PUBLICATION

Zebrafish Lmx1b.1 and Lmx1b.2 are required for maintenance of the isthmic organizer

Authors

O'Hara, F.P., Beck, E., Barr, L.K., Wong, L.L., Kessler, D.S., and Riddle, R.D.

ID

ZDB-PUB-050610-13

Date

2005

Source

Development (Cambridge, England) 132(14): 3163-3173 (Journal)

Registered Authors

Wong, Lily

Keywords

Isthmus, Lmx1b, Mesencephalon, Metencephalon, Pax, Wnt, Zebrafish

MeSH Terms

Amino Acid Sequence
Animals
DNA-Binding Proteins/metabolism
Fibroblast Growth Factor 8
Fibroblast Growth Factors/genetics
Fibroblast Growth Factors/metabolism
Gene Expression Regulation, Developmental/physiology
Homeodomain Proteins/genetics
Homeodomain Proteins/physiology*
Intercellular Signaling Peptides and Proteins/biosynthesis
Intercellular Signaling Peptides and Proteins/genetics
LIM-Homeodomain Proteins
Mesencephalon/embryology*
Metencephalon/embryology*
Molecular Sequence Data
PAX2 Transcription Factor
Protein Isoforms/genetics
Protein Isoforms/physiology
Transcription Factors/genetics
Transcription Factors/metabolism
Transcription Factors/physiology*
Wnt Proteins
Wnt1 Protein
Zebrafish/embryology*
Zebrafish/genetics
Zebrafish Proteins

(all 26)

PubMed

15944182 Full text @ Development

Abstract

The mesencephalic and metencephalic region (MMR) of the vertebrate central nervous system develops in response to signals produced by the isthmic organizer (IsO). We have previously reported that the LIM homeobox transcription factor Lmx1b is expressed within the chick IsO, where it is sufficient to maintain expression of the secreted factor wnt1. In this paper, we show that zebrafish express two Lmx1b orthologs, lmx1b.1 and lmx1b.2, in the rostral IsO, and demonstrate that these genes are necessary for key aspects of MMR development. Simultaneous knockdown of Lmx1b.1 and Lmx1b.2 using morpholino antisense oligos results in a loss of wnt1, wnt3a, wnt10b, pax8 and fgf8 expression at the IsO, leading ultimately to programmed cell death and the loss of the isthmic constriction and cerebellum. Single morpholino knockdown of either Lmx1b.1 or Lmx1b.2 has no discernible effect on MMR development. Maintenance of lmx1b.1 and lmx1b.2 expression at the isthmus requires the function of no isthmus/pax2.1, as well as Fgf signaling. Transient misexpression of Lmx1b.1 or Lmx1b.2 during early MMR development induces ectopic wnt1 and fgf8 expression in the MMR, as well as throughout much of the embryo. We propose that Lmx1b.1- and Lmx1b.2-mediated regulation of wnt1, wnt3a, wnt10b, pax8 and fgf8 maintains cell survival in the isthmocerebellar region.

Genes / Markers

Marker	Marker Type	Name
en2b	GENE	engrailed homeobox 2b
epha4a	GENE	eph receptor A4a
fgf8a	GENE	fibroblast growth factor 8a
lmx1ba	GENE	LIM homeobox transcription factor 1, beta a
lmx1bb	GENE	LIM homeobox transcription factor 1, beta b
mab21l2	GENE	mab-21-like 2
otx2b	GENE	orthodenticle homeobox 2b
pax2a	GENE	paired box 2a
pax2b	GENE	paired box 2b
pax5	GENE	paired box 5

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Figures

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Expression

Gene	Fish	Conditions	Stage	Qualifier	Anatomy	Assay	Figure
en2b	TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-5		cerebellum	ISH	Fig. 6
en2b	TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-5		midbrain hindbrain boundary	ISH	Fig. 6
en2b	TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-5		optic tectum	ISH	Fig. 6
epha4a	TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-5		rhombomere 1	ISH	Fig. 6
fgf8a	TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-5	Not Detected	midbrain hindbrain boundary	ISH	text only
fgf8a	TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	14-19 somites to 20-25 somites		midbrain hindbrain boundary	ISH	Fig. 5
lmx1ba	TL	standard conditions	Bud		axis	ISH	Fig. 2
lmx1ba	TL	standard conditions	10-13 somites		diencephalon	ISH	Fig. 2
lmx1ba	TL	standard conditions	Prim-5		hindbrain	ISH	Fig. 3
lmx1ba	TL	standard conditions	10-13 somites		hindbrain	ISH	Fig. 2

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Phenotype

Fish	Conditions	Stage	Phenotype	Figure
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-5	cell proliferation in hindbrain process quality, normal	Fig. 7
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-5	hindbrain apoptotic, abnormal	Fig. 7
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-15	cerebellum aplastic, abnormal	Fig. 4
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-15	midbrain hindbrain boundary aplastic, abnormal	Fig. 4
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-25	cerebellum aplastic, abnormal	Fig. 4
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Prim-25	midbrain hindbrain boundary aplastic, abnormal	Fig. 4
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Long-pec	blood circulation disrupted, abnormal	Fig. 4
TL + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Long-pec	pericardium edematous, abnormal	Fig. 4
pax2a^unspecified	standard conditions	Prim-5	midbrain apoptotic, abnormal	Fig. 7
rw0Tg + MO1-lmx1ba + MO1-lmx1bb	standard conditions	Long-pec	oculomotor nucleus aplastic, abnormal	Fig. 7

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Mutations / Transgenics

Allele	Construct	Type	Affected Genomic Region
pax2a_unspecified		Unspecified	pax2a
rw0Tg	Tg(isl1a:GFP)	Transgenic Insertion

Human Disease / Model

Sequence Targeting Reagents

Target	Reagent	Reagent Type
lmx1ba	MO1-lmx1ba	MRPHLNO
lmx1bb	MO1-lmx1bb	MRPHLNO

Fish

Antibodies

Orthology

Engineered Foreign Genes

Mapping

O'Hara et al., 2005 ZDB-PUB-050610-13 PMID:15944182

Zebrafish Lmx1b.1 and Lmx1b.2 are required for maintenance of the isthmic organizer

O'Hara et al., 2005

ZDB-PUB-050610-13
PMID:15944182