Project description:How evolutionary changes in genes and neurons encode species variation in complex motor behaviors are largely unknown. Here, we develop genetic tools that permit a neural circuit comparison between the model speciesDrosophila melanogasterand the closely-related speciesD. yakuba, who has undergone a lineage-specific loss of sine song, one of the two major types of male courtship song inDrosophila. Neuroanatomical comparison of song patterning neurons called TN1 across the phylogeny demonstrates a link between the loss of sine song and a reduction both in the number of TN1 neurons and the neurites serving the sine circuit connectivity. Optogenetic activation confirms that TN1 neurons inD. yakubahave lost the ability to drive sine song, while maintaining the ability to drive the singing wing posture. Single-cell transcriptomic comparison shows thatD. yakubaspecifically lacks a cell type corresponding to TN1A neurons, the TN1 subtype that is essential for sine song. Genetic and developmental manipulation reveals a functional divergence of the sex determination genedoublesexinD. yakubato reduce TN1 number by promoting apoptosis. Our work illustrates the contribution of motor patterning circuits and cell type changes in behavioral evolution, and uncovers the evolutionary lability of sex determination genes to reconfigure the cellular makeup of neural circuits.
Project description:Transcriptional profiling of courtship song stimulated females in Drosophila melanogaster comparing females exposed to conspecific song to those exposed to either white-noise (control) or heterospecific song (D. simulans)
Project description:Birdsong is powerful model for the neural mechanisms underlying motor skill learning. The success of this model is in part due to the experimental advantages of the song system, the anatomically and functionally discrete neural circuit dedicated to song. Despite a detailed understanding of the physiological and systems levels properties of this circuit, we still lack a comprehensive understanding of what cell types are present in each region of the song system and how these cell types compare to those found in the brains of other vertebrates. Here, we characterize the cellular repertoire of the song motor pathway using single-cell RNA-sequencing.
Project description:Transcriptional profiling of courtship song stimulated females in Drosophila melanogaster comparing females exposed to conspecific song to those exposed to either white-noise (control) or heterospecific song (D. simulans) Three condition experiment, D. melanogaster (mel_song) song stimulated vs. Control (no_song) and vs. D. simulans (sim_song) stimulated females. Biological replicates: 7 for D_mel_song, 4 for no_song, 3 for D_sim_song. One replicate per array. Each sample contains 120 pooled female heads, collected from three independent experiments. Technical replication: two arrays with reverse labeling for each contrast.
Project description:Production of learned vocalizations requires precise selection and accurate sequencing of appropriate vocal-motor actions. The basal ganglia are essential for the selection and sequencing of motor actions, but the cellular specializations and circuit mechanisms governing accurate sequencing of vocalizations are unknown. Here, we use single-nucleus RNA sequencing and genetic manipulations to map basal ganglia cell types and circuits involved in the production of songbird vocal sequences. We identify cell-type specializations in direct-like and indirect-like basal ganglia pathways, including evolutionary expansion of striatal and arkypallidal cell-types that could facilitate vocal sequencing. We also reversibly reduced the expression of FoxP2 with a viral knockdown. For birds in which FoxP2 was knocked down, striatal neurons exhibited decreased expression of Drd1 and showed an increased ratio of Drd2/Drd1 expression. These findings identify key evolutionary specializations and circuits essential for selection and sequencing of vocal-motor actions necessary for vocal communication.
Project description:How evolutionary changes in genes and neurons encode species variation in complex motor behaviors are largely unknown. Here, we develop genetic tools that permit a neural circuit comparison between the model species Drosophila melanogaster and the closely-related species D. yakuba, who has undergone a lineage-specific loss of sine song, one of the two major types of male courtship song in Drosophila. Neuroanatomical comparison of song patterning neurons called TN1 across the phylogeny demonstrates a link between the loss of sine song and a reduction both in the number of TN1 neurons and the neurites serving the sine circuit connectivity. Optogenetic activation confirms that TN1 neurons in D. yakuba have lost the ability to drive sine song, while maintaining the ability to drive the singing wing posture. Single-cell transcriptomic comparison shows that D. yakuba specifically lacks a cell type corresponding to TN1A neurons, the TN1 subtype that is essential for sine song. Genetic and developmental manipulation reveals a functional divergence of the sex determination gene doublesex in D. yakuba to reduce TN1 number by promoting apoptosis. Our work illustrates the contribution of motor patterning circuits and cell type changes in behavioral evolution, and uncovers the evolutionary lability of sex determination genes to reconfigure the cellular makeup of neural circuits.
