December 12, 1997;
An interferon regulatory factor-related gene (xIRF-6) is expressed in the posterior mesoderm during the early development of Xenopus laevis.
Out of a Xenopus neurula
cDNA library, we isolated a clone which encodes a 52.4-kDa protein highly similar to the mouse interferon regulatory factor, IRF-6, whose function is unknown. The mRNA of this gene, named xIRF-6, seems to be maternally transmitted, but its amount rapidly decreases after the tailbud
stage. Whole-mount in situ hybridization showed that xIRF-6 mRNA is expressed in the presumptive somitic mesoderm
in the late gastrula
, and then confined to a segment of posterior somite
during the neurula
through the tailbud
stage. The temporally and spatially limited expression of the xIRF-6 gene product may contribute to the transcriptional regulation of specific genes which are necessary for the development of the posterior somites
[+] show captions
Fig. 1. Structure of the xIRF-6 cDNA and its encoded protein. (A) Nucleotide sequence of the xIRF-6 cDNA and its predicted amino acid sequence.
The signals for mRNA destabilization in the 3¾ UTR are underlined. The data were submitted to DDBJ, EMBL and GenBank under accession
number D86492. (B) Alignment of the putative DNA-binding domains of xIRF-6 and mouse IRF-6, IRF-1, IRF-2 and human IRF-5. Circles
denote tryptophan residues conserved among Myb and Ets families. Amino acid residues identical to those in xIRF-6 are indicated by dots. The
dash (—) represents a gap inserted for maximal alignment.
Fig. 2. Northern blot analysis of xIRF-6 mRNA. (A) Specific expres-
sion of xIRF-6 mRNA during early development. Each lane contained
5 mg of poly (A)+ RNA isolated from whole embryos. The quality
quantity of RNA in each lane were assessed with 28S and 18S
ribosomal RNAs stained with ethidium bromide. Lanes 1–10 contain
RNA from embryos or larvae at stage 6, 8, 10, 14, 16, 18, 20, 25, 35 and washing conditions. and 45, respectively. (B) Tissue blot. Each lane contained 5 mg of poly
(A)+ RNA isolated from adult frog tissues. The same blot was reprobed
Fig. 3. Whole-mount in situ hybridization analysis of xIRF-6 mRNA in Xenopus embryos. (A) Lateral and (B) dorsal views of a late gastrula
(stage 12). xIRF-6 is expressed at the presumptive mesoderm except for the notochord. (C) Lateral and (D) dorsal views of a neurula (stage 18),
showing expression in a limited region of the presumptive somitic mesoderm, except the notochord. (E) Lateral and (F) dorsal views of a tailbud
(stage 25), showing the signals remained in the somitic mesoderm of the tailbud as a pair of small regions adjacent to the midline. (G) and (H)
Dorsal views of an embryo at the same stage as (D) and (F), showing the XMyf5 signals. Note the overlapping expression of xIRF-6 and XMyf5.
xIRF-6 signal at the posterior part is indicated with arrowheads. Notochord is indicated by a filled circle ($) in (B) and (D). XMyf5 at the
posterior part is indicated by asterisks (*).