Polyglutamine Disease Modeling: Epitope Based Screen for Homologous Recombination using CRISPR/Cas9 System.

We have previously reported the genetic correction of Huntington's disease (HD) patient-derived induced pluripotent stem cells using traditional homologous recombination (HR) approaches. To extend this work, we have adopted a CRISPR-based genome editing approach to improve the efficiency of recombination in order to generate allelic isogenic HD models in human cells. Incorporation of a rapid antibody-based screening approach to measure recombination provides a powerful method to determine relative efficiency of genome editing for modeling polyglutamine diseases or understanding factors that modulate CRISPR/Cas9 HR.

Structural basis for the prion-like MAVS filaments in antiviral innate immunity.

Mitochondrial antiviral signaling (MAVS) protein is required for innate immune responses against RNA viruses. In virus-infected cells MAVS forms prion-like aggregates to activate antiviral signaling cascades, but the underlying structural mechanism is unknown. Here we report cryo-electron microscopic structures of the helical filaments formed by both the N-terminal caspase activation and recruitment domain (CARD) of MAVS and a truncated MAVS lacking part of the proline-rich region and the C-terminal transmembrane domain. Both structures are left-handed three-stranded helical filaments, revealing specific interfaces between individual CARD subunits that are dictated by electrostatic interactions between neighboring strands and hydrophobic interactions within each strand. Point mutations at multiple locations of these two interfaces impaired filament formation and antiviral signaling. Super-resolution imaging of virus-infected cells revealed rod-shaped MAVS clusters on mitochondria. These results elucidate the structural mechanism of MAVS polymerization, and explain how an α-helical domain uses distinct chemical interactions to form self-perpetuating filaments. DOI: http://dx.doi.org/10.7554/eLife.01489.001.

Novel modification of tracheostomy tube to allow speech and manage tracheal stenosis.

Mid-tracheal, postintubation stenosis can be managed with an extended length tracheostomy tube to bypass the stenotic area. However these extra-long tracheostomy tubes are not fenestrated, and when the stenotic tracheal lumen sits against the tracheostomy tube, phonation is not possible as there is no translaryngeal airflow. A 59-year-old man developed distal tracheal stenosis following a prolonged intubation and tracheostomy after a motorcycle accident. He eventually required an extra-long tracheostomy tube to bypass the stenotic region. We modified a silicone tracheostomy tube by creating a fenestration on its posterior wall. This relieved the obstruction while still allowing phonation and speech.

Tendon sheath fibroma in the thigh.

Tendon sheath fibromas are rare, benign soft tissue tumors that are predominantly found in the fingers, hands, and wrists of young adult men. This article describes a tendon sheath fibroma that developed in the thigh of a 70-year-old man, the only known tendon sheath fibroma to form in this location. Similar to tendon sheath fibromas that develop elsewhere, our patient's lesion presented as a painless, slow-growing soft tissue nodule. Physical examination revealed a firm, nontender mass with no other associated signs or symptoms. Although the imaging appearance of tendon sheath fibromas varies, our patient's lesion appeared dark on T1- and bright on T2-weighted magnetic resonance imaging. It was well marginated and enhanced with contrast.Histologically, tendon sheath fibromas are composed of dense fibrocollagenous stromas with scattered spindle-shaped fibroblasts and narrow slit-like vascular spaces. Most tendon sheath fibromas can be successfully removed by marginal excision, although 24% of lesions recur. No lesions have metastasized. Our patient's tendon sheath fibroma was removed by marginal excision, and the patient remained disease free 35 months postoperatively. Despite its rarity, tendon sheath fibroma should be included in the differential diagnosis of a thigh mass on physical examination or imaging, especially if it is painless, nontender, benign appearing, and present in men.

Recurrent lipoma-like hibernoma.

This is the fifth report of the rare lipoma-like variant of hibernoma, the 19th case reported, and the first documented as recurring after excision. Our patient was a 56-year-old man whose painful lipoma-like hibernoma (LLH) in the pelvis/buttock was initially treated with marginal excision 15 years earlier. Nine years after treatment, the LLH recurred locally. The recurrence was treated with partial excision and embolization, which alleviated symptoms. The disease was stable 26 months after repeat excision and 202 months after initial treatment. LLH is 1 of the 4 histologic variants of hibernomas, which are rare benign lipomatous tumors distinguished from other lipomas by their brown-fat component. Only minimal information is available regarding the clinicopathologic characteristics of the individual variants. Reviewing the literature, we found that LLH predominantly develops in the fifth and sixth decades, and mean age at diagnosis is 41 years (age range, 2-66 years). LLH has a slight male predilection of 10:9. It most commonly develops in the thigh, with other occurrences reported in the hip, trunk, knee, and calf. The magnetic resonance imaging signal of LLH mirrors fat in all sequences. Presence of internal septations and enhancement with contrast are variable. Histologically, LLH is defined as a hibernoma composed predominantly of univacuolated white-fat cells and only scattered granular or pale hibernoma cells. The literature provides only a few treatment details regarding this variant.

