C/EBPβ Isoforms Expression in the Rat Brain during the Estrous Cycle.

Valeria Hansberg-Pastor,Ana Gabriela Piña-Medina,Ignacio Camacho-Arroyo,Aliesha González-Arenas

doi:10.1155/2015/674915

Abstract

The CCAAT/enhancer-binding protein beta (C/EBPβ) is a transcription factor expressed in different areas of the brain that regulates the expression of several genes involved in cell differentiation and proliferation. This protein has three isoforms (LAP1, LAP2, and LIP) with different transcription activation potential. The role of female sex hormones in the expression pattern of C/EBPβ isoforms in the rat brain has not yet been described. In this study we demonstrate by western blot that the expression of the three C/EBPβ isoforms changes in different brain areas during the estrous cycle. In the cerebellum, LAP2 content diminished on diestrus and proestrus and LIP content diminished on proestrus and estrus days. In the prefrontal cortex, LIP content was higher on proestrus and estrus days. In the hippocampus, LAP isoforms presented a switch on diestrus day, since LAP1 content was the highest while that of LAP2 was the lowest. The LAP2 isoform was the most abundant one in all the three brain areas. The LAP/LIP ratio changed throughout the cycle and was tissue specific. These results suggest that C/EBPβ isoforms expression changes in a tissue-specific manner in the rat brain due to the changes in sex steroid hormone levels presented during the estrous cycle.

Highlights

The CCAAT/enhancer-binding proteins (C/EBP) is a family of transcription factors that consist of six members (C/EBPαC/EBPζ) named according to their chronological order of discovery
In this study we demonstrated that the expression of the three C/EBPβ isoforms in different brain areas depends on sex hormone level variations presented throughout the estrous cycle
LAP2 content diminished on diestrus and proestrus days, while LIP showed a reduced content during proestrus and estrus (Figure 1)

Summary

Introduction

The CCAAT/enhancer-binding proteins (C/EBP) is a family of transcription factors that consist of six members (C/EBPαC/EBPζ) named according to their chronological order of discovery. These proteins are solely eukaryotic and bind as dimers to specific DNA sequences to regulate gene transcription. They have a highly conserved C-terminal bZIP domain comprising a leucine-zipper dimerization domain and a basic DNA binding region. C/EBPβ isoforms were first identified in the liver and known as LAP1 and LAP2 (for liver activating proteins) and LIP (for liver inhibitory protein). The transactivation potential of these isoforms depends on the LAP/LIP ratio, which is important to modulate cell fate

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