Sepehr Ehsani

Notes/Highlights from Recent Literature

[2019-06-07] Developmental Biology: "Since their discovery in 1868, neural crest cells, which are present in all vertebrates, have fascinated developmental biologists [... partly because of] their extraordinary multipotency: They form cartilage, muscle, neurons, glia, pigment cells, adrenal cells, and so on. No other embryonic cell type can differentiate into so many different kinds of cells" (Mayor, Science 7 Jun 2019; Link to commentary)

--- 2017 ---

[2017-06-29] Physical Chemistry: "Small changes to molecular structures can transform how reactions occur, but studying reaction mechanisms directly is difficult. An imaging technique that provides direct insights into competing mechanisms might improve matters" (Vallance, Nature 29 Jun 2017; Link to commentary)

--- 2016 ---

[2016-06-15] Lipid Biology: "In vitro synthesis of membrane proteins into [...] asymmetric giant vesicles revealed that the lipid asymmetry in bilayer membranes improves the reconstitution ratio of membrane proteins" (Kamiya et al., Nat Chem 13 Jun 2016; Link to article)

[2016-06-10] Prion/Zinc Biology: "Zinc transporter ZIP10 forms a heteromer with ZIP6 which regulates embryonic development and cell migration" (Taylor et al., Biochem J 7 Jun 2016; Link to article)

[2016-06-09] Biophysics: "Although many molecular determinants control the tangential expansion of the cortex, the size, shape, placement and orientation of the folds arise through iterations and variations of an elementary mechanical instability modulated by early fetal brain geometry" (Tallinen, Chung et al., Nat Phys 1 Feb 2016; Link to article)

[2016-05-20] Genomics: "Nongenetic functions of the genome include nuclear assembly [and structure], response to mechanical forces, cell migration, intra- and extranuclear signaling, and, at the physiological level, enhanced nocturnal vision" (Bustin and Misteli, Science 6 May 2016; Link to article)

[2016-03-08] Cancer Biology: "Although the majority of cell protein is comprised of amino acids imported from the environment, why do cultured cells — awash in amino-acid-rich culture medium — utilize glutamine to synthesize other amino acids de novo even when those amino acids are available for import? Might this have to do with limited import capacity, or is there a separate unforeseen advantage to biosynthesis? Finally, the finding that glucose-derived carbon contributes to a small fraction of cell mass raises still more questions. Why don't proliferating cells utilize the large amounts of carbon consumed as glucose to meet their biosynthetic needs? What is the purpose of such a carbon-wasting metabolic program? Is it simply that this program enables the rapid production of adequate ATP while maintaining the NAD/NADH redox balance, or is there more to it?" (Tanner and Rutter, Dev Cell 7 Mar 2016; Link to commentary)

[2016-03-07] Plant Biology: "Polyhedral-shaped plant cells have faces, corners, and edges that can have different material properties. As Kirchhelle et al. now show, RAB-A5c reveals a trafficking compartment that localizes to the edges where two cell walls meet, with a potential role in mediating local wall stiffness" (Rahni and Birnbaum, Dev Cell 22 Feb 2016; Link to commentary)

[2016-02-22] Neurodegenerative Diseases: "An important issue raised by [Gomm et al.] and similar studies of drugs that may increase risk of dementia is whether a careful evaluation of cognitive changes and/or neuropathology should be a component of the evaluation of drugs that are widely used among the elderly" (Kuller, JAMA Neurol 15 Feb 2016; Link to commentary)

[2016-02-01] Prion Biology: "Amyloid-β pathology and cerebral amyloid angiopathy are frequent in iatrogenic Creutzfeldt-Jakob disease after dural grafting" (Frontzek et al., Swiss Med Wkly 26 Jan 2016; Link to article)

[2016-01-27] Protein Expression: "Codon content modulates a kinetic competition between protein elongation and mRNA degradation that is a central feature of the physiology and also possibly the regulation of translation in E. coli" (Boël et al., Nature 21 Jan 2016; Link to article)

[2016-01-21] Prion Genetics: "Missense variants in PRNP previously reported to be pathogenic are at least 30 times more common in the population than expected on the basis of genetic prion disease prevalence. Although some of this excess can be attributed to benign variants falsely assigned as pathogenic, other variants have genuine effects on disease susceptibility but confer lifetime risks ranging from <0.1 to ~100%" (Minikel et al., Sci Transl Med 20 Jan 2016; Link to article)

