P-420 ALG3 is a new novel marker in preeclampsia
Authors: Sun F , Wei Y , Song M , Jie Q , Lin D , Ma Y 
Published: July 2024

Abstract

Study question
To investigate the potential function of ALG3 (Asparagine-Linked Glycosylation 3, Alpha-1,3-Mannosyltransferase Homolog) in the pathogenesis of preeclampsia(PE).

Summary answer
ALG3 plays an important role in the pathogenesis of PE by influencing the function of the trophoblast cells.

What is known already
PE is the leading cause of maternal and perinatal mortality and morbidity. The underlying mechanism is still unclear. Disorder migration and invasion function of trophoblasts are one of the mechanisms in PE. ALG3 regulates the Dol-P-Man-dependent mannosylation, leading to the formation of a polyterpene alcohol-oligosaccharide precursor and subsequent N-glycan synthesis. The expression of ALG3 in villus tissue during the early stages of preeclampsia is significantly reduced, as indicated by public databases (GSE12767). The investigation into the potential role of ALG3 in early trophoblast development and its contribution to the pathogenesis of PE holds significant scientific interest.

Study design, size, duration
The placental samples were acquired quickly (&lt;30 mins) from a group of normal pregnant women (without PE or other complications) (n = 15) and PE patients (n = 20) to investigate the expression of ALG3. Secondly, lentiviral systems were employed to establish loss and gain of function models in the trophoblast cell lines JEG3 and HTR8/Sneov for elucidating the role of ALG3 in the pathogenesis of PE.

Participants/materials, setting, methods
We examined the expression of ALG3 both in placental tissues from PE and normal pregnant. Meanwhile, we generated ALG3 loss and gain of function models in JEG3 and HTR8/Sneov cells by lentivirus systems. Transwell assays, scratch-wound assays, EDU and plate clone formation assays, and villous explant culture were used to examine the function of ALG3 in JEG3 and HTR8/Sneov cells model. The effect of ALG3 on N-glycosylation in trophoblasts was analyzed using label-free quantitative proteomics.

Main results and the role of chance
In this study, ALG3 was significantly decreased in PE placentas by immunohistochemistry. And further confirmed the expression of ALG3 in placental tissues by qRT-PCR and Western blot. We demonstrated that the knockdown of ALG3 in trophoblasts dramatically decreased cell proliferation, migration, and invasion. Extravillous explants transfected with siALG3 inhibited the expansion of the EVT outgrowth across and into the Matrigel. While overexpression of ALG3 in trophoblasts significantly increased the ability of cell proliferation, migration, and invasion. Further, we demonstrated that ALG3 regulated the N-glycosylation of EGFR in trophoblasts and regulated the EGFR/ERK/MMP9 signal pathway. Therefore, the functional axis, ALG3/EGFR/ERK axis, plays an important role in PE initiation and development. These findings uncover a novel N-glycosylation mechanism of the ALG3 in PE pathogenesis.

Limitations, reasons for caution
Although we show that ALG3 played an important role in the function of trophoblasts, the study of the working mechanism of ALG3 in PE is still limited. The crucial role it plays in early placentation has yet to be fully elucidated. More studies will be performed to explore underline mechanisms.

Wider implications of the findings
This study was the first time to explore the role of ALG3 and N-glycosylation in trophoblast. It will help us to better understand the pathogenesis of PE, which might be helpful in the future application of novel therapeutic targets in PE.

Trial registration number
not applicable