Pathologic and Phenotypic Alterations in a Mouse Expressing a Connexin47 Missense Mutation That Causes Pelizaeus-Merzbacher–Like Disease in Humans

Gap junction channels are intercellular conduits that allow diffusional exchange of ions, second messengers, and metabolites. Human oligodendrocytes express the gap junction protein connexin47 (Cx47), which is encoded by the GJC2 gene. The autosomal recessive mutation hCx47M283T causes Pelizaeus-Merzbacher–like disease 1 (PMLD1), a progressive leukodystrophy characterized by hypomyelination, retarded motor development, nystagmus, and spasticity. We introduced the human missense mutation into the orthologous position of the mouse Gjc2 gene and inserted the mCx47M282T coding sequence into the mouse genome via homologous recombination in embryonic stem cells. Three-week-old homozygous Cx47M282T mice displayed impaired rotarod performance but unchanged open-field behavior. 10-15-day-old homozygous Cx47M282T and Cx47 null mice revealed a more than 80% reduction in the number of cells participating in glial networks after biocytin injections into oligodendrocytes in sections of corpus callosum. Homozygous expression of mCx47M282T resulted in reduced MBP expression and astrogliosis in the cerebellum of ten-day-old mice which could also be detected in Cx47 null mice of the same age. Three-month-old homozygous Cx47M282T mice exhibited neither altered open-field behavior nor impaired rotarod performance anymore. Adult mCx47M282T expressing mice did not show substantial myelin alterations, but homozygous Cx47M282T mice, additionally deprived of connexin32, which is also expressed in oligodendrocytes, died within six weeks after birth and displayed severe myelin defects accompanied by astrogliosis and activated microglia. These results strongly suggest that PMLD1 is caused by the loss of Cx47 channel function that results in impaired panglial coupling in white matter tissue

Neuron

In axons, an action potential (AP) is thought to be broadcast as an unwavering binary pulse over its arbor driving neurotransmission uniformly at release sites. Yet, by recording from axons of cerebellar stellate cell (SC) interneurons, we show that AP width varies between presynaptic bouton sites, even within the same axon branch. The varicose geometry of SC boutons, alone, does not impose differences in spike duration. Rather, axonal patching revealed heterogeneous peak conductance densities of currents mediated mainly by fast-activating K(v)3-type potassium channels, with clustered hot-spots at boutons and restricted expression at adjoining shafts. Blockade of K(v) channels at individual boutons indicates that currents immediately local to a release site directs spike repolarization at that location. Thus, the clustered arrangement and variable expression density of K(v)3 channels at boutons are key determinants underlying compartmentalized control of AP width in a near synapse-by-synapse manner, multiplying the signaling capacity of these structures

Botanica Marina

Official Full-Text Publication: Primary utricle structure of six Halimeda species and potential relevance for ocean acidification tolerance on ResearchGate, the professional network for scientists

ACS Chemical Biology

Cell surface proteins (CSPs) are vital molecular mediators for cells and their extracellular environment. Thus, understanding which CSPs are displayed on cells, especially in different cell states, remains an important endeavor in cell biology. Here, we describe the integration of cell surface engineering with radical-mediated protein biotinylation to profile CSPs. This method relies on the prefunctionalization of cells with cholesterol lipid groups, followed by sortase-catalyzed conjugation with an APEX2 ascorbate peroxidase enzyme. In the presence of biotin-phenol and H2O2, APEX2 catalyzes the formation of highly reactive biotinyl radicals that covalently tag electron-rich residues within CSPs for subsequent streptavidin-based enrichment and analysis by quantitative mass spectrometry. While APEX2 is traditionally used to capture proximity-based interactomes, we envisioned using it in a “baitless” manner on cell surfaces to capture CSPs. We evaluate this strategy in light of another CSP labeling method that relies on the presence of cell surface sialic acid. Using the APEX2 strategy, we describe the CSPs found in three mammalian cell lines and compare CSPs in adherent versus three-dimensional pancreatic adenocarcinoma cells

Neuron

In visual cortex, signals from the two eyes merge to form a coherent binocular representation. Here we investigate the synaptic interactions underlying the binocular representation of stimulus orientation in ferret visual cortex with in vivo calcium imaging of layer 2/3 neurons and their dendritic spines. Individual neurons with aligned somatic responses received a mixture of monocular and binocular synaptic inputs. Surprisingly, monocular pathways alone could not account for somatic alignment because ipsilateral monocular inputs poorly matched somatic preference. Binocular inputs exhibited different degrees of interocular alignment, and those with a high degree of alignment (congruent) had greater selectivity and somatic specificity. While congruent inputs were similar to others in measures of strength, simulations show that the number of active congruent inputs predicts aligned somatic output. Our study suggests that coherent binocular responses derive from connectivity biases that support functional amplification of aligned signals within a heterogeneous binocular intracortical network

eLife

A novel region in the CaV2.1 α1 subunit regulates coupling of synaptic vesicles to CaV2.1 calcium channels, synaptic vesicle release and docking, and the size of the fast and total releasable pools of synaptic vesicles