Project description:Astrocytes, the most prominent glial cell type in the brain, send specialized processes called endfeet around blood vessels and express a large molecular repertoire regulating the cerebrovascular system physiology. One of the most striking properties of astrocyte endfeet is their enrichment in gap junction protein Connexin 43 and 30 (Cx43 and Cx30) allowing in particular for direct intercellular trafficking of ions and small signaling molecules through perivascular astroglial networks. In this study, we addressed the specific role of Cx30 at the gliovascular interface. Using an inactivation mouse model for Cx30 (Cx30M-NM-^T/M-NM-^T), we showed that absence of Cx30 does not affect blood-brain barrier (BBB) organization and permeability. However, it results in the cerebrovascular fraction, in a strong upregulation of Sgcg encoding g-Sarcoglycan (SG), a member of the Dystrophin-associated protein complex (DAPC) connecting cytoskeleton and the extracellular matrix. The same molecular event occurs in Cx30T5M/T5M mutated mice, where Cx30 channels are closed, demonstrating that Sgcg regulation relied on Cx30 channel functions. We further characterized the cerebrovascular Sarcoglycan complex (SGC) and showed the presence of M-NM-1-, M-NM-2-, M-NM-4-, M-NM-3-, M-NM-5- and M-NM-6- SG, as well as Sarcospan. Altogether, our results suggest that the Sarcoglycan complex is present in the cerebrovascular system, and that expression of one of its members, g-Sarcoglycan, depends on Cx30 channels. As described in skeletal muscles, the SGC may contribute to membrane stabilization and signal transduction in the cerebrovascular system, which may therefore be regulated by Cx30 channel-mediated functions. Comparison of 3-month-old Cx30 deleted mice against WT genetic background.
Project description:Astrocytes, the most prominent glial cell type in the brain, send specialized processes called endfeet around blood vessels and express a large molecular repertoire regulating the cerebrovascular system physiology. One of the most striking properties of astrocyte endfeet is their enrichment in gap junction protein Connexin 43 and 30 (Cx43 and Cx30) allowing in particular for direct intercellular trafficking of ions and small signaling molecules through perivascular astroglial networks. In this study, we addressed the specific role of Cx30 at the gliovascular interface. Using an inactivation mouse model for Cx30 (Cx30Δ/Δ), we showed that absence of Cx30 does not affect blood-brain barrier (BBB) organization and permeability. However, it results in the cerebrovascular fraction, in a strong upregulation of Sgcg encoding g-Sarcoglycan (SG), a member of the Dystrophin-associated protein complex (DAPC) connecting cytoskeleton and the extracellular matrix. The same molecular event occurs in Cx30T5M/T5M mutated mice, where Cx30 channels are closed, demonstrating that Sgcg regulation relied on Cx30 channel functions. We further characterized the cerebrovascular Sarcoglycan complex (SGC) and showed the presence of α-, β-, δ-, γ-, ε- and ζ- SG, as well as Sarcospan. Altogether, our results suggest that the Sarcoglycan complex is present in the cerebrovascular system, and that expression of one of its members, g-Sarcoglycan, depends on Cx30 channels. As described in skeletal muscles, the SGC may contribute to membrane stabilization and signal transduction in the cerebrovascular system, which may therefore be regulated by Cx30 channel-mediated functions.
Project description:Gene duplication events provide redundancy to complex organisms, and homologous genes and their encoded proteins are potential replacements to treat loss-of-function genetic syndromes. Skeletal muscle possesses redundant molecular mechanisms that partially or fully compensate for loss of gene function. Within the dystrophin-glycoprotein complex (DGC), utrophin is known to substitute for dystrophin. However, there has been little investigation of the orthologous relationships within the sarcoglycan subcomplex of the DGC. In skeletal muscle, the sarcoglycan complex canonically consists of alpha-, beta-, gamma- and delta-subunits, with gamma- and delta-sarcoglycan showing the greatest homology but no functional redundancy. We show that sarcospan, a transmembrane scaffolding protein, mediates assembly of a compensatory DGC with gamma-sarcoglycan replacement by zeta-sarcoglycan. This alternative complex improved pathology ingamma-sarcoglycan muscular dystrophy, but not alpha- or beta-sarcoglycan muscular dystrophy where sarcospan was unable to form compensatory complexes. Three-dimensional modeling of the compensatory DGC reveals that zeta-sarcoglycan maintains specific hydrophobic interactions with sarcospan and preserves overall quaternary arrangement. This compensatory DGC protects the cell membrane from contraction-induced damage and all secondary consequences of disease. These findings demonstrate a novel mechanism stabilizing the DGC by leveraging protein redundancy, with an important role for sarcospan in assembly and scaffolding of a compensatory DGC.
