Eya2 is required to mediate the pro-metastatic functions of Six1 via the induction of TGF-ß signaling, epithelial-mesenchymal transition, and cancer stem cell properties.

Six1 is a critical regulator of embryonic development that requires interaction with the Eya family of proteins (Eya1-4) to activate the transcription of genes involved in neurogenesis, myogenesis and nephrogenesis. Although expression of Six1 and Eya family members is predominantly observed in development, their overexpression is observed in numerous cancers. Importantly, both Six1 and Eya have independently been shown to mediate breast cancer metastasis, but whether they functionally interact during tumor progression has not been explored. Herein, we demonstrate that knockdown of Eya2 in MCF7 mammary carcinoma cells reverses the ability of Six1 to induce transforming growth factor-ß signaling, as well as to induce characteristics associated with epithelial-mesenchymal transition and cancer stem cells, suggesting that Six1 is dependent on Eya2 to mediate numerous pro-metastatic characteristics. The importance of the Six1-Eya interaction in human breast cancer is underscored by the finding that high levels of Six1 correlate with shortened time to relapse and metastasis as well as decreased survival only when co-expressed with high levels of Eya2. Overall, these data implicate Eya2 as a necessary co-factor for many of the metastasis promoting functions of Six1, suggesting that targeting the Six1-Eya interaction may inhibit breast cancer progression. As Six1 and Eya2 are not highly expressed in most adult tissues, the Six1-Eya interaction may be a valuable future therapeutic target whose inhibition would be expected to impair breast cancer progression while conferring limited side effects.

Effects of deafening on the calls and warble song of adult budgerigars (Melopsittacus undulatus).

Budgerigars are small Australian parrots that learn new vocalizations throughout adulthood. Earlier work has shown that an external acoustic model and auditory feedback are necessary for the development of normal contact calls in this species. Here, the role of auditory feedback in the maintenance of species-typical contact calls and warble song in adult budgerigars is documented. Deafened adult birds (five male, one female) vocalized less frequently and showed both suprasegmental and segmental changes in their contact calls and warble song. Contact calls of all adult-deafened budgerigars showed abnormalities in acoustic structure within days to a few weeks following surgery. Within 6 months of surgery, nearly all contact calls produced by deafened birds were strikingly abnormal, showing highly variable patterns of frequency modulation and duration. The warble song of deafened male budgerigars also differed significantly from that of normal budgerigars on several acoustic measures. These results show that auditory feedback is necessary for the maintenance of a normal, species-typical vocal repertoire in budgerigars.

Hearing and vocalizations of wild-caught Australian budgerigars (Melopsittacus undulatus).

This study examined the hearing and contact calls of wild-caught Australian budgerigars (Melopsittacus undulatus) and compared these data to hearing and vocalizations in the much more extensively studied domesticated budgerigar. The spectral energy in the contact calls of both wild-caught and domesticated budgerigars falls almost exclusively in the frequency of 2-4 kHz. Absolute and masked thresholds were similar in both groups of birds. Similar to the results found in domesticated birds, critical ratio functions for the wild-caught budgerigars decreased at frequencies of 1.0 kHz-2.86 kHz and then increased again dramatically at frequencies above 2.86 kHz.

Vocal development in budgerigars (Melopsittacus undulatus): contact calls.

Budgerigars have a complex vocal repertoire, some of which develops through learning. The authors examined the course of vocal development in budgerigars from hatching to about 4 weeks postfledging (approximately 85 days old). Food-begging calls showed changes in duration, peak frequency, bandwidth, and frequency modulation with age. Within a week of fledging, each bird produced a contact call bearing a strong resemblance to a shortened version of its patterned food-begging call. By 4 weeks postfledging, budgerigar contact call repertoires often contained more than one call type, and there was clear evidence of sharing and imitation among the calls of parents, fledglings, and other social companions. Perceptual testing showed that whereas acoustic variation in the structure of developing calls decreased both within and between nestling birds, the discrimination of these calls was easier for adult birds as young birds matured. These results suggest parallels with certain aspects of language development in humans.

A non-thalamic pathway contributes to a whole body map in the brain of the budgerigar.

Nucleus basalis (Bas) of the budgerigar contains an ordered, but distorted, somatotopic representation of the whole body, as does the primary somatosensory cortex (SI) of mammals. Unlike SI, however, the beak and body regions of Bas receive their sensory input via disynaptic pathways relaying in the pons. That to the body parts originates in a previously undescribed nucleus that receives its inputs from primary afferents via a novel, ipsilateral somatosensory pathway.

Reciprocal connections between primary and secondary auditory pathways in the telencephalon of the budgerigar (Melopsittacus undulatus).