[2016-01-11] Neurodegenerative Diseases: "ADAM10, the principal neuronal α-secretase, interacted and cofractionated with γ-secretase endogenously in cells and mouse brain [...] Cells possess large multiprotease complexes capable of sequentially and efficiently processing transmembrane substrates through a spatially coordinated [regulated intramembrane proteolysis] mechanism" (Chen et al., J Cell Biol 21 Dec 2015; Link to article)

--- 2015 ---

[2015-12-20] Cancer Biology: "Yun et al. show that high doses of vitamin C selectively kill colorectal cancer cells carrying activating mutations in the oncogenes KRAS or BRAF, which are often refractory to approved targeted therapies" (Reczek and Chandel, Science 11 Dec 2015; Link to commentary)

[2015-12-20] Protein Structure: "Three main [protein] assembly steps are possible: cyclization, dimerization, and subunit addition. By combining these in different ways, a large set of possible quaternary structure topologies can be generated" (Ahnert et al., Science 11 Dec 2015; Link to article)

[2015-12-07] Cancer Biology: "Osswald et al. report that, in some types of brain tumour, structures called microtubes connect tumour cells, allowing them to act as a single, organism-like unit. Tumour microtubes facilitate invasion into healthy brain tissue" and "the spread of toxic molecules such as calcium ions (Ca2+) that build up during radiation therapy" (Sontheimer, Nature 3 Dec 2015; Link to commentary)

[2015-11-22] Linguistics: "Linear order is not available to the systems of syntax and semantics. It is an ancillary feature of language, probably a reflex of properties of the sensorimotor system that requires it for externalization, and constrained by conditions imposed by sensorimotor modalities" (Everaert et al., Trends Cogn Sci 9 Nov 2015; Link to article)

[2015-11-19] Antimicrobial Resistance: "The emergence of mcr-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance [...] Our findings highlight the urgent need for coordinated global action in the fight against extensively-resistant and pan-resistant Gram-negative bacteria" (Liu, Wang, et al., Lancet Infect Dis 18 Nov 2015; Link to article)

[2015-10-09] Water Structure: "Despite decades of study, the structures adopted to accommodate an excess proton in water and the mechanism by which they interconvert remain elusive." "From time-dependent shifts of the stretch-bend cross peak, we determined a lower limit on the lifetime of [the Zundel complex, [H(H2O)2]+] of 480 femtoseconds. These results suggest a key role for the Zundel complex in aqueous proton transfer" (Thämer et al., Science 2 Oct 2015; Link to article)

[2015-09-26] Circannual Rhythms: "Binary switching of calendar cells in the pituitary defines the phase of the circannual cycle in mammals" (Wood et al., Curr Biol 24 Sep 2015; Link to article)

[2015-09-03] Lymphatic System: "The first description of a lymphatic circulation in the head was soon forgotten (G. Schwalbe Z. Med. Wiss. 7, 465-467; 1869), as were other early landmark experiments (J. B. Brierley and E. J. Field J. Anat. 82, 153-166; 1948) [...] [The] group led by the late neurologist Endre Csanda and lymphologist Mihaly Földi [...] identified 'well-defined connections between the subarachnoid space and the cervical lymph system in the nasal cavity, in the orbita and in the region of the jugular foramen' (M. Földi et al. Angiologica 5, 250-262; 1968)" (Mezey and Palkovits, Nature 27 Aug 2015; Link to correspondence)

[2015-08-18] Biophysics: "An open channel enables particles to exert significant hydrodynamic forces over very long distances" (Buchanan, Nat Phys 31 Jul 2015; Link to article)

[2015-08-04] Protein Aggregation: "Lanosterol plays a key role in inhibiting lens protein aggregation and reducing cataract formation" (Zhao et al., Nature 30 Jul 2015; Link to article)

[2015-07-13] Calcium Biology: "Differential regulation of multiple steps in inositol 1,4,5- trisphosphate [IP3] signaling by protein kinase C [PKC] shapes hormone-stimulated Ca2+ oscillations" (Bartlett et al., J Biol Chem 15 Jun 2015; Link to article)

[2015-06-19] Metastasis: "PDAC- [pancreatic ductal adenocarcinoma-] derived exosomes induce liver pre-metastatic niche formation in naive mice and consequently increase liver metastatic burden" (Costa-Silva et al., Nat Cell Biol 18 May 2015; Link to article)

