Mutations in the pleckstrin homology domain of dynamin 2 cause dominant intermediate Charcot-Marie-Tooth disease.

Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous group of peripheral neuropathies. Different chromosomal loci have been linked with three autosomal dominant, 'intermediate' types of CMT: DI-CMTA, DI-CMTB and DI-CMTC. We refined the locus associated with DI-CMTB on chromosome 19p12-13.2 to 4.2 Mb in three unrelated families with CMT originating from Australia, Belgium and North America. After screening candidate genes, we identified unique mutations in dynamin 2 (DNM2) in all families. DNM2 belongs to the family of large GTPases and is part of the cellular fusion-fission apparatus. In transiently transfected cell lines, mutations of DNM2 substantially diminish binding of DNM2 to membranes by altering the conformation of the beta3/beta4 loop of the pleckstrin homology domain. Additionally, in the Australian and Belgian pedigrees, which carry two different mutations affecting the same amino acid, Lys558, CMT cosegregated with neutropenia, which has not previously been associated with CMT neuropathies.

Realveolarization with inhalable mucus-penetrating lipid nanoparticles for the treatment of pulmonary fibrosis in mice.

The stemness loss-associated dysregeneration of impaired alveolar type 2 epithelial (AT2) cells abolishes the reversible therapy of idiopathic pulmonary fibrosis (IPF). We here report an inhalable mucus-penetrating lipid nanoparticle (LNP) for codelivering dual mRNAs, promoting realveolarization via restoring AT2 stemness for IPF treatment. Inhalable LNPs were first formulated with dipalmitoylphosphatidylcholine and our in-house-made ionizable lipids for high-efficiency pulmonary mucus penetration and codelivery of dual messenger RNAs (mRNAs), encoding cytochrome b5 reductase 3 and bone morphogenetic protein 4, respectively. After being inhaled in a bleomycin model, LNPs reverses the mitochondrial dysfunction through ameliorating nicotinamide adenine dinucleotide biosynthesis, which inhibits the accelerated senescence of AT2 cells. Concurrently, pathological epithelial remodeling and fibroblast activation induced by impaired AT2 cells are terminated, ultimately prompting alveolar regeneration. Our data demonstrated that the mRNA-LNP system exhibited high protein expression in lung epithelial cells, which markedly extricated the alveolar collapse and prolonged the survival of fibrosis mice, providing a clinically viable strategy against IPF.

mRNA-Laden Lipid-Nanoparticle-Enabled in Situ CAR-Macrophage Engineering for the Eradication of Multidrug-Resistant Bacteria in a Sepsis Mouse Model.

Sepsis, which is the most severe clinical manifestation of acute infection and has a mortality rate higher than that of cancer, represents a significant global public health burden. Persistent methicillin-resistant Staphylococcus aureus (MRSA) infection and further host immune paralysis are the leading causes of sepsis-associated death, but limited clinical interventions that target sepsis have failed to effectively restore immune homeostasis to enable complete eradication of MRSA. To restimulate anti-MRSA innate immunity, we developed CRV peptide-modified lipid nanoparticles (CRV/LNP-RNAs) for transient in situ programming of macrophages (MΦs). The CRV/LNP-RNAs enabled the delivery of MRSA-targeted chimeric antigen receptor (CAR) mRNA (SasA-CAR mRNA) and CASP11 (a key MRSA intracellular evasion target) siRNA to MΦs in situ, yielding CAR-MΦs with boosted bactericidal potency. Specifically, our results demonstrated that the engineered MΦs could efficiently phagocytose and digest MRSA intracellularly, preventing immune evasion by the "superbug" MRSA. Our findings highlight the potential of nanoparticle-enabled in vivo generation of CAR-MΦs as a therapeutic platform for multidrug-resistant (MDR) bacterial infections and should be confirmed in clinical trials.

Cell-Cell Interactions Enhance Cartilage Zonal Development in 3D Gradient Hydrogels.

