Novel brain-penetrant inhibitor of G9a methylase blocks Alzheimer's disease proteopathology for precision medication

Current amyloid beta-targeting approaches for Alzheimer's disease (AD) therapeutics only slow cognitive decline for small numbers of patients. This limited efficacy exists because AD is a multifactorial disease whose pathological mechanism(s) and diagnostic biomarkers are largely unknown. Here we report a new mechanism of AD pathogenesis in which the histone methyltransferase G9a noncanonically regulates translation of a hippocampal proteome that defines the proteopathic nature of AD. Accordingly, we developed a novel brain-penetrant inhibitor of G9a, MS1262, across the blood-brain barrier to block this G9a-regulated, proteopathologic mechanism. Intermittent MS1262 treatment of multiple AD mouse models consistently restored both cognitive and noncognitive functions to healthy levels. Comparison of proteomic/phosphoproteomic analyses of MS1262-treated AD mice with human AD patient data identified multiple pathological brain pathways that elaborate amyloid beta and neurofibrillary tangles as well as blood coagulation, from which biomarkers of early stage of AD including SMOC1 were found to be affected by MS1262 treatment. Notably, these results indicated that MS1262 treatment may reduce or avoid the risk of blood clot burst for brain bleeding or a stroke. This mouse-to-human conservation of G9a-translated AD proteopathology suggests that the global, multifaceted effects of MS1262 in mice could extend to relieve all symptoms of AD patients with minimum side effect. In addition, our mechanistically derived biomarkers can be used for stage-specific AD diagnosis and companion diagnosis of individualized drug effects.

Self-reported Learning and Study Strategies in First and Second Year Medical Students

Medical school presents a unique challenge to the average learner as the instructional strategies used in medical curricula are often different than what the student has experienced prior. The large volume of information taught in medical school is delivered with a variety of techniques. After the educational material has been delivered, it is the student's responsibility to study and learn the information for future exams and for their future patients. The current study aims to explore what learning activities and teaching strategies first (M1) and second year (M2) medical students use and prefer. Additionally, the study aims to determine if there are cohort differences in classroom and study habits. A group of 95 M1 students and 109 M2 students were recruited to participate in this online survey study. The analyses indicated statistical differences between M1 and M2 student cohorts with M1 students preferring group work and small group discussions more than M2 students. Classic didactic lecturing was preferred by 71.6% of students surveyed. M1 students reported a greater tendency for self-testing and group study versus M2 students. GPA and study technique preference were not correlated. These findings indicate that medical students are not using research-based learning and study strategies at the possible detriment of long-term knowledge retention. Modeling of research-based learning and study strategies by medical educators is one possible solution to encourage medical students to change their study practice. Future work should focus on how medical student learning preferences change as they progress through medical school.

Pdgfrα-Cre mediated knockout of the aryl hydrocarbon receptor protects mice from high-fat diet induced obesity and hepatic steatosis

Aryl hydrocarbon receptor (AHR) agonists such as dioxin have been associated with obesity and the development of diabetes. Whole-body Ahr knockout mice on high-fat diet (HFD) have been shown to resist obesity and hepatic steatosis. Tissue-specific knockout of Ahr in mature adipocytes via adiponectin-Cre exacerbates obesity while knockout in liver increases steatosis without having significant effects on obesity. Our previous studies demonstrated that treatment of subcutaneous preadipocytes with exogenous or endogenous AHR agonists disrupts maturation into functional adipocytes in vitro. Here, we used platelet-derived growth factor receptor alpha (Pdgfrα)-Cre mice, a Cre model previously established to knock out genes in preadipocyte lineages and other cell types, but not liver cells, to further define AHR's role in obesity. We demonstrate that Pdgfrα-Cre Ahr-floxed (Ahrfl/fl) knockout mice are protected from HFD-induced obesity compared to non-knockout Ahrfl/fl mice (control mice). The Pdgfrα-Cre Ahrfl/fl knockout mice were also protected from increased adiposity, enlargement of adipocyte size, and liver steatosis while on the HFD compared to control mice. On a regular control diet, knockout and non-knockout mice showed no differences in weight gain, indicating the protective phenotype arises only when animals are challenged by a HFD. At the cellular level, cultured cells from brown adipose tissue (BAT) of Pdgfrα-Cre Ahrfl/fl mice were more responsive than cells from controls to transcriptional activation of the thermogenic uncoupling protein 1 (Ucp1) gene by norepinephrine, suggesting an ability to burn more energy under certain conditions. Collectively, our results show that knockout of Ahr mediated by Pdgfrα-Cre is protective against diet-induced obesity and suggest a mechanism by which enhanced UCP1 activity within BAT might confer these effects.

