Prof Ivan Rodriguez

The claustro-insular region is an evolutionarily conserved and extensively interconnected brain area, critical for functions such as attention, cognitive flexibility, interoception, and affective processing. Despite its importance, its cellular composition and organization remain poorly characterized, hindering a comprehensive understanding of the mechanisms underlying its diverse functions. By combining single-cell RNA sequencing and spatial transcriptomics, we create a high-resolution atlas of this region in mice, uncovering distinct neuronal subtypes and unexpected complexity. Leveraging this atlas, we investigate the role of NR4A2, a neuropsychiatric risk factor expressed in several claustro-insular neuronal subtypes. In an Nr4a2 haploinsufficiency model, we find that only claustrum neurons exhibited shifts in molecular identity. This identity shift, which involves the activation of a transcription factor cascade, is associated with alterations in neuronal firing activity. Our findings provide new insights into the cellular architecture of the claustro-insular region and highlights Nr4a2 as a key regulator of its component's identities.

The claustro-insular region is an evolutionarily conserved and extensively interconnected brain area, critical for functions such as attention, cognitive flexibility, interoception, and affective processing. Despite its importance, its cellular composition and organization remain poorly characterized, hindering a comprehensive understanding of the mechanisms underlying its diverse functions. By combining single-cell RNA sequencing and spatial transcriptomics, we created a high-resolution atlas of this region in mice, uncovering distinct neuronal subtypes and unexpected complexity. Leveraging this atlas, we investigated the role of NR4A2, a neuropsychiatric risk factor expressed in several claustro-insular neuronal subtypes. In an Nr4a2 haploinsufficiency model, we found that only claustrum neurons exhibited shifts in molecular identity. This identity shift, which involved the activation of a transcription factor cascade, was associated with alterations in neuronal firing activity. Our findings provide new insights into the cellular architecture of the claustro-insular region and highlights Nr4a2 as a master regulator of its component’s identities.

Working memory (WM) enables the mammalian brain to temporarily store and manipulate information, supporting cognitive tasks and communication processes1,2. Rather than depending on a single specialized area, WM is thought to operate through a distributed network spanning cortical and subcortical regions3–5. A dedicated WM storage area would likely require broad reciprocal connections with various cortical regions to accommodate the diverse range of information WM retains. The claustrum (CLA), with its extensive bidirectional connections to the neocortex6–9, presents a compelling candidate for such a role. Here, we examined the involvement of the CLA in WM processes by recording CLA neuronal activity in mice engaged in olfactory and tactospatial delayed non-match-to-sample WM tasks. We identified cue- selective and delay-specific neurons in the CLA that maintained activity for tens of seconds after the stimulus presentation ended. Additionally, population activity in the CLA allowed for decoding of cue identity post-stimulus, although this signal gradually declined over time, aligning with animal behavior. Remarkably, both chemo- and optogenetic inhibition of CLA neurons severely impaired WM performance across multiple types of stored information, highlighting the CLA’s critical role during both cue encoding, delay periods, and target comparison phases. These findings challenge the view that no single brain area is essential for WM storage and support a role for the CLA as an essential WM storage hub.

The claustrum (CLA), a subcortical nucleus in mammals, essentially composed of excitatory projection neurons and known for its extensive connections with the neocortex, has recently been associated with a variety of functions ranging from consciousness to impulse control. However, research on the CLA has been challenging due to difficulties in specifically and comprehensively targeting its neuronal populations. In various cases, this limitation has led to inconsistent findings and a lack of reliable data. In the present work, we describe the expression profile of the Smim32 gene, which is almost exclusively transcribed in excitatory neurons of the CLA and the endopiriform nucleus, as well as in inhibitory neurons of the thalamic reticular nucleus. Leveraging this unique expression pattern, we developed a series of Cre- and Flippase-expressing knockin and BAC transgenic mouse lines with different expression profiles. With these novel tools in hand, we propose new standards for the interrogation of CLA function.

The consolidation and recall of episodic memories rely on distributed cortical activity. The claustrum, a subcortical structure reciprocally connected to most of the cortex, may facilitate inter-areal communication necessary for these processes. We report here that the functional inhibition of claustral projection neurons affects directional interactions and the coordination of oscillatory neuronal patterns in the fronto-parietal network. Moreover, the inhibition of these neurons has a detrimental effect on concurrent oscillatory events relevant to the consolidation of contextual fear memory. Last, we demonstrate that biasing the directional flow of information between the latter two cortical areas enhances the retrieval of a remote contextual memory. We propose that the claustrum orchestrates inter-areal cortical interactions relevant to contextual memory processes by affecting the latency of neuronal responses.

Rodents perceive pheromones via vomeronasal receptors encoded by highly evolutionarily dynamic Vr and Fpr gene superfamilies. We report here that high numbers of V1r pseudogenes are scattered in mammalian genomes, contrasting with the clustered organization of functional V1r and Fpr genes. We also found that V1r pseudogenes are more likely to be expressed when located in a functional V1r gene cluster than when isolated. To explore the potential regulatory role played by the association of functional vomeronasal receptor genes with their clusters, we dissociated the mouse from its native cluster via transgenesis. Singular and specific transgenic transcription was observed in young vomeronasal neurons but was only transient. Our study of natural and artificial dispersed gene duplications uncovers the existence of transcription-stabilizing elements not coupled to vomeronasal gene units but rather associated with vomeronasal gene clusters and thus explains the evolutionary conserved clustered organization of functional vomeronasal genes.

Palcewska et al. first demonstrated near infrared (NIR) visual response in human volunteers upon two-photon absorption (TPA), in a seminal work of 2014, and assessed the process in terms of wavelength- and power-dependence on murine ex-vivo retinas. In the present study, ex-vivo electroretinography (ERG) is further developed to perform a complete characterization of the effect of NIR pulse duration, energy, and focal spot size on the response. The same set of measurements is successively tested on living mice. We discuss how the nonlinear intensity dependence of the photon absorption process is transferred to the amplitude of the visual response acquired by ERG. Finally, we show that the manipulation of the spectral phase of NIR pulses can be translated to predictable change in the two-photon induced response under physiological excitation conditions.

In mammals, chemoperception relies on a diverse set of neuronal sensors able to detect chemicals present in the environment, and to adapt to various levels of stimulation. The contribution of endogenous and external factors to these neuronal identities remains to be determined. Taking advantage of the parallel coding lines present in the olfactory system, we explored the potential variations of neuronal identities before and after olfactory experience. We found that at rest, the transcriptomic profiles of mouse olfactory sensory neuron populations are already divergent, specific to the olfactory receptor they express, and are associated with the sequence of these latter. These divergent profiles further evolve in response to the environment, as odorant exposure leads to reprogramming via the modulation of transcription. These findings highlight a broad range of sensory neuron identities that are present at rest and that adapt to the experience of the individual, thus adding to the complexity and flexibility of sensory coding.