Biology Reference
In-Depth Information
Table 13.1 References describing specific localization of TR
b
(TR
a
is apparently
ubiquitious) and deiodinase expression in embryonic X. laevis and X. tropicalis(
*
)
Spinal
chord
Notochord
Brain
Retina
Otic vesicle
Tr
Havis
et al.
(2006)
Cossette and
Drysdale (2004)
,
Havis et al. (2006)
;
Oofusa et al. (2001)
Havis et al.
(2006)
b
Dio2
Tindall
et
al.
(2007)
*
Morvan
Dubois
et al.
(2006)
Morvan Dubois
et al. (2006)
,
Tindall et al.
(2007)
*
Morvan Dubois
et
al. (2006)
,
Tindall et al.
(2007)
*
Morvan
Dubo
is et al.
(2006)
,
Tindall
et al. (2007)
*
Dio3
Tindall
et al.
(2007)
*
Morvan
Dubois
et al.
(2006)
Morvan Dubois
et al. (2006)
,
Tindall et al.
(2007)
*
Morvan Dubois
et al. (2006)
,
Tindall et al.
(2007)
*
Interestingly, specifically in the brain of early stage
X. laevis
, we also saw
higher expression of
dio2
as compared to the other deiodinases transcripts
(
Fini, Le M´vel, et al., 2012
).
Dio3
mRNA levels in embryos are fairly con-
stant, but low, throughout early embryogenesis, only increasing at stage
NF37, then continuing to rise through stages NF41-48 (
Fini, Le M´vel,
et al., 2012
). Interestingly, similar results to those found for
X. laevis
were
obtained for
Dio2
mRNA expression in
X. tropicalis
(
Tindall, Morris,
Pownall, & Isaacs, 2007
), suggesting conservation in the mechanisms regu-
lating transcription and potential functions (
Table 13.1
).
Dio1
mRNA
expression has not been investigated in
X. tropicalis
.
In chick, the three deiodinases are expressed early on during develop-
ment (
Van Herck, Geysens, Delbaere, Tylzanowski, & Darras, 2012
). These
authors measured both mRNA levels and deiodinase activity during the first
half of embryogenesis. Although
Dio1
mRNA expression was found, no
activity could be detected, whereas both
Dio2
expression and D2 activity
increased steadily from E4 to E12 in all brain areas examined, that is, telen-
cephalon, diencephalon, mesencephalon, and rhombencephalon. In contrast,
in the same brain areas,
Dio3
mRNA levels showed decreasing levels as de-
velopment progressed from stage E4 to E12, but the corresponding D3 activ-
ity, though highly variable in the same areas over the same developmental
time frame, showed a distinct peak in the mesencephalon at E8.
Dio2
is in
particular expressed in the developing hypothalamus, devoid of
Dio3
mRNA
during chicken hypothalamic ontogenesis.
Dio3
is expressed in developing
