Epigenetic regulation of retroelements by TET enzymes in neural precursor cells

• Grant number: 15/15231-3
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: January 11, 2016
• End date: July 08, 2016
• Field of knowledge: Biological Sciences - Genetics - Human and Medical Genetics
• Principal Investigator: Luiz Gonzaga Tone
• Grantee: Karina Bezerra Salomão Xavier
• Supervisor: Miguel Branco
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Institution abroad: Blizard Institute, England
• Associated to the scholarship: 13/15125-3 - Study of TET gene expression and hydroxymethylation levels in medulloblastoma., BP.DR

Abstract

Long interspersed nuclear elements (LINE-1 or L1) are classified as non-long terminal repeat (LTR) retroelements, which have the ability to replicate and reintegrate in the host genome. In neuronal precursor cells (NPCs), L1s are expressed and mobile. Somatic L1 insertions have been detected in protein-coding and tissue-specific genes. L1s therefore generate genetic somatic mosaicism in the brain, and it has been argued that this could contribute to neuronal diversity. On the other hand, increased L1 activity in the brain has been linked to schizophrenia. During neuronal differentiation, TCF/LEF, Wnt3 and YY1 transcription factors bind the L1 promoter region, concomitant with a decrease in Sox2- and MeCP2-mediated repression. Furthermore, there is a reduction of DNA methylation levels in this region. In the present project, we hypothesize that DNA demethylation at the L1 promoter is catalyzed by TET enzymes, which oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and other derivatives. Recent data from the host lab shows that TET enzymes positively regulate L1 elements in embryonic stem cells, suggesting that a similar mechanism may activate L1s in NPCs, where TET expression is high. Here, we propose to test this hypothesis by performing TET1 and TET3 knockdown in NPCs using lentiviral shRNAs or an inducible knockdown system, and measuring the expression levels of LINE1 and others retroelements. To test the effects of TET enzymes on DNA modifications, we will measure 5mC and 5hmC levels at the same elements. This work may reveal a previously uncharacterized pathway for L1 activation in NPCs, with implications for neural differentiation and disease. (AU)