Date of Award

Spring 6-14-2025

Document Type

Undergraduate Honors Thesis

Degree Name

B.S. in Molecular Biology

Organizational Unit

College of Natural Science and Mathematics, Biological Sciences

First Advisor

Joseph K. Angleson

Copyright Statement / License for Reuse

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Keywords

Synaptotagmin isoforms, Sex hormone secretion, Anterior pituitary, Gonadotropin-releasing hormone (GnRH), Follicle-stimulating hormone (FSH), Luteinizing hormone (LH)

Abstract

The anterior pituitary is comprised of five cell types which secrete regulatory hormones into the bloodstream. Specifically, gonadotrophs synthesize and release sex hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in response to gonadotropin-releasing hormone (GnRH). GnRH signals from the hypothalamus regulate the differential secretion of LH and FSH from the anterior pituitary. Exocytosis of FSH and LH from dense core vesicles (DCVs) occurs in response to an intracellular calcium signal, sensed by the synaptotagmins proteins. Various isoforms of synaptotagmins exist and each isoform has varying affinity for calcium, causing calcium-regulated exocytosis to be finely controlled. Because LH and FSH are sex hormones that directly impact fertility, understanding the role of synaptotagmins is critical to understanding sex hormone secretion.

In this study, I used the model gonadotroph cell line LßT2 to characterize the synaptotagmin isoforms that are associated with sex hormone secretion. Synaptotagmin 5/9 and synaptotagmin 7 are expressed in the LßT2 cell line, while synaptotagmin 1 is not expressed. Quantitative immunofluorescent staining indicates that there is an increase protein levels of LH beta in response to treatment of GnRH by a factor of ~2.6. In addition, quantitative immunofluorescent staining indicates that the protein levels of both synaptotagmin 5/9 and synaptotagmin 7 increase in response to GnRH treatment. With GnRH treatments, double staining of synaptotagmin 5/9 or synaptotagmin 7 with DCV marker LH beta show low colocalization in general with some puncta clearly colocalizing as well. Strikingly, in untreated cells, co-staining of synaptotagmin 5/9 and synaptotagmin 7 show strong straining of both synaptotagmins that also have high colocalization of puncta in roughly 10% of cells. Preliminary experiments using western blots tested the effects of steroids known to alter LH secretion. These studies show preliminary data and lay the groundwork for further analysis of synaptotagmin isoforms in sex hormone secretion.

Copyright Date

5-26-2025

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Rights Holder

Caitlin Vahl

Provenance

Received from author

File Format

application/pdf

Language

English (eng)

Extent

30 pgs

File Size

2.0 MB

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