First published online June 15, 2006
Journal of Experimental Biology 209, 2432-2441 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02269
Somite formation and expression of MyoD, myogenin and myosin in Atlantic halibut (Hippoglossus hippoglossus L.) embryos incubated at different temperatures: transient asymmetric expression of MyoD
Trina F. Galloway1,*,
Tora Bardal1,
Sylvia N. Kvam1,
Stine W. Dahle1,
Gaute Nesse2,
Markus Randøl2,
Elin Kjørsvik1 and
Øivind Andersen2
1 Department of Biology, Brattøra Research Centre, Norwegian
University of Science and Technology (NTNU), N-7491 Trondheim,
Norway
2 Institute of Aquaculture Research (AKVAFORSK), PO Box 5010, N-1430
Ås, Norway

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Fig. 1. Atlantic halibut MyoD cDNA and predicted amino acid sequences,
which are numbered on the right. The bHLH domain is shaded. The locations of
the two introns in the genomic sequence are indicated.
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Fig. 2. Atlantic halibut myogenin cDNA and predicted amino acid sequences,
which are numbered on the right. The bHLH domain is shaded. The locations of
the two introns in the genomic sequence are indicated. Alternative splicing by
skipping exon 2 (underlined) generated a shorter transcript because of a
premature stop codon (bold) in the changed reading frame.
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Fig. 3. Alignment of the conserved Cys-rich motif and the boxed bHLH and HIII of
Atlantic halibut MyoD and myogenin and their orthologues from gilthead
seabream (GenBank accession no. AAL85338), zebrafish (AAK06755, AAM82616),
Atlantic cod (AAK17969), pufferfish (AAV70941), common carp (BAA33565,
BAA33564), rainbow trout (CAA87010), Xenopus (CAA34232, AAL05070) and
mouse (NP_112466, NP_034996). Conserved residues of both MyoD and myogenin are
shaded in dark grey; distinct residues of the two factors are shaded in light
grey. The major determinant of the differential functions of MyoD and myogenin
is indicated by an arrow (Bergstrom and
Tapscott, 2001 ).
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Fig. 4. Somite formation at different egg incubation temperatures. Each point
represents one embryo/larva. Sigmoid curves were fitted for each incubation
temperature
[y=a/(1+e(xx0/b)),
where y refers to number of somites and x to number of
d° after fertilisation].
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Fig. 5. Spatial and temporal expression of MyoD, myogenin and
MyHC mRNA in halibut embryos and larvae with similar numbers of
somites. All specimens are dorsal views with the head towards the upper right
corner of the picture. Arrowheads indicate the first somite with expression in
lateral cells; arrows, the first somite with expression in adaxial cells; dot,
asymmetric expression. Scale bar, 0.5 mm for all images.
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Fig. 6. Temporal expression of MyLC2a and MyLC2b during somitogenesis in Atlantic
halibut. The presence of reverse-transcribed cDNAs was verified by amplifying
ß-actin cDNA.
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© The Company of Biologists Ltd 2006