Cartilage tissue is characterized by zonal organization with gradual transitions of biochemical and mechanical cues from superficial to deep zones. We previously reported that 3D gradient hydrogels made of polyethylene glycol and chondroitin sulfate can induce zonal-specific responses of chondrocytes, resulting in zonal cartilage formation that mimics native tissues. While the role of cell-matrix interactions has been studied extensively, how cell-cell interactions across different zones influence cartilage zonal development remains unknown. The goal of this study is to harness gradient hydrogels as a tool to elucidate the role of cell-cell interactions in driving cartilage zonal development. When encapsulated in intact gradient hydrogels, chondrocytes exhibited strong zonal-specific responses that mimic native cartilage zonal organization. However, the separate culture of each zone of gradient hydrogels resulted in a significant decrease in cell proliferation and cartilage matrix deposition across all zones, while the trend of zonal dependence remains. Unexpectedly, mixing the coculture of all five zones of hydrogels in the same culture well largely abolished the zonal differences, with all zones behaving similarly to the softest zone. These results suggest that paracrine signal exchange among cells in different zones is essential in driving cartilage zonal development, and a spatial organization of zones is required for proper tissue zonal development. Intact, separate, or coculture groups resulted in distinct gene expression patterns in mechanosensing and cartilage-specific markers, suggesting that cell-cell interactions can also modulate mechanosensing. We further showed that 7 days of priming in intact gradient culture was sufficient to instruct the cells to complete the zonal development, and the separate or mixed coculture after 7 days of intact culture had minimal effects on cartilage formation. This study highlights the important role of cell-cell interactions in driving cartilage zonal development and validates gradient hydrogels as a useful tool to elucidate the role of cell-matrix and cell-cell interactions in driving zonal development during tissue morphogenesis and regeneration.

Improved inherited peripheral neuropathy genetic diagnosis by whole-exome sequencing.

Inherited peripheral neuropathies (IPNs) are a group of related diseases primarily affecting the peripheral motor and sensory neurons. They include the hereditary sensory neuropathies (HSN), hereditary motor neuropathies (HMN), and Charcot-Marie-Tooth disease (CMT). Using whole-exome sequencing (WES) to achieve a genetic diagnosis is particularly suited to IPNs, where over 80 genes are involved with weak genotype-phenotype correlations beyond the most common genes. We performed WES for 110 index patients with IPN where the genetic cause was undetermined after previous screening for mutations in common genes selected by phenotype and mode of inheritance. We identified 41 missense sequence variants in the known IPN genes in our cohort of 110 index patients. Nine variants (8%), identified in the genes MFN2, GJB1, BSCL2, and SETX, are previously reported mutations and considered to be pathogenic in these families. Twelve novel variants (11%) in the genes NEFL, TRPV4, KIF1B, BICD2, and SETX are implicated in the disease but require further evidence of pathogenicity. The remaining 20 variants were confirmed as polymorphisms (not causing the disease) and are detailed here to help interpret sequence variants identified in other family studies. Validation using segregation, normal controls, and bioinformatics tools was valuable as supporting evidence for sequence variants implicated in disease. In addition, we identified one SETX sequence variant (c.7640T>C), previously reported as a putative mutation, which we have confirmed as a nonpathogenic rare polymorphism. This study highlights the advantage of using WES for genetic diagnosis in highly heterogeneous diseases such as IPNs and has been particularly powerful in this cohort where genetic diagnosis could not be achieved due to phenotype and mode of inheritance not being previously obvious. However, first tier testing for common genes in clinically well-defined cases remains important and will account for most positive results.

The MFN2 V705I Variant Is Not a Disease-Causing Mutation: A Segregation Analysis in a CMT2 Family.

Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous group of disorders affecting both motor and sensory neurons in the peripheral nervous system. Mutations in the MFN2 gene cause an axonal form of CMT, CMT2A. The V705I variant in MFN2 has been previously reported as a disease-causing mutation in families with CMT2. We identified an affected index patient from an Australian multigenerational family with the V705I variant. Segregation analysis showed that the V705I variant did not segregate with the disease phenotype and was present in control individuals with an allele frequency of 4.4%. We, therefore, propose that the V705I variant is a polymorphism and not a disease-causing mutation as previously reported.

Refined localization of dominant intermediate Charcot-Marie-Tooth neuropathy and exclusion of seven known candidate genes in the region.

Charcot-Marie-Tooth (CMT) neuropathy is one of the most common hereditary disorders of the human peripheral nervous system. The CMT syndrome includes weakness and atrophy of distal muscles, high arched feet (pes cavus), depressed or absent deep tendon reflexes, and mild sensory loss. Dominant intermediate CMT (DI-CMT) neuropathy is a form of CMT with intermediate median motor nerve conduction velocities. We previously localized the DI-CMT locus to a 16.8-cM region on chromosome 19p12-p13.2. Extended haplotype analysis and clinical assessment of additional family members and a report of a second family linked to this locus has enabled us to narrow the candidate region to a 6-cM interval flanked by D19S558 and D19S432. Selection of positional candidate genes for screening was performed on the basis of neural expression and microarray analysis of Schwann cell differentiation in vivo. Seven candidate genes have been investigated. These include six genes localized in the original linkage interval and one in the newly refined region. They are excluded as a cause for DI-CMT neuropathy.