Features of the structure, development, and activity of the zebrafish noradrenergic system explored in new CRISPR transgenic lines
JOURNAL OF COMPARATIVE NEUROLOGY
Authors: Farrar, Matthew J.; Kolkman, Kristine E.; Fetcho, Joseph R.
Abstract
The noradrenergic (NA) system of vertebrates is implicated in learning, memory, arousal, and neuroinflammatory responses, but is difficult to access experimentally. Small and optically transparent, larval zebrafish offer the prospect of exploration of NA structure and function in an intact animal. We made multiple transgenic zebrafish lines using the CRISPR/Cas9 system to insert fluorescent reporters upstream of slc6a2, the norepinephrine transporter gene. These lines faithfully express reporters in NA cell populations, including the locus coeruleus (LC), which contains only about 14 total neurons. We used the lines in combination with two-photon microscopy to explore the structure and projections of the NA system in the context of the columnar organization of cell types in the zebrafish hindbrain. We found robust alignment of NA projections with glutamatergic neurotransmitter stripes in some hindbrain segments, suggesting orderly relations to neuronal cell types early in life. We also quantified neurite density in the rostral spinal cord in individual larvae with as much as 100% difference in the number of LC neurons, and found no correlation between neuronal number in the LC and projection density in the rostral spinal cord. Finally, using light sheet microscopy, we performed bilateral calcium imaging of the entire LC. We found that large-amplitude calcium responses were evident in all LC neurons and showed bilateral synchrony, whereas small-amplitude events were more likely to show interhemispheric asynchrony, supporting the potential for targeted LC neuromodulation. Our observations and new transgenic lines set the stage for a deeper understanding of the NA system.
Multivariate permutation analysis associates multiple polymorphisms with subphenotypes of major depression
GENES BRAIN AND BEHAVIOR
Authors: Hahn, M. K.; Blackford, J. U.; Haman, K.; Mazei-Robison, M.; English, B. A.; Prasad, H. C.; Steele, A.; Hazelwood, L.; Fentress, H. M.; Myers, R.; Blakely, R. D.; Sanders-Bush, E.; Shelton, R.
Abstract
Unipolar major depressive disorder (MDD) is a prevalent, disabling condition with multiple genetic and environmental factors impacting disease risk. The diagnosis of MDD relies on a cumulative measure derived from multiple trait dimensions and alone is limited in elucidating MDD genetic determinants. We and others have proposed that MDD may be better dissected using paradigms that assess how specific genes associate with component features of MDD. This within-disease design requires both a well-phenotyped cohort and a robust statistical approach that retains power with multiple tests of genetic association. In the present study, common polymorphic variants of genes related to central monoaminergic and cholinergic pathways that previous studies align with functional change in vitro or depression associations in vivo were genotyped in 110 individuals with unipolar MDD. Subphenotypic characteristics were examined using responses to individual items assessed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (DSM IV), the 17-item Hamilton Rating Scale for Depression (HAM-D) and the NEO Five Factor Inventory. Multivariate Permutation Testing (MPT) was used to infer genotype-phenotype relationships underlying dimensional findings within clinical categories. MPT analyses show significant associations of the norepinephrine transporter (NET, SLC6A2) -182 T/C (rs2242446) with recurrent depression [odds ratio, OR = 4.15 (1.91 - 9.02)], NET -3081 A/T (rs28386840) with increase in appetite [OR = 3.58 (1.53 - 8.39)] and the presynaptic choline transporter (CHT, SLC5A7) Ile89Val (rs1013940) with HAM-D-17 total score {i.e. overall depression severity [OR = 2.74 (1.05 - 7.18)]}. These relationships illustrate an approach to the elucidation of gene influences on trait components of MDD and with replication, may help identify MDD subpopulations that can benefit from more targeted pharmacotherapy.