basis for further investigation into the molecular mechanisms employed by SEPHS1. Furthermore, our data suggest that variants in SEPHS1 are associated with a neurodevelopmental disorder.

The challenge of hypophosphatasia diagnosis in adults: results from the HPP International Working Group Literature Surveillance.

Hypophosphatasia (HPP) is an inborn error of metabolism caused by reduced or absent activity of the tissue non-specific alkaline phosphatase (TNSALP) enzyme, resulting from pathogenic variants in the ALPL gene. Clinical presentation of HPP is highly variable, including lethal and severe forms in neonates and infants, a benign perinatal form, mild forms manifesting in adulthood, and odonto-HPP. Diagnosis of HPP remains a challenge in adults, as signs and symptoms may be mild and non-specific. Disease presentation varies widely; there are no universal signs or symptoms, and the disease often remains underdiagnosed or misdiagnosed, particularly by clinicians who are not familiar with this rare disorder. The absence of diagnosis or a delayed diagnosis may prevent optimal management for patients with this condition. Formal guidelines for the diagnosis of adults with HPP do not exist, complicating efforts for consistent diagnosis. To address this issue, the HPP International Working Group selected 119 papers that explicitly address the diagnosis of HPP in adults through a Medline, Medline In-Process, and Embase search for the terms "hypophosphatasia" and "HPP," and evaluated the pooled prevalence of 17 diagnostic characteristics, initially selected by a group of HPP clinical experts, in eligible studies and in patients included in these studies. Six diagnostic findings showed a pooled prevalence value over 50% and were considered for inclusion as major diagnostic criteria. Based on these results and according to discussion and consideration among members of the Working Group, we finally defined four major diagnostic criteria and five minor diagnostic criteria for HPP in adults. Authors suggested the integrated use of the identified major and minor diagnostic criteria, which either includes two major criteria, or one major criterion and two minor criteria, for the diagnosis of HPP in adults.

Hypophosphatasia diagnosis: current state of the art and proposed diagnostic criteria for children and adults.

BACKGROUND: This manuscript provides a summary of the current evidence to support the criteria for diagnosing a child or adult with hypophosphatasia (HPP). The diagnosis of HPP is made on the basis of integrating clinical features, laboratory profile, radiographic features of the condition, and DNA analysis identifying the presence of a pathogenic variant of the tissue nonspecific alkaline phosphatase gene (ALPL). Often, the diagnosis of HPP is significantly delayed in both adults and children, and updated diagnostic criteria are required to keep pace with our evolving understanding regarding the relationship between ALPL genotype and associated HPP clinical features. METHODS: An International Working Group (IWG) on HPP was formed, comprised of a multidisciplinary team of experts from Europe and North America with expertise in the diagnosis and management of patients with HPP. Methodologists (Romina Brignardello-Petersen and Gordon Guyatt) and their team supported the IWG and conducted systematic reviews following the GRADE methodology, and this provided the basis for the recommendations. RESULTS: The IWG completed systematic reviews of the literature, including case reports and expert opinion papers describing the phenotype of patients with HPP. The published data are largely retrospective and include a relatively small number of patients with this rare condition. It is anticipated that further knowledge will lead to improvement in the quality of genotype-phenotype reporting in this condition. CONCLUSION: Following consensus meetings, agreement was reached regarding the major and minor criteria that can assist in establishing a clinical diagnosis of HPP in adults and children.

Proposed diagnostic criteria for the diagnosis of hypophosphatasia in children and adolescents: results from the HPP International Working Group.

