Faculty Collaboration Database

Traumatic brain injury increased IGF-1B mRNA and altered IGF-1 exon 5 and promoter region epigenetic characteristics in the rat pup hippocampus. J Neurotrauma 2012 Jul 20;29(11):2075-85

Date

03/15/2012

Pubmed ID

22413999

DOI

10.1089/neu.2011.2276

Scopus ID

2-s2.0-84864629719 (requires institutional sign-in at Scopus site)   37 Citations

Abstract

Traumatic brain injury (TBI) is a major cause of acquired cognitive disability in childhood. Such disability may be blunted by enhancing the brain's endogenous neuroprotective response. An important endogenous neuroprotective response is the insulin-like growth factor-1 (IGF-1) mRNA variant, IGF-1B. IGF-1B mRNA, characterized by exon 5 inclusion, encodes the IGF-1 and Eb peptides. IGF-1A mRNA excludes exon 5 and encodes the IGF-1 and Ea peptides. A region in the human IGF-1B homologue acts as an exon-splicing enhancer (ESE) to increase IGF-1B mRNA. It is not known if TBI is associated with increased brain IGF-1B mRNA. Epigenetic modifications may underlie altered gene expression in the brain after TBI. We hypothesized that TBI would increase hippocampal IGF-1B mRNA in 17-day-old rats, associated with DNA methylation and/or histone modifications at the promoter site 1 (P1) or exon 5/ESE region. Hippocampi from rat pups after controlled cortical impact (CCI) were used to measure IGF-1B mRNA, DNA methylation, and histone modifications at the P1, P2, and exon5/ESE regions. In CCI hippocampi, IGF-1B mRNA peaked at post-injury day (PID) 2 (1700±320% sham), but normalized by PID 14. IGF-1A peaked at PID 3 (280±52% sham), and remained elevated at PID 14. Increased IGF-1B mRNA was associated with increased methylation at P1, and increased histone modifications associated with gene activation at P2 and exon5/ESE, together with differential methylation in the exon 5/ESE regions. We report for the first time that hippocampal IGF-1B mRNA increased after developmental TBI. We speculate that epigenetic modifications at the P2 and exon 5/ESE regions are important in the regulation of IGF-1B mRNA expression. The exon 5/ESE region may present a means for future therapies to target IGF-1B transcription after TBI.

Author List

Schober ME, Ke X, Xing B, Block BP, Requena DF, McKnight R, Lane RH

MESH terms used to index this publication - Major topics in bold

Animals
Brain Injuries
Chromatin Immunoprecipitation
Disease Models, Animal
Epigenesis, Genetic
Exons
Hippocampus
Insulin-Like Growth Factor I
Male
Promoter Regions, Genetic
RNA, Messenger
Rats
Rats, Sprague-Dawley
Real-Time Polymerase Chain Reaction
Reverse Transcriptase Polymerase Chain Reaction