LncRNA Jpx induces Xist expression in mice using both trans and cis mechanisms

Abstract

Mammalian X chromosome dosage compensation balances X-linked gene products between sexes and is coordinated by the long noncoding RNA (lncRNA) Xist. Multiple cis and trans-acting factors modulate Xist expression; however, the primary competence factor responsible for activating Xist remains a subject of dispute. The lncRNA Jpx is a proposed competence factor, yet it remains unknown if Jpx is sufficient to activate Xist expression in mice. Here, we utilize a novel transgenic mouse system to demonstrate a dose-dependent relationship between Jpx copy number and ensuing Jpx and Xist expression. By localizing transcripts of Jpx and Xist using RNA Fluorescence in situ Hybridization (FISH) in mouse embryonic cells, we provide evidence of Jpx acting in both trans and cis to activate Xist. Our data contribute functional and mechanistic insight for lncRNA activity in mice, and argue that Jpx is a competence factor for Xist activation in vivo.

Functional conservation of lncRNAJPXdespite sequence and structural divergence

“…Average expression ± SEM are shown from at least three independent transfections (**, P < 0.01 from one-tail paired Student t-tests in comparison to 'WT; Vector'). An increase of Xist expression by Jpx overexpression is consistent with previous reports (Carmona et al, 2018;Sun et al, 2013b).…”

The how and why of lncRNA function: An innate immune perspective

“…To prove genetically that a lncRNA is functioning in trans, a trans rescue experiment can be performed using transgenic mice that constitutively express a lncRNA. This rescue strategy has been utilized in some studies including Evf2 [194,195], Jpx [196], as well as Pnky [197] which both demonstrate successful rescue experiments where the phenotype from germline ablation of a lncRNA is rescued through generation and crossing with a transgenic animal.…”

Genetic Models Reveal cis and trans Immune-Regulatory Activities for lincRNA-Cox2

“…The tremendous number of newly annotated lincRNAs and their low evolutionary conservation has led to debates about their functionality (Bassett et al, 2014). However, the number of characterized lincRNAs is growing, and this class of gene has been shown to control various biological processes, including somatic tissue differentiation (Kretzetal.,2013),Xchro- mosome inactivation (Carmona et al, 2018; Engreitz et al, 2013; Jégu et al, 2017), and organ development (Anderson et al, 2016). …”

“…However, like most lincRNAs and protein-coding genes, the cis - and frans -regulatory elements encoded within the locus remain unstudied in vivo. Most recently, some lincRNAs have been discovered to have the ability to function both in cis and in frans (Carmona et al, 2018; Li et al, 2012; Yin et al, 2015). …”