Hypophosphatasia (HPP) is a rare inborn error of metabolism that presents variably in both age of onset and severity. HPP is caused by pathogenic variants in the ALPL gene, resulting in low activity of tissue nonspecific alkaline phosphatase (TNSALP). Patients with HPP tend have a similar pattern of elevation of natural substrates that can be used to aid in diagnosis. No formal diagnostic guidelines currently exist for the diagnosis of this condition in children, adolescents, or adults. The International HPP Working Group is a comprised of a multidisciplinary team of experts from Europe and North America who have expertise in the diagnosis and management of patients with HPP. This group reviewed 93 papers through a Medline, Medline In-Process, and Embase search for the terms "HPP" and "hypophosphatasia" between 2005 and 2020 and that explicitly address either the diagnosis of HPP in children, clinical manifestations of HPP in children, or both. Two reviewers independently evaluated each full-text publication for eligibility and studies were included if they were narrative reviews or case series/reports that concerned diagnosis of pediatric HPP or included clinical aspects of patients diagnosed with HPP. This review focused on 15 initial clinical manifestations that were selected by a group of clinical experts.The highest agreement in included literature was for pathogenic or likely pathogenic ALPL variant, elevation of natural substrates, and early loss of primary teeth. The highest prevalence was similar, including these same three parameters and including decreased bone mineral density. Additional parameters had less agreement and were less prevalent. These were organized into three major and six minor criteria, with diagnosis of HPP being made when two major or one major and two minor criteria are present.

The Global ALPL gene variant classification project: Dedicated to deciphering variants.

BACKGROUND: Hypophosphatasia (HPP) is an inherited multisystem disorder predominantly affecting the mineralization of bones and teeth. HPP is caused by pathogenic variants in ALPL, which encodes tissue non-specific alkaline phosphatase (TNSALP). Variants of uncertain significance (VUS) cause diagnostic delay and uncertainty amongst patients and health care providers. RESULTS: The ALPL gene variant database (https://alplmutationdatabase.jku.at/) is an open-access archive for interpretation of the clinical significance of variants reported in ALPL. The database contains coding and non-coding variants, including single nucleotide variants, insertions/deletions and structural variants affecting coding or non-coding sequences of ALPL. Each variant in the database is displayed with details explaining the corresponding pathogenicity, and all reported genotypes and phenotypes, including references. In 2021, the ALPL gene variant classification project was established to reclassify VUS and continuously assess and update genetic, phenotypic, and functional variant information in the database. For this purpose, the database provides a unique submission system for clinicians, geneticists, genetic counselors, and researchers to submit VUS within ALPL for classification. An international, multidisciplinary consortium of HPP experts has been established to reclassify the submitted VUS using a multi-step process adhering to the stringent ACMG/AMP variant classification guidelines. These steps include a clinical phenotype assessment, deep literature research including artificial intelligence technology, molecular genetic assessment, and in-vitro functional testing of variants in a co-transfection model to measure ALP residual activity. CONCLUSION: This classification project and the ALPL gene variant database will serve the global medical community, widen the genotypic and phenotypic HPP spectrum by reporting and characterizing new ALPL variants based on ACMG/AMP criteria and thus facilitate improved genetic counseling and medical decision-making for affected patients and families. The project may also serve as a gold standard framework for multidisciplinary collaboration for variant interpretation in other rare diseases.

Jansen-de Vries syndrome: Expansion of the PPM1D clinical and phenotypic spectrum in 34 families.

Jansen-de Vries syndrome (JdVS) is a neurodevelopmental condition attributed to pathogenic variants in Exons 5 and 6 of PPM1D. As the full phenotypic spectrum and natural history remain to be defined, we describe a large cohort of children and adults with JdVS. This is a retrospective cohort study of 37 individuals from 34 families with disease-causing variants in PPM1D leading to JdVS. Clinical data were provided by treating physicians and/or families. Of the 37 individuals, 27 were male and 10 female, with median age 8.75 years (range 8 months to 62 years). Four families document autosomal dominant transmission, and 32/34 probands were diagnosed via exome sequencing. The facial gestalt, including a broad forehead and broad mouth with a thin and tented upper lip, was most recognizable between 18 and 48 months of age. Common manifestations included global developmental delay (35/36, 97%), hypotonia (25/34, 74%), short stature (14/33, 42%), constipation (22/31, 71%), and cyclic vomiting (6/35, 17%). Distinctive personality traits include a hypersocial affect (21/31, 68%) and moderate-to-severe anxiety (18/28, 64%). In conclusion, JdVS is a clinically recognizable neurodevelopmental syndrome with a characteristic personality and distinctive facial features. The association of pathogenic variants in PPM1D with cyclic vomiting bears not only medical attention but also further pathogenic and mechanistic evaluation.

Approach to the Patient: Pharmacological Therapies for Fracture Risk Reduction in Adults With Osteogenesis Imperfecta.