This is Not Your Grandfather's Medical School: Novel Tools to Enhance Medical Education

As new medical students start their journey to become the next generation of physicians, they are in awe of the wealth of knowledge at their fingertips as they begin medical school. Every student brings with them a unique story, and most bring with them a high tolerance for technology. The internet, smart phones, and the personal computer have shrunk the academic world and allowed students access to entire libraries that fit within their pockets. Medical school curricula continues to try to evolve to meet students in their increasingly technology filled world. How are medical schools evolving to integrate technology into their curricula? What follows is a review of the application of different technologies in medical education and a close look at the most efficient uses of technology within medical school curricula. This discussion is followed by perspectives from professors and a student on the use of a variety of different technologies for teaching and learning including podcasts, YouTube, Twitter, and varying online resources.

Abstract 1368: RABL6A, a novel critical regulator of Akt-mTOR signaling in pancreatic neuroendocrine tumor cells

Introduction: A better molecular understanding of pancreatic neuroendocrine tumors (PNETs) is needed to improve patient diagnosis and treatment. Everolimus (mTOR inhibitor) is a standard-of-care therapy for PNET patients based on aberrant activation of the PI3K/Akt/mTOR kinase pathway in tumors. However, sustained mTOR inhibition paradoxically promotes Akt kinase hyperactivation due to loss of negative feedback regulation and tumors become drug resistant. Our data reveal that RABL6A, a novel oncoprotein amplified in PNETs, is a key regulator of this clinically relevant pathway.

Methods: RABL6A and Akt protein levels were manipulated using viral shRNAs in BON1 PNET cells. Transcript levels were assayed by microarray and qRT-PCR, proteins assessed by western blotting, and cell proliferation and survival measured by cell counts, trypan blue exclusion and EdU incorporation. Effect of RABL6A expression on sensitivity to clinically relevant drugs, MK2206 (Akt inhibitor) and everolimus, were tested.

Results: Silencing of RABL6A in PNET cells causes G1 and G2/M cell cycle arrest, and pathway analysis of microarray data suggested inactivation of Akt signaling in the arrested cells. Immunoblotting confirmed dramatic loss of Akt phosphorylation at Ser-473 along with impaired phosphorylation and activation of its targets, PRAS40 and FOXO-1/3. Phosphorylation of S6K, a downstream target of Akt-mTOR signaling, was also reduced by RABL6A deficiency. The mechanism by which RABL6A controls Akt-S473 phosphorylation is currently not known although we demonstrated that mTORC2 (the kinase that phosphorylates Akt at Ser473) remains active in RABL6A deficient cells since the phosphorylation of other mTORC2 substrates (SGK1 and PKCα) is unaffected. Given the central role of Akt1 in tumorigenesis, we hypothesized that reinstating its activity may rescue the arrest phenotype caused by RABL6A loss. Restoration of Akt1 in RABL6A-depleted cells partially rescued the G1 phase arrest and induced S phase entry but was insufficient to allow mitosis, suggesting RABL6A regulates other factors required for cell division. Finally, drug response assays showed that RABL6A loss desensitizes PNET cells to Akt and mTOR inhibitors.

Conclusion: Our previous work showed RABL6A promotes G1 progression in PNET cells by inactivating Rb1, an established suppressor of PNET pathogenesis. We now show that RABL6A also controls Akt phosphorylation and is essential for Akt-mTOR activation. Thus, RABL6A controls multiple cancer pathways necessary for PNET cell cycle progression and survival. We are testing if RABL6A status in PNETs predicts responsiveness to combination therapies targeting Akt and mTOR. Overall, this work identifies RABL6A as a new essential activator of Akt1-mTOR signaling, suggesting it is a new potential biomarker and target for anticancer therapy in PNET patients.

