Biology subjects

Espejo-Serrano, C.

Publications and source records attributed to Espejo-Serrano, C..

3 recordsLinked to original sources

bioRxiv2023

Specific genomic targeting of the RNF12/RLIM E3 ubiquitin ligase selectively programmes developmental transcription

The E3 ubiquitin ligase RNF12/RLIM controls developmental gene expression and is mutated in the X-linked intellectual disability disorder Tonne-Kalscheuer syndrome (TOKAS). However, the mechanisms by which RNF12 E3 ubiquitin ligase activity controls specific gene expression signatures are not known. Here, we show that chromatin forms a regulatory platform for RNF12 substrate ubiquitylation and transcriptional patterning. RNF12 is recruited to specific genomic regions via a distinct consensus sequence motif, which enables targeting to key transcription factor substrate REX1. Mechanistically, RNF12 chromatin recruitment is largely REX1 independent, but is achieved via the conserved basic region (BR) adjacent to the RING domain. This region is critical for REX1 ubiquitylation on chromatin and downstream RNF12-dependent gene regulation. Furthermore, we find that RNF12 N-terminal sequences suppress chromatin recruitment and substrate ubiquitylation, uncovering a previously unappreciated autoinhibitory mechanism that governs genome targeting. Taken together, our results provide insight into mechanisms by which selective substrate targeting of an E3 ubiquitin ligase enables specific programming of gene expression.

cell biology↗

bioRxiv2022

Cell autonomous requirement of imprinted XCI inextra-embryonic polar trophoblast cells

In female mice the gene dosage from X chromosomes is adjusted by a process called X chromosome inactivation (XCI) that occurs in two steps. An imprinted form of XCI (iXCI) silencing the paternally inherited X chromosome (Xp) is initiated at the 2-4 cell stages. As extraembryonic cells including trophoblasts keep the Xp silenced, epiblast cells that give rise to the embryo proper reactivate the Xp and undergo a random form of XCI (rXCI) during peri-implantation stages. Lack of X dosage compensation leads to peri-implantation lethality due to inhibition of trophoblast stem cells. However, as the epiblast regulates the trophoblast lineage, the roles of iXCI vs rXCI in the early lethal phenotype remains unclear. We have investigated functions and expression of Rlim (Rnf12), an E3 ubiquitin ligase, and its target protein Rex1 (Zfp42) that control iXCI. Consistent with functions specifically for iXCI, we show an inverse correlation in the expression of Rlim and Rex1 throughout pre-implantation development, but an Rlim-independent downregulation of Rex1 in epiblast cells upon implantation. Moreover, disturbing the functional Rlim-Rex1 dynamics in females leads to cell fate confusion and premature differentiation specifically of the polar trophoblast stem cell pool. Thus, controlled by the Rlim-Rex1 axis, female mouse development requires iXCI in the polar trophoblast cell lineage.

developmental biology↗

bioRxiv2020

A novel RLIM/RNF12 variant disrupts protein stability and function to cause severe Tonne-Kalscheuer syndrome

Tonne-Kalscheuer syndrome (TOKAS) is an X-linked intellectual disability syndrome associated with variable clinical features including craniofacial abnormalities, hypogenitalism and diaphragmatic hernia. TOKAS is caused exclusively by variants in the gene encoding the E3 ubiquitin ligase gene RLIM, also known as. Here we report identification of a novel RLIM missense variant, c.1262A>G p.(Tyr421Cys) adjacent to the regulatory basic region, which causes a severe form of TOKAS resulting in perinatal lethality by diaphragmatic hernia. Inheritance and X-chromosome inactivation patterns implicate RLIM p.(Tyr421Cys) as the likely pathogenic variant in the affected individual and within the kindred. We show that the RLIM p.(Tyr421Cys) variant disrupts both expression and function of the protein in an embryonic stem cell model. RLIM p.(Tyr421Cys) is correctly localised to the nucleus, but is readily degraded by the proteasome. The RLIM p.(Tyr421Cys) variant also displays significantly impaired E3 ubiquitin ligase activity, which interferes with RLIM function in Xist long-non-coding RNA induction that initiates imprinted X-chromosome inactivation. Our data uncover a highly disruptive missense variant in RLIM that causes a severe form of TOKAS, thereby expanding our understanding of the molecular and phenotypic spectrum of disease severity.

developmental biology↗