Transcriptional control in the murine adrenal cortex and testis
Year: 2016
Type: dissertation
Abstract: The main steroidogenic organs in mammals, the adrenal glands and gonads, arise from a common pool of mesodermal progenitor cells during embryogenesis. Precise gene regulation controls cell differentiation, growth, and homeostasis in the developing embryo and the adult. Disruptions of these spatiotemporal processes are linked to a variety of diseases, including developmental disorders, malignant transformations, and infertility. This dissertation focuses on the molecular mechanisms that regulate normal and neoplastic cell development in the adrenal cortex and testis of the mouse. The initiation of gene transcription requires the binding of transcription factors to specific cis-regulatory elements within DNA. Methylation of cytosine residues affects transcription factor binding to these regulatory elements; hypermethylation results in condensed chromatin that is inaccessible to the transcriptional machinery, whereas hypomethylation is an indicator of active gene transcription. Alterations in DNA methylation have been linked to neoplasia. We used a novel method of genome-wide methylation profiling, termed Laser Capture Microdissection-Reduced Representation Bisulfite Sequencing, to characterize the changes in promoter methylation associated with gonadectomy-induced adrenocortical neoplasia in the mouse. One of the genes upregulated during gonadectomy-induced adrenocortical neoplasia is Gata4, a transcription factor normally absent in the adult adrenal gland. To determine whether GATA4 directly modulates tumorigenesis we analyzed mice with germline or conditional loss-of-function mutations in this gene. GATA4 deficiency was associated with reduced tumor growth and decreased expression of sex steroidogenic markers. GATA4 is expressed in testicular Leydig cells. To gain insight into the role of GATA4 in this cell type, we performed gene silencing experiments in a mouse Leydig cell tumor line (mLTC-1) and in primary mouse Leydig cells. Comprehensive analyses, including transcriptomic and metabolomic profiling, showed that Gata4 silencing was associated with diminished sex steroid production and impaired glycolysis. Conditional deletion of Gata4 in another testicular somatic cell type, the Sertoli cell, has been reported to increase the permeability of the blood-testis barrier (BTB) and disrupt spermatogenesis in adult mice. To elucidate the molecular underpinnings of these phenotypic abnormalities, we performed Gata4 gene silencing experiments in an immortalized Sertoli cell line (TM4) and in primary mouse Sertoli cells. GATA4 depletion was associated with altered expression of genes involved in BTB maintenance, including components of tight/adherens junctions (e.g., Tjp1, Cldn12) and the extracellular matrix (e.g., Lamc1, Col4a5). Gata4 gene silencing impaired the production of lactate, a key Sertoli cell-derived nutrient that is essential for proper spermatogenesis.
Source: Työväentutkimus Vuosikirja
Author: Anja Schrade
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2299019138