Abstract:The NEUROGENINS (NGNs) are neural-specific basic helix-loop-helix (bHLH) transcription factors. Mouse embryos lacking ngn1 fail to generate the proximal subset of cranial sensory neurons. ngn1 is required for the activation of a cascade of downstream bHLH factors, including NeuroD, MATH3, and NSCL1. ngn1 is expressed by placodal ectodermal cells and acts prior to neuroblast delamination. Moreover, NGN1 positively regulates the Delta homolog DLL1 and can be negatively regulated by Notch signaling. Thus, ngn1 fu… Show more
“…Ngn-1 is essential for the specification of trigeminal sensory neurons (Ma et al, 1998). The present RT-PCR experiments demonstrate that ngn-1 expression at the trigeminal ganglion axial level is positively regulated by Shh signaling.…”
Section: Participation Of Shh Signaling In the Specification Of Trigesupporting
confidence: 51%
“…It has been reported that ngn-2 is a specification factor for distal placode-derived sensory neurons in epibranchial ganglia (Fode et al, 1998). In the same ganglia, ngn-1 is essential for the specification of proximal neural crest-derived sensory neurons (Ma et al, 1998). Thus, ngn-1 and ngn-2 function in different regions in epibranchial ganglia.…”
Section: Effects Of Signaling Molecules On the Expression Of Neurogeninsmentioning
confidence: 99%
“…The promotion of ngn-1 expression by Shh treatment suggests that Shh acts on the development of trigeminal sensory neurons, because ngn-1 is expressed in trigeminal sensory neuron precursors (Ma et al, 1998).…”
Section: Shh Promotes Ngn-1 Expression In Trigeminal Neural Crest Cellsmentioning
We have examined the roles of signaling molecules in the mechanisms underlying the induction of neurogenin (ngn)-1 expression. ngn-1 is a basic helix-loop-helix (bHLH) transcription factor, which is essential for the specification of trigeminal sensory neurons. Semiquantitative reverse transcriptase-polymerase chain reaction using cranial explants in organ cultures showed that sonic hedgehog (Shh) promotes ngn-1 expression. This promoting activity was not observed in other signaling molecules examined. The promotion of ngn-1 expression by Shh, furthermore, was inhibited by cyclopamine, a specific inhibitor of Shh signaling. Shh did not affect the expression of ngn-2, a bHLH transcription factor that plays an important role in the specification of epibranchial placode-derived sensory neurons.
“…Ngn-1 is essential for the specification of trigeminal sensory neurons (Ma et al, 1998). The present RT-PCR experiments demonstrate that ngn-1 expression at the trigeminal ganglion axial level is positively regulated by Shh signaling.…”
Section: Participation Of Shh Signaling In the Specification Of Trigesupporting
confidence: 51%
“…It has been reported that ngn-2 is a specification factor for distal placode-derived sensory neurons in epibranchial ganglia (Fode et al, 1998). In the same ganglia, ngn-1 is essential for the specification of proximal neural crest-derived sensory neurons (Ma et al, 1998). Thus, ngn-1 and ngn-2 function in different regions in epibranchial ganglia.…”
Section: Effects Of Signaling Molecules On the Expression Of Neurogeninsmentioning
confidence: 99%
“…The promotion of ngn-1 expression by Shh treatment suggests that Shh acts on the development of trigeminal sensory neurons, because ngn-1 is expressed in trigeminal sensory neuron precursors (Ma et al, 1998).…”
Section: Shh Promotes Ngn-1 Expression In Trigeminal Neural Crest Cellsmentioning
We have examined the roles of signaling molecules in the mechanisms underlying the induction of neurogenin (ngn)-1 expression. ngn-1 is a basic helix-loop-helix (bHLH) transcription factor, which is essential for the specification of trigeminal sensory neurons. Semiquantitative reverse transcriptase-polymerase chain reaction using cranial explants in organ cultures showed that sonic hedgehog (Shh) promotes ngn-1 expression. This promoting activity was not observed in other signaling molecules examined. The promotion of ngn-1 expression by Shh, furthermore, was inhibited by cyclopamine, a specific inhibitor of Shh signaling. Shh did not affect the expression of ngn-2, a bHLH transcription factor that plays an important role in the specification of epibranchial placode-derived sensory neurons.
“…For example, members of the basic helixloop-helix transcription factor family, neurogenin1 (ngn1) and neurogenin2 (ngn2) are expressed in different subsets of ganglia dependent on species, and functional analyses showed that ngn genes are important for the development of the epibranchial ganglia (Fode et al, 1998;Ma et al, 1998;Schlosser and Northcutt, 2000;AbuElmagd et al, 2001;Andermann et al, 2002). Indeed, ectopic expression of ngn1 induces formation of excessive neurons in Xenopus and zebrafish embryos (Ma et al, 1996;Blader et al, 1997).…”
In vertebrates, cranial sensory ganglia are mainly derived from ectodermal placodes, which are focal thickenings at characteristic positions in the embryonic head. Here, we provide the first description of the early development of the epibranchial placode in zebrafish embryos using sox3 as a molecular marker. By the one-somite stage, we saw a pair of single sox3-expressing domains appear lateral to the future hindbrain. The sox3 domain, which is referred to here as the early lateral placode, is segregated during the early phase of segmentation to form a pax2a-positive medial area and a pax2a-negative lateral area. The medial area subsequently developed to form the otic placode, while the lateral area was further segregated along the anteroposterior axis, giving rise to four sox3-positive subdomains by 26 hr postfertilization. Given their spatial relationship with the expression of the markers for the epibranchial ganglion, as well as their positions and temporal changes, we propose that these four domains correspond to the facial, glossopharyngeal, vagal, and posterior lateral line placodes in an anterior-to-posterior order. The expression of sox3 in the early lateral placode was absent in mutants lacking functional fgf8, while implantation of fibroblast growth factor (FGF) beads restored the sox3 expression. Using SU5402, which inhibits the FGF signal, we were able to demonstrate that formation of both the early lateral domains and later epibranchial placodes depends on the FGF signal operating at the beginning of somitogenesis. Together, these data provide evidence for the essential role of FGF signals in the development of the epibranchial placodes. Developmental Dynamics 236:564 -571, 2007.
“…Transcription factors neurogenin, foxd3 and NeuroD (Fode et al, 1998;Ma et al, 1998;Kim et al, 2001;Andermann et al, 2002), chemokine guidance receptor Cxcr4b (Knaut et al, 2005;Haas and Gilmour, 2006), and cell adhesion molecule cadherin-2 (Kerstetter et al, 2004) have been implicated in the development of the cranial ganglia and/or lateral line system.…”
We previously reported that cadherin-4 (also called R-cadherin) was expressed by the majority of the developing zebrafish cranial and lateral line ganglia. Cadherin-4 (Cdh4) function in the formation of these structures in zebrafish was studied using morpholino antisense technology. Differentiation of the cranial and lateral line ganglia and lateral line nerve and neuromasts of the cdh4 morphants was analyzed using multiple neural markers. We found that a subset of the morphant cranial and lateral line ganglia were disorganized, smaller, with reduced staining, and/or with altered shape compared to control embryos. Increased cell death in the morphant ganglia likely contributed to these defects. Moreover, cdh4 morphants had shorter lateral line nerves and a reduced number of neuromasts, which was likely caused by disrupted migration of the lateral line primordia. These results indicate that Cdh4 plays a role in the normal formation of the zebrafish lateral line system and a subset of the cranial ganglia. Developmental Dynamics 236:893-902, 2007.
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