Xenopus etr-1; nervous system, neural
Xenopus elav-type ribonucleoprotein, Xl etr-1, nucleic acid
Pictures from Anne Knecht and Richard Harland, text from Peter Good and
Anne Knecht.
Developmental Northern Blot for etr-1. 
The cDNA corresponding to the etr-1 gene (17-5) was isolated in a screen
for markers of the embryonic nervous system. The gene is activated shortly
after gastrulation (Northern Blot). The 17-5 cDNA encodes a predicted
protein of 462 amino acids that is a member of a large family of genes
characterized by encoding an RNA recognition motif (RRM). The RRM has two
highly conserved regions, referred to as RNP1 and RNP2; each RRM of the
17-5 protein matches a consensus sequence for these regions, but the 17-5
RRMs are distinct from sequences in other identified RNA binding proteins.
The arrangement of RRMs in 17-5 is most similar to proteins in the
RRM-containing subfamily named the elav-like gene family whose members are
mostly expressed in the nervous system. Two consecutive RRMs are in the
amino-terminal half, connected by a tether region to the third RRM at the
carboxy terminus. The 17-5 gene is highly conserved through evolution,
with a similar sequence identified by random isolation of localized cDNAs
in the mouse brain (accession #X61451) and by random cloning of a human
expressed sequence tag isolated from a brain cDNA library (accession
#T08930). We have named the corresponding gene elav-type
ribonucleoprotein 1, etr-1.
(these thumbprints are linked to large, high resolution jpg files, about 0.3 mb compressed)
Stage 18 
Stage 24
Forebrain X-section 
By whole mount in situ hybridization, etr-1 is expressed throughout the
neural plate at stage 13, with strongest expression in the anterior
two-thirds. Later, salt-and-pepper-type expression continues in the neural
folds, and small patches of expression lateral to the brain appear (Stage
18). These patches probably represent future trigeminal ganglia, where
etr-1 is strongly expressed by stage 20. In the early tailbud stages
(Stage 24), etr-1 is expressed in the spinal cord, hindbrain, and ventral
fore- and midbrain (Forebrain X-section); it is absent or very weak in the
dorsal fore- and midbrain, except for the future epiphysis and a small
patch in the dorsal forebrain. Expression levels increase during the late
tailbud stages, and the dorsal forebrain patch expands, such that by stage
38 etr-1 is expressed strongly throughout the CNS, including eyes,
epiphysis, nasal pits, and cranial ganglia and nerves, but excluding a gap
between the midbrain and hindbrain. Thus etr-1 is specific to neural
tissue, but not all neural tissue; particularly during tailbud stages it
marks a complex pattern in the fore- and midbrain, including mainly the
ventral floor of these regions.
- Reference: Knecht, A.K., Good, P.J., Dawid, I.B., and Harland,
R.M. (1995)Dorsal-Ventral Patterning and Differentiation of
Noggin-Induced NeuralTissue in the Absence of Mesoderm Development 121,
1927-1936.
Richter, K., H. Grunz, and I.B. Dawid. 1988. Gene
expression in the embryonic nervous system of Xenopus laevis. Proc. Natl.
Acad. Sci. 85:8086-8090. - Plasmid name; p17-5a (download restriction map)
- etr-1 cDNA in
pBluescriptKS (Fragment A from the 17-5 lambda clone).
- download sequnce
- Genbank accession number;
U16800.
- For in situ probe cut with XbaI and transcribe with
T3
- Available from Peter
Good
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