CONTEXT: Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility largely caused by defects in structure, synthesis, or post-translational processing of type I collagen. The effectiveness of medications used for fracture reduction in adults with OI is understudied and practice recommendations are not well established. Drugs currently used to improve skeletal health in OI were initially developed to treat osteoporosis. Oral and intravenous bisphosphonates have been shown to improve bone mineral density (BMD) in adults with OI and are commonly used; however, conclusive data confirming fracture protection are lacking. Similarly, teriparatide appears to increase BMD, an effect that seems to be limited to individuals with type I OI. The role of denosumab, abaloparatide, romosozumab, and estradiol/testosterone in adult OI have not been systematically studied. Anti-sclerostin agents and transforming growth factor-beta antagonists are under investigation in clinical trials. OBJECTIVE: This review summarizes current knowledge on pharmacologic treatment options for reducing fracture risk in adults with OI. METHODS: A PubMed online database search of all study types published in the English language using the terms "osteogenesis imperfecta," "OI," and "brittle bone disease" was performed in June 2022. Articles screened were restricted to adults. Additional sources were identified through manual searches of reference lists. CONCLUSION: Fracture rates are elevated in adults with OI. Although clinical trial data are limited, bisphosphonates and teriparatide may be useful in improving BMD. Further research is needed to develop medications for adults with OI that will lead to definite fracture rate reduction.

Development of a Multidisciplinary Clinic for Patients with Ehlers Danlos Syndromes: Considerations and Strategies.

Ehlers-Danlos Syndromes (EDS) is a group of connective tissue disorders often encountered within rheumatology clinics and is associated with several overlapping symptoms, which may require attention from other medical subspecialities. Barriers exist to implementing multidisciplinary care for EDS, including a lack of knowledge, comfort, and time managing EDS. In the absence of multidisciplinary care, patients are often forced to self-coordinate care. This can lead to gaps in care and a lack of clarity of medical ownership over the patient's care. Integrated multidisciplinary clinics are sorely needed, but the development and implementation of such clinics is limited by resources and personnel. As such, the development of a multidisciplinary clinic can be daunting and may serve to discourage providers with competencies in EDS from attempting to develop this service. In this editorial, we share our experiences in developing a multidisciplinary clinic for EDS at a moderately-sized children's hospital, relying on several core disciplines with established EDS clinical loads (ie, rheumatology, cardiology, genetics, and psychology). We discuss considerations for the expansion of this service, pitfalls, and barriers throughout the development of the clinic, and our rationale underlying our process-related decisions. Development of a greater number of multidisciplinary EDS clinics, even in the potential absence of larger institutional support, is both possible and imperative for improving EDS care globally.

Insurance denials and diagnostic rates in a pediatric genomic research cohort.

PURPOSE: This study aimed to assess the amount and types of clinical genetic testing denied by insurance and the rate of diagnostic and candidate genetic findings identified through research in patients who faced insurance denials. METHODS: Analysis consisted of review of insurance denials in 801 patients enrolled in a pediatric genomic research repository with either no previous genetic testing or previous negative genetic testing result identified through cross-referencing with insurance prior-authorizations in patient medical records. Patients and denials were also categorized by type of insurance coverage. Diagnostic findings and candidate genetic findings in these groups were determined through review of our internal variant database and patient charts. RESULTS: Of the 801 patients analyzed, 147 had insurance prior-authorization denials on record (18.3%). Exome sequencing and microarray were the most frequently denied genetic tests. Private insurance was significantly more likely to deny testing than public insurance (odds ratio = 2.03 [95% CI = 1.38-2.99] P = .0003). Of the 147 patients with insurance denials, 53.7% had at least 1 diagnostic or candidate finding and 10.9% specifically had a clinically diagnostic finding. Fifty percent of patients with clinically diagnostic results had immediate medical management changes (5.4% of all patients experiencing denials). CONCLUSION: Many patients face a major barrier to genetic testing in the form of lack of insurance coverage. A number of these patients have clinically diagnostic findings with medical management implications that would not have been identified without access to research testing. These findings support re-evaluation of insurance carriers' coverage policies.

