Null and missense mutations of ERI1 cause a recessive phenotypic dichotomy in humans.

ERI1 is a 3'-to-5' exoribonuclease involved in RNA metabolic pathways including 5.8S rRNA processing and turnover of histone mRNAs. Its biological and medical significance remain unclear. Here, we uncover a phenotypic dichotomy associated with bi-allelic ERI1 variants by reporting eight affected individuals from seven unrelated families. A severe spondyloepimetaphyseal dysplasia (SEMD) was identified in five affected individuals with missense variants but not in those with bi-allelic null variants, who showed mild intellectual disability and digital anomalies. The ERI1 missense variants cause a loss of the exoribonuclease activity, leading to defective trimming of the 5.8S rRNA 3' end and a decreased degradation of replication-dependent histone mRNAs. Affected-individual-derived induced pluripotent stem cells (iPSCs) showed impaired in vitro chondrogenesis with downregulation of genes regulating skeletal patterning. Our study establishes an entity previously unreported in OMIM and provides a model showing a more severe effect of missense alleles than null alleles within recessive genotypes, suggesting a key role of ERI1-mediated RNA metabolism in human skeletal patterning and chondrogenesis.

Novel compound heterozygous mutations in UHRF1 are associated with atypical immunodeficiency, centromeric instability and facial anomalies syndrome with distinctive genome-wide DNA hypomethylation.

Immunodeficiency, centromeric instability and facial anomalies (ICF) syndrome is in most cases caused by mutations in either DNA methyltransferase (DNMT)3B, zinc finger and BTB domain containing 24, cell division cycle associated 7 or helicase lymphoid-specific. However, the causative genes of a few ICF patients remain unknown. We, herein, identified ubiquitin-like with plant homeodomain and really interesting new gene finger domains 1 (UHRF1) as a novel causative gene of one such patient with atypical symptoms. This patient is a compound heterozygote for two previously unreported mutations in UHRF1: c.886C > T (p.R296W) and c.1852C > T (p.R618X). The R618X mutation plausibly caused nonsense-mediated decay, while the R296W mutation changed the higher order structure of UHRF1, which is indispensable for the maintenance of CG methylation along with DNMT1. Genome-wide methylation analysis revealed that the patient had a centromeric/pericentromeric hypomethylation, which is the main ICF signature, but also had a distinctive hypomethylation pattern compared to patients with the other ICF syndrome subtypes. Structural and biochemical analyses revealed that the R296W mutation disrupted the protein conformation and strengthened the binding affinity of UHRF1 with its partner LIG1 and reduced ubiquitylation activity of UHRF1 towards its ubiquitylation substrates, histone H3 and proliferating cell nuclear antigen -associated factor 15 (PAF15). We confirmed that the R296W mutation causes hypomethylation at pericentromeric repeats by generating the HEK293 cell lines that mimic the patient's UHRF1 molecular context. Since proper interactions of the UHRF1 with LIG1, PAF15 and histone H3 are essential for the maintenance of CG methylation, the mutation could disturb the maintenance process. Evidence for the importance of the UHRF1 conformation for CG methylation in humans is, herein, provided for the first time and deepens our understanding of its role in regulation of CG methylation.

Dyssegmental dysplasia Rolland-Desbuquois type is caused by pathogenic variants in HSPG2 - a founder haplotype shared in five patients.

Dyssegmental dysplasia (DD) is a severe skeletal dysplasia comprised of two subtypes: lethal Silverman-Handmaker type (DDSH) and nonlethal Rolland-Desbuquois type (DDRD). DDSH is caused by biallelic pathogenic variants in HSPG2 encoding perlecan, whereas the genetic cause of DDRD remains undetermined. Schwartz-Jampel syndrome (SJS) is also caused by biallelic pathogenic variants in HSPG2 and is an allelic disorder of DDSH. In SJS and DDSH, 44 and 8 pathogenic variants have been reported in HSPG2, respectively. Here, we report that five patients with DDRD carried four pathogenic variants in HSPG2: c.9970 G > A (p.G3324R), c.559 C > T (p.R187X), c7006 + 1 G > A, and c.11562 + 2 T > G. Two patients were homozygous for p.G3324R, and three patients were heterozygous for p.G3324R. Haplotype analysis revealed a founder haplotype spanning 85,973 bp shared in the five patients. SJS, DDRD, and DDSH are allelic disorders with pathogenic variants in HSPG2.

