Inner/Outer Nuclear Membrane Fusion in Nuclear Pore Assembly: Biochemical Demonstration and Molecular Analysis

The nuclear pore complex (NPC) is characterized by a long-lived membrane-lined channel connecting the inner and outer nuclear membranes. This stabilized membrane channel, within which the nuclear pore is built, has little evolutionary precedent. In this report we demonstrate and map the inner/outer nuclear membrane fusion in NPC assembly

Pathogenic Variants in NUP214 Cause “Plugged” Nuclear Pore Channels and Acute Febrile Encephalopathy

We report biallelic missense and frameshift pathogenic variants in the gene encoding human nucleoporin NUP214 causing acute febrile encephalopathy. Clinical symptoms include neurodevelopmental regression, seizures, myoclonic jerks, progressive microcephaly, and cerebellar atrophy. NUP214 and NUP88 protein levels were reduced in primary skin fibroblasts derived from affected individuals, while the total number and density of nuclear pore complexes remained normal. Nuclear transport assays exhibited defects in the classical protein import and mRNA export pathways in affected cells. Direct surface imaging of fibroblast nuclei by scanning electron microscopy revealed a large increase in the presence of central particles (known as “plugs”) in the nuclear pore channels of affected cells. This observation suggests that large transport cargoes may be delayed in passage through the nuclear pore channel, affecting its selective barrier function. Exposure of fibroblasts from affected individuals to heat shock resulted in a marked delay in their stress response, followed by a surge in apoptotic cell death. This suggests a mechanistic link between decreased cell survival in cell culture and severe fever-induced brain damage in affected individuals. Our study provides evidence by direct imaging at the single nuclear pore level of functional changes linked to a human disease

Postmitotic nuclear pore assembly proceeds by radial dilation of small membrane openings

The nuclear envelope has to be reformed after mitosis to create viable daughter cells with closed nuclei. How membrane sealing of DNA and assembly of nuclear pore complexes (NPCs) are achieved and coordinated is poorly understood. Here, we reconstructed nuclear membrane topology and the structures of assembling NPCs in a correlative 3D EM time course of dividing human cells. Our quantitative ultrastructural analysis shows that nuclear membranes form from highly fenestrated ER sheets whose holes progressively shrink. NPC precursors are found in small membrane holes and dilate radially during assembly of the inner ring complex, forming thousands of transport channels within minutes. This mechanism is fundamentally different from that of interphase NPC assembly and explains how mitotic cells can rapidly establish a closed nuclear compartment while making it transport competent

Suppressor role of activating transcription factor 2 (ATF2) in skin cancer

Activating transcription factor 2 (ATF2) regulates transcription in response to stress and growth factor stimuli. Here, we use a mouse model in which ATF2 was selectively deleted in keratinocytes. Crossing the conditionally expressed ATF2 mutant with K14-Cre mice (K14.ATF2f/f) resulted in selective expression of mutant ATF2 within the basal layer of the epidermis. When subjected to a two-stage skin carcinogenesis protocol [7,12-dimethylbenz[a]anthracene/phorbol 12-tetradecanoate 13-acetate (DMBA/TPA)], K14.ATF2f/f mice showed significant increases in both the incidence and prevalence of papilloma development compared with the WT ATF2 mice. Consistent with these findings, keratinocytes of K14.ATF2f/f mice exhibit greater anchorage-independent growth compared with ATF2 WT keratinocytes. Papillomas of K14.ATF2f/f mice exhibit reduced expression of presenilin1, which is associated with enhanced β-catenin and cyclin D1, and reduced Notch1 expression. Significantly, a reduction of nuclear ATF2 and increased β-catenin expression were seen in samples of squamous and basal cell carcinoma, as opposed to normal skin. Our data reveal that loss of ATF2 transcriptional activity serves to promote skin tumor formation, thereby indicating a suppressor activity of ATF2 in skin tumor formation

Critical Concepts of Mentoring in an Urban Context

Given the increasing challenges faced by high-poverty urban schools, mentoring has become the panacea for policy makers interested in a quick-fix solution to the teacher quality dilemma. As a result, mentoring programs have experienced exponential growth with little empirical attention during the last decade. This 16-month qualitative investigation within a large city in the northeastern United States, sought to better understand the work of mentors in high-poverty urban schools. Analysis of the data collected led to the identification of three assertions that highlight the interplay that occurs in the urban teacher mentoring context between four critical concepts: novice teacher survival, novice teacher success, onus of responsibility, and a social justice stance. Implications are discussed related to the need for adequate resources, placement, and preparation of mentors in high-poverty schools. Additionally, the study also asserts the role that a passion for or a disposition toward social justice plays in the success and survival of both mentors and novice teachers in urban contexts