Healthcare and Medicine Reference
In-Depth Information
Nasal
Retinal explant position
Temporal
1
2
3
4
5
6
7
8
0%
15%
50%
100%
FIGURE 6.14 Retinal axon outgrowth, with variation in both retinal position and Ephrin-A2 concentra-
tion. Representative photographs showing outgrowth from the eight contiguous explant positions (numbered
1 through 8) across the nasal-temporal axis of the retina, grown on substrates containing different propor-
tions of membranes from Ephrin-A2 DNA-transfected and untransfected cells. Outgrowth varies with both
retinal position and Ephrin concentration. Responses to Ephrin-A2 membranes vary from total outgrowth
inhibition (at higher concentrations and more temporal positions) to several-fold outgrowth promotion (at
lower concentrations and nasal positions). (After Hansen et al., 2004)
Reverse
signaling
D
D
ephrin-B
ephrin-B1/B2
tectum
Xenopus
retina
EphB2
EphB1
EphB
ephrin-B
V
V
Forward
signaling
M
ephrin-B1/B2
D
ephrin-B1
retina
superior
colliculus
mouse
EphB2/B3/B4
EphB2/B3
ephrin-B
EphB
V
L
FIGURE 6.15 Topographic mapping of the dorsal ventral retina onto the mediolateral tectum. In Xenopus,
Ephrin-B expressing retinal ganglion cells from the dorsal retina via reverse-signaling are attracted to the
high levels of Eph-B in the lateral tectum, while in chicks Eph-B expressing retinal ganglion cells are attracted
via forward signaling to the high levels of Ephrin-B in the medial tectum. Abbreviations: D, dorsal; V, ventral;
M, medial; L, lateral. (From Pittman and Chien, 2002)
Search Pocayo ::




Custom Search