Jagged-Notch Signaling is Involved in Zebrafish Notochord Development
Mai Yamamoto1, Kunihiro Matsumoto1, Shigenobu Yonemura2, Koichi Kawakami3, ○Motoyuki Itoh1
1) Nagoya University, Nagoya, Japan,
2) RIKEN CDB, Kobe, Japan,3)NIG, Mishima, Japan
The notochord is an early midline structure of mesodermal origin.
As the notochord differentiates, a large vacuole is inflated within cells
and the peri-notochordal basement membrane is formed. This structure
development is important for the notochord to serves as the axial skeleton.
Many studies have revealed its early patterning roles. However the
mechanism by which the notochord structure is formed and maintained is
not fully understood.
The Notch signaling pathway plays an important role in the
determination of cell fate/differentiation in a number of organs. We found
inhibition of Jagged-Notch signaling led to morphological defects of the
notochord. In Notch signaling deficient embryos such as mind bomb
mutants, jagged1a /1b or su(H) morphants, the notochord cells became
vacuolated but were more spherical instead of rod-like shape. Time-
lapse analysis revealed notochord cells differentiated into two types of
cells, vacuolated and non-vacuolated cells. We found that the number of
vacuolated cell was increased, but non-vacuolated cells were decreased in
Jagged-Notch signaling deficient embryos. We also found type II collagen
protein in the peri-notochordal basement membrane was decreased in
Jagged-Notch signaling deficient embryos. This observation is consistent
with the reduction of non-vacuolated cells because the production of type
II collagen mainly depends on non-vacuolated cells but not on vacuolated
cells. Furthermore notochord cell specific activation of notch by GAL4UAS system resulted in ectopic collagen production and reduction of
vacuolated cells. Thus, our data suggest Jagged-Notch signaling controls
commitment to a non-vacuolated cell fate to enable peri-notochordal
basement formation required for notochord structural integrity.