MAML1: a coregulator that alters endometrial epithelial cell adhesive capacity

Sadaf Zafir,Leilani Santos,Evdokia Dimitriadis,Wei Zhou,Ellen Menkhorst

doi:10.1186/s40738-021-00100-y

Sadaf Zafir, Leilani Santos

Open Access

https://doi.org/10.1186/s40738-021-00100-y

Copy DOI

Abstract

BackgroundAbnormalities in endometrial receptivity has been identified as a major barrier to successful embryo implantation. Endometrial receptivity refers to the conformational and biochemical changes occurring in the endometrial epithelial layer which make it adhesive and receptive to blastocyst attachment. This takes place during the mid-secretory phase of woman’s menstrual cycle and is a result of a delicate interplay between numerous hormones, cytokines and other factors. Outside of this window, the endometrium is refractory to an implanting blastocyst. It has been shown that Notch ligands and receptors are dysregulated in the endometrium of infertile women. Mastermind Like Transcriptional Coactivator 1 (MAML1) is a known coactivator of the Notch signaling pathway. This study aimed to determine the role of MAML1 in regulating endometrial receptivity.MethodsThe expression and localization of MAML1 in the fertile human endometrium (non-receptive proliferative phase versus receptive mid-secretory phase) were determined by immunohistochemistry. Ishikawa cells were used as an endometrial epithelial model to investigate the functional consequences of MAML1 knockdown on endometrial adhesive capacity to HTR8/SVneo (trophoblast cell line) spheroids. After MAML1 knockdown in Ishikawa cells, the expression of endometrial receptivity markers and Notch dependent and independent pathway members were assessed by qPCR. Two-tailed unpaired or paired student’s t-test were used for statistical analysis with a significance threshold of P < 0.05.ResultsMAML1 was localized in the luminal epithelium, glandular epithelium and stroma of human endometrium and the increased expression identified in the mid-secretory phase was restricted only to the luminal epithelium (P < 0.05). Functional analysis using Ishikawa cells demonstrated that knockdown of MAML1 significantly reduced epithelial adhesive capacity (P < 0.01) to HTR8/SVneo (trophoblast cell line) spheroids compared to control. MAML1 knockdown significantly affected the expression of classical receptivity markers (SPP1, DPP4) and this response was not directly via hormone receptors. The expression level of Hippo pathway target Ankyrin repeat domain-containing protein 1 (ANKRD1) was also affected after MAML1 knockdown in Ishikawa cells.ConclusionOur data strongly suggest that MAML1 is involved in regulating the endometrial adhesive capacity and may facilitate embryo attachment, either directly or indirectly through the Notch signaling pathway.

Highlights

Abnormalities in endometrial receptivity has been identified as a major barrier to successful embryo implantation
Hairy and enhancer of split (HES) 1, Hairy and enhancer of split 5 (HES5) and Hairy/enhancer-of-split related with YRPW motif protein 1 (HEY1) are most commonly used to investigate Notch pathway transcriptional activity [7, 37] and were chosen for qPCR analysis
In conclusion, our study has provided the first evidence that Mastermind Like Transcriptional Coactivator 1 (MAML1) may be a critical component in the regulation of endometrial epithelial cell adhesive capacity during endometrial receptivity and blastocyst implantation

Summary

Introduction

Abnormalities in endometrial receptivity has been identified as a major barrier to successful embryo implantation. Endometrial receptivity refers to the conformational and biochemical changes occurring in the endometrial epithelial layer which make it adhesive and receptive to blastocyst attachment This takes place during the mid-secretory phase of woman’s menstrual cycle and is a result of a delicate interplay between numerous hormones, cytokines and other factors. It is known that endometrial tissue is only receptive to a competent blastocyst during the window of implantation which occurs during the mid-secretory phase (days 19–23 of a 28-day cycle) of the menstrual cycle and is otherwise refractory to blastocyst adhesion [4, 6] Such cycle-dependent functional changes require delicate interplay between numerous hormones, cytokines and signaling pathways and are essential to secure a successful embryo attachment and implantation. It has been identified that Jagged, Jagged, DLL1 and Notch Receptor 1 (NOTCH1) expression are significantly lower at the mid-secretory phase in women with infertility, compared to fertile subjects [7, 17, 18]

Objectives

Methods

Results

Discussion

Conclusion