RESEARCH ARTICLES CURRENT SCIENCE, VOL. 88, NO. 3, 10 FEBRUARY 2005 455 *For correspondence. (e-mail: ghaskadbi@vsnl.net) Developmental alterations in chick embryo by β-microseminoprotein are closely associated with modulation of goosecoid and noggin expression Aditi Karandikar and Surendra Ghaskadbi* Division of Animal Sciences, Agharkar Research Institute, G.G. Agarkar Road, Pune 411 004, India β-Microseminoprotein (MSP)-induced enhancement of mesodermal structures in chick embryo is brought about through modulation of expression of Brachyury and is often associated with abnormal nervous system devel- opment. In the present study, carried out to further elucidate the mechanism of action of MSP, we find that treatment with MSP leads to up-regulation of goose- coid and down-regulation of noggin in cultured chick embryos. These observations correlate well with stimu- lation of axis elongation and interference with neural tube pattern formation due to MSP. The results show that the molecular mechanism of action of MSP involves goosecoid and noggin, in addition to Brachyury, and further support our contention that MSP-related mole- cules play an important role in the embryonic devel- opment of chick. HUMAN β-microseminoprotein (MSP; also known as human seminal plasma inhibin, hSPI or prostatic secretory protein of 94 amino acid, PSP 94 ) brings about enhancement in the development of mesodermal structures in the chick embryo explants cultured in vitro 1 . We have recently shown that this action of MSP is exerted through modulation of expres- sion of Brachyury 2 . The product of Brachyury is a transcrip- tion factor, which interacts with a number of downstream genes leading to the formation of mesoderm and gastrula- tion movements 3 . MSP-induced enhancement of development of mesoder- mal structures in chick embryos is often associated with abnormal development of neural structures 1,2 . MSP also leads to elongation of the anteroposterior axis 1,2 and increased cellular movements through the Hensen’s node 2 . An impor- tant protein that controls cell migration during gastrula- tion is the product of goosecoid 4 . This is a homeobox gene that is expressed in the organizer region during gastrulation of Xenopus 5 , chick 6 and mouse 7 . Brachyury has been shown to interact with goosecoid in Xenopus 8 . Morphological changes and modulation of Brachyury in developing chick embryo due to MSP suggest that the latter may exert its effects through modulation of goosecoid, either directly or indirectly. A prominent effect of MSP in the chick embryo is abnor- malities in the patterning of the nervous system 1,9 . We there- fore studied the expression of noggin, a gene important in neural tube patterning in chick. In Xenopus, Noggin is one of the neural inducers 10,11 and its neural inducing action is the result of its capacity to neutralize BMP4. In the chick embryo, noggin is expressed at sites comparable to those in Xenopus, but it does not appear to function as a neural inducer 12 . Misexpression of noggin does not lead to for- mation of neural plate at ectopic sites in chick 13 . Noggin is therefore believed to participate in the patterning of the neural tube in chick. In view of the effects of MSP on the development of axial structures, neural patterning, morphogenetic movements and expression of Brachyury in chick embryo, the present study was undertaken to analyse the influence of MSP on the expression of goosecoid and noggin. The results show that MSP differentially modulates the expression of these two developmentally crucial genes and further support our hypothesis that MSP-related molecules play an important role in early chick embryonic development. Materials and methods Materials Freshly laid White Leghorn chicken eggs were obtained either from Central Hatchery, Pune or Institute of Veterinary Biological Products, Pune. In vitro culture, staging and treatment of chick embryo explants: The eggs were incubated at 37.5°C for required duration to obtain the desired stages of development. Chick embryos were dissected in Pannet–Compton saline (PC saline, pH 7.4) 14 and cultured in vitro using New’s single ring technique 15 . The embryos were staged on the basis of morphological criteria 16 . Gastrulating chick embryos of Hamburger–Hamilton (HH) stages 3, 4, 5, 8 and 11 were used in the present study. Embryos were treated as described earlier 2,17 . One hundred microlitres of PC saline containing MSP (kind gift from S. R. Moodbidri, NIRRH, Mumbai)