A high sensitivity ZENK monoclonal antibody to map neuronal activity in Aves

Night-time neuronal activation of Cluster N in a North American songbird

Night-migrating songbirds utilize the Earth's magnetic field to help navigate to and from their breeding sites each year. A region of the avian forebrain called Cluster N has been shown to be activated during night migratory behavior and it has been implicated in processing geomagnetic information. Previous studies with night-migratory European songbirds have shown that neuronal activity at Cluster N is higher at night than during the day. Comparable work in North American migrants has only been performed in one species of swallows, so extension of examination for Cluster N in other migratory birds is needed. In addition, it is unclear if Cluster N activation is lateralized and the full extent of its boundaries in the forebrain have yet to be described. We used sensory-driven gene expression based on ZENK and the Swainson's thrush, a night-migratory North American songbird, to fill these knowledge gaps. We found elevated levels of gene expression in night- vs. day-active thrushes and no evidence for lateralization in this region. We further examined the anatomical extent of neural activation in the forebrain using 3D reconstruction topology. Our findings demonstrate that Swainson's thrushes possess an extensive bilateral night-activated Cluster N region in the forebrain similar to other European avian species, suggesting that Cluster N is highly conserved in nocturnal migrants.

Functional neurogenomic responses to acoustic threats, including a heterospecific referential alarm call and its referent, in the auditory forebrain of red-winged blackbirds

In animal communication, functionally referential alarm calls elicit the same behavioral responses as their referents, despite their typically distinct bioacoustic traits. Yet the auditory forebrain in at least one songbird species, the black-capped chickadee Poecile atricapillus, responds similarly to threat calls and their referent predatory owl calls, as assessed by immediate early gene responses in the secondary auditory forebrain nuclei. Whether and where in the brain such perceptual and cognitive equivalence is processed remains to be understood in most other avian systems. Here, we studied the functional neurogenomic (non-) equivalence of acoustic threat stimuli perception by the red-winged blackbird Agelaius phoeniceus in response to the actual calls of the obligate brood parasitic brown-headed cowbird Molothrus ater and the referential anti-parasitic alarm calls of the yellow warbler Setophaga petechia, upon which the blackbird is known to eavesdrop. Using RNA-sequencing from neural tissue in the auditory lobule (primary and secondary auditory nuclei combined), in contrast to previous findings, we found significant differences in the gene expression profiles of both an immediate early gene, ZENK (egr-1), and other song-system relevant gene-products in blackbirds responding to cowbird vs. warbler calls. In turn, direct cues of threats (including conspecific intruder calls and nest-predator calls) elicited higher ZENK and other differential gene expression patterns compared to harmless heterospecific calls. These patterns are consistent with a perceptual non-equivalence in the auditory forebrain of adult male red-winged blackbirds in response to referential calls and the calls of their referents.

Cell assembly analysis of neural circuits for innate behavior in Drosophila melanogaster using an immediate early gene stripe/egr-1

Innate behavior, such as courtship behavior, is controlled by a genetically defined set of neurons. To date, it remains challenging to visualize and artificially control the neural population that is active during innate behavior in a whole-brain scale. Immediate early genes (IEGs), whose expression is induced by neural activity, can serve as powerful tools to map neural activity in the animal brain. We screened for IEGs in vinegar fly Drosophila melanogaster and identified stripe/egr-1 as a potent neural activity marker. Focusing on male courtship as a model of innate behavior, we demonstrate that stripe-GAL4-mediated reporter expression can label fruitless (fru)-expressing neurons involved in courtship in an activity (experience)-dependent manner. Optogenetic reactivation of the labeled neurons elicited sexual behavior in males, whereas silencing of the labeled neurons suppressed courtship and copulation. Further, by combining stripe-GAL4-mediated reporter expression and detection of endogenous Stripe expression, we established methods that can label neurons activated under different contexts in separate time windows in the same animal. The cell assembly analysis of fru neural population in males revealed that distinct groups of neurons are activated during interactions with a female or another male. These methods will contribute to building a deeper understanding of neural circuit mechanisms underlying innate insect behavior.

Dim artificial light at night alters immediate early gene expression throughout the avian brain

Artificial light at night (ALAN) is a pervasive pollutant that alters physiology and behavior. However, the underlying mechanisms triggering these alterations are unknown, as previous work shows that dim levels of ALAN may have a masking effect, bypassing the central clock. Light stimulates neuronal activity in numerous brain regions which could in turn activate downstream effectors regulating physiological response. In the present study, taking advantage of immediate early gene (IEG) expression as a proxy for neuronal activity, we determined the brain regions activated in response to ALAN. We exposed zebra finches to dim ALAN (1.5 lux) and analyzed 24 regions throughout the brain. We found that the overall expression of two different IEGs, cFos and ZENK, in birds exposed to ALAN were significantly different from birds inactive at night. Additionally, we found that ALAN-exposed birds had significantly different IEG expression from birds inactive at night and active during the day in several brain areas associated with vision, movement, learning and memory, pain processing, and hormone regulation. These results give insight into the mechanistic pathways responding to ALAN that underlie downstream, well-documented behavioral and physiological changes.

