Mice with an isoform-ablating Mecp2 exon 1 mutation recapitulate the neurologic deficits of Rett syndrome.

Mutations in MECP2 cause the neurodevelopmental disorder Rett syndrome (RTT OMIM 312750). Alternative inclusion of MECP2/Mecp2 exon 1 with exons 3 and 4 encodes MeCP2-e1 or MeCP2-e2 protein isoforms with unique amino termini. While most MECP2 mutations are located in exons 3 and 4 thus affecting both isoforms, MECP2 exon 1 mutations but not exon 2 mutations have been identified in RTT patients, suggesting that MeCP2-e1 deficiency is sufficient to cause RTT. As expected, genetic deletion of Mecp2 exons 3 and/or 4 recapitulates RTT-like neurologic defects in mice. However, Mecp2 exon 2 knockout mice have normal neurologic function. Here, a naturally occurring MECP2 exon 1 mutation is recapitulated in a mouse model by genetic engineering. A point mutation in the translational start codon of Mecp2 exon 1, transmitted through the germline, ablates MeCP2-e1 translation while preserving MeCP2-e2 production in mouse brain. The resulting MeCP2-e1 deficient mice developed forelimb stereotypy, hindlimb clasping, excessive grooming and hypo-activity prior to death between 7 and 31 weeks. MeCP2-e1 deficient mice also exhibited abnormal anxiety, sociability and ambulation. Despite MeCP2-e1 and MeCP2-e2 sharing, 96% amino acid identity, differences were identified. A fraction of phosphorylated MeCP2-e1 differed from the bulk of MeCP2 in subnuclear localization and co-factor interaction. Furthermore, MeCP2-e1 exhibited enhanced stability compared with MeCP2-e2 in neurons. Therefore, MeCP2-e1 deficient mice implicate MeCP2-e1 as the sole contributor to RTT with non-redundant functions.

Gender Diversity and Research Productivity of Journal Editorial and Professional Society Board Members in Medical Education.

Purpose: To describe gender diversity and research productivity among medical education boards. Methods: We examined gender, training status, and research productivity of board members of Journal Citation Reports-listed medical education journals and affiliated professional societies. We determined gender using gendered pronouns and-if unavailable-software. We evaluated differences using χ2 and t-tests. Results: Overall, half of board members but 44% of editors-in-chief and 20% of society leaders were female. Female-led journals and societies had higher female representation than their non-female-led counterparts; trainee board members were more likely to be female. Conclusions: Gender disparities exist among executives on journal and affiliated professional society boards in medical education.

Comparison of the Infiniti vision and the series 20,000 Legacy systems.

PURPOSE: To compare the efficiency of the Infiniti vision system and the Series 20,000 Legacy system phacoemulsification units during routine cataract extraction. METHODS: Thirty-nine eyes of 39 patients were randomized to have their cataract removed using either the Infiniti or the Legacy system, both using the Neosonix handpiece. System settings were standardized. Ultrasound time, amount of balanced salt solution (BSS) used intraoperatively, and postoperative visual acuity at postoperative days 1, 7 and 30 were evaluated. RESULTS: Preoperatively, best corrected visual acuity was significantly worse in the Infiniti group compared to the Legacy group (0.38 +/- 0.23 and 0.21 +/- 0.16, respectively; p = 0.012). The mean phacoemulsification time was 39.6 +/- 22.9 s (range 6.0-102.0) for the Legacy group and 18.3 +/-19.1 s (range 1.0-80.0) for the Infiniti group (p = 0.001). The mean amounts of intraoperative BSS used were 117 +/- 37.7 ml (range 70-195) in the Legacy group and 85.3 +/- 38.9 ml (range 40-200) in the Infiniti group (p = 0.005). No differences in postoperative visual acuity were found. CONCLUSION: The ability to use higher flow rates and vacuum settings with the Infiniti vision system allowed for cataract removal with less phacoemulsification time than when using the Legacy system.

Epithelia: Understanding the Cell Biology of Intestinal Barrier Dysfunction.

Barrier dysfunction in the intestine is a common characteristic of aging organisms. A recent study provides new insight into the cell biology of this phenomenon.

Cellular and subcellular imaging of motor protein-based behavior in embryonic rat brain.

Development of the cerebral cortex is a very dynamic process, involving a series of complex morphogenetic events. Following division of progenitor cells in the ventricular zone, neurons undergo a series of morphological changes and migrate outward toward the cortical plate, where they differentiate and integrate into functional circuits. Errors at several of stages during neurogenesis and migration cause a variety of severe cortical malformations. A number of disease genes encode factors associated with the cytoskeleton, which plays a crucial role throughout cortical development. Methods for regulating gene expression coupled with imaging of subcellular structures have provided important insight into the mechanisms governing normal and abnormal brain development. We describe here a series of protocols for imaging motor protein-dependent processes in real time in the developing rat brain.

