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Mutations affecting the formation of posterior lateral line system in Medaka, Oryzias latipes
Ist Teil von
Mechanisms of development, 2004-07, Vol.121 (7), p.729-738
Ort / Verlag
Ireland: Elsevier Ireland Ltd
Erscheinungsjahr
2004
Quelle
Access via ScienceDirect (Elsevier)
Beschreibungen/Notizen
We performed a systematic screen for mutations affecting the trajectory of axons visualized by immunohistochemical staining of Medaka embryos with anti-acetylated tubulin antibody. Among the mutations identified,
yanagi (
yan) and
kazura (
kaz) mutations caused specific defects in projection of the posterior lateral line (PLL) nerve. In
yan and
kaz mutant embryos, the PLL nerve main bundle was misrouted ventrally and dorsally or anteriorly. Medaka
semaphorin3A,
sdf1, and
cxcr4 cDNA fragments were cloned to allow analysis of these mutants. There were no changes in
semaphorin3A or
sdf1 expression in mutant embryos, suggesting that the tissues expressing
semaphorin3A or
sdf1 that are involved in PLL nerve guidance are present in these mutant embryos. Double staining revealed that the mislocated PLL primordium and growth cone of the ectopically projected PLL nerve were always colocalized in both
yan and
kaz mutant embryos, suggesting that migration of PLL primordia and PLL nerve growth cones are not uncoupled in these mutants. Although homozygous
yan larvae showed incomplete migration of the PLL primordium along the anteroposterior axis, ventral proneuromast migration was complete, suggesting that ventral migration of the proneuromast does not require the signaling affected in
yan mutants. In addition to the PLL system, the distribution of primordial germ cells (PGCs) was also affected in both
yan and
kaz mutant embryos, indicating that
yan and
kaz genes are required for the migration of both PLL primordia and PGCs. Genetic linkage analysis indicated that
kaz is linked to
cxcr4, but
yan is not linked to
sdf1 or
cxcr4. These mutations will provide genetic clues to investigate the molecular mechanism underlying formation of the PLL system.