Effect of estradiol and predator cues on behavior and brain responses of captive female house sparrows (Passer domesticus)

The presence of predators can cause major changes in animal behavior, but how this interacts with hormonal state and brain activity is poorly understood. We gave female house sparrows (Passer domesticus) in post-molt condition an estradiol (n = 17) or empty implant (n = 16) for 1 week. Four weeks after implant removal, a time when female sparrows show large differences in neuronal activity to conspecific vs. heterospecific song, we exposed birds to either 30 min of conspecific song or predator calls, and video recorded their behavior. Females were then euthanized, and we examined neuronal activity using the expression of the immediate early gene (IEG) ZENK to identify how the acoustic stimuli affected neuronal activation. We predicted that if female sparrows with estradiol implants reduce neuronal activity in response to predator calls as they do to neutral tones and non-predatory heterospecifics, they would show less fear behavior and a decreased ZENK response in brain regions involved in auditory (e.g., caudomedial mesopallium) and threat perception functions (e.g., medial ventral arcopallium) compared to controls. Conversely, we predicted that if females maintain auditory and/or brain sensitivity towards predator calls, then female sparrows exposed to estradiol would not show any differences in ZENK response regardless of playback type. We found that female sparrows were less active during predator playbacks independent of hormone treatment and spent more time feeding during conspecific playback if they had previously been exposed to estradiol. We observed no effect of hormone or sound treatment on ZENK response in any region of interest. Our results suggest that female songbirds maintain vigilance towards predators even when in breeding condition.

A hierarchical processing unit for multi-component behavior in the avian brain

Multi-component behavior is a form of goal-directed behavior that depends on the ability to execute various responses in a precise temporal order. Even though this function is vital for any species, little is known about how non-mammalian species accomplish such behavior and what the underlying neural mechanisms are. We show that humans and a non-mammalian species (pigeons) perform equally well in multi-component behavior and provide a validated experimental approach useful for cross-species comparisons. Applying molecular imaging methods, we identified brain regions most important for the examined behavioral dynamics in pigeons. Especially activity in the nidopallium intermedium medialis pars laterale (NIML) was specific to multi-component behavior since only activity in NIML was predictive for behavioral efficiency. The data suggest that NIML is important for hierarchical processing during goal-directed behavior and shares functional characteristics with the human inferior frontal gyrus in multi-component behavior.

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Pigeons and humans perform equally well in the STOP-CHANGE paradigm

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We identified relevant brain regions for the examined behavioral dynamics in pigeons

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ZENK expression in NIML was predictive for behavioral efficiency

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This study provides a validated experimental approach for cross-species comparisons

Neuronal circuits and the magnetic sense: central questions

Magnetoreception is the ability to sense the Earth's magnetic field, which is used for orientation and navigation. Behavioural experiments have shown that it is employed by many species across all vertebrate classes; however, our understanding of how magnetic information is processed and integrated within the central nervous system is limited. In this Commentary, we review the progress in birds and rodents, highlighting the role of the vestibular and trigeminal systems as well as that of the hippocampus. We reflect on the strengths and weaknesses of the methodologies currently at our disposal, the utility of emerging technologies and identify questions that we feel are critical for the advancement of the field. We expect that magnetic circuits are likely to share anatomical motifs with other senses, which culminates in the formation of spatial maps in telencephalic areas of the brain. Specifically, we predict the existence of spatial cells that encode defined components of the Earth's magnetic field.

Hybridoma technology a versatile method for isolation of monoclonal antibodies, its applicability across species, limitations, advancement and future perspectives

The advancements in technology and manufacturing processes have allowed the development of new derivatives, biosimilar or advanced improved versions for approved antibodies each year for treatment regimen. There are more than 700 antibody-based molecules that are in different stages of phase I/II/ III clinical trials targeting new unique targets. To date, approximately more than 80 monoclonal antibodies (mAbs) have been approved. A total of 7 novel antibody therapeutics had been granted the first approval either in the United States or European Union in the year 2019, representing approximately 20% of the total number of approved drugs. Most of these licenced mAbs or their derivatives are either of hybridoma origin or their improvised engineered versions. Even with the recent development of high throughput mAb generation technologies, hybridoma is the most favoured method due to its indigenous nature to preserve natural cognate antibody pairing information and preserves innate functions of immune cells. The recent advent of antibody engineering technology has superseded the species level barriers and has shown success in isolation of hybridoma across phylogenetically distinct species. This has led to the isolation of monoclonal antibodies against human targets that are conserved and non-immunogenic in the rodent. In this review, we have discussed in detail about hybridoma technology, its expansion towards different animal species, the importance of antibodies isolated from different animal sources that are useful in biological applications, advantages, and limitations. This review also summarizes the challenges and recent progress associated with hybridoma development, and how it has been overcome in these years to provide new insights for the isolation of mAbs.

Immediate early gene fingerprints of multi-component behaviour

The ability to execute different responses in an expedient temporal order is central for efficient goal-directed actions and often referred to as multi-component behaviour. However, the underlying neural mechanisms on a cellular level remain unclear. Here we establish a link between neural activity at the cellular level within functional neuroanatomical structures to this form of goal-directed behaviour by analyzing immediate early gene (IEG) expression in an animal model, the pigeon (Columba livia). We focus on the group of zif268 IEGs and ZENK in particular. We show that when birds have to cascade separate task goals, ZENK expression is increased in the avian equivalent of the mammalian prefrontal cortex, i.e. the nidopallium caudolaterale (NCL) as well as in the homologous striatum. Moreover, in the NCL as well as in the medial striatum (MSt), the degree of ZENK expression was highly correlated with the efficiency of multi-component behaviour. The results provide the first link between cellular IEG expression and behavioural outcome in multitasking situations. Moreover, the data suggest that the function of the fronto-striatal circuitry is comparable across species indicating that there is limited flexibility in the implementation of complex cognition such as multi-component behaviour within functional neuroanatomical structures.