[2015-05-31] Oncology: "It is widely assumed that driver mutations occur infrequently in long-lived lineages of cells, and that most arise in cancerous tissue that is too small to be clinically detectable." Martincorena et al. "reveal that sun-exposed normal skin is already a polyclonal quilt of driver mutations subjected to selection—a field of preprocancers, as it were—that nevertheless functions as a skin" (Brash, Science 22 May 2015; Link to article)

[2015-05-25] Neurodegenerative Diseases: "Because of the uncertainty about whether and when an amyloid-positive individual without dementia will develop dementia, amyloid positivity in these individuals should not be equated with impending clinical dementia but rather be seen as a risk state" (Jansen et al., JAMA 19 May 2015; Link to article)

[2015-05-16] Seasonality: "Widespread seasonal gene expression reveals annual differences in human immunity and physiology" (Dopico et al., Nat Commun 12 May 2015; Link to article)

[2015-05-06] Statistics: "Replacing P values with Bayes factors or another statistic is ultimately about choosing a different trade-off of true positives and false positives. Arguing about the P value is like focusing on a single misspelling, rather than on the faulty logic of a sentence" (Leek and Peng, Nature 30 Apr 2015; Link to article)

[2015-05-06] Clinical Trials/'Personalized Medicine': "For every person they do help, the ten highest-grossing" medicines in the U.S. (for schizophrenia, heartburn, arthritis, high cholesterol, depression, asthma, psoriasis, Crohn's disease, multiple sclerosis and neutropenia) do not "improve the conditions of between 3 and 24 people (based on published number needed to treat (NNT) figures)" (Schork, Nature 30 Apr 2015; Link to article)

[2015-05-02] Geochemistry: "How can molecules seemingly evade both chance and thermodynamics? The answer appears to relate to the biological assembly of molecules from nonidentical substrate binding sites under irreversible conditions" (Passey, Science 24 Apr 2015; Link to article)

[2015-04-24] Ecology: "Even lineages that have traditionally been classified as separate species with pronounced phenotypic variation cannot always be differentiated via high-throughput sequencing" (Mason and Taylor, Mol Ecol 30 Mar 2015; Link to article)

[2015-04-16] Physical/Theoretical Chemistry: Lawrencium (Lr) "has the lowest first ionization potential of all the lanthanide and actinide elements. This confirms the proposed picture of the arrangement of the element's outer electrons: the 5f orbitals are filled with 14 electrons; a relativistically stabilized 7s orbital contains two electrons; and an additional, weakly bound electron resides in the 7p1/2 valence orbital" (Türler, Nature 9 Apr 2015; Link to commentary)

[2015-04-15] Prion Biology: The mammalian prion protein (PrP) "functions as a ferrireductase partner for ZIP14 and DMT1" (Tripathi et al., Free Radic Biol Med 8 Apr 2015; Link to article)

[2015-03-28] Cell Biology: "Evidence that mutation accumulation does not cause aging" in yeast (Kaya, Lobanov and Gladyshev, Aging Cell 22 Feb 2015; Link to article)

[2015-03-20] Astrophysics: "The multiple components that compose our universe: dark energy comprises 69% of the mass energy density of the universe, dark matter comprises 25%, and 'ordinary' atomic matter makes up 5%. There are other observable subdominant components: three different types of neutrinos comprise at least 0.1%, the cosmic background radiation makes up 0.01%, and black holes comprise at least 0.005%" (Spergel, Science 6 Mar 2015; Link to article)

[2015-03-19] Cell Biology: Transcription, not translation, chiefly determines protein abundance in mammals (Li and Biggin, Science 6 Mar 2015; Link to article)

[2015-03-10] Statistics: The significance test controversy revisited: the fiducial Bayesian alternative (Lecoutre and Poitevineau, 2014; Link to book)

[2015-03-03] Linguistics: Minimalist thesis of language's hierarchical syntactic structure (Bolhuis, Tattersall, Chomsky and Berwick, PLOS Biol 13 Feb 2015; Link to article)

[2015-03-02] Cancer Biology: Evidence for a surprisingly large role of "replicative mutations" in susceptibility to cancer (Tomasetti and Vogelstein, Science 13 Feb 2015; Link to correspondence)

Department of Philosophy

University College London

ehsani [at] uclmail.net

ehsani [at] csail.mit.edu

 

Current Areas of Study:

Philosophical Biology (PhilBio);

Theoretical/Computational Biology

 

ORCID identifier:

orcid.org/0000-0002-9613-6898

 

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Ronin Institute