Recurrent FOXP4 nonsense variant in two unrelated patients: Association with neurodevelopmental disease and congenital diaphragmatic hernia.

De novo variants in FOXP4 were recently associated with a neurodevelopmental disorder characterized by speech and language delay, growth abnormalities, hypotonia, and variable congenital abnormalities, including congenital diaphragmatic hernia, cervical spine abnormalities, strabismus, cryptorchidism, and ptosis. The variant spectrum in this small cohort was limited to de novo missense except for one frameshift, the inheritance of which was unknown. Variants tested in vitro exhibited reduced repressor transcriptional activity, indicating loss of function is the likely mechanism of disease, but only one frameshift variant was reported. Here, we report four affected individuals from two unrelated families heterozygous for a nonsense variant, c.1893C > G, p.Tyr631*, in FOXP4. The phenotype of the affected children includes developmental delay, feeding difficulties in infancy, and similar facial features. In both cases, the variant was inherited from a parent with mild or even subclinical features. Interestingly, one patient presented with congenital diaphragmatic hernia, as reported in two other FOXP4 patients. This report implicates FOXP4 truncating variants in human disease and highlights the wide phenotypic spectrum and variable expressivity.

Gender dysphoria in adolescents with Ehlers-Danlos syndrome.

Objectives: Ehlers-Danlos Syndrome represents a family of heritable connective tissue disorders that include joint hypermobility, tissue fragility, and skin hyperextensibility. Ehlers-Danlos Syndrome presents with clinical sequela across multiple body systems that require multidisciplinary care. Little is known about adolescents with Ehlers-Danlos Syndrome who are transgender and gender diverse. To date, there have been no reports of transgender and gender diverse youth in pediatric patients with Ehlers-Danlos Syndrome. The objective of this study was to characterize transgender and gender diverse adolescents with Ehlers-Danlos Syndrome seen in a pediatric multidisciplinary specialty clinic. Methods: A retrospective chart review was performed and it was found that 28 patients were seen in the Ehlers-Danlos Syndrome multidisciplinary clinic were reported being transgender and gender diverse. Chart review included analysis of all documents in the electronic medical record, including demographic data, gender identity, chosen pronouns, specialty care previously received for Ehlers-Danlos Syndrome, symptoms and conditions related to it, and medications. Results: Of the 166 total adolescents seen in the pediatric multidisciplinary Ehlers-Danlos Syndrome clinic during the study period, 17% reported gender dysphoria. The average age at Ehlers-Danlos Syndrome diagnosis was 13.5 years (range 8-17 years). Most (61%) reported their gender identity as transgender, followed by nonbinary (14%). Most had preferred male (he/him) pronouns (47%), followed by nonbinary (they/them) pronouns (39%). The vast majority reported fatigue (75%), musculoskeletal issues (96%), psychiatric issues (86%), cardiac issues (71%), gastrointestinal issues (68%), and neurologic issues (79%). Conclusions: Here we report the first cohort of transgender and gender diverse adolescents in the Ehlers-Danlos syndrome population and show an association between the two. This report increases awareness for providers who care for patients with Ehlers-Danlos Syndrome. As care for those with Ehlers-Danlos Syndrome is often complex and multidisciplinary, providers should adopt practices of gender-affirming medical care that contribute to improved care and outcomes.

Molecular Diagnoses of X-Linked and Other Genetic Hypophosphatemias: Results From a Sponsored Genetic Testing Program.