Citation Format: Shaik Amjad Ume Salma, Jussara Hagen, Jacki Reilly, Ryan Sheehy, Nitija Tiwari, Jackson Nteeba, Scott K. Sherman, Thomas M. O'Dorisio, James R. Howe, Andrew M. Bellizzi, Benjamin W. Darbro, Dawn E. Quelle. RABL6A, a novel critical regulator of Akt-mTOR signaling in pancreatic neuroendocrine tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1368. doi:10.1158/1538-7445.AM2017-1368

Nails or plates for fracture of the distal femur?

Aims

Fractures of the distal femur are an important cause of morbidity. Their optimal management remains controversial. Contemporary implants include angular-stable anatomical locking plates and locked intramedullary nails (IMNs). We compared the long-term patient-reported functional outcome of fixation of fractures of the distal femur using these two methods of treatment.

Patients and Methods

A total of 297 patients were retrospectively identified from a State-wide trauma registry in Australia: 195 had been treated with a locking plate and 102 with an IMN. Baseline characteristics of the patients and their fractures were recorded. Health-related quality-of-life, functional and radiographic outcomes were compared using mixed effects regression models at six months and one year.

Results

There was a clinically relevant and significant difference in quality-of-life at six months in favour of fixation with an IMN (mean difference in EuroQol-5 Dimensions Score (EQ-5D) = 0.12; 95% CI 0.02 to 0.22; p = 0.025). There was weak evidence that this trend continued to one year (mean difference EQ-5D = 0.09; 95% CI -0.01 to 0.19; p = 0.073). There was a significant although very small reduction in angular deformity using an IMN (mean difference -1.02; 95% CI -1.99 to -0.06; p = 0.073). There was no evidence that there was a difference in any other outcomes at any time point. Take home message: IMN may be a superior treatment compared with anatomical locking plates for fractures of the distal femur. These findings are concordant with other data from pilot randomised studies which favour treatment of these fractures with an IMN. This study strongly supports the need for a definitive randomised trial. Cite this article: Bone Joint J 2016;98-B:846–50.

Role of bradykinin in myocardial preconditioning

The role of bradykinin in the cardioprotective action of ischemic preconditioning was investigated in an anesthetized, open-chest rabbit model of acute coronary occlusion. A branch of the left main coronary artery was reversibly ligated to produce ischemia followed by reperfusion, after which the degree of myocardial necrosis (infarct size as a percent of area at risk) was assessed by tetrazolium staining. Before 30 min of coronary occlusion, rabbits received either ischemic preconditioning (5 min occlusion followed by 10 min reperfusion), no preconditioning, H-D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Tic-Oic-Arg-OH (HOE 140) i.v. (bradykinin receptor antagonist, 1 micrograms/kg) plus preconditioning, HOE 140 alone, a 5-min intra-atrial bradykinin infusion (250 micrograms/kg/min) followed by a 10-min recovery period or HOE 140 plus bradykinin infusion with 10 min recovery. Systemic hemodynamic responses were similar between treatment groups except that both bradykinin infusion groups had a significantly depressed rate of left ventricular pressure development (LV+dP/dtmax) after the 10-min recovery period. Preconditioning reduced infarct size significantly (12 +/- 2%, compared to non-preconditioned controls at 41 +/- 6%), whereas pretreatment with HOE 140 abolished the cardioprotective effect (41 +/- 4%). In addition, bradykinin infusion reduced infarct size significantly (16 +/- 1%), an effect which was also prevented by HOE 140 (41 +/- 5%). HOE 140 alone did not exacerbate the degree of myocardial necrosis (43 +/- 4%). Myocardial area at risk as a percentage of total left ventricular mass was not different between the six treatment groups. The results indicate that endogenously generated bradykinin may mediate the cardioprotective events associated with ischemic preconditioning.

