A preliminary investigation into the etiology of agar-like zona pellucida in human oocytes
摘要
To investigate the structural characteristics and origin of agar-like zona pellucida (ZP).
MethodsSeven patients with oocytes showing agar-like ZP and four controls with normal ZP were included. Peripheral blood or MI oocytes were analyzed using whole-exome sequencing (WES), Sanger sequencing, qPCR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). ATRX was overexpressed in human cells.
ResultsAfter screening the variants detected by WES according to the standard procedure and eliminating those that were also present in the normal control group, only one common variant, namely the ATRX point mutation (c.2785G > C), remained among the seven patients presenting an agar-like ZP phenotype. SEM and TEM analyses revealed structural abnormalities in the agar-like ZP, characterized by an abnormally increased density of fiber cross-linking. qPCR demonstrated downregulation of ATRX and concurrent upregulation of ZP1 in human oocytes with agar-like ZP. Furthermore, ATRX overexpression significantly reduced ZP1 mRNA levels in 293 T cells.
ConclusionsThe abnormal structure of the agar-like ZP is attributed to excessive cross-linking among the ZP fibers. ZP1 is accountable for the cross-linking among ZP fibers. The abnormal transcriptional up-regulation of ZP1 may be associated with both excessive cross-linking among ZP fibers and the formation of the agar-like ZP. As a negative regulatory factor of ZP1, the downregulation of ATRX in agar-like ZP oocytes might be the cause of the abnormal upregulation of ZP1. Additionally, the formation of the agar-like ZP does not involve mutations in the ZP1-ZP4 genes, yet it could be associated with the ATRX (c.2785G > C) point mutation.