Heterozygous mutations in the straitjacket region of the latency-associated peptide domain of TGFB2 cause Camurati-Engelmann disease type II.

Camurati-Engelmann disease (CED) is an autosomal dominant bone dysplasia characterized by progressive hyperostosis of the skull base and diaphyses of the long bones. CED is further divided into two subtypes, CED1 and CED2, according to the presence or absence of TGFB1 mutations, respectively. In this study, we used exome sequencing to investigate the genetic cause of CED2 in three pedigrees and identified two de novo heterozygous mutations in TGFB2 among the three patients. Both mutations were located in the region of the gene encoding the straitjacket subdomain of the latency-associated peptide (LAP) of pro-TGF-ß2. Structural simulations of the mutant LAPs suggested that the mutations could cause significant conformational changes and lead to a reduction in TGF-ß2 inactivation. An activity assay confirmed a significant increase in TGF-ß2/SMAD signaling. In vitro osteogenic differentiation experiment using iPS cells from one of the CED2 patients showed significantly enhanced ossification, suggesting that the pathogenic mechanism of CED2 is increased activation of TGF-ß2 by loss-of-function of the LAP. These results, in combination with the difference in hyperostosis patterns between CED1 and CED2, suggest distinct functions between TGFB1 and TGFB2 in human skeletal development and homeostasis.

Impact of vessel volume on thermodilution measurements in patients with coronary microvascular dysfunction.

BACKGROUND: Two invasive methods are available to estimate microvascular resistance: bolus and continuous thermodilution. Comparative studies have revealed a lack of concordance between measurements of microvascular resistance obtained through these techniques. AIMS: This study aimed to examine the influence of vessel volume on bolus thermodilution measurements. METHODS: We prospectively included patients with angina with non-obstructive coronary arteries (ANOCA) undergoing bolus and continuous thermodilution assessments. All patients underwent coronary CT angiography to extract vessel volume. Coronary microvascular dysfunction was defined as coronary flow reserve (CFR) < 2.0. Measurements of absolute microvascular resistance (in Woods units) and index of microvascular resistance (IMR) were compared before and after volumetric adjustment. RESULTS: Overall, 94 patients with ANOCA were included in this study. The mean age was 64.7 ± 10.8 years, 48% were female, and 19% had diabetes. The prevalence of CMD was 16% based on bolus thermodilution, while continuous thermodilution yielded a prevalence of 27% (Cohen's Kappa 0.44, 95% CI 0.23-0.65). There was no correlation in microvascular resistance between techniques (r = 0.17, 95% CI -0.04 to 0.36, p = 0.104). The adjustment of IMR by vessel volume significantly increased the agreement with absolute microvascular resistance derived from continuous thermodilution (r = 0.48, 95% CI 0.31-0.63, p < 0.001). CONCLUSIONS: In patients with ANOCA, invasive methods based on coronary thermodilution yielded conflicting results for the assessment of CMD. Adjusting IMR with vessel volume improved the agreement with continuous thermodilution for the assessment of microvascular resistance. These findings strongly suggest the importance of considering vessel volume when interpreting bolus thermodilution assessment.

A quantitative model used to compare within-host SARS-CoV-2, MERS-CoV, and SARS-CoV dynamics provides insights into the pathogenesis and treatment of SARS-CoV-2.