X-linked hypophosphatemia (XLH), a dominant disorder caused by pathogenic variants in the PHEX gene, affects both sexes of all ages and results in elevated serum fibroblast growth factor 23 (FGF23) and below-normal serum phosphate. In XLH, rickets, osteomalacia, short stature, and lower limb deformity may be present with muscle pain and/or weakness/fatigue, bone pain, joint pain/stiffness, hearing difficulty, enthesopathy, osteoarthritis, and dental abscesses. Invitae and Ultragenyx collaborated to provide a no-charge sponsored testing program using a 13-gene next-generation sequencing panel to confirm clinical XLH or aid diagnosis of suspected XLH/other genetic hypophosphatemia. Individuals aged ≥6 months with clinical XLH or suspected genetic hypophosphatemia were eligible. Of 831 unrelated individuals tested between February 2019 and June 2020 in this cross-sectional study, 519 (62.5%) individuals had a pathogenic or likely pathogenic variant in PHEX (PHEX-positive). Among the 312 PHEX-negative individuals, 38 received molecular diagnoses in other genes, including ALPL, CYP27B1, ENPP1, and FGF23; the remaining 274 did not have a molecular diagnosis. Among 319 patients with a provider-reported clinical diagnosis of XLH, 88.7% (n = 283) had a reportable PHEX variant; 81.5% (n = 260) were PHEX-positive. The most common variant among PHEX-positive individuals was an allele with both the gain of exons 13-15 and c.*231A>G (3'UTR variant) (n = 66/519). Importantly, over 80% of copy number variants would have been missed by traditional microarray analysis. A positive molecular diagnosis in 41 probands (4.9%; 29 PHEX positive, 12 non-PHEX positive) resulted in at least one family member receiving family testing. Additional clinical or family member information resulted in variant(s) of uncertain significance (VUS) reclassification to pathogenic/likely pathogenic (P/LP) in 48 individuals, highlighting the importance of segregation and clinical data. In one of the largest XLH genetic studies to date, 65 novel PHEX variants were identified and a high XLH diagnostic yield demonstrated broad insight into the genetic basis of XLH. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

A novel likely pathogenic variant in a patient with Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) is a genetic disorder characterized by oculocutaneous albinism and variable pulmonary fibrosis, granulomatous colitis, or immunodeficiency. The diagnosis relies on clinical findings, platelet transmission electron microscopy studies showing absent dense granules, or the identification of a pathogenic genotype in one of 11 associated genes, including HPS1 We report a 2-wk-old male with significant iris transillumination defects, a pale fundus, and mild corectopia found by clinical exome sequencing to have a previously reported pathogenic variant, c.972dupC p.(Met325HisfsTer128), and a variant of uncertain significance, c.1846G>A p.(Glu616Lys), in HPS1 To determine whether his phenotype was consistent with HPS, follow-up studies of whole blood lumiaggregometry and platelet transmission electron microscopy were performed that revealed absent or markedly reduced platelet ATP secretion and virtually absent platelet dense granules, thus confirming the diagnosis. To the best of our knowledge, our case is the first in which the c.1846G>A p.(Glu616Lys) variant is identified in a patient with HPS. In addition, the case also highlights the importance of leveraging appropriate confirmatory clinical testing and reverse phenotyping, which allowed the care team to establish the clinical diagnosis of HPS and reclassify the previously reported variant of uncertain significance in HPS1 to likely pathogenic.

Investigation of ALPL variant states and clinical outcomes: An analysis of adults and adolescents with hypophosphatasia treated with asfotase alfa.

