Developmental Regulation of Gonadotropin-releasing Hormone Gene Expression by the MSX and DLX Homeodomain Protein Families

Abstract

Gonadotropin-releasing hormone (GnRH) is the central regulator of the hypothalamic-pituitary-gonadal axis, controlling sexual maturation and fertility in diverse species from fish to humans. GnRH gene expression is limited to a discrete population of neurons that migrate through the nasal region into the hypothalamus during embryonic development. The GnRH regulatory region contains four conserved homeodomain binding sites (ATTA) that are essential for basal promoter activity and cell-specific expression of the GnRH gene. MSX and DLX are members of the Antennapedia class of non-Hox homeodomain transcription factors that regulate gene expression and influence development of the craniofacial structures and anterior forebrain. Here, we report that expression patterns of the Msx and Dlx families of homeodomain transcription factors largely coincide with the migratory route of GnRH neurons and co-express with GnRH in neurons during embryonic development. In addition, MSX and DLX family members bind directly to the ATTA consensus sequences and regulate transcriptional activity of the GnRH promoter. Finally, mice lacking MSX1 or DLX1 and 2 show altered numbers of GnRH-expressing cells in regions where these factors likely function. These findings strongly support a role for MSX and DLX in contributing to spatiotemporal regulation of GnRH transcription during development. Gonadotropin-releasing hormone (GnRH) is the central regulator of the hypothalamic-pituitary-gonadal axis, controlling sexual maturation and fertility in diverse species from fish to humans. GnRH gene expression is limited to a discrete population of neurons that migrate through the nasal region into the hypothalamus during embryonic development. The GnRH regulatory region contains four conserved homeodomain binding sites (ATTA) that are essential for basal promoter activity and cell-specific expression of the GnRH gene. MSX and DLX are members of the Antennapedia class of non-Hox homeodomain transcription factors that regulate gene expression and influence development of the craniofacial structures and anterior forebrain. Here, we report that expression patterns of the Msx and Dlx families of homeodomain transcription factors largely coincide with the migratory route of GnRH neurons and co-express with GnRH in neurons during embryonic development. In addition, MSX and DLX family members bind directly to the ATTA consensus sequences and regulate transcriptional activity of the GnRH promoter. Finally, mice lacking MSX1 or DLX1 and 2 show altered numbers of GnRH-expressing cells in regions where these factors likely function. These findings strongly support a role for MSX and DLX in contributing to spatiotemporal regulation of GnRH transcription during development. Proper sexual maturation and fertility are dependent upon the correct function of the hypothalamic-pituitary-gonadal axis, initiated by a small, yet critical population of gonadotropin-releasing hormone (GnRH) 1The abbreviations used are: GnRH, gonadotropin-releasing hormone; dpc, days postcoitum; EMSA, electromobility shift assay; DIG, digoxigenin; CNS, central nervous system. neurons. The GnRH gene is expressed in a complex spatiotemporal manner during embryonic development and into postnatal life with several populations of GnRH-expressing neurons originating at different developmental stages and locations. These populations include the classical, septohypothalamic neurons, as well as populations in the lateral septum, posterior bed nucleus stria terminalis (pBNST), and tectum (1Wu T.J. Gibson M.J. Silverman A.J. J. Neuroendocrinol. 1995; 7: 899-902Crossