Secondary motoneuron axons localize DM-GRASP on their fasciculated segments

The dorsal hindbrain includes distinct classes of neurons for processing various sensory stimuli, but the developmental aspects of these neurons remain largely unknown. We identify here two distinct classes of neurons in the dorsal hindbrain of developing zebrafish: (1) neurons that express the inhibitory neuronal marker Gad1/2, and (2) neurons that express the zn-5 antigen and Lhx2/9 and require the basic helix-loop-helix transcription factor Atoh1a for development. Neurons were traced to their axon terminals by expressing green fluorescent protein using the Gal4VP16-UAS (UAS, upstream activating sequences) system in combination with the promoter/enhancer regions of gad2 for the Gad1/2(؉) neurons and zic1 for the zn-5(؉)Lhx2/9(؉) neurons. The Gad1/2(؉) neurons projected to the contralateral hindbrain, while the zn-5(؉)Lhx2/9(؉) neurons projected to the contralateral midbrain torus semicircularis, suggesting a role in auditory and lateral line sensory processing. Comparison of these projections with those from the cochlear nuclei to the inferior colliculus in mammals suggests similarities across vertebrate species. Developmental Dynamics 236:706 -718, 2007.

Section: Two Distinct Classes Of Neurons In the Dorsal Hindbrain Basementioning

confidence: 75%

Section: In Situ Hybridization and Immunohistochemistrymentioning

confidence: 99%

Visualization of two distinct classes of neurons by gad2 and zic1 promoter/enhancer elements in the dorsal hindbrain of developing zebrafish reveals neuronal connectivity related to the auditory and lateral line systems

Sassa

Aizawa

Okamoto

2007

“…M,N: Immunostaining with zn8 antibody at 30 hpf in a wild-type embryo (M) and a Df w5 mutant coinjected with wnt3a-MO and wnt8b-MO (N). The zn8 antibody recognizes a cell adhesion molecule related to DM-Grasp (Fashena and Westerfield, 1999) and normally labels commissural neurons (cn), some cranial ganglia, pharyngeal arches, floor plate, and heart (Trevarrow et al, 1990). Commissural neurons are not produced in the wnt-deficient embryo.…”

Section: Resultsmentioning

confidence: 99%

Rhombomere boundaries are Wnt signaling centers that regulate metameric patterning in the zebrafish hindbrain

Riley

Chiang

Storch

et al. 2004

The vertebrate hindbrain develops from a series of segments (rhombomeres) distributed along the anteroposterior axis. We are studying the roles of Wnt and Delta-Notch signaling in maintaining rhombomere boundaries as organizing centers in the zebrafish hindbrain. Several wnt genes (wnt1, wnt3a, wnt8b, and wnt10b) show elevated expression at rhombomere boundaries, whereas several delta genes (dlA, dlB, and dlD) are expressed in transverse stripes flanking rhombomere boundaries. Partial disruption of Wnt signaling by knockdown of multiple wnt genes, or the Wnt mediator tcf3b, ablates boundaries and associated cell types. Expression of dlA is chaotic, and cell types associated with rhombomere centers are disorganized. Similar patterning defects are observed in segmentation mutants spiel-ohne-grenzen (spg) and valentino (val), which fail to form rhombomere boundaries due to faulty interactions between adjacent rhombomeres. Stripes of wnt expression are variably disrupted, with corresponding disturbances in metameric patterning. Mutations in dlA or mind bomb (mib) disrupt Delta-Notch signaling and cause a wide range of patterning defects in the hindbrain. Stripes of wnt1 are initially normal but subsequently dissipate, and metameric patterning becomes increasingly disorganized. Driving wnt1 expression using a heat-shock construct partially rescues metameric patterning in mib mutants. Thus, rhombomere boundaries act as Wnt signaling centers required for precise metameric patterning, and Delta signals from flanking cells provide feedback to maintain wnt expression at boundaries. Similar feedback mechanisms operate in the Drosophila wing disc and vertebrate limb bud, suggesting coaptation of a conserved signaling module that spatially organizes cells in complex organ systems.

“…It was reported that retinal ganglion cells differentiate in apc mutant zebrafish, even though they are disorganized (Nadauld et al, 2006;Paridaen et al, 2009). To examine the molecular basis of this phenotype we performed in situ hybridization and immunohistochemistry on 38 and 48 hpf wild-type and apc mutant embryos with the retinal ganglion cell marker Zn8 (Fashena and Westerfield, 1999). Rather than observing a general disorganization of RGCs in apc mutant eyes, we detected that due to the central shift of atoh7 expression, cell differentiation only occurs in central regions of the retina, as revealed by labeling of the RGCs with the Zn8 antibody (Fig.…”

Section: Developmental Dynamicsmentioning

confidence: 99%

Loss of adenomatous polyposis coli (apc) results in an expanded ciliary marginal zone in the zebrafish eye

Stephens

Senecal

Nguyen

et al. 2010

The distal region of neural retina (ciliary marginal zone [CMZ]) contains stem cells that produce non-neural and neuronal progenitors. We provide a detailed gene expression analysis of the eyes of apc mutant zebrafish where the Wnt/b-catenin pathway is constitutively active. Wnt/b-catenin signaling leads to an expansion of the CMZ accompanied by a central shift of the retinal identity gene sox2 and the proneural gene atoh7. This suggests an important role for peripheral Wnt/b-catenin signaling in regulating the expression and localization of neurogenic genes in the central retina. Retinal identity genes rx1 and vsx2, as well as meis1 and pax6a act upstream of Wnt/b-catenin pathway activation. Peripheral cells that likely contain stem cells can be identified by the expression of follistatin, otx1, and axin2 and the lack of expression of myca and cyclinD1. Our results introduce the zebrafish apc mutation as a new model to study signaling pathways regulating the CMZ.