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Comment |
Oro AE, et al reported that the Drosophila retinoid X receptor homolog ultraspiracle
functions in both female reproduction and eye morphogenesis.
Ultraspiracle (usp) encodes the Drosophila cognate of RXR, the human retinoid
X receptor. To examine how RXR subfamily members function in development,
we have undertaken a phenotypic analysis of usp mutants. usp is required at
multiple stages of development for functions that occur in a wide variety of
tissues. usp is required in the eye-antennal imaginal disc for normal eye
morphogenesis and in the somatic and germline tissues of adult females for
fertilization, eggshell morphogenesis and embryonic development. An unusual
sunken eye phenotype with marked ventral-dorsal polarity appears to be caused
by a lack of usp function in the imaginal disc cells that reside between the eye and
antennal anlage. The usp functions include cell autonomous and non-cell
autonomous components, suggesting that usp controls the production of factors
important for both cell-cell communication and cellular differentiation. These usp
signalling pathways have mechanistic parallels to steroid and retinoid action in
developing vertebrate tissues.
Genes whose expression is detected by cDNA array hybridization: GDP/GTP exchangers, GTPase stimulators and inhibitors, apoptosis Rozenn Dalbi?Tran and Pascal Mermilloda
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Comment |
Schweigert FJ, et al reported the immunolocalization of retinol-binding protein, cellular
retinoic acid-binding protein I and retinoid X receptor beta in
the porcine reproductive tract during the oestrous cycle.
Retinoid-binding proteins and nuclear receptors are expressed in the
reproductive tissues of different species and their expression is hormonally
regulated. In the present study, the authors demonstrated immuno cyto chemically the
temporal and spatial localization of retinol-binding protein (RBP), cellular
retinoic acid-binding protein I (CRABPI) and retinoid X receptor beta (RXR
beta) in porcine ovary, oviduct and uterus during the oestrous cycle. RBP and
CRABPI were localized in the cytoplasm, whereas RXR beta occurred in the
nucleus. CRABPI was present in luteal cells of the ovary only
during dioestrus and in glandular and ciliated cells of the oviduct during
oestrus. In the ovary, RXR beta was always present in granulosa cells and
germinal epithelium, with highest levels observed during oestrus. The results show that the
occurrence of retinoid-binding proteins and nuclear receptors in individual
tissues of the reproductive tract are strongly dependent on the stage of the
oestrous cycle. The association of expression in different
sections of the reproductive tissues investigated shows that the presence of
specific proteins involved in retinoid metabolism was dependent on events
associated with ovulation, the migration of the oocyte through the oviduct and
the possible implantation of the blastocyst into the uterus.
Mohan M, et al reported that bovine cumulus-granulosa cells contain biologically active retinoid receptors that can respond to retinoic acid.
Retinoids, a class of compounds that include retinol and its metabolite, retinoic acid, are absolutely essential for ovarian steroid production, oocyte maturation, and early embryogenesis. Previous studies have detected high concentrations of retinol in bovine large follicles. Further, administration of retinol in vivo and supplementation of retinoic acid during in vitro maturation results in enhanced embryonic development. In the present study, we hypothesized that retinoids administered either in vivo previously or in vitro can exert receptor-mediated effects in cumulus-granulosa cells. Total RNA extracted from in vitro cultured cumulus-granulosa cells was subjected to reverse transcription polymerase chain reaction (RT-PCR) and mRNA expression for RARalpha, RARbeta, RARgamma, RXRalpha, RXRbeta, RALDH-2, and PPARgamma. Transcripts were detected for RBP, RARalpha, RARgamma, RXRalpha, RXRbeta, RALDH-2, and PPARgamma. Expression of RARbeta was not detected in cumulus-granulosa cells. Using western blotting, immunoreactive RARalpha, and RXRbeta protein was also detected in bovine cumulus-granulosa cells. The biological activity of these endogenous retinoid receptors was tested using a transient reporter assay using the pAAV-MCS-betaRARE-Luc vector. Addition of 0.5 and 1 uM all-trans retinoic acid significantly (P < 0.05) increased the activity of the pAAV-MCS-betaRARE-Luc reporter compared to cells transfected with the control reporter lacking a retinoic acid response element. Addition of 5 or 10 uM all-trans retinol stimulated a mild increase in reporter activity, however, the increase was not statistically significant. Based on these results we conclude that cumulus cells contain endogenously active retinoid receptors and may also be competent to synthesize retinoic acid using the precursor, retinol. These results also indirectly provide evidence that retinoids administered either in vivo previously or in vitro may have exerted a receptor-mediated effect on cumulus-granulosa cells.
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