Competence for Chemical Reprogramming of Sexual Fate Correlates with an Intersexual Molecular Signature inCaenorhabditis elegans

Abstract

In multicellular organisms, genetic programs guide cells to adopt cell fates as tissues are formed during development, maintained in adults, and repaired after injury. Here we explore how a small molecule in the environment can switch a genetic program from one fate to another. Wild-type Caenorhabditis elegans XX adult hermaphrodites make oocytes continuously, but certain mutant XX adults make sperm instead in an otherwise hermaphrodite soma. Thus, puf-8; lip-1 XX adults make only sperm, but they can be switched from sperm to oocyte production by treatment with a small-molecule MEK inhibitor. To ask whether this chemical reprogramming is common, we tested six XX sperm-only mutants, but found only one other capable of cell fate switching, fbf-1; lip-1. Therefore, reprogramming competence relies on genotype, with only certain mutants capable of responding to the MEK inhibitor with a cell fate change. To gain insight into the molecular basis of competence for chemical reprogramming, we compared polyadenylated transcriptomes of competent and noncompetent XX sperm-only mutants in the absence of the MEK inhibitor and hence in the absence of cell fate reprogramming. Despite their cellular production of sperm, competent mutants were enriched for oogenic messenger RNAs relative to mutants lacking competence for chemical reprogramming. In addition, competent mutants expressed the oocyte-specific protein RME-2, whereas those lacking competence did not. Therefore, mutants competent for reprogramming possess an intersexual molecular profile at both RNA and protein levels. We suggest that this intersexual molecular signature is diagnostic of an intermediate network state that poises the germline tissue for changing its cellular fate in response to environmental cues. C ELLS in multicellular organisms acquire specific fates, either during development as tissues are generated or during adulthood as tissues are renewed or repaired. A classical view holds that during development, a cell follows a specific genetic program to determine its differentiated fate, but more recent studies reveal that cells can be induced to switch from one genetic program to another. Such "reprogramming" of a cell fate program can occur in vivo in cancer (Friedl and Alexander 2011;Byun and Gardner 2013), wound healing (Wong et al. 2013), and regeneration (Xin et al. 2013;Ziv et al. 2013). Moreover, reprogramming can be stimulated by introduction of transcription factors (Takahashi and Yamanaka 2006) or small molecules (Morgan et al. 2010;Zhu et al. 2010;Li et al. 2014). Here we explore the effect of genotype on the capacity for a particular case of chemically induced cell fate reprogramming within an organism.The Caenorhabditis elegans germline provides a tractable model for analyses of cell fate reprogramming. The adult germline is an elongate tissue with 2000 cells, including germline stem cells (GSCs) (Figure 1A, yellow). GSCs continuously generate daughter cells that enter the meiotic cell cycle ( Figure 1A, green) and then differentiate as...

Diverse Roles of PUF Proteins in Germline Stem and Progenitor Cell Development in C. elegans

“…Therefore, regulation of MPK-1 activity by PUF-8 and FBF-1 reviewed above contributes to germline sex determination. Hyperactivation of MPK-1 and excessive spermatogenesis were observed in puf-8; lip-1 as well as in fbf-1; lip-1 genetic backgrounds (Morgan et al, 2010;Sorokin et al, 2014). In these genetic backgrounds, spermatogenesis was dependent on MPK-1 activity and repressed by a small molecule MEK inhibitor U0126 (Morgan et al, 2010;Sorokin et al, 2014).…”

“…Hyperactivation of MPK-1 and excessive spermatogenesis were observed in puf-8; lip-1 as well as in fbf-1; lip-1 genetic backgrounds (Morgan et al, 2010;Sorokin et al, 2014). In these genetic backgrounds, spermatogenesis was dependent on MPK-1 activity and repressed by a small molecule MEK inhibitor U0126 (Morgan et al, 2010;Sorokin et al, 2014). Activation of MPK-1 in fbf-1; lip-1 genetic background likely results from the loss of FBF-mediated repression of mpk-1 translation and the loss of LIP-1-mediated post-translational inhibition of MPK-1 (Lee et al, 2007a).…”

DIV-1/PolA2 Promotes GLP-1/Notch-Mediated Cellular Events inCaenorhabditis elegans

“…Interestingly, we found that the Glp phenotype of fbf-1 fbf-2 mutants was sufficiently suppressed by additional removal of PUF-8 (another PUF protein) (Fig. 5A and 5B), a key regulator for C. elegans germline development (Subramaniam and Seydoux, 2003; Ariz et al, 2009; Cha et al, 2012; Racher and Hansen, 2012; Pushpa et al, 2013; Vaid et al, 2013; Datla et al, 2014; Sorokin et al, 2014; Priti and Subramaniam, 2015). The puf-8 fbf-1 fbf-2 triple mutants displayed mitotically dividing cells in the germline (Fig.…”

Insight into Sperm-less Conception of Virgin Mary from Reproductive Biology Perspective

“…The sperm and egg in the same flower are fertilized to form new embryos. A similar form of reproduction is seen in hermaphrodite nematodes, called C. elegans [29][30][31][32]. There are also case reports of the co-presence of both the gonad and testis tissues in humans [33].…”