Project description:[original Title] Rapid and synchronous clearance of PcG histone modifications from Hox genes anticipates motor neuron differentiation. Hox genes are expressed in patterns that are spatially and temporally collinear with their chromosomal organization. This feature is an evolutionarily conserved hallmark of embryonic development, and in vertebrates it is critical, among others, for the specification of motor neuron subtypes and the wiring of sensory-motor circuits. We show here that the differentiation of motor neurons from stem cells is accompanied by a synchronous, domain-wide clearance of M-bM-^@M-^\repressiveM-bM-^@M-^] Polycomb (PcG)-dependent histone methylation from Hox gene chromatin domains. These findings argue against the idea, advanced recently, that the collinear dynamics of Hox gene expression invariably reflects the progressive clearance of repressive chromatin modifications. The rapid establishment of stable chromatin domains in response to a transient patterning signal likely serves as a molecular correlate of enduring rostro-caudal neural identity, which underlies the specification of postmitotic motor neuron subtype diversity and neuronal circuit assembly. The differentiation of ventral motor neurons is induced by treating embryonic stem cell cultures with retinoic acid and hedgehog agonist. Here, ChIP-chip using a custom Agilent array is used to profile the occupancy of H3K27me3, H3K4me3, and H3K79me2 at various defined stages during the differentiation process.
Project description:The fidelity of motor control requires the precise positional arrangement of motor pools and the establishment of synaptic connections between these pools. In the developing spinal cord, motor nerves project to specific target muscles and receive proprioceptive input from the muscles via the sensorimotor circuit. LIM-homeodomain transcription factors are known to successively restrict specific motor neuronal fates during neural development; however, it remains unclear to what extent they contribute to limb-based motor pools and locomotor circuits. Here, we showed in mice that deletion of Isl2 resulted in scattered motor pools, primarily in the median motor column and lateral LMC (LMCl) populations, and lacked Pea3 expression in the hindlimb motor pools, accompanied by reduced terminal axon branching and disorganized neuromuscular junctions. Transcriptomic analysis of Isl2-deficient spinal cords revealed that a variety of genes involved in motor neuron differentiation, axon development, and synapse organization were downregulated in hindlimb motor pools. Moreover, the loss of Isl2 impaired sensorimotor connectivity and hindlimb locomotion. Together, our studies indicate that Isl2 plays a critical role in organizing motor pool position and sensorimotor circuits in hindlimb motor pools.
Project description:[original Title] Rapid and synchronous clearance of PcG histone modifications from Hox genes anticipates motor neuron differentiation. Hox genes are expressed in patterns that are spatially and temporally collinear with their chromosomal organization. This feature is an evolutionarily conserved hallmark of embryonic development, and in vertebrates it is critical, among others, for the specification of motor neuron subtypes and the wiring of sensory-motor circuits. We show here that the differentiation of motor neurons from stem cells is accompanied by a synchronous, domain-wide clearance of “repressive” Polycomb (PcG)-dependent histone methylation from Hox gene chromatin domains. These findings argue against the idea, advanced recently, that the collinear dynamics of Hox gene expression invariably reflects the progressive clearance of repressive chromatin modifications. The rapid establishment of stable chromatin domains in response to a transient patterning signal likely serves as a molecular correlate of enduring rostro-caudal neural identity, which underlies the specification of postmitotic motor neuron subtype diversity and neuronal circuit assembly.