Undergraduate Honors Theses

Thesis Defended

Spring 2011

Document Type

Thesis

Department

Molecular, Cellular, & Developmental Biology

First Advisor

Rui Yi

Abstract

MicroRNAs (miRNAs) are a family of small, non-coding RNA molecules that play an important regulatory role in many biological processes. However, the precise molecular mechanism of miRNA-mediated regulation is not clear. Here I focused on the role of a deeply conserved miRNA, miR-203, which is one of the most specifically and highly expressed miRNAs in mammalian skin. Previous studies demonstrated that miR-203 is significantly upregulated and, as a result, promotes cell cycle exit during epidermal stem cell differentiation. To examine the precise dynamics of miR-203-mediated inhibition of self-renewal and dissect the underlying molecular mechanism, I isolated epidermal stem cells from a transgenic miR-203 inducible mouse model. By inducing miR-203’s expression in cultured epidermal stem cells, I demonstrated that miR-203, in a short term, potently inhibits the cell cycle transition between G1 MicroRNAs (miRNAs) are a family of small, non-coding RNA molecules that play an important regulatory role in many biological processes. However, the precise molecular mechanism of miRNA-mediated regulation is not clear. Here I focused on the role of a deeply conserved miRNA, miR-203, which is one of the most specifically and highly expressed miRNAs in mammalian skin. Previous studies demonstrated that miR-203 is significantly upregulated and, as a result, promotes cell cycle exit during epidermal stem cell differentiation. To examine the precise dynamics of miR-203-mediated inhibition of self-renewal and dissect the underlying molecular mechanism, I isolated epidermal stem cells from a transgenic miR-203 inducible mouse model. By inducing miR-203’s expression in cultured epidermal stem cells, I demonstrated that miR-203, in a short term, potently inhibits the cell cycle transition between G1 MicroRNAs (miRNAs) are a family of small, non-coding RNA molecules that play an important regulatory role in many biological processes. However, the precise molecular mechanism of miRNA-mediated regulation is not clear. Here I focused on the role of a deeply conserved miRNA, miR-203, which is one of the most specifically and highly expressed miRNAs in mammalian skin. Previous studies demonstrated that miR-203 is significantly upregulated and, as a result, promotes cell cycle exit during epidermal stem cell differentiation. To examine the precise dynamics of miR-203-mediated inhibition of self-renewal and dissect the underlying molecular mechanism, I isolated epidermal stem cells from a transgenic miR-203 inducible mouse model. By inducing miR-203’s expression in cultured epidermal stem cells, I demonstrated that miR-203, in a short term, potently inhibits the cell cycle transition between G1 MicroRNAs (miRNAs) are a family of small, non-coding RNA molecules that play an important regulatory role in many biological processes. However, the precise molecular mechanism of miRNA-mediated regulation is not clear. Here I focused on the role of a deeply conserved miRNA, miR-203, which is one of the most specifically and highly expressed miRNAs in mammalian skin. Previous studies demonstrated that miR-203 is significantly upregulated and, as a result, promotes cell cycle exit during epidermal stem cell differentiation. To examine the precise dynamics of miR-203-mediated inhibition of self-renewal and dissect the underlying molecular mechanism, I isolated epidermal stem cells from a transgenic miR-203 inducible mouse model. By inducing miR-203’s expression in cultured epidermal stem cells, I demonstrated that miR-203, in a short term, potently inhibits the cell cycle transition between G1 MicroRNAs (miRNAs) are a family of small, non-coding RNA molecules that play an important regulatory role in many biological processes. However, the precise molecular mechanism of miRNA-mediated regulation is not clear. Here I focused on the role of a deeply conserved miRNA, miR-203, which is one of the most specifically and highly expressed miRNAs in mammalian skin. Previous studies demonstrated that miR-203 is significantly upregulated and, as a result, promotes cell cycle exit during epidermal stem cell differentiation. To examine the precise dynamics of miR-203-mediated inhibition of self-renewal and dissect the underlying molecular mechanism, I isolated epidermal stem cells from a transgenic miR-203 inducible mouse model. By inducing miR-203’s expression in cultured epidermal stem cells, I demonstrated that miR-203, in a short term, potently inhibits the cell cycle transition between G1 and S phases as early as six hours after induction and, in a long term, reatly reduces the self-renewal capacity of epidermal - depending on the length of time it is induced int he epidermal stem cells. To examine how miR-203’s targets mediate its function, I showed that individual expression of miR-203 target genes, including Msi2, p63, and Skp2, has distinct phenotypes of rescue in the presence of miR-203. Taken together, these results suggest that miR-203 has a profound impact during epidermal stem cell differentiation and that this regulatory role is mediated by specific target genes with unique cellular functions. These findings provide a novel insight into miRNA-mediated regulation and shed light on the importance of miRNA targeting of multiple target genes with unique cellular functions to regulate broad cellular processes. These observations also raise a possibility about the role of miR-203 and its target genes in skin cancer, as well as other types of epithelial cancers.

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