The scientific community is focused on developing antiviral therapies to mitigate the impacts of the ongoing novel coronavirus disease 2019 (COVID-19) outbreak. This will be facilitated by improved understanding of viral dynamics within infected hosts. Here, using a mathematical model in combination with published viral load data, we compare within-host viral dynamics of SARS-CoV-2 with analogous dynamics of MERS-CoV and SARS-CoV. Our quantitative analyses using a mathematical model revealed that the within-host reproduction number at symptom onset of SARS-CoV-2 was statistically significantly larger than that of MERS-CoV and similar to that of SARS-CoV. In addition, the time from symptom onset to the viral load peak for SARS-CoV-2 infection was shorter than those of MERS-CoV and SARS-CoV. These findings suggest the difficulty of controlling SARS-CoV-2 infection by antivirals. We further used the viral dynamics model to predict the efficacy of potential antiviral drugs that have different modes of action. The efficacy was measured by the reduction in the viral load area under the curve (AUC). Our results indicate that therapies that block de novo infection or virus production are likely to be effective if and only if initiated before the viral load peak (which appears 2-3 days after symptom onset), but therapies that promote cytotoxicity of infected cells are likely to have effects with less sensitivity to the timing of treatment initiation. Furthermore, combining a therapy that promotes cytotoxicity and one that blocks de novo infection or virus production synergistically reduces the AUC with early treatment. Our unique modeling approach provides insights into the pathogenesis of SARS-CoV-2 and may be useful for development of antiviral therapies.

Predictors of Hypotension After Angiotensin Receptor-Neprilysin Inhibitor Administration in Patients with Heart Failure.

Angiotensin receptor-neprilysin inhibitors (ARNI) are effective against heart failure (HF) with reduced ejection fraction, but hypotension is a significant complication. Predictors of ARNI-associated hypotension remain unclear. This study aimed to determine predictors of hypotension after administering an ARNI to patients with HF accompanied by ARNI.This retrospective multicenter observational study analyzed data from 138 consecutive patients with HF treated with an ARNI between August 2020 and July 2021. Hypotension attributed to an ARNI after treatment was defined as (A) systolic blood pressure (SBP) below the 1st quartile ≤ 25 mmHg, and as (B) absolute SBP ≤ 103 mmHg. SBP was measured at baseline, after ARNI treatment, at first follow-up as outpatients and on day 7 for inpatients. Presence of atrial fibrillation, and greater BUN/Cr ratio, and SBP at baseline were significant independent predictors for hypotension after ARNI administration on multivariate analyses. Among 43 patients with AF, fine f-waves on electrocardiograms were significantly more prevalent in the hypotensive group.A robust reduction in blood pressure after ARNI administration is associated with AF and elevated BUN/Cr. This highlights the need for caution when administering ARNI to patients with HF.

Potential Anti-Mpox Virus Activity of Atovaquone, Mefloquine, and Molnupiravir, and Their Potential Use as Treatments.

BACKGROUND: Mpox virus (MPXV) is a zoonotic orthopoxvirus and caused an outbreak in 2022. Although tecovirimat and brincidofovir are approved as anti-smallpox drugs, their effects in mpox patients have not been well documented. In this study, by a drug repurposing approach, we identified potential drug candidates for treating mpox and predicted their clinical impacts by mathematical modeling. METHODS: We screened 132 approved drugs using an MPXV infection cell system. We quantified antiviral activities of potential drug candidates by measuring intracellular viral DNA and analyzed the modes of action by time-of-addition assay and electron microscopic analysis. We further predicted the efficacy of drugs under clinical concentrations by mathematical simulation and examined combination treatment. RESULTS: Atovaquone, mefloquine, and molnupiravir exhibited anti-MPXV activity, with 50% inhibitory concentrations of 0.51-5.2 µM, which was more potent than cidofovir. Whereas mefloquine was suggested to inhibit viral entry, atovaquone and molnupiravir targeted postentry processes. Atovaquone was suggested to exert its activity through inhibiting dihydroorotate dehydrogenase. Combining atovaquone with tecovirimat enhanced the anti-MPXV effect of tecovirimat. Quantitative mathematical simulations predicted that atovaquone can promote viral clearance in patients by 7 days at clinically relevant drug concentrations. CONCLUSIONS: These data suggest that atovaquone would be a potential candidate for treating mpox.

Breakpoints in complex chromosomal rearrangements correspond to transposase-accessible regions of DNA from mature sperm.

