Second-order projection from the posterior lateral line in the early zebrafish brain.
BACKGROUND
Mechanosensory information gathered by hair cells of the fish lateral-line system is collected by sensory neurons and sent to the ipsilateral hindbrain. The information is then conveyed to other brain structures through a second-order projection. In the adult, part of the second-order projection extends to the contralateral hindbrain, while another part connects to a midbrain structure, the torus semicircularis.


RESULTS
In this paper we examine the second-order projection from the posterior lateral-line system in late embryonic/early larval zebrafish. At four days after fertilization the synaptic field of the sensory neurons can be accurately targeted, allowing a very reproducible labeling of second-order neurons. We show that second-order projections are highly stereotyped, that they vary according to rhombomeric identity, and that they are almost completely lateralized. We also show that the projections extend not only to the contralateral hindbrain and torus semicircularis but to many other brain centers as well, including gaze- and posture-controlling nuclei in the midbrain, and presumptive thalamic nuclei.


CONCLUSIONS
We propose that the extensive connectivity observed in early brain development reveals a basic scaffold common to most vertebrates, from which different subsets are later reinforced in various vertebrate groups. The large repertoire of projection targets provides a promising system to study the genetic encoding of this differential projection capacity.
Fame
Ryann M
RM
Laboratory of Neurogenetics, INSERM E343, Université Montpellier II, place E Bataillon, 34095 Montpellier, France. rmfame@fas.harvard.edu
Brajon
Carole
C
Ghysen
Alain
A
D000344:Afferent Pathways / Q000033:anatomy & histology / Q000196:embryology* / Q000254:growth & development*; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D001921:Brain / Q000033:anatomy & histology / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D004625:Embryo, Nonmammalian; D007839:Functional Laterality; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007814:Larva; D053403:Lateral Line System / Q000166:cytology / Q000196:embryology / Q000254:growth & development; D009475:Neurons, Afferent / Q000502:physiology*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
D000596:Amino Acids; D029961:Zebrafish Proteins; C098463:dolaisoleucine; D049452:Green Fluorescent Proteins