The following is a summary of “RNA-seq analysis identifies age-dependent changes in expression of mRNAs – encoding N-glycosylation pathway enzymes in mouse gonadotropes,” published in the August 2023 issue of Molecular and Cellular Endocrinology by McDonald et al.

Follicle-stimulating hormone (FSH) is a glycoprotein synthesized as a heterodimer of α/β subunits in gonadotropes. Each subunit is composed of two N-glycan chains. Researchers’ previous in vivo medical studies have identified that at least one N-glycan chain on the FSHβ subunit is necessary to assemble and process FSH dimers efficiently. Furthermore, macro heterogeneity in human FSHβ leads to ratiometric alterations in age-specific FSH glycoforms, especially during the menopausal transition. Despite the acknowledgment of numerous significant functions of sugars on follicle-stimulating hormones (FSH), such as dimer formation and release, duration in the bloodstream, binding to receptors, and transmission of signals, the N-glycosylation apparatus in gonadotropes has yet to be characterized. This study utilized a mouse model wherein gonadotropes were labeled with GFP in vivo.

Subsequently, a swift purification of GFP-positive gonadotropes was accomplished from the pituitaries of female mice at various stages of reproductive age, including young, middle-aged, and elderly. Researchers have identified through RNA-seq analysis a total of 52 messenger RNAs (mRNAs) that encode enzymes involved in the N-glycosylation pathway. These mRNAs were found to be expressed in gonadotropes of mice aged 3 and 8-10 months. The enzymes were hierarchically mapped and localized to specific subcellular organelles within the N-glycosylation biosynthetic pathway. Among the 52 messenger ribonucleic acids (mRNAs) analyzed, it was observed that 27 mRNAs exhibited differential expression patterns when comparing mice aged 3 months and those aged 8-10 months. Researchers subsequently identified 8 messenger ribonucleic acids (mRNAs) that showed different alterations in expression levels. These mRNAs were chosen to further validate their abundance in living organisms through quantitative polymerase chain reaction (qPCR) analysis. Researchers utilized a broader range of aging time points, specifically focusing on two distinct age groups: 8 and 14 months. 

The real-time quantitative polymerase chain reaction (qPCR) analysis revealed dynamic fluctuations in the expression of messenger RNAs (mRNAs) encoding enzymes involved in the N-glycosylation pathway throughout an individual’s lifespan. Significantly, the computational analysis indicated that the promoters of genes encoding these eight mRNAs exhibit multiple high-probability binding sites for estrogen receptor-1 and progesterone receptor. The researcher’s investigations delineate the N-glycome and ascertain age-specific dynamic alterations in mRNAs encoding N-glycosylation pathway enzymes in murine gonadotropes. Researcher’s research indicates that the decrease in ovarian hormones associated with aging may influence the activity of N-glycosylation enzymes in the gonadotropes of mice, which could potentially account for the observed changes in N-glycosylation patterns of the FSHβ subunit in the pituitaries of women as they age.

Source: sciencedirect.com/science/article/abs/pii/S0303720723001223