Zebra finch sexual differentiation: The aromatization hypothesis revisited

Wade, Juli

doi:10.1002/jemt.1148

Cited by 54 publications

(60 citation statements)

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“…Like the d30 results, the density of ZENK immunoreactive neurons in Area X was significantly lower than that in the mMSt of males that heard conspecific songs (t(5) = 3.82, p = 0.012), and no difference in ZENK immunoreactivity was found between the female lMSt and mMSt(t(5) = 0.41, p = 0.697). Also similar to those data from d30 birds, no significant main effects or interactions were uncovered in d45 birds using the FOS analysis, and the levels were quite low.The present data on ZENK labeling parallel the sex difference observed in the MSt with Nissl staining, in that Area X is distinct from the surrounding MSt only in males (reviewed in [34]) and, interestingly, following only conspecific song presentations. The morphological difference is therefore mirrored by a functional one: ZENK is not induced in Area X in males with song presentations but is up-regulated within the corresponding region in females similar to the rest of the MSt.…”

supporting

confidence: 81%

“…The present data on ZENK labeling parallel the sex difference observed in the MSt with Nissl staining, in that Area X is distinct from the surrounding MSt only in males (reviewed in [34]) and, interestingly, following only conspecific song presentations. The morphological difference is therefore mirrored by a functional one: ZENK is not induced in Area X in males with song presentations but is up-regulated within the corresponding region in females similar to the rest of the MSt.…”

supporting

confidence: 81%

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Sexual dimorphism in song-induced ZENK expression in the medial striatum of juvenile zebra finches

Bailey

Wade

2006

Neuroscience Letters

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In the brains of male zebra finches (Taeniopygia guttata), the nuclei that direct song learning and production are larger than the corresponding regions in females, who do not sing. The dimorphism in Area X of the medial striatum (MSt), an area important for song learning, is even more dramatic in that it is identifiable in males but not females by Nissl stain. In the present study, conspecific song, but not other auditory stimuli, induced expression of the immediate early gene ZENK in the MSt surrounding but not within Area X in juvenile males (30 and 45 days post-hatch). ZENK immunoreactivity following conspecific songs was homogeneous throughout the MSt of females at the same ages. Little to no FOS immunoreactivity was observed in Area X or the rest of the MSt, and levels were not influenced by the type of auditory stimulus presented. Thus, the clear morphological difference in the lateral MSt (Area X) of males and females is mirrored by a specific functional one, and the data suggest a role for ZENK expression in the MSt outside of Area X in responding to relevant song stimuli. KeywordsSong perception; Immediate early gene; Area X; Basal ganglia; Song learning; Sex difference Nottebohm and Arnold [23] first described dramatic sexual dimorphisms in the brains of adult zebra finches and canaries wherein regions that control song learning and production are larger in males that sing than in females that do not. One of these regions, Area X of the medial striatum (MSt), is not identifiable via Nissl stains in females. Area X plays an integral role in male song learning and possibly song production in adulthood. For example, juvenile males with Area X ablated produce abnormal song in adulthood, although in adult males lesions of the nucleus have no detectable effect on song production or quality [26,31]. Interestingly, neurons in Area X show singing-related electrophysiological activity that declines slowly after song stops being produced [11], suggesting a function for the region outside of the sensitive period for song learning. Cells in this region in both juveniles and adults also display longterm potentiation [7]. In birds that hear song and sing in response, ZENK expression is increased in Area X compared to birds that hear song only or birds that hear no song [13][14][15]24]. Additionally, when the tracheosyringeal nerve is axotomized in developing males, the electrophysiological activity of some neurons within Area X is then tuned to the abnormal, axotomized bird's own song as well as the tutor's song, suggesting that neurons within Area X are important for vocal practice [32]. In males, the Nissl-defined volume of Area X increases between d10 and d40, when the adult volume is reached [20], and this change in volume is due in part to the addition of neurons during that period in males but not females [16,21].While it is clear that Area X is highly sexually dimorphic and important for the development of song in males, it was unknown whether the corresponding lateral region of MSt in females is resp...