Characterization of the effects of aryl-azido compounds and UVA irradiation on the viral proteins and infectivity of human immunodeficiency virus type 1.

Hydrophobic UV-activatable compounds have been shown to partition into the hydrophobic region of biological membranes to selectively label transmembrane proteins, and to inactivate enveloped viruses. Here, we analyze various UV-activatable azido- and iodo-based hydrophobic compounds for their ability to inactivate a model-enveloped virus, human immunodeficiency virus (HIV-1 MN). Treatment of HIV-1 with 1,5-diazidonapthalene (DAN), 1-iodo, 5-azidonaphthalene (INA), 1-azidonaphthalene (AzNAP) or 4,4'-diazidobiphenyl (DABIPH) followed by UVA irradiation for 2 min resulted in complete viral inactivation, whereas treatment using analogous non-azido-containing controls had no effect. Incorporation of an azido moiety within these hydrophobic compounds to promote photoinduced covalent reactions with proteins was found to be the primary mechanism of viral inactivation for this class of compounds. Prolonged UVA irradiation of the virus in the presence of these azido compounds resulted in further modifications of viral proteins, due to the generation of reactive oxygen species, leading to aggregation as visualized via Western blot analysis, providing additional viral modifications that may inhibit viral infectivity. Furthermore, inactivation using these compounds resulted in the preservation of surface antigenic structures (recognized by neutralizing antibodies b12, 2g12 and 4e10), which is favorable for the creation of vaccines from these inactivated virus preparations.

Early pleomorphic hyalinizing angiectatic tumor: precursor or distinct lesion?

Early pleomorphic hyalinizing angiectatic tumor is a rare and recently described soft tissue lesion. Originally believed to be a precursor lesion to neoplastic pleomorphic hyalinizing angiectatic tumor, and possibly identical to hemosiderotic fibrohistiocytic lipomatous lesion/tumor, there have been recent suggestions that it is distinct from pleomorphic hyalinizing angiectatic tumor and is instead a reactive process. This article reports a case of a mass in the foot of a 45-year-old woman, which is 1 of only 15 published cases of early pleomorphic hyalinizing angiectatic tumor and is the first case to describe its radiographic appearance. Early pleomorphic hyalinizing angiectatic tumor predominantly develops in the fourth to sixth decades (average age, 45 years, range, 10-67 years). Females predominate 4 to 1. The foot/ankle is the most common site (67%). On magnetic resonance imaging (MRI), the mass appeared inhomogeneously dark on T1-weighted sequences and inhomogeneously bright on fat-suppressed T2-weighted sequences. Forty-four percent of resected lesions recur locally, but no early pleomorphic hyalinizing angiectatic tumor lesion has ever metastasized. These clinical characteristics of early pleomorphic hyalinizing angiectatic tumors closely mirror those of hemosiderotic fibrohistiocytic lipomatous lesions/tumors and are dissimilar to those for classic pleomorphic hyalinizing angiectatic tumors. Therefore, although the 3 entities share several histologic features, we believe early pleomorphic hyalinizing angiectatic tumor is equivalent to hemosiderotic fibrohistiocytic lipomatous lesion/tumor and is not a true precursor to classic pleomorphic hyalinizing angiectatic tumor.

Fibroma of tendon sheath in the knee: a report of three cases and literature review.

Fibroma of tendon sheath (FTS) is a rare and benign soft-tissue tumor. It is predominantly found in the fingers, hands, and wrists of young, adult males. We describe a series of three cases all presenting in the atypical knee location. We also review the literature on FTS, located both in the knee and elsewhere, looking for common clinical, imaging, and histologic patterns to help differentiate it from similar knee lesions. FTS typically presents as a painless, slow-growing, solid nodule. In the knee though, 71% of lesions present with pain/discomfort and 31% present with a palpable mass. Physical exam for knee FTS commonly reveals painful range of motion (50%), decreased range of motion (42%), and a palpable non-tender mass (33%). MRI of FTS usually reveals a well-defined soft-tissue mass, with low signal on T1, variable signal on T2, and variable enhancement. Histologically, the tumors are composed of a dense fibrocollagenous stroma with scattered spindle-shaped fibroblasts and narrow slit-like vascular spaces. Most FTS are removed by marginal excision, with 24% of lesions subsequently recurring. No lesion has ever metastasized. Despite its rarity, this lesion should be included in the differential diagnosis of a knee mass on physical exam or imaging, especially if it is painful, benign appearing, and present in a middle-aged male.