Chromosomal localization of the human proenkephalin and prodynorphin genes

DNA probes derived from rat and human proenkephalin and prodynorphin genes have been used to localize these two opiate neuropeptide genes on human chromosomes. Hybridization of probes to Southern blots made with DNAs from a rodent-human somatic-cell hybrid panel indicates localization of proenkephalin to human chromosome 8 and of prodynorphin to human chromosome 20. In situ hybridization to metaphase chromosomes confirms these assignments and indicates regional localizations of proenkephalin to 8q23-q24 and of prodynorphin to 20p12-pter. A human genomic prodynorphin clone reveals a frequent two-allele TaqI polymorphism.

Seven polymorphic loci mapping to human chromosomal region 11q22-qter

Seven polymorphic loci that map to human chromosomal region 11q22-qter are revealed by DNA probes isolated from a chromosome-specific phage library constructed from a human X mouse somatic cell hybrid that has retained an 11q;16q translocation as the only human DNA. Three probes, each of which reveals a two-allele polymorphism, and four probes, each of which detects two linked RFLPs, have been characterized. Using a somatic cell hybrid mapping panel that divides 11q into four discrete sections, the seven clones have been localized to specific chromosomal regions. Localization of one of the clones has been confirmed and refined by in situ hybridization.

A hypervariable region at the D19S11 locus

The polymorphic locus D19S11 consists of four closely linked RFLPs: alpha, beta, delta, and gamma on chromosome 19p13.2----19cen, revealed by subclones p13-1-82 and p13-2-21 from cosmid 1-13. Here, we report that p13-1-25, an additional subclone of c1-13, reveals three insertion/deletion RFLPs, alpha, epsilon, and phi, at the D19S11 locus. In situ hybridization of p13-1-25 to metaphase chromosomes from a carrier of a 19/X translocation with a breakpoint near the centromere confirms localization of D19S11 to 19p. Studies with hydatidiform moles have generated assignments of specific restriction fragments to these three loci, and genotypic studies in three-generation families have indicated that they are closely linked. Loci alpha (also detected by p13-1-82) and phi each have but two common alleles, whereas epsilon has at least 33 alleles, including a null allele. Fifty unrelated individuals tested displayed unique fragment patterns on Taq I blots probed with p13-1-25. Applications of this probe include monitoring loss of chromosome 19 during tumorigenesis, monitoring engraftment of donor bone marrow after transplantation, testing for paternity, and mapping disease genes on chromosome 19.

Further cytologic evidence for Xp-Yp translocation in XX males using in situ hybridization with Y-derived probe

Chromosome preparations from seven subjects with aberrations of sex chromosomes were utilized for in situ hybridization studies with the tritium-labeled Y-derived probe p50f. Two subjects had a pseudodicentric chromosome consisting of two copies of Yp and a portion of Y long arm; two were XX males [46,XX,t(Xp;Yp)], one was missing part of the Y short arm, and another had t(5p;Yq); in addition cells from an XYY male as well as a normal 46,XY male, and a 46,XX female, were hybridized with the same probe. The hybridization technique of Harper and Saunders (1981) was used. There was excess labeling of the Yp/paracentromeric regions in the cases with the normal Y, the XYY, the pseudodicentric Y, and the 5/Y translocation. No significant label was seen on metaphases from the normal 46,XX female or the female with the partially missing Y short arm. Excess label was present on the X short arm in the cases of the XX males; there were 8% and 9.5% of cells with label. The combined cytogenetic and hybridization data indicate that one X short arm in these XX males has undergone a translocation with Yp, and that genes for sex determination probably reside on the distal half of the Y short arm.

A highly polymorphic locus on chromosome 16q revealed by a probe from a chromosome-specific cosmid library

A cosmid library was constructed from genomic DNA of a human-mouse somatic cell hybrid containing an 11q-16q translocation chromosome as the only human DNA. Cosmids with human inserts were prehybridized with total human DNA and were screened to find probes that revealed highly polymorphic loci. From one such cosmid, CF33-79, a single-copy subclone was isolated which revealed an insertion/deletion polymorphism with at least 11 alleles and a PIC of 0.77. Using a somatic cell hybrid mapping panel, the subclone was mapped to chromosome 16. By in situ hybridization with the entire cosmid used as a probe, chromosomal localization was shown at 16q22----24.