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supporting

confidence: 81%

supporting

confidence: 81%

Sexual dimorphism in song-induced ZENK expression in the medial striatum of juvenile zebra finches

Bailey

Wade

2006

Neuroscience Letters

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“…(ii) Blocking these hormones in males has not prevented the normal development of song (16,17). (iii) Females induced to form testes during early development do not develop a masculine song system or sing, even though they are exposed to testicular hormones (18,19). (iv) Genetically male and female brain tissue differ in their sexual phenotype even if they reside in the same bird and are exposed to the same gonadal hormonal milieu (20).…”

mentioning

confidence: 99%

Sexually dimorphic expression of trkB, a Z-linked gene, in early posthatch zebra finch brain

Chen

Agate²,

Itoh³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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Sexual differentiation of the zebra finch (Taeniopygia guttata) neural song circuit is thought to be initiated by sex differences in sex chromosome gene expression in brain cells. One theory is that Z-linked genes, present in the male's ZZ genome at double the dose of females' (ZW), are expressed at higher levels and trigger masculine patterns of development. We report here that trkB (tyrosine kinase receptor B) is Z-linked in zebra finches. trkB is the receptor for neurotrophic factors BDNF and neurotrophin 4, and mediates their influence on neuronal survival, migration, and specification. trkB mRNA is expressed at a higher level in the male telencephalon or whole brain than in corresponding regions of the female in adulthood, and at posthatch day (P) 6, when the song circuit is undergoing sexual differentiation. Moreover, this expression is higher in the song nucleus high vocal center (HVC) than in the surrounding telencephalon at P6, and in males relative to females. In addition, trkB protein is expressed more highly in male than female whole brain at P6. These results establish trkB as a candidate factor that contributes to masculine differentiation of HVC because of its Z-linkage, which leads to sex differences in expression. BDNF is known to be stimulated by estrogen and to be expressed at higher levels in males than females at later ages in HVC. Thus, the trkB-BDNF system may be a focal point for convergent masculinizing influences of Z-linked factors and hormones.sex determination ͉ song ͉ Z chromosome

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“…If E2 does normally masculinize males, then some mechanism should exist to increase its availability or activity in this sex, but oestrogen receptors in the song system appear limited overall and comparable in males and females. Similarly, consistent sex differences in plasma E2 and brain oestrogen synthesis during development have not been detected [13]. Interestingly, post-hatching E2 can have opposite, demasculinizing, effects on tissues outside the neural song circuit in zebra finches.…”

Section: Songbirdsmentioning

confidence: 91%

Genetic regulation of sex differences in songbirds and lizards

Wade

2016

Phil. Trans. R. Soc. B

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One contribution of 16 to a theme issue 'Multifaceted origins of sex differences in the brain'. Sex differences in the morphology of neural and peripheral structures related to reproduction often parallel the frequency of particular behaviours displayed by males and females. In a variety of model organisms, these sex differences are organized in development by gonadal steroids, which also act in adulthood to modulate behavioural expression and in some cases to generate parallel anatomical changes on a seasonal basis. Data collected from diverse species, however, suggest that changes in hormone availability are not sufficient to explain sex and seasonal differences in structure and function. This paper pulls together some of this literature from songbirds and lizards and considers the information in the broader context of taking a comparative approach to investigating genetic mechanisms associated with behavioural neuroendocrinology.

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Zebra finch sexual differentiation: The aromatization hypothesis revisited

Cited by 54 publications

References 64 publications

Sexual dimorphism in song-induced ZENK expression in the medial striatum of juvenile zebra finches

Sexual dimorphism in song-induced ZENK expression in the medial striatum of juvenile zebra finches

Sexually dimorphic expression of trkB, a Z-linked gene, in early posthatch zebra finch brain

Genetic regulation of sex differences in songbirds and lizards

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