Turing's Reaction-Diffusion System - 1 by Vidyanand Nanjundiah

Discussion Meeting Thirsting for Theoretical Biology (ONLINE) ORGANIZERS: Vaishnavi Ananthanarayanan (UNSW & EMBL Australia), Vijaykumar Krishnamurthy (ICTS-TIFR, India) and Vidyanand Nanjundiah (Centre for Human Genetics, India) DATE: 11 January 2021 to 22 January 2021 VENUE: Online Contemporary research in biology is increasingly becoming more quantitative in nature. As such, "...we are drowning in a sea of data and thirsting for some theoretical framework with which to understand it" [Brenner (2012)]. The absence of meaningful exchanges between experimentalists and theoreticians is a glaring reason for this state of affairs. The broad aim of the second edition of "Thirsting for theoretical biology" is to expose people who have a background in the physical and mathematical sciences to a range of interesting biological phenomena at the cellular and tissue level as experimentalists view them. The meeting will showcase examples of theory-experiment interactions that can deepen our understanding of living matter and will also feature a panel discussion titled 'What is theoretical biology?'. In addition, there will be a discussion, aimed mainly at students, on why theoretical and quantitative biology offers exciting prospects for a research career. The topics to be covered in the meeting will include the regulation of genetic activity, chromosome dynamics, cytoskeletal organisation, molecular motors, cellular energetics, stem cell behaviour, cell-cell interactions, developmental homeostasis and morphogenesis. CONTACT US: ttb@icts.res.in PROGRAM LINK: https://www.icts.res.in/discussion-meeting/ttb2021 Table of Contents (powered by https://videoken.com) 0:00:00 Turing's reaction-diffusion system - 1 0:00:10 Vidyanand Nanjundah Centre for Human genetics & ICTS Bangalore 0:01:11 THE CHEMICAL BASIS OF MORPHOGENESIS 0:01:24 Outline 0:01:43 (Life cycle) 0:02:24 What is development? 0:03:04 Already at the first cleavage, cells are specified (W. Roux, 1888) 0:03:10 Cells remain totipotent even after first two divisions, (H. Driesch, 1892) 0:08:08 Some cells are special ("Organiser" experiment of H. Spemann and H. Mangold, 1924) 0:09:59 Conceptual constructs (late 1800s-early1900s) 0:12:51 Chemical morphogenesis in regulative systems: assumptions 0:14:44 Non-selectionist, 'structuralist' origin of form and symmetry (D'Arcy Thompson) 0:15:46 Mach bands (Hartline, 1956) 0:17:00 "Reaction"-diffusion equations and pattern (Lotka-Volterra, Kolmogorov et al., Fisher, Rashevsky, Hodgkin-Huxley) 0:18:24 Turing 0:18:27 Alan Turing (1912-1954) 0:18:33 What was Turing hoping to achieve? 0:19:35 Chemical reaction combined with diffusion 0:20:27 Why peaks? 0:23:15 Linear stability analysis; cells distributed in a ring 0:23:58 Periodic pattern in 1 dimension (non-linear effects added) 0:24:28 'Dappled' pattern in two dimensions (non-linear effects added) 0:24:43 Post-Turing 0:25:11 Curt Stern (1902 -1981) pattern 0:28:48 Bristle patterns in Drosophila: "Turing" prepattern (Maynard Smith and Sondhi, 1961) 0:31:30 Positional information vis-a-vis Prepattern 0:35:29 Positional homology between Drosophila body parts (Postlethwait and Schneiderman, 1971) 0:37:06 Alfred Gierer (1929-) and Hans Meinhardt (1938-2016) 0:37:23 Activator-Inhibitor Model (Gierer and Meinhardt, 1972) 0:40:56 How well do the predictions work? (Bard and Lauder, 1974) 0:42:10 Two-compartment Rashevsky-Turing scheme 0:43:28 Reaction-diffusion system for chick limb patterning (Newman and Frisch, 1979) 0:44:28 When is the uniform steady-state unstable? 0:45:18 Secondary axis formation in Polysphondylium (McNally, Byrne, Fey, Cox, 1986+) 0:47:55 Demonstration of Turing pattern in defined system (Castets et al. 1990) 0:48:35 Patterning along with growth (Meinhardt, 1995) 0:49:06 Stripe formation in Zebrafish: signalling, movement + Turing? (Singh and Nusslein-Volhard, 2014 foll.) 0:49:50 SHIGERU KONDO 0:50:18 Beyond Turing 0:58:55 Turing: "..intended to defeat the argument from design" (comment in letter to friend Robin Gandy) 1:07:25 The evolutionary epigenetic landscape (Sewall Wright, 1934) 1:08:54 Fossil limbs simulated with a reaction-diffusion scheme 1:10:43 Watching the daisies grow 1:12:28 How well do the predictions work? (Bard and Lauder, 1974) 1:18:42 Turing: "..intended to defeat the argument from design" (comment in letter to friend Robin Gandy) 1:25:53 [Code Walkthrough]