Overexpression of human NR2B receptor subunit in LMAN causes stuttering and song sequence changes in adult zebra finches

Mukta Chakraborty,Rebecca A Senft,Marguerita E Klein,Abhra Sarkar,Emma E Fridel,Erich D Jarvis,Liang-Fu Chen

doi:10.1038/s41598-017-00519-8

Abstract

Zebra finches (Taeniopygia guttata) learn to produce songs in a manner reminiscent of spoken language development in humans. One candidate gene implicated in influencing learning is the N-methyl-D-aspartate (NMDA) subtype 2B glutamate receptor (NR2B). Consistent with this idea, NR2B levels are high in the song learning nucleus LMAN (lateral magnocellular nucleus of the anterior nidopallium) during juvenile vocal learning, and decreases to low levels in adults after learning is complete and the song becomes more stereotyped. To test for the role of NR2B in generating song plasticity, we manipulated NR2B expression in LMAN of adult male zebra finches by increasing its protein levels to those found in juvenile birds, using a lentivirus containing the full-length coding sequence of the human NR2B subunit. We found that increased NR2B expression in adult LMAN induced increases in song sequence diversity and slower song tempo more similar to juvenile songs, but also increased syllable repetitions similar to stuttering. We did not observe these effects in control birds with overexpression of NR2B outside of LMAN or with the green fluorescent protein (GFP) in LMAN. Our results suggest that low NR2B subunit expression in adult LMAN is important in conserving features of stereotyped adult courtship song.

Highlights

To test the hypothesis that NR2B levels in adult lateral part of MAN (LMAN) influence song stereotypy, we developed a lentiviral construct eGFPhNR2B (Fig. 2a) containing the human NR2B tagged with enhanced green fluorescent protein (GFP), overexpressed it in LMAN of male zebra finches (NR2B group), and examined singing behavior
We discovered that overexpression of NR2B bilaterally in LMAN causes aberrant repetition of beginning and end-syllables similar to stuttering, and reversion back to more of a juvenile state to the lengthening of the song motif duration and increased variability of song sequencing and global acoustic structure
Considering that in adult zebra finches lesions of LMAN do not result in robust changes in the overall structure of the song[6, 21, 57], or in variability in syllable sequencing[6, 21, 30], these findings indicate that overexpression of NR2B to a more juvenile state reactivates a more dominant role of LMAN in influencing song plasticity

Summary

Introduction

One candidate gene implicated in influencing learning is the N-methyl-Daspartate (NMDA) subtype 2B glutamate receptor (NR2B). Consistent with this idea, NR2B levels are high in the song learning nucleus LMAN (lateral magnocellular nucleus of the anterior nidopallium) during juvenile vocal learning, and decreases to low levels in adults after learning is complete and the song becomes more stereotyped. To test for the role of NR2B in generating song plasticity, we manipulated NR2B expression in LMAN of adult male zebra finches by increasing its protein levels to those found in juvenile birds, using a lentivirus containing the full-length coding sequence of the human NR2B subunit. Proposed to have arisen by duplication of these preexisting motor areas[23], suggesting that discoveries in the song learning systems could be relevant to understanding sensorimotor learning broadly

Methods

Results

Conclusion