BACKGROUND: Hypophosphatasia (HPP), a rare metabolic disease, can be inherited in an autosomal recessive (biallelic) or an autosomal dominant (monoallelic) manner. Most of the severe, early-onset, frequently lethal HPP in infants is acquired through recessive inheritance; less severe, later-onset, typically nonlethal HPP phenotypes are acquired through either dominant or recessive inheritance. HPP's variable clinical presentation arises from >400 identified ALPL pathogenic variants with likely variable penetrance, especially with autosomal dominant inheritance. This post hoc analysis investigated the relationship between ALPL variant state (biallelic and monoallelic) and clinical outcomes with asfotase alfa in HPP. METHODS: Data were pooled from two phase 2, randomized, open-label studies in adolescents and adults with HPP; one study evaluated the efficacy and safety of different doses of asfotase alfa (n = 25), and the other assessed the pharmacodynamics and safety of asfotase alfa (n = 19). Patients were grouped by ALPL variant state (biallelic or monoallelic). Available data from both studies included ALPL pathogenic variant state, Baseline characteristics, HPP-specific medical history, and Baseline TNSALP substrate levels (inorganic pyrophosphate [PPi] and pyridoxal 5'-phosphate [PLP]) concentrations). Clinical outcomes over 5 years of treatment were available from only the efficacy and safety study. RESULTS: In total, 44 patients with known variant status were included in the pooled analysis (biallelic, n = 30; monoallelic, n = 14). The most common pathogenic variant was c.571G > A (p.Glu191Lys) in biallelic patients (allele frequency: 19/60) and c.1133A > T (p.Asp378Val) in monoallelic patients (allele frequency: 7/28). Median (min, max) Baseline PPi concentrations were significantly higher in patients with a biallelic vs monoallelic variant state (5.3 [2.2, 12.1] vs 4.3 [3.5, 7.4] µM; P = 0.0113), as were Baseline PLP concentrations (221.4 [62.4, 1590.0] vs 75.1 [28.8, 577.0] ng/mL; P= 0.0022). HPP-specific medical history was generally similar between biallelic and monoallelic patients in terms of incidence and type of manifestations; notable exceptions included fractures, which were more common among monoallelic patients, and delayed walking and bone deformities such as abnormally shaped chest and head and bowing of arms or legs, which were more common among biallelic patients. Data from the efficacy and safety study (n = 19) showed that median PPi and PLP concentrations were normalized over 5 years of treatment in patients with both variant states. Median % predicted distance walked on the 6-Minute Walk Test remained within the normal range for monoallelic patients over 4 years of treatment, and improved from below normal (<84%) to normal in biallelic patients. CONCLUSIONS: Although patients with biallelic variants had significantly higher Baseline PPi and PLP levels than monoallelic variants, both groups generally showed similar pretreatment Baseline clinical characteristics. Treatment with asfotase alfa for up to 5 years normalized TNSALP substrate concentrations and improved functional outcomes, with no clear differences between biallelic and monoallelic variant states. This study suggests that patients with HPP have significant disease burden, regardless of ALPL variant state.

Nager syndrome in patient lacking acrofacial dysostosis: Expanding the phenotypic spectrum of SF3B4-related disease.

Nager syndrome epitomizes the acrofacial dysostoses, which are characterized by craniofacial and limb defects. The craniofacial defects include midfacial retrusion, downslanting palpebral fissures, prominent nasal bridge, and micrognathia. Limb malformations typically include hypoplasia or aplasia of radial elements including the thumb. Nager syndrome is caused by haploinsufficiency of SF3B4, encoding a spliceosomal protein called SAP49. Here, we report a patient with a loss of function variant in SF3B4 without acrofacial dysostosis or limb defects, whose reason for referral was developmental and growth delay. This patient is evidence of a broader phenotypic spectrum associated with SF3B4 variants than previously appreciated.

Mutations in GRK2 cause Jeune syndrome by impairing Hedgehog and canonical Wnt signaling.

Mutations in genes affecting primary cilia cause ciliopathies, a diverse group of disorders often affecting skeletal development. This includes Jeune syndrome or asphyxiating thoracic dystrophy (ATD), an autosomal recessive skeletal disorder. Unraveling the responsible molecular pathology helps illuminate mechanisms responsible for functional primary cilia. We identified two families with ATD caused by loss-of-function mutations in the gene encoding adrenergic receptor kinase 1 (ADRBK1 or GRK2). GRK2 cells from an affected individual homozygous for the p.R158* mutation resulted in loss of GRK2, and disrupted chondrocyte growth and differentiation in the cartilage growth plate. GRK2 null cells displayed normal cilia morphology, yet loss of GRK2 compromised cilia-based signaling of Hedgehog (Hh) pathway. Canonical Wnt signaling was also impaired, manifested as a failure to respond to Wnt ligand due to impaired phosphorylation of the Wnt co-receptor LRP6. We have identified GRK2 as an essential regulator of skeletogenesis and demonstrate how both Hh and Wnt signaling mechanistically contribute to skeletal ciliopathies.

A second cohort of CHD3 patients expands the molecular mechanisms known to cause Snijders Blok-Campeau syndrome.