Huntington disease-linked restriction fragment length polymorphism localized within band p16.1 of chromosome 4 by in situ hybridization

A 5.5-kilobase (kb) single sequence DNA fragment (G8) reveals the DNA polymorphic locus D4S10 on Southern blot analysis. This locus is closely linked to Huntington disease and has been mapped to chromosome 4 short arm using human-mouse somatic cell hybrids, and specifically to chromosome 4 band p16 using DNA from individuals with deletions of chromosome 4 short arm who exhibit Wolf-Hirschhorn syndrome. With in situ hybridization techniques, we have confirmed the location of D4S10 on chromosome 4 and further localized it within band p16 utilizing five patients, four with overlapping chromosome 4 short-arm aberrations. The DNA segment G8 was hybridized to the mataphase chromosomes of the five patients. Two of them have different interstitial deletions of one of the chromosome 4 short arms (TA and BA), two have different chromosome 4 short-arm terminal deletions (RG and DQ), and one has a normal male karyotype. By noting the presence or absence of hybridization to the partially deleted chromosomes with known precise breakpoints, we were able to more accurately localize probe G8 to the distal half of band p16.1 of chromosome 4.

A polymorphic locus on the long arm of chromosome 20 defined by two probes from a single cosmid

Two probes from the random human cosmid c1-37 detect restriction fragment length polymorphisms in humans. The loci revealed by these probes are in linkage equilibrium and constitute a compound polymorphic locus with a polymorphism information content of 0.54. A somatic cell hybrid panel has been used to map the probes to chromosome 20; in situ hybridization studies confirm this localization and indicate that the locus is on 20q13. This is the first polymorphic locus to be assigned to the long arm of chromosome 20.

Characterization of the supernumerary chromosome in cat eye syndrome

Most individuals with cat eye syndrome (CES) have a supernumerary bisatellited chromosome which, on the basis of cytogenetic evidence, has been reported to originate from either chromosome 13 or 22. To resolve this question, a single-copy DNA probe, D22S9, was isolated and localized to 22q11 by in situ hybridization to metaphase chromosomes. The number of copies of this sequence was determined in CES patients by means of Southern blots and densitometry analysis of autoradiographs. In patients with the supernumerary chromosome, four copies were found, whereas in one patient with a duplication of part of chromosome 22, there were three copies. Therefore, the syndrome results from the presence of either three or four copies of DNA sequences from 22q11; there is no evidence that sequences from other chromosomes are involved. This work demonstrates how DNA sequence dosage analysis can be used to study genetic disorders that are not readily amenable to standard cytogenetic analysis.

A highly polymorphic locus in human DNA revealed by probes from cosmid 1-5 maps to chromosome 2q35----37

The highly polymorphic locus D2S3 is revealed by three single-copy probes from cosmid C1-5. These probes, 1-30, 1-32, and 2-96, collectively reveal seven restriction fragment length polymorphisms. Fifty-three of 56 unrelated individuals (93%) were heterozygous at one or more of the seven loci, making the compound locus a very useful marker for gene mapping. Chromosomal assignment of D2S3 was obtained using a panel of human X hamster and human X mouse somatic cell hybrids. Molecular hybridization of EcoRI-digested DNA from these cell lines with the DNA inserts from subclones 1-30, 1-32, and 2-96 showed that all three probes mapped to the long arm of chromosome 2. Additionally, in situ hybridization of [3H]-labeled probe 2-96 to metaphase chromosome preparations allowed more precise assignment of the locus to the region 2q35----37.

Abnormal binding of spectrin to the membrane of erythrocytes in some cases of hereditary spherocytosis

In two cases of hereditary spherocytosis that we have examined, spectrin was bound abnormally tightly to the erythrocyte membrane, and could not be released by low ionic strength dialysis. This type of behaviour occurs in normal red cells only after heating above 50 degrees C. It appears that some cases of spherocytosis may be due to the presence of a protein which is abnormally temperature sensitive.