Genome-wide CRISPR screenings identified SMCHD1 as a host-restricting factor for AAV transduction.

AAV-mediated gene therapy typically requires a high dose of viral transduction, risking acute immune responses and patient safety, part of which is due to limited understanding of the host-viral interactions, especially post-transduction viral genome processing. Here, through a genome-wide CRISPR screen, we identified SMCHD1 (Structural Maintenance of Chromosomes Hinge Domain 1), an epigenetic modifier, as a critical broad-spectrum restricting host factor for post-entry AAV transgene expression. SMCHD1 knock-down by RNAi and CRISPRi or knock-out by CRISPR all resulted in significantly enhanced transgene expression across multiple viral serotypes, as well as for both single-strand and self-complementary AAV genome types. Mechanistically, upon viral transduction, SMCHD1 effectively repressed AAV transcription by the formation of an LRIF1-HP1-containing protein complex and directly binding with the AAV genome to maintain a heterochromatin-like state. SMCHD1-KO or LRIF1-KD could disrupt such a complex and thus result in AAV transcriptional activation. Together, our results highlight the host factor-induced chromatin remodeling as a critical inhibitory mechanism for AAV transduction and may shed light on further improvement in AAV-based gene therapy.

Dental niche cells directly contribute to tooth reconstitution and morphogenesis.

Mammalian teeth develop from the inductive epithelial-mesenchymal interaction, an important mechanism shared by many organs. The cellular basis for such interaction remains elusive. Here, we generate a dual-fluorescence model to track and analyze dental cells from embryonic to postnatal stages, in which Pitx2+ epithelium and Msx1+ mesenchyme are sufficient for tooth reconstitution. Single-cell RNA sequencing and spatial mapping further revealed critical cellular dynamics during molar development, where tooth germs are organized by Msx1+Sdc1+ dental papilla and surrounding dental niche. Surprisingly, niche cells are more efficient in tooth reconstitution and can directly regenerate papilla cells through interaction with dental epithelium. Finally, from the dental niche, we identify a group of previously unappreciated migratory Msx1+ Sox9+ cells as the potential cell origin for dental papilla. Our results indicate that the dental niche cells directly contribute to tooth organogenesis and provide critical insights into the essential cell composition for tooth engineering.

MR perfusion-weighted imaging and quantitative analysis of cerebral hemodynamics with symptom provocation in unmedicated patients with obsessive-compulsive disorder.

We evaluated the potential effectiveness of dynamic contrast-enhanced perfusion-weighted images (PWI) in determining hemodynamic activation in brain structures that may be involved in mediating the symptomatology of patients with obsessive-compulsive disorder (OCD), as manifested by contamination obsessions with washing compulsions. Ten unmedicated female patients with OCD were subjected to PWI, and relative cerebral blood flow (rCBF) in each region of interest (ROI) and self-ratings of OCD symptoms were compared before and after symptom provocation. We found that increases in the Anxiety Analogue Scale (AAS) and OCD Analogue Scale (OCDAS) scores were each significantly associated with provocation. The correlations between OCDAS and AAS scores were also statistically significant during both the control and provoked conditions. Compared with the control state, there was a significant increase in rCBF during the symptomatic state in the right head of caudate nucleus, thalamus, and bilateral orbitofrontal cortices (OFC). No statistical changes in rCBF were found in the bilateral anterior cingulate cortices (ACC). These findings demonstrate that OCD symptomatology is accompanied by anxiety, and that abnormal features are particularly apparent in the orbitofrontal-subcortical circuits.