Development of topographic connections between the isthmic nuclei and optic tecta in the frog Limnodynastes dorsalis

1990 ◽  
Vol 181 (2) ◽  
Author(s):  
J.F. Dann ◽  
L.D. Beazley
Keyword(s):  
Isthmic Nuclei

Specification of the anterior hindbrain and establishment of a normal mid/hindbrain organizer is dependent on Gbx2 gene function

Development ◽  
1997 ◽  
Vol 124 (15) ◽  
pp. 2923-2934 ◽  
Author(s):  
K.M. Wassarman ◽  
M. Lewandoski ◽  
K. Campbell ◽  
A.L. Joyner ◽  
J.L. Rubenstein ◽  
...  
Keyword(s):  
Normal Development ◽  
Motor Nerve ◽  
Homeobox Gene ◽  
Neural Plate ◽  
Mouse Embryos ◽  
Loss Of Function ◽  
Isthmic Nuclei ◽  
Signaling Center ◽  
Derivatives Of ◽  
Anterior Posterior

Analysis of mouse embryos homozygous for a loss-of-function allele of Gbx2 demonstrates that this homeobox gene is required for normal development of the mid/hindbrain region. Gbx2 function appears to be necessary at the neural plate stage for the correct specification and normal proliferation or survival of anterior hindbrain precursors. It is also required to maintain normal patterns of expression at the mid/hindbrain boundary of Fgf8 and Wnt1, genes that encode signaling molecules thought to be key components of the mid/hindbrain (isthmic) organizer. In the absence of Gbx2 function, isthmic nuclei, the cerebellum, motor nerve V, and other derivatives of rhombomeres 1–3 fail to form. Additionally, the posterior midbrain in the mutant embryos appears to be extended caudally and displays abnormalities in anterior/posterior patterning. The failure of anterior hindbrain development is presumably due to the loss of Gbx2 function in the precursors of the anterior hindbrain. However, since Gbx2 expression is not detected in the midbrain it seems likely that the defects in midbrain anterior/posterior patterning result from an abnormal isthmic signaling center. These data provide genetic evidence for a link between patterning of the anterior hindbrain and the establishment of the mid/hindbrain organizer, and identify Gbx2 as a gene required for these processes to occur normally.

The histogenesis of the isthmic nuclei in chick embryos (Gallus domesticus)

1973 ◽  
Vol 142 (3) ◽  
pp. 283-314 ◽  
Author(s):  
Sigmund Vaage
Keyword(s):  
Gallus Domesticus ◽  
Chick Embryos ◽  
Isthmic Nuclei

Neurogenesis and cell death in the isthmic nuclei of the frogLimnodynastes dorsalis

1989 ◽  
Vol 283 (1) ◽  
pp. 28-37 ◽  
Author(s):  
J. F. Dann ◽  
L. D. Beazley
Keyword(s):  
Cell Death ◽  
Isthmic Nuclei

FGF8 induces formation of an ectopic isthmic organizer and isthmocerebellar development via a repressive effect on Otx2 expression

Development ◽  
1999 ◽  
Vol 126 (6) ◽  
pp. 1189-1200 ◽  
Author(s):  
S. Martinez ◽  
P.H. Crossley ◽  
I. Cobos ◽  
J.L. Rubenstein ◽  
G.R. Martin
Keyword(s):  
Neural Tube ◽  
Lateral Wall ◽  
Mirror Image ◽  
Repressive Effect ◽  
Isthmic Nuclei ◽  
Signaling Center ◽  
The One ◽  
The Brain ◽  
Morphogenetic Effects ◽  
Wnt1 Expression

Beads containing recombinant FGF8 (FGF8-beads) were implanted in the prospective caudal diencephalon or midbrain of chick embryos at stages 9–12. This induced the neuroepithelium rostral and caudal to the FGF8-bead to form two ectopic, mirror-image midbrains. Furthermore, cells in direct contact with the bead formed an outgrowth that protruded laterally from the neural tube. Tissue within such lateral outgrowths developed proximally into isthmic nuclei and distally into a cerebellum-like structure. These morphogenetic effects were apparently due to FGF8-mediated changes in gene expression in the vicinity of the bead, including a repressive effect on Otx2 and an inductive effect on En1, Fgf8 and Wnt1 expression. The ectopic Fgf8 and Wnt1 expression domains formed nearly complete concentric rings around the FGF8-bead, with the Wnt1 ring outermost. These observations suggest that FGF8 induces the formation of a ring-like ectopic signaling center (organizer) in the lateral wall of the brain, similar to the one that normally encircles the neural tube at the isthmic constriction, which is located at the boundary between the prospective midbrain and hindbrain. This ectopic isthmic organizer apparently sends long-range patterning signals both rostrally and caudally, resulting in the development of the two ectopic midbrains. Interestingly, our data suggest that these inductive signals spread readily in a caudal direction, but are inhibited from spreading rostrally across diencephalic neuromere boundaries. These results provide insights into the mechanism by which FGF8 induces an ectopic organizer and suggest that a negative feedback loop between Fgf8 and Otx2 plays a key role in patterning the midbrain and anterior hindbrain.

The isthmic nuclei providing parallel feedback connections to the avian tectum have different neurochemical identities: Expression of glutamatergic and cholinergic markers in the chick (Gallus gallus)

2015 ◽  
Vol 523 (9) ◽  
pp. 1341-1358 ◽  
Author(s):  
Cristian González-Cabrera ◽  
Florencia Garrido-Charad ◽  
Alejandro Roth ◽  
Gonzalo J. Marín
Keyword(s):  
Gallus Gallus ◽  
Isthmic Nuclei ◽  
Feedback Connections ◽  
Cholinergic Markers

Developmental changes of NADPH-diaphorase positive structures in the isthmic nuclei of the chick

2000 ◽  
Vol 201 (6) ◽  
pp. 509-519 ◽  
Author(s):  
Quan Xiao ◽  
Hong-Yan Xu ◽  
Shu-Rong Wang ◽  
G. Lázár
Keyword(s):  
Nadph Diaphorase ◽  
Developmental Changes ◽  
Isthmic Nuclei

A Golgi study of the isthmic nuclei in the pigeon (Columba Iivia)

1987 ◽  
Vol 248 (2) ◽  
Author(s):  
Onur G�nt�rk�n
Keyword(s):  
Golgi Study ◽  
Isthmic Nuclei
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