There has been one previous report of a cohort of patients with variants in Chromodomain Helicase DNA-binding 3 (CHD3), now recognized as Snijders Blok-Campeau syndrome. However, with only three previously-reported patients with variants outside the ATPase/helicase domain, it was unclear if variants outside of this domain caused a clinically similar phenotype. We have analyzed 24 new patients with CHD3 variants, including nine outside the ATPase/helicase domain. All patients were detected with unbiased molecular genetic methods. There is not a significant difference in the clinical or facial features of patients with variants in or outside this domain. These additional patients further expand the clinical and molecular data associated with CHD3 variants. Importantly we conclude that there is not a significant difference in the phenotypic features of patients with various molecular disruptions, including whole gene deletions and duplications, and missense variants outside the ATPase/helicase domain. This data will aid both clinical geneticists and molecular geneticists in the diagnosis of this emerging syndrome.

Dual X-ray absorptiometry has limited utility in detecting bone pathology in children with hypophosphatasia: A pooled post hoc analysis of asfotase alfa clinical trial data.

Asfotase alfa is an enzyme replacement therapy approved for treatment of patients with pediatric-onset hypophosphatasia (HPP), a rare, inherited, systemic disease causing impaired skeletal mineralization, short stature, and reduced physical function in children. The role of dual X-ray absorptiometry (DXA) in the assessment of children with HPP has been insufficiently explored. This post hoc analysis included pooled DXA data from 2 open-label, multicenter studies in 19 children with HPP. The study population was aged ≥5 to <18 years and had received asfotase alfa for ≤6.6 years at enrollment (male: 79%; median age at enrollment: 10.4 y [range: 5.9-16.7]; treatment duration: 6.3 y [range: 0.1-6.6]. Baseline height Z-scores indicated short stature (median [min, max]: -1.26 [-6.6, 0]); mean [SD]: -2.30 [1.97]), thus requiring height adjustment of DXA Z-scores. At Baseline, few patients had height-adjusted bone mineral density (BMDht) Z-scores of -2 or less for whole body (n = 3) or lumbar spine (n = 5). In treated patients, mean whole body and lumbar spine BMDhtZ-scores did not change over time, but whole body and lumbar spine height- adjusted bone mineral content (BMCht) Z-scores increased significantly from Baseline to Last Assessment (P ≤ 0.0056). Improvements in Radiographic Global Impression of Change (RGI-C) scale scores correlated significantly with increases in whole body and lumbar spine BMChtZ-scores (P < 0.05) but not BMDhtZ-Scores. Improvements in Rickets Severity Score (RSS) correlated significantly with increases in lumbar spine BMDhtZ-scores and whole body BMCht Z-scores (P < 0.05). No significant correlations were observed between any DXA and bone histomorphometry measure. These findings suggest that DXA BMD Z-scores, which are commonly used in clinical practice, have limited utility in assessing deficient bone mineralization in patients with HPP. Although BMChtZ-scores increased significantly over time with asfotase alfa therapy, the lack of significant changes in more than one DXA parameter suggests that this tool may not be useful in everyday clinical practice. Furthermore, the use of BMC as an independent metric is not typical or recommended by guidelines. Complementary measures, such as skeletal radiographs supplemented with age-appropriate functional assessments, should be considered.

De novo heterozygous missense and loss-of-function variants in CDC42BPB are associated with a neurodevelopmental phenotype.

CDC42BPB encodes MRCKß (myotonic dystrophy-related Cdc42-binding kinase beta), a serine/threonine protein kinase, and a downstream effector of CDC42, which has recently been associated with Takenouchi-Kosaki syndrome, an autosomal dominant neurodevelopmental disorder. We identified 12 heterozygous predicted deleterious variants in CDC42BPB (9 missense, 2 frameshift, and 1 nonsense) in 14 unrelated individuals (confirmed de novo in 11/14) with neurodevelopmental disorders including developmental delay/intellectual disability, autism, hypotonia, and structural brain abnormalities including cerebellar vermis hypoplasia and agenesis/hypoplasia of the corpus callosum. The frameshift and nonsense variants in CDC42BPB are expected to be gene-disrupting and lead to haploinsufficiency via nonsense-mediated decay. All missense variants are located in highly conserved and functionally important protein domains/regions: 3 are found in the protein kinase domain, 2 are in the citron homology domain, and 4 in a 20-amino acid sequence between 2 coiled-coil regions, 2 of which are recurrent. Future studies will help to delineate the natural history and to elucidate the underlying biological mechanisms of the missense variants leading to the neurodevelopmental and behavioral phenotypes.