P-804 Smchd1 is a key regulator of epigenetic cellular memory induced by morphine in mouse embryonic stem cells (mESC)
Authors: Araolaza M 
Published: July 2024

Study question

Can morphine induce stable epigenetic changes that persist mitotically in mESC?

Summary answer

SMCHD1 is a key regulator of epigenetic cellular memory induced by morphine, whose deregulation can be memorized by mESC and upon embryo development.

What is known already

Epigenetic cellular memory induced by environmental factors implies the existence of mitotically heritable changes that influence gene expression without altering DNA sequence, leading to the propagation of heritable changes in phenotype. X chromosome inactivation (XCI) is an important epigenetic process, which takes places during embryo development and is maintained in the adulthood. Since XCI is part of normal development, changes induced by environmental factors might affect embryo development and lead to health problems. As morphine can easily pass through the placental barrier and reach the embryo, our aim is to elucidate whether morphine causes epigenetic regulation on XCI process.

Study design, size, duration

Epigenetic cellular memory induced by environmental factors implies the existence of mitotically heritable changes that influence gene expression without altering DNA sequence, leading to the propagation of heritable changes in phenotype. To evaluate if morphine can induce cellular epigenetic memory, we analyzed the dynamic epigenetic changes over the time in the absence of morphine. For that purpose, OCT4-reported mESCs were chronically treated with morphine during 24h (10-5 mM)

Participants/materials, setting, methods

• Transcriptomic analysis by RNA-Sequencing and gene expression validation by qRT-PCR.

• Epigenetic analysis by H3K27me3 ChIP-Sequencing and WGBS-Sequencing.

• Smchd1 gene silencing by Crisper-Cas9.

Main results and the role of chance

Morphine induced cellular epigenetic memory upon embryo development. mESCs can memorize morphine exposure and induces transcriptional changes that can persist over the time, even in the absence of morphine. RNA-seq has shown that morphine chronic treatment produces a transcriptional deregulation of 932 genes in P1 just after the treatment and this amount increased after treatment withdrawal (1196 genes, P2 and 2138 in P3). Integrative analyses between P1, P2 and P3 identifies Smchd1 gene as a potential regulator of epigenetic cellular memory induced by morphine. Crisper-Cas9 silencing analyses confirmed that Structural maintenance of chromosomes flexible hinge domain-containing 1 (Smchd1), an architectural factor critical for X-chromosome inactivation (XCI), is a morphine-sensitive target gene. Morphine reduced the gene expression of Smchd1 in mESC at different time points, which is consistent with an increase of H3K27me3 and DNA methylation at promoter. Morphine alters normal X chromosome wide silencing. Our results identified Smchd1 a key regulator of epigenetic cellular memory induced by morphine, whose deregulation can be memorized by the cell, providing an epigenetic mechanism that is maintained into cell-to-cell memory and cell differentiation process, which might cause diseases or health problems during the adulthood.

Limitations, reasons for caution

To perform the in-vitro analysis in mouse

Wider implications of the findings

Our results provide insights into the epigenetic mechanisms induced by morphine and establish the bases to understand how environmental factors can cause epigenetic changes that cause health problems or diseases, since a skewed XCI pattern is behind the higher incidence on different neurological diseases such as Alzheimer or Autism

Trial registration number

not applicable