Constitutional complex chromosomal rearrangements (CCRs) are rare cytogenetic aberrations arising in the germline via an unknown mechanism. Here we analyzed the breakpoint junctions of microscopically three-way or more complex translocations using comprehensive genomic and epigenomic analyses. All of these translocation junctions showed submicroscopic genomic complexity reminiscent of chromothripsis. The breakpoints were clustered within small genomic domains with junctions showing microhomology or microinsertions. Notably, all of the de novo cases were of paternal origin. The breakpoint distributions corresponded specifically to the ATAC-seq (assay for transposase-accessible chromatin with sequencing) read data peak of mature sperm and not to other chromatin markers or tissues. We propose that DNA breaks in CCRs may develop in an accessible region of densely packaged chromatin during post-meiotic spermiogenesis.

Selective inhibition of hepatitis B virus internalization by oxysterol derivatives.

Given that the current approved anti-hepatitis B virus (HBV) drugs suppress virus replication and improve hepatitis but cannot eliminate HBV from infected patients, new anti-HBV agents with different mode of action are urgently needed. In this study, we identified a semi-synthetic oxysterol, Oxy185, that can prevent HBV infection in a HepG2-based cell line and primary human hepatocytes. Mechanistically, Oxy185 inhibited the internalization of HBV into cells without affecting virus attachment or replication. We also found that Oxy185 interacted with an HBV entry receptor, sodium taurocholate cotransporting polypeptide (NTCP), and inhibited the oligomerization of NTCP to reduce the efficiency of HBV internalization. Consistent with this mechanism, Oxy185 also inhibited the hepatitis D virus infection, which relies on NTCP-dependent internalization, but not hepatitis A virus infection, and displayed pan-genotypic anti-HBV activity. Following oral administration in mice, Oxy185 showed sustained accumulation in the livers of the mice, along with a favorable liver-to-plasma ratio. Thus, Oxy185 is expected to serve as a useful tool compound in proof-of-principle studies for HBV entry inhibitors with this novel mode of action.

Relationship between coronary volume, myocardial mass, and post-PCI fractional flow reserve.

BACKGROUND: Fractional flow reserve (FFR) measured after percutaneous coronary intervention (PCI) carries prognostic information. Yet, myocardial mass subtended by a stenosis influences FFR. We hypothesized that a smaller coronary lumen volume and a large myocardial mass might be associated with lower post-PCI FFR. AIM: We sought to assess the relationship between vessel volume, myocardial mass, and post-PCI FFR. METHODS: This was a subanalysis with an international prospective study of patients with significant lesions (FFR ≤ 0.80) undergoing PCI. Territory-specific myocardial mass was calculated from coronary computed tomography angiography (CCTA) using the Voronoi's algorithm. Vessel volume was extracted from quantitative CCTA analysis. Resting full-cycle ratio (RFR) and FFR were measured before and after PCI. We assessed the association between coronary lumen volume (V) and its related myocardial mass (M), and the percent of total myocardial mass (%M) with post-PCI FFR. RESULTS: We studied 120 patients (123 vessels: 94 left anterior descending arteries, 13 left Circumflex arteries, 16 right coronary arteries). Mean vessel-specific mass was 61 ± 23.1 g (%M 39.6 ± 11.7%). The mean post-PCI FFR was 0.88 ± 0.06 FFR units. Post-PCI FFR values were lower in vessels subtending higher mass (0.87 ± 0.05 vs. 0.89 ± 0.07, p = 0.047), and with lower V/M ratio (0.87 ± 0.06 vs. 0.89 ± 0.07, p = 0.02). V/M ratio correlated significantly with post-PCI RFR and FFR (RFR r = 0.37, 95% CI: 0.21-0.52, p < 0.001 and FFR r = 0.41, 95% CI: 0.26-0.55, p < 0.001). CONCLUSION: Post-PCI RFR and FFR are associated with the subtended myocardial mass and the coronary volume to mass ratio. Vessels with higher mass and lower V/M ratio have lower post-PCI RFR and FFR.

Should a viral genome stay in the host cell or leave? A quantitative dynamics study of how hepatitis C virus deals with this dilemma.