Project description:Astrocytes are intimately linked with brain blood vessels, a relationship critical for neuronal function. However, astroglial factors driving these physical and functional associations during postnatal brain development have yet to be identified. By characterizing structural and transcriptional changes in mouse cortical astrocytes during the first two postnatal weeks, we find that high-mobility group box 1 (Hmgb1), normally upregulated with injury and involved in adult cerebrovascular repair, is highly expressed in astrocytes at birth and then decreases rapidly. Astrocyte-selective ablation of Hmgb1 at birth affects astrocyte morphology and endfoot placement, alters distribution of endfoot proteins connexin43 and aquaporin-4, induces transcriptional changes in astrocytes related to cytoskeleton remodeling, and profoundly disrupts endothelial ultrastructure. While lack of astroglial Hmgb1 does not affect the blood-brain barrier or angiogenesis postnatally, it impairs neurovascular coupling and behavior in adult mice. These findings identify astroglial Hmgb1 as a key player in postnatal gliovascular maturation.
Project description:Astrocytes are intimately linked with brain vessels, a relationship that is critical for neuronal health and function. However, key astroglial molecular factors that drive these physical and functional associations during postnatal brain development have not yet been identified. We characterized structural and transcriptional changes in mouse cortical astrocytes and microvessels during the first two postnatal weeks and found that high-mobility group box 1 (Hmgb1), normally upregulated with injury and involved in adult cerebrovascular repair, was highly expressed in astrocytes at birth to then decreased rapidly. Astrocyte-selective ablation of Hmgb1 in newborn mice affected astrocyte morphology and endfoot placement, induced disruption of endfoot proteins connexin43 and aquaporin-4, induced transcriptional changes in astrocytes, and profoundly altered endothelial cell ultrastructure. While lack of astroglial Hmgb1 did not affect the blood-brain barrier or angiogenesis postnatally, it impaired neurovascular coupling and behavior in adult mice. These findings identify astroglial Hmgb1 as a key player in postnatal gliovascular maturation.
Project description:LC/MS/MS analysis was performed on astroglial exosome samples (3 biological replicates) to identify proteins expressed on the surface of astroglial exosomes. Thes astroglial exosome samples were purified using size-exclusion column from astrocyte conditioned medium (ACM) of primary astrocyte cultures.
Project description:Dysfunction of the dystrophin-glycoprotein complex (DGC) is a frequent cause of hereditary forms of muscular dystrophy. Although DGC function in maintaining skeletal muscle integrity has been well characterized, little is known about how the DGC complex is coordinately regulated at the transcriptional level. To test this hypothesis, we engineered HDAC4 stably overexpressing and control myotubes in an in vitro model of muscle differentiation. Here we present evidence that HDAC4, a neural activity-responsive histone deacetylase, is a critical transcriptional regulator of the DGC complex. We show that HDAC4 can repress multiple components of the DGC complex, including dystrophin and sarcoglycan family members in both cultured myotubes. To confirm this finding, the protein levels of core DGC complex members including dystrophin, sarcoglycan complex members, and additional dystrophin-associated proteins were evaluated in differentiated myotubes by western analysis. Keywords: genetic modification and cell type comparison of muscle cells
Project description:Dysfunction of the dystrophin-glycoprotein complex (DGC) is a frequent cause of hereditary forms of muscular dystrophy. Although DGC function in maintaining skeletal muscle integrity has been well characterized, little is known about how the DGC complex is coordinately regulated at the transcriptional level. To test this hypothesis, we engineered HDAC4 stably overexpressing and control myotubes in an in vitro model of muscle differentiation. Here we present evidence that HDAC4, a neural activity-responsive histone deacetylase, is a critical transcriptional regulator of the DGC complex. We show that HDAC4 can repress multiple components of the DGC complex, including dystrophin and sarcoglycan family members in both cultured myotubes. To confirm this finding, the protein levels of core DGC complex members including dystrophin, sarcoglycan complex members, and additional dystrophin-associated proteins were evaluated in differentiated myotubes by western analysis. C2C12 mouse myotubes were infected with either a HDAC4 expressing or control (Neo) retroviruses. After stable selection, myotubes were differentiated at 90% confluency in 2% horse serum (Hyclone) for 4 days. At this time point, RNA was extracted and the two types of cells compared in a microarray analysis.