Cdk1 Activates Pre-mitotic Nuclear Envelope Dynein Recruitment and Apical Nuclear Migration in Neural Stem Cells.

Dynein recruitment to the nuclear envelope is required for pre-mitotic nucleus-centrosome interactions in nonneuronal cells and for apical nuclear migration in neural stem cells. In each case, dynein is recruited to the nuclear envelope (NE) specifically during G2 via two nuclear pore-mediated mechanisms involving RanBP2-BicD2 and Nup133-CENP-F. The mechanisms responsible for cell-cycle control of this behavior are unknown. We now find that Cdk1 serves as a direct master controller for NE dynein recruitment in neural stem cells and HeLa cells. Cdk1 phosphorylates conserved sites within RanBP2 and activates BicD2 binding and early dynein recruitment. Late recruitment is triggered by a Cdk1-induced export of CENP-F from the nucleus. Forced NE targeting of BicD2 overrides Cdk1 inhibition, fully rescuing dynein recruitment and nuclear migration in neural stem cells. These results reveal how NE dynein recruitment is cell-cycle regulated and identify the trigger mechanism for apical nuclear migration in the brain.

Acute suprachoroidal hemorrhage during clear corneal phacoemulsification using topical and intracameral anesthesia.

Shallowing of the anterior chamber and hardening of the eye occurred just before commencement of irrigation/aspiration of cortex in an 80-year-old man having temporal clear corneal cataract surgery under topical and intracameral anesthesia. Nucleus removal had been completed and was uneventful. Intraoperative fundus examination with the indirect ophthalmoscope disclosed a choroidal hemorrhage. The wound was immediately closed with sutures, and intravenous mannitol was administered. The hemorrhage remained localized. The red reflex remained unchanged at all times, and there was no prolapse of intraocular contents. A high index of suspicion is critical to the early diagnosis and management of choroidal hemorrhage.

Predictive formula for calculating the probability of LASIK enhancement.

PURPOSE: To develop a formula to predict a patient's need for laser in situ keratomileusis (LASIK) enhancement. SETTING: Northwestern Laser Vision Center, Department of Ophthalmology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA. METHODS: In this retrospective study, charts of patients who received LASIK with the Visx Star excimer laser for myopia and myopic astigmatism were reviewed. Laser in situ keratomileusis enhancement was performed in 130 of 720 eyes. Variables such as age, keratometry, spherical power, power and axis of astigmatism, and surgeon factor were compared in patients who required retreatment and those who did not. Multivariate logistic regression analysis was used to determine a formula for the probability of enhancement surgery. RESULTS: Age (P<.0001), preoperative cycloplegic sphere (P<.0001), and surgeon (P<.0001) were the statistically significant factors for predicting retreatment. The predictive formula derived from these factors had a sensitivity of 79%, a specificity of 61%, and positive and negative predictive values of 31% and 93%, respectively. CONCLUSIONS: Older age, higher preoperative cycloplegic sphere, and surgeon significantly influenced a patient's likelihood for LASIK retreatment. A formula based on these predisposing factors helps to more accurately predict the need for retreatment.

Staining characteristics of preserved human amniotic membrane.

PURPOSE: Amniotic membrane is an ultra-thin cellophane-like membrane that is used in ocular surface reconstruction. We evaluated the staining characteristics of commonly available dyes on preserved human amniotic membrane to aid in handling of amniotic membrane during transplantation. METHODS: Five dyes, indocyanine green (2.5%, 1.0%, and 0.5%), fluorescein (0.25%), rose bengal (1%), lissamine green B (1%), and trypan blue (0.5%), were used to stain amniotic membrane. After staining, the specimens were observed under a dissecting microscope to evaluate for the uptake of the stains. Positively stained membranes were evaluated for the persistence of staining by placing them in 2 to 3 mL of balanced saline solution that was changed every 30 minutes over 6 hours. RESULTS: Preserved human amniotic membrane is stained by indocyanine green, rose bengal, lissamine green B, and trypan blue. Of these four dyes, only the membrane stained with 1% lissamine green B was free of stain after 120 minutes. Indocyanine green, rose bengal, and trypan blue continued to strongly stain the membrane after 24 hours. CONCLUSIONS: Indocyanine green, rose bengal, trypan blue, and lissamine green B all stain amniotic membrane. Lissamine green B appears to have advantages over the other dyes in that it will stain the membrane well, and in our model, dissipate in 120 minutes. Intraoperative staining with lissamine green B may be a simple and effective way to assist surgeons in the proper handling of amniotic membrane.