Project Summary/Abstract
Although ovarian aging is a natural physiological process, cessation of ovarian function at midlife increases
susceptibility to the development of co-morbidities, such as osteoporosis, which decrease quality of life and
increases healthcare burden. There is currently no intervention for preventing/delaying this, highlighting an
unmet need for novel approaches, e.g. extending ovarian lifespan, to tackle this. Key mediators of ovarian
function are follicle stimulating hormone (FSH) and its receptor (FSHR). FSH is a glycoprotein hormone, with
two predominant glycoforms identified; partially glycosylated FSH (FSH18/21) and fully glycosylated FSH
(FSH24). FSH glycoforms have distinct functional properties, with FSH18/21 displaying faster binding kinetics
and more potent and distinct signal pathway activation than FSH24. Interestingly, age-related changes in human
pituitary extracts have been reported, with FSH18/21 predominant in women of reproductive prime and FSH24
predominant in peri-menopausal/menopausal women. The increase in less potent FSH24 coincides with
increasing ovarian resistance to FSH reported during peri-menopause. Yet, how these functional differences
in FSH modulate the actions of FSHR within the aging ovary remain unknown and will be explored by
this project. Increasingly important ways that G protein-coupled receptors direct signal and functional diversity
is via oligomerization (association of receptor protomers into dimers and oligomers), and endosomal trafficking.
Our recent work suggests that FSH18/21 and FSH24 distinctly modulate FSHR oligomerization, correlating with
differences in FSH glycoform-dependent cAMP production. Our preliminary data suggest that FSH glycoforms
may route FSHR to different endosomal compartments, with cAMP production dependent on FSHR
internalization. This project aims to determine how FSH glycoforms modulate FSHR oligomerization and
trafficking in young and aging ovaries, and functional impact thereof. The working hypothesis is FSH glycoforms
mediate distinct FSHR oligomerization signatures and FSHR trafficking within the young and aging ovary, with
defined functional consequences. Using a novel N terminal tagged FLAG-FSHR knock in mouse, high resolution
imaging and multiomics ATACseq and RNAseq approaches, Aim 1 will determine how FSHR oligomerization
and signaling is modulated in granulosa cells during folliculogenesis and aging, and how disrupting FSHR
oligomerization impacts FSH glycoform function. Aim 2 will determine how FSH glycoforms direct FSHR
endosomal routing and role of these compartment in signal activation and downstream functions. Successful
completion of these aims will elucidate how unique ovarian FSHR oligomerization and trafficking
signatures direct signal pathway activation and transcriptomic and functional outputs by FSH
glycoforms, during aging. This is the first step in the discovery pipeline to identifying novel strategies to improve
ovarian function and health in aging women.
