RAMANUJAN FELLOWS 61

ProfilePramod Pullarkat obtained his B.Sc. degree from Calicut University (1991) and M.Sc. in Physics from the Indian Institute of Technology-Madras (1993). He obtained his Ph.D. degree in 1999 from JNU-Delhi for his work on new defect-mediated structures in Liquid Crystals performed at RRI. Subsequently, he shifted his research interest to biological systems starting off as a post-doctoral fellow at Institut Curie, Paris, investigating cell mechanical responses. In 2001 he joined the University of Bayreuth, Germany as an independent investigator and studied shape instabilities occurring in axons, axonal mechanics, cell rheology, etc. He became Associate Professor a RRI in 2008 and has setup a full-fledged biophysics laboratory there, including some home-developed equipment for interrogating biophysical phenomena.

research DescriPtion Neuronal cells generate long tubular protrusions known as axons and dendrites. Axons can grow to lengths of the same order as the size of the parent organism with a nearly uniform diameter of about a micrometer. And unlike many other cell types, these cells have to be repaired and maintained throughout the lifetime of the organism as they are not easily replicated. Such morphological

Pramod A. PullarkatAssociate Professor (Biophysics)Soft Condensed Matter group,Raman Research Institute (RRI),C. V. Raman Avenue, Sadashivanagar,Bangalore—560 080pramod@rri.res.in

and functional characteristics are largely regulated by the cell plasma membrane and the cytoskeleton—a biopolymer network along with associated proteins. The cytoskeleton provides structural integrity to the cell but is highly dynamics as required for neuronal plasticity. The dynamics may be regulated by molecular motor proteins which can generate active stresses in the cytoskeleton.

The research activities of Pramod Pullarkat’s group mainly addresses the following questions. (i) How do perturbations to the cytoskeletal elements lead to morphological changes and axonal atrophy? This activity is aimed at understanding the mechanism behind morphological changes observed in axons under natural neurodegenerative conditions. For this the group uses biochemical and physical methods to induce such morphological changes. Genetically modified cells expressing fluorescent cytoskeletal elements are used to follow the resulting dynamics. (ii) How are active stresses generated in axons and what are its functional consequences? This is motivated by several indications that mechanical tension influences several aspects of neuronal development like branch formation, synaptogenesis, axonal retraction during rewiring, etc. For this the group has built a special force apparatus which can probe the passive and active mechanical responses of axons to applied perturbations while allowing simultaneous fluorescence imaging and biochemical modifications.

comPlete list of Publications as a ramanujan fellow 1. “The role of the cytoskeleton in volume regulation

and beading transitions in PC12 neurites”, Pablo Fernandez and Pramod Pullarkat, Biophysical Journal, vol . 99, pp. 3571 (2010).

2. “Optical fiber-based force transducer for microscale samples”, Seshagiri Rao R. V., Chirag Kalelkar, and Pramod A. Pullarkat, Review of Scientific Instruments, vol. 84, pp. 105107 (2013); doi: 10.1063/1.4824198