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

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.

Divergent low-density lipoprotein receptor (LDLR) linked to low VSV G-dependent viral infectivity and unique serum lipid profile in zebra finches

“…VSV G-based transgenesis in finch compared to chicken and quail (12,14), two species with an intact LDLR. We also note that even in studies reporting behavioral effects from brain gene manipulations using VSV G LVs in finches, the number of infected cells is typically quite low (15)(16)(17).…”

Divergence in problem-solving skills is associated with differential expression of glutamate receptors in wild finches

“…The receptors that are up-regulated in L. barbadensis are those that promote neuronal plasticity (GRIN2B, GRIN1, and GRIN3), whereas the ones that are up-regulated in T. bicolor are receptors that diminish it (GRIN2A, GRM2, GRM3, and GRM4). The association between the GRIN2B/GRIN2A ratio and behavioral divergence between L. barbadensis and T. bicolor is particularly appealing, considering that (i) this ratio is one of the most promising candidates to explain variation in mammalian intelligence ( 27 ); (ii) in songbirds, this ratio changes in the song-learning nuclei and is thought to contribute to changes in the critical period for vocal learning as the animals become adults ( 30 , 31 ); and (iii) glutamate receptors are highly conserved ( 32 ) and their functions are thought to be similar across species ( 33 ). Up to now, studies on GRIN2B/GRIN2A ratio variation have been based on experimental comparisons of transgenic or aging rodents and normal versus neurologically diseased humans ( 27 ).…”

Involvement of the cortico-basal ganglia-thalamo-cortical loop in developmental stuttering.

“…As mentioned in a previous section, song nuclei and the connectivity among vocal learning pathways found in songbirds have important parallels to brain areas and neural pathways supporting human speech production (Pidoux et al, 2018;Schneider and Mooney, 2018;Jarvis, 2019). Selective manipulation or lesioning of specific regions within the songbird basal ganglia-thalamocortical homologue pathway has been shown to induce stuttering in songbirds (Kubikova et al, 2014;Chakraborty et al, 2017). The specific regions affected that led to stuttering included premotor cortex and basal ganglia (striatum) homologues, which coincide with findings in human stuttering literature that have reported neuroanatomical differences in these regions in people who stutter (Giraud et al, 2008;Chang and Zhu, 2013;Garnett et al, 2018).…”

“…Abbreviations: AF, Arcuate fasciculus; BA, Brodmann area; CST, Corticospinal tract; CWS, Children who stutter; dIFo, Inferior frontal gyrus pars opercularis, dorsal division; dMC, (Primary) motor cortex, dorsal division; DWI, Diffusion weighted imaging; FA, Fractional anisotropy; FDR, False discovery rate; FDT, FMRIB's diffusion toolbox; FWE, Family-wise error; GM, Gray matter; IFo, Inferior frontal gyrus, pars opercularis; MNI, Montreal Neurological Institute; NBS, Network-based statistic; PDS, Persistent developmental stuttering; PFS, Person(s) with fluent speech; PWS, Person(s) who stutter; ROI, Region of interest; SLP, Speech language pathologist; SSI, Stuttering severity instrument; TBSS, Tract-based spatial statistic; TE, Echo time; TFCE, Threshold-free cluster enhancement; TI, Inversion time; TR, Repetition time; WM, White matter. LMAN function (Chakraborty et al, 2017), induced stuttering in songbirds. The songbirds exhibited increased repetition of syllables at the end of song motifs, usually the first motif of a bout, indicating that the birds were being stuck in transitioning from one motif sequence to the next.…”