Document Type

Student Research Paper

Date

Spring 2019

Academic Department

Biology

Faculty Advisor(s)

Diana Bridge

Abstract

The freshwater cnidarians of the genus Hydra are a potential system for the study of aging. Hydra vulgaris shows negligible senescence. Hydra oligactis, on the other hand, shows rapid aging after it has been induced to sexually reproduce. Understanding the onset of aging in H. oligactis may provide insights relevant to aging and the accompanying diseases in humans. One attractive pathway for study is the insulin/IGF-1 signaling (ISS) pathway, a conserved pathway which affects lifespan in both invertebrate and vertebrate model organisms. In H. vulgaris, activation of the ISS pathway is thought to reduce activities of the transcription factor FoxO and induce differentiation of stem cells. The purpose of this experiment was to determine whether expression of the insulin-like peptide receptor HTK7 gene changes in H. oligactis once aging is induced. It was expected that HTK7 would be expressed in stem cells in aging H. oligactis, causing the pre-mature differentiation of these cells, and contributing to the onset of aging. Expression of HTK7 was analyzed using whole-mount RNA in situ hybridization. H. oligactis showed highest HTK7 expression in epithelial cells in regions where differentiation takes place: at the base of the tentacles and adjacent to the basal disk. When analyzing the foot region of the polyps, it was seen that the foot became larger in aging H. oligactis. This phenotype mimicked ones previously seen in FoxO-deficient H. vulgaris, indicating that HTK7 could be pre-maturely downregulating FoxO in the foot region and contributing to the onset of aging.

Notes

Senior thesis.

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