Virus proliferation involves gene replication inside infected cells and transmission to new target cells. Once positive-strand RNA virus has infected a cell, the viral genome serves as a template for copying ("stay-strategy") or is packaged into a progeny virion that will be released extracellularly ("leave-strategy"). The balance between genome replication and virion release determines virus production and transmission efficacy. The ensuing trade-off has not yet been well characterized. In this study, we use hepatitis C virus (HCV) as a model system to study the balance of the two strategies. Combining viral infection cell culture assays with mathematical modeling, we characterize the dynamics of two different HCV strains (JFH-1, a clinical isolate, and Jc1-n, a laboratory strain), which have different viral release characteristics. We found that 0.63% and 1.70% of JFH-1 and Jc1-n intracellular viral RNAs, respectively, are used for producing and releasing progeny virions. Analysis of the Malthusian parameter of the HCV genome (i.e., initial proliferation rate) and the number of de novo infections (i.e., initial transmissibility) suggests that the leave-strategy provides a higher level of initial transmission for Jc1-n, whereas, in contrast, the stay-strategy provides a higher initial proliferation rate for JFH-1. Thus, theoretical-experimental analysis of viral dynamics enables us to better understand the proliferation strategies of viruses, which contributes to the efficient control of virus transmission. Ours is the first study to analyze the stay-leave trade-off during the viral life cycle and the significance of the replication-release switching mechanism for viral proliferation.

Efficacy of Antiseizure Medications in Wolf-Hirschhorn Syndrome.

Wolf-Hirschhorn syndrome (WHS) is caused by deletion of the terminal region of chromosome 4 short arm and is frequently associated with intractable epilepsy. This article evaluates the clinical features of epileptic seizures in WHS and the therapeutic efficacy of oral antiseizure medications (ASMs). Patients with WHS who were treated for epilepsy at the Saitama Children's Medical Center under 5 years of age were included. WHS was diagnosed based on genetic tests and clinical symptoms. Medical records regarding the age of onset of epilepsy, seizure type, treatment of status epilepticus (SE), and effectiveness of ASMs were retrospectively reviewed. Oral ASMs were considered effective when seizures were reduced by at least 50% compared with the premedication level. Eleven patients were included in the study. The median age at the onset of epilepsy was 9 months (range: 5-32 months). Unknown-onset bilateral tonic-clonic seizure was the most common type of seizure, occurring in 10 patients. Focal clonic seizures occurred in four patients. Ten patients exhibited recurrent episodes of SE, and its frequency during infancy was monthly in eight patients and yearly in two. SE occurrence peaked at 1 year of age and decreased after 3 years of age. The most effective ASM was levetiracetam. Although WHS-associated epilepsy is intractable with frequent SE occurrence during infancy, improvement in seizure control is expected with age. Levetiracetam may be a novel ASM for WHS.

RASopathies and spinal deformities for screening of scoliosis.

BACKGROUND: The RASopathies (Noonan syndrome [NS] and Costello syndrome [CS]) are rare disorders. Although these have been characterized, precise delineation of the differences in the spinal deformities associated with RASopathy has not been described. This study characterized the spinal deformities found in NS and CS and describes a strategy for the screening of scoliosis. METHODS: The clinical records and spinal X-rays of 35 consecutive NS and CS patients were reviewed. Spinal X-rays were assessed to define the presence and progression of scoliosis. Clinical records were examined to identify the risk factors associated with scoliosis. In addition, we investigated the association between clinical records and scoliosis using logistic regression analysis. RESULTS: Twenty-four patients with NS and 11 with CS were included. Nine patients with NS and five with CS showed scoliosis. The mean ± SD age at diagnosis was 12.6 ± 2.4 years in NS and 11.4 ± 2.5 years in CS (p = 0.55), and mean follow-up period was 4.8 ± 2.6 years and 6.3 ± 2.4 years (p = 0.42), respectively. The coronal angular deformity at final follow-up was 27.3 ± 8.5° in NS and 19.4 ± 6.9° in CS (p = 0.030) with a mean annual progression of 2.8 ± 1.1° in NS 1.0 ± 1.0° in CS (p = 0.030). Cardiac disease was present in eight out of nine patients with NS with concomitant scoliosis in NS, and significantly more than in CS (p = 0.007). PTPN11 significantly correlated with scoliosis (odds ratio 12.4 0.035, 95% confidence interval: 1.20-128.00). CONCLUSIONS: Spinal deformity in NS is more severe than in CS. This study identified a relationship between PTPN11 and scoliosis. Therefore, PTPN11 can be used for the screening of scoliosis.

