TY - JOUR T1 - S. mediterranea ETS-1 regulates the function of cathepsin-positive cells and the epidermal lineage landscape via basement membrane remodeling. JF - J Cell Sci Y1 - 2022 A1 - Dubey, Vinay Kumar A1 - Sarkar, Souradeep R A1 - Lakshmanan, Vairavan A1 - Dalmeida, Rimple A1 - Gulyani, Akash A1 - Palakodeti, Dasaradhi KW - Animals KW - Basement Membrane KW - Cathepsins KW - Cell Differentiation KW - Epidermis KW - Humans KW - Matrix Metalloproteinases KW - Mediterranea KW - Planarians KW - Transcription Factors AB -

Extracellular matrix (ECM) is an important component of stem cell niche. Remodeling of ECM mediated by ECM regulators, such as matrix metalloproteinases (MMPs) plays a vital role in stem cell function. However, the mechanisms that modulate the function of ECM regulators in the stem cell niche are understudied. Here, we explored the role of the transcription factor (TF) ETS-1, which is expressed in the cathepsin-positive cell population, in regulating the expression of the ECM regulator, mt-mmpA, thereby modulating basement membrane thickness. In planarians, the basement membrane around the gut/inner parenchyma is thought to act as a niche for pluripotent stem cells. It has been shown that the early epidermal progenitors migrate outwards from this region and progressively differentiate to maintain the terminal epidermis. Our data shows that thickening of the basement membrane in the absence of ets-1 results in defective migration of stem cell progeny. Furthermore, the absence of ets-1 leads to a defective epidermal progenitor landscape, despite its lack of expression in those cell types. Together, our results demonstrate the active role of ECM remodeling in regulating tissue homeostasis and regeneration in the planarian Schmidtea mediterranea. This article has an associated First Person interview with one of the co-first authors of the paper.

VL - 135 IS - 20 ER - TY - JOUR T1 - Hierarchies in light sensing and dynamic interactions between ocular and extraocular sensory networks in a flatworm. JF - Sci Adv Y1 - 2017 A1 - Shettigar, Nishan A1 - Joshi, Asawari A1 - Dalmeida, Rimple A1 - Gopalkrishna, Rohini A1 - Chakravarthy, Anirudh A1 - Patnaik, Siddharth A1 - Mathew, Manoj A1 - Palakodeti, Dasaradhi A1 - Gulyani, Akash AB -

Light sensing has independently evolved multiple times under diverse selective pressures but has been examined only in a handful among the millions of light-responsive organisms. Unsurprisingly, mechanistic insights into how differential light processing can cause distinct behavioral outputs are limited. We show how an organism can achieve complex light processing with a simple "eye" while also having independent but mutually interacting light sensing networks. Although planarian flatworms lack wavelength-specific eye photoreceptors, a 25 nm change in light wavelength is sufficient to completely switch their phototactic behavior. Quantitative photoassays, eye-brain confocal imaging, and RNA interference/knockdown studies reveal that flatworms are able to compare small differences in the amounts of light absorbed at the eyes through a single eye opsin and convert them into binary behavioral outputs. Because planarians can fully regenerate, eye-brain injury-regeneration studies showed that this acute light intensity sensing and processing are layered on simple light detection. Unlike intact worms, partially regenerated animals with eyes can sense light but cannot sense finer gradients. Planarians also show a "reflex-like," eye-independent (extraocular/whole-body) response to low ultraviolet A light, apart from the "processive" eye-brain-mediated (ocular) response. Competition experiments between ocular and extraocular sensory systems reveal dynamic interchanging hierarchies. In intact worms, cerebral ocular response can override the reflex-like extraocular response. However, injury-regeneration again offers a time window wherein both responses coexist, but the dominance of the ocular response is reversed. Overall, we demonstrate acute light intensity-based behavioral switching and two evolutionarily distinct but interacting light sensing networks in a regenerating organism.

VL - 3 IS - 7 ER -