Cell Biology & Molecular Genetics
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Item Mating can initiate stable RNA silencing that overcomes epigenetic recovery(Springer Nature, 2021-07-09) Devanapally, Sindhuja; Raman, Pravrutha; Chey, Mary; Allgood, Samual; Ettefa, Farida; Diop, Maïgane; Lin, Yixin; Cho, Yongyi E.; Jose, Antony M.Stable epigenetic changes appear uncommon, suggesting that changes typically dissipate or are repaired. Changes that stably alter gene expression across generations presumably require particular conditions that are currently unknown. Here we report that a minimal combination of cis-regulatory sequences can support permanent RNA silencing of a singlecopy transgene and its derivatives in C. elegans simply upon mating. Mating disrupts competing RNA-based mechanisms to initiate silencing that can last for >300 generations. This stable silencing requires components of the small RNA pathway and can silence homologous sequences in trans. While animals do not recover from mating-induced silencing, they often recover from and become resistant to trans silencing. Recovery is also observed in most cases when double-stranded RNA is used to silence the same coding sequence in different regulatory contexts that drive germline expression. Therefore, we propose that regulatory features can evolve to oppose permanent and potentially maladaptive responses to transient change.Item PERPETUATION OF NON-GENETIC CHANGES AT A TRANSGENE LOCUS IN C. ELEGANS(2018) Devanapally, Sindhuja; Jose, Antony M; Molecular and Cell Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Development of a multicellular organism from a single cell or from a few cells in every generation relies on the reproducible expression pattern of genes. At the beginning of every generation in every organism, at least a single progenitor cell is necessary to produce the organism. This cell is subjected to reprogramming mechanisms that erase epigenetic information transmitted from the previous generation and as it develops, the organism goes through experiences that affect gene expression. Despite this, developmental processes give rise to nearly the same organism in the next generation, suggesting that the components in the cells are similarly regulated in every generation. How a complex organism can develop and reproduce its gene expression pattern using only the information present within the progenitor cell is not understood. Here, we describe an engineered genetic locus in the nematode worm C. elegans that shows robust transgenerational expression like many loci in the genome but, unlike other tested loci, can be uniquely susceptible to transgenerational silencing by one of two distinct processes. This locus could be silenced by double-stranded RNA (dsRNA) transported from neurons and could also be silenced when inherited solely from the male parent in a genetic cross. Each process could initiate transgenerational silencing within the germline that lasted for >25 generations. The two processes depended on distinct mechanisms to initiate silencing – while neuronal dsRNA required the conserved dsRNA importer SID-1 and the Argonaute RDE-1, mating-induced silencing required the Piwi-interacting Argonaute PRG-1. Both processes engaged the same germline Argonaute HRDE-1 to maintain heritable silencing suggesting that both processes trigger silencing independently but converge on the same pathway for maintenance. No other locus that was tested showed such indefinite silencing by either mechanism, suggesting that most loci are resistant to changes in gene expression. Thus, the discovery of a locus that is susceptible to transgenerational change provides us with the first instance of how a single change at a gene sequence can be used to explain evolution of gene regulation.