Anti-hepatitis C Virus Activity of Juglorubin Derivatives.

Juglorubin is a natural dye isolated from the culture of Streptomyces sp. 3094, 815, and GW4184. It has been previously synthesized via the biomimetic dimerization of juglomycin C, a plausible genetic precursor. In this study, the derivatives of juglorubin, 1-O-acetyljuglorubin dimethyl ester and juglorubin dimethyl ester, were found to exhibit antiviral activity against hepatitis C virus (HCV) without exerting any remarkable cytotoxicity against host Huh-7 cells. They also inhibited liver X receptor α activation and lipid droplet accumulation in Huh-7 cells. These findings suggest that 1-O-acetyljuglorubin dimethyl ester and juglorubin dimethyl ester targeted the host factors required for HCV production.

Identification of Methylsulochrin as a Partial Agonist for Aryl Hydrocarbon Receptors and Its Antiviral and Anti-inflammatory Activities.

Although aryl hydrocarbon receptors (AhRs) are related to the metabolic pathway of xenobiotics, recent studies have revealed that this receptor is also associated with the life cycle of viruses and inflammatory reactions. For example, flutamide, used to treat prostate cancer, inhibits hepatitis C virus proliferation by acting as an AhR antagonist, and methylated-pelargonidin, an AhR agonist, suppresses pro-inflammatory cytokine production. To discover a novel class of AhR ligands, we screened 1000 compounds derived from fungal metabolites using a reporter assay and identified methylsulochrin as a partial agonist of the aryl hydrocarbon receptor. Methylsulochrin was found to inhibit the production of hepatitis C virus (HCV) in Huh-7.5.1 cells. Methylsulochrin also suppressed the production of interleukin-6 in RAW264.7 cells. Furthermore, a preliminary structure-activity relationship study using sulochrin derivatives was performed. Our findings suggest the use of methylsulochrin derivatives as anti-HCV compounds with anti-inflammatory activity.

Phenotypic and mutational spectrum of ROR2-related Robinow syndrome.

Robinow syndrome is characterized by a triad of craniofacial dysmorphisms, disproportionate-limb short stature, and genital hypoplasia. A significant degree of phenotypic variability seems to correlate with different genes/loci. Disturbances of the noncanonical WNT-pathway have been identified as the main cause of the syndrome. Biallelic variants in ROR2 cause an autosomal recessive form of the syndrome with distinctive skeletal findings. Twenty-two patients with a clinical diagnosis of autosomal recessive Robinow syndrome were screened for variants in ROR2 using multiple molecular approaches. We identified 25 putatively pathogenic ROR2 variants, 16 novel, including single nucleotide variants and exonic deletions. Detailed phenotypic analyses revealed that all subjects presented with a prominent forehead, hypertelorism, short nose, abnormality of the nasal tip, brachydactyly, mesomelic limb shortening, short stature, and genital hypoplasia in male patients. A total of 19 clinical features were present in more than 75% of the subjects, thus pointing to an overall uniformity of the phenotype. Disease-causing variants in ROR2, contribute to a clinically recognizable autosomal recessive trait phenotype with multiple skeletal defects. A comprehensive quantitative clinical evaluation of this cohort delineated the phenotypic spectrum of ROR2-related Robinow syndrome. The identification of exonic deletion variant alleles further supports the contention of a loss-of-function mechanism in the etiology of the syndrome.

Germline-Activating RRAS2 Mutations Cause Noonan Syndrome.

