Wearable backpack stimulator for chronic in vivo stimulation of live aquatic animals
| Collaborating Team: Dr. Wei Tan (Department of Electrical Engineering) Craig Duran and Dr. Delia Valles-Rosales (Department of Industrial Engineering) Evan Salazar and Michael Harris (Visgence, Inc. Las Cruces, NM) The instrumentation currently available to manipulate and record the output of nervous systems in terrestrial animals from small insects to large mammals is extensive. In contrast, little to no instrumentation is currently available to study the regulation of electrical activity in aquatic vertebrates. To address this limitation we have begun to develop new instrumentation that allows chronic electrical stimulation and recording in live aquatic teleost fish. Previous studies in the Unguez lab generated and tested an approach for chronic stimulation/recording of teleost fish wherein electrodes were implanted in the fish tissues and secured on the skin of the fish. However, this set up is limiting due to the length of wires exposed to water drag from the fish to the outside of the tank, which leads to detachment of electrodes within three to four days of implantation. To solve this problem, the Unguez lab has teamed with the laboratories of Drs. Wei Tan and Valles-Rosales and Visgence, Inc. to design a 3-D printed “backpack” that holds a stimulator circuit and battery – a set up that shortens the electrode-wire-stimulator interface. To date, a prototype has been generated that is tailored to the fish body and designed to carry waterproof enclosures for the miniaturized stimulator and battery (Figure 1). The 3D printed backpack consists of two rings and two sidebars (Figure 1). The head ring and tail rings are used to clamp the backpack on the fish, while the two sidebars hold two sealed boxes for stimulator electronics and the battery. The fish is then fitted into the backpack (Figure 1).
Figure 1: Wearable 3D printed backpack by free-swimming fish. S. macrurus wearing the backpack in tank without the battery and circuit enclosure. |
Effects of electrical inactivation on gene expression
| Electrically active cell types such as muscle fibers and neurons exhibit enormous phenotypic plasticity in response to alterations in their activity patterns. This phenotypic plasticity enables us to use and optimize abilities such as athletic performance and memory. These adaptations are most commonly studied in mammalian species and have been shown to rely extensively on regulation of gene expression patterns. Previous research from our lab had shown that the muscle-derived electric organ in the weakly electric teleost fish S. macrurus requires electrical input from motoneurons in the spinal cord that innervate the cells of the electric organ. Further work showed that the cells of the electric organ also require electrical input in order to maintain their distinct properties. Robert’s work is focused on identifying the effects of electrical inactivation on the properties and gene expression patterns in muscle and electric organ cells in S. macrurus in order to identify conserved and novel effects of electrical inactivity in these tissues compared to mammalian tissues as well as to start to identify the molecular pathways that mediate these effects. |
Role of microRNAs in regulating gene expression
| The weakly electric fish, Sternopygus macrurus is a powerful model system whose electric organ cells (electrocytes) are formed by the fusion of skeletal muscle fibers. Previous studies have shown that the regulation of skeletal muscle gene expression in electrocytes is not completely regulated at the level of mRNA production. Matt’s research is focused on elucidating the role played by microRNAs in the regulation of the differential expression of skeletal muscle genes in electrocytes and skeletal muscle cells in S. macrurus. |
Determining how skeletal muscle forms the electric organ
| In regards to one of his main interests in the lab, “How is the skeletal muscle (SM) program altered to form an electric organ (EO)?”; currently, Michael aids students in three projects: verifying the comparative transcriptomes of EO and SM with qPCR, elucidating the role microRNAs play in shaping the EO by cloning miRNA expression plasmids, and isolation and electrical manipulation of satellite cells from regenerated S. macrurus tails. |
Conservation of MyoD across species
| The myogenic regulatory factor MyoD is the “master-switch” of the muscle system. Iliana’s project looks at the conservation of MyoD between three electric fish species: Eigenmannia virescens, Electrophorus electricus, and Sternopygus macrurus, and its ability to induce a muscle phenotype in mouse fibroblasts, as well as the similarity in target genes. |
Order of sarcomere disassembly during regeneration
| Several studies have been conducted to determine how muscle fibers and, more specifically, the contractile units (sarcomeres) arise, but little is known about how they disassemble. In the S. macrurus regenerating blastema, muscle fibers disassemble to give rise to electrocytes. Using electron microscopy and immunofluorescence techniques, Cindy looks at the patterns of different regions of the sarcomere in hopes of finding more information about how these muscle fibers disassemble.
Left: TEM image of sarcomeres dissociating. Right: Immunofluorescence image of two-week regenerated tail labeled with Z-disk antibody EA53 (anti-alpha actinin, green) and I-band stain phalloidin (actin, red). |
Correlation between electrical activity and mitochondria shape & distribution
Heather is currently working on the correlation between electrical activity levels and mitochondria shape and distribution. Although studies have been done between mammalian species and organs, there is yet very little known as to whether this correlation holds true between the skeletal muscle cells and electrocytes of S. macrurus. As both of these cells are progenitors of myoblasts, yet display very different phenotypic properties, the model system being utilized provides a novel approach to this question.  |
Role of calcium on gene expression
| Alex’s current project explores the influence of calcium ions in gene transcription. Focusing on two proteins (ORAI and STIM) he hopes to discover the difference in Ca2+ handling between two myoblast-derived cell types (electrocyte and skeletal muscle) and determine how that difference influences the phenotype and function of the cell. Techniques used include PCR, qPCR, and immunohistochemistry. |