The bHLH Protein NEUROGENIN 2 Is a Determination Factor for Epibranchial Placode–Derived Sensory Neurons

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.

Section: Effects Of Signaling Molecules On the Expression Of Neurogeninsmentioning

confidence: 99%

Induction of neurogenin‐1 expression by sonic hedgehog: Its role in development of trigeminal sensory neurons

Ota

2003

“…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).…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, ectopic expression of ngn1 induces formation of excessive neurons in Xenopus and zebrafish embryos (Ma et al, 1996;Blader et al, 1997). Gene targeting in mice showed that Ngn2 is required for delamination, migration, and differentiation of neurons in the facial and glossopharyngeal placodes (Fode et al, 1998), and morpholino knockdown of ngn1 in zebrafish blocked differentiation of all cranial ganglia (Andermann et al, 2002). Furthermore, many studies have shown that sox2 and sox3, members of the Sox gene family, are expressed in the epibranchial placodes at the earliest stage of placode development in chicks Ishii et al, 2001), frogs (Mizuseki et al, 1998), medaka (Koster et al, 2000), and zebrafish (Okuda et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Initial specification of the epibranchial placode in zebrafish embryos depends on the fibroblast growth factor signal

Nikaido

Doi

Shimizu³

et al. 2006

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.…”

Section: Introductionmentioning

confidence: 99%

Cadherin‐4 plays a role in the development of zebrafish cranial ganglia and lateral line system

Wilson

Shen

Clendenon

et al. 2007

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.