Among avian species that learn their vocalizations, budgerigars have been thought to be unusual in receiving auditory input to the vocal control circuitry of the telencephalon via an auditory component of nucleus basalis (NB), rather than via Field L2, the end station of the classical thalamofugal pathway. In the present study, however, the application of neural tracing techniques showed the two auditory pathways to be reciprocally connected within the telencephalon. The implication is, therefore, that auditory information essential for vocal learning and vocal production in the budgerigar is derived from the primary as well as the secondary auditory pathway.

Organization of afferent and efferent projections of the nucleus basalis prosencephali in a passerine, Taeniopygia guttata.

The connections of nucleus basalis (NB) of the rostral forebrain of the zebra finch were investigated electrophysiologically and with anterograde and retrograde tracing methods to determine their functional organization, the sources of their pontine afferents, and the targets of their telencephalic efferents. The nucleus was found to be partitioned into three major components, a rostral lingual part that received a hypoglossal projection via a lateral subnucleus of the principal sensory trigeminal nucleus (PrV), a middle beak part that received a trigeminal projection via a medial subnucleus of PrV, and a caudal auditory part that received a short latency auditory projection via the intermediate nucleus of the lateral lemniscus. Beak NB also received a projection from a paralateral lemniscal nucleus, and the dorsocaudal part of auditory NB and the medially adjacent neostriatum also received a projection from a lateral subnucleus of the superior vestibular nucleus (VS). The efferent projections of each of the three major parts of NB were mainly to the adjacent neostriatum frontale (NF), which then provided projections to the lobus parolfactorius (exclusive of area X), the lateral archistriatum intermedium (Ail), and the lateral neostriatum caudale (NCl). Ail received a projection from NCl and provided terminal fields to the contralateral NCl and the NF. The major projections of Ail, however, descended bilaterally through the brainstem via the occipitomesencephalic tracts, with dense terminations in the medial spiriform nucleus and with extensive bilateral terminations throughout the lateral reticular formation of the pons and medulla. For the most part, jaw, tongue, and tracheosyringeal motor nuclei did not receive terminations. The results suggest that NB in zebra finch, like NB in pigeon and duck, is likely to be a major component of trigeminal sensorimotor circuitry involved in feeding and in other oral-manipulative behaviors. Results also show that the auditory component of NB is not directly linked to the vocal control system at telencephalic levels, but the possibility remains that the lingual, beak, and auditory parts of NB play a role in vocalization by multisynaptic influences on cranial nerve motor nuclei innervating various parts of the vocal tract.

Effect of syringeal denervation in the budgerigar (Melopsittacus undulatus): the role of the syrinx in call production.

In the budgerigar, the left and right tracheosyringeal nerves (ts) were sectioned both above and below the common anastomosis in order to assess the roles of the hypoglossal nuclei and syringeal muscle halves in the control of call production. Signal processing software was used to quantify changes in contact call fundamental frequency and duration, and similarity analysis for pre- and postsurgical contact calls was performed by means of spectrogram cross-correlation. After resecting a portion of either the right or left ts nerve above the anastomosis (thereby eliminating the input from the ipsilateral half of the brainstem), contact call fundamental frequency decreased 40-50% on Day 1 postsurgery, while call structure and duration remained largely unaffected. Fundamental frequency returned to normal within 4-7 days after surgery. In contrast, nerve sectioning below the anastomosis on either side of the syrinx (thereby eliminating input to the ipsilateral half of the syringeal muscles) resulted in moderately noisy harsh-sounding calls with little change in temporal characteristics. Thus, budgerigars differ from many oscines studied to date in that they do not demonstrate laterality in vocal control at the level of the syrinx. Vocalizations produced by birds after bilateral syringeal denervation were abnormal, consisting entirely of broadband harmonic sounds with very low fundamental frequencies (i.e., less than 900 Hz) and poor frequency modulation. In contrast, individual call durations, as well as the rhythm and patterning of vocalizations resembling warble song, were remarkably similar to presurgical recordings after both unilateral and bilateral ts nerve resection.(ABSTRACT TRUNCATED AT 250 WORDS)

Vocal plasticity in budgerigars (Melopsittacus undulatus): evidence for social factors in the learning of contact calls.

Distance or contact calls of 6 unrelated adult male budgerigars (Melopsittacus undulatus) were recorded before and during 8 weeks of social contact. The 6 birds were housed in 2 separate groups of 3 each in adjoining cages. Birds in each cage could hear but not see the birds in the neighboring cage. At the beginning of the study, none of the birds shared any contact call types. The first appearance of 1 bird's imitation of a cagemate's contact call type occurred after 1 week. Call type repertoires continued to change; some call types dropped out of the repertoires, and others were modified over time. Birds in the same cage shared the same dominant call type 8 weeks later, and the dominant call types differed between the 2 cages. Thus, budgerigars can learn calls as adults, and call type convergence is achieved through mutual vocal imitation of social companions. In the absence of social but not aural contact, vocal imitation was greatly reduced.