Organization and development of zebra finch HVC and paraHVC based on expression of zRalDH, an enzyme associated with retinoic acid production

Abstract

The zRalDH gene encodes an aldehyde dehydrogenase associated with the conversion of retinaldehyde (the main vitamin A metabolite) into retinoic acid and its expression is highly enriched in the song control system of adult zebra finches (T. gutatta). Within song control nucleus HVC, zRalDH is specifically expressed in the neurons that project to area X of the striatum. It is also expressed in paraHVC, commonly considered a medial extension of HVC that is closely associated with auditory areas in the caudomedial telencephalon. Here we used in situ hybridization to generate a detailed analysis of HVC and paraHVC based on expression of zRalDH for adult zebra finches of both sexes and for males during the song learning period. We demonstrate that the distribution of zRalDH-positive cells can be used for accurate assessments of HVC and paraHVC in adult and juvenile males. We describe marked developmental changes in the numbers of zRalDH-expressing cells in HVC and paraHVC, reaching a peak at day 50 posthatch, an effect potentially due to dynamic changes in the population of X-projecting cells in HVC. We also show that zRalDH-expressing cells in adult females, although much less numerous than in males, have a surprisingly broad distribution along the medial-to-lateral extent of HVC but are lacking where paraHVC is found in adult males. Our study thus contributes to our understanding of the nuclear organization of the song system and the dynamics of its developmental changes during the song learning period.

Axial Organization of a Brain Region That Sequences a Learned Pattern of Behavior

“…Following the method of Olson et al (2011), tools in Neurolucida were used to quantify the density of IEG labeling across the medio-lateral axis of each coronal section (or the rostro-caudal axis of each sagittal section) at 100μm increments. For each bird’s HVC, these values were then normalized to the 100-μm segment with the highest density of IEG labeling.…”

Seasonal changes in the song control nuclei of the Rufous‐bellied Thrush, Turdus rufiventris (Oscine, Passeriformes, and Turdidae)

“…The border of HVC was outlined in each Nissl‐stained section containing HVC (viewed at ×40 magnification). The total volume of HVC was estimated by multiplying the outlined HVC area in one brain section by the interval between measured sections (400 µm), and then adding all partial volumes, as in Olson, Rodrigues, Jeong, Prahl, and Mello (). Student's t test (unpaired, parametric, and two‐tailed test) was performed using the GraphPad Prism version 7.05 for Windows, GraphPad Software, La Jolla, CA, http://www.graphpad.com.…”

Talking Convergence: Growing Evidence Links FOXP2 and Retinoic Acid in Shaping Speech-Related Motor Circuitry

“…Expression is especially high in the song-learning related area X of the striatum at the time when songs are acquired (Haesler et al, 2004; Thompson et al, 2013), and FoxP2 knockdown during this period disrupts social modulation of song variability (Murugan et al, 2013). Similar to the mouse striatal network, FoxP2 knockdown in the juvenile zebra finch leads to specific reductions of D1R and Darpp-32 expression in the dorsolateral striatum, specifically in area X (Denisenko-Nehrbass et al, 2000; Haesler et al, 2004, 2007; Olson et al, 2011; Murugan et al, 2013; Roeske et al, 2014). It should be noted that in the songbird striatum, D1R and D2R expression in MSNs overlap to a greater degree than in the mouse (Kubikova et al, 2010).…”

“…Interestingly, FoxP2 and RA signaling have also been found (separately) to be involved in vocal production learning in a songbird model (Denisenko-Nehrbass et al, 2000; Olson et al, 2011; Roeske et al, 2014; Wohlgemuth et al, 2014). Even though direct evidence of synergies between FoxP2 and RA signaling is still lacking beyond cell models, the hypothesis that they are parts of the same regulatory network (e.g.…”