Noonan syndrome (NS) is characterized by distinctive craniofacial appearance, short stature, and congenital heart disease. Approximately 80% of individuals with NS harbor mutations in genes whose products are involved in the RAS/mitogen-activating protein kinase (MAPK) pathway. However, the underlying genetic causes in nearly 20% of individuals with NS phenotype remain unexplained. Here, we report four de novo RRAS2 variants in three individuals with NS. RRAS2 is a member of the RAS subfamily and is ubiquitously expressed. Three variants, c.70_78dup (p.Gly24_Gly26dup), c.216A>T (p.Gln72His), and c.215A>T (p.Gln72Leu), have been found in cancers; our functional analyses showed that these three changes induced elevated association of RAF1 and that they activated ERK1/2 and ELK1. Notably, prominent activation of ERK1/2 and ELK1 by p.Gln72Leu associates with the severe phenotype of the individual harboring this change. To examine variant pathogenicity in vivo, we generated zebrafish models. Larvae overexpressing c.70_78dup (p.Gly24_Gly26dup) or c.216A>T (p.Gln72His) variants, but not wild-type RRAS2 RNAs, showed craniofacial defects and macrocephaly. The same dose injection of mRNA encoding c.215A>T (p.Gln72Leu) caused severe developmental impairments and low dose overexpression of this variant induced craniofacial defects. In contrast, the RRAS2 c.224T>G (p.Phe75Cys) change, located on the same allele with p.Gln72His in an individual with NS, resulted in no aberrant in vitro or in vivo phenotypes by itself. Together, our findings suggest that activating RRAS2 mutations can cause NS and expand the involvement of RRAS2 proto-oncogene to rare germline disorders.

Bi-allelic CSF1R Mutations Cause Skeletal Dysplasia of Dysosteosclerosis-Pyle Disease Spectrum and Degenerative Encephalopathy with Brain Malformation.

Colony stimulating factor 1 receptor (CSF1R) plays key roles in regulating development and function of the monocyte/macrophage lineage, including microglia and osteoclasts. Mono-allelic mutations of CSF1R are known to cause hereditary diffuse leukoencephalopathy with spheroids (HDLS), an adult-onset progressive neurodegenerative disorder. Here, we report seven affected individuals from three unrelated families who had bi-allelic CSF1R mutations. In addition to early-onset HDLS-like neurological disorders, they had brain malformations and skeletal dysplasia compatible to dysosteosclerosis (DOS) or Pyle disease. We identified five CSF1R mutations that were homozygous or compound heterozygous in these affected individuals. Two of them were deep intronic mutations resulting in abnormal inclusion of intron sequences in the mRNA. Compared with Csf1r-null mice, the skeletal and neural phenotypes of the affected individuals appeared milder and variable, suggesting that at least one of the mutations in each affected individual is hypomorphic. Our results characterized a unique human skeletal phenotype caused by CSF1R deficiency and implied that bi-allelic CSF1R mutations cause a spectrum of neurological and skeletal disorders, probably depending on the residual CSF1R function.

De novo heterozygous variants in KIF5B cause kyphomelic dysplasia.

Kyphomelic dysplasia is a heterogeneous group of skeletal dysplasias characterized by severe bowing of the limbs associated with other variable findings, such as narrow thorax and abnormal facies. We searched for the genetic etiology of this disorder. Four individuals diagnosed with kyphomelic dysplasia were enrolled. We performed whole-exome sequencing and evaluated the pathogenicity of the identified variants. All individuals had de novo heterozygous variants in KIF5B encoding kinesin-1 heavy chain: two with c.272A>G:p.(Lys91Arg), one with c.584C>A:p.(Thr195Lys), and the other with c.701G>T:p.(Gly234Val). All variants involved conserved amino acids in or close to the ATPase activity-related motifs in the catalytic motor domain of the KIF5B protein. All individuals had sharp angulation of the femora and humeri, distinctive facial features, and neonatal respiratory distress. Short stature was observed in three individuals. Three developed postnatal osteoporosis with subsequent fractures, two showed brachycephaly, and two were diagnosed with optic atrophy. Our findings suggest that heterozygous KIF5B deleterious variants cause a specific form of kyphomelic dysplasia. Furthermore, alterations in kinesins cause various symptoms known as kinesinopathies, and our findings also extend the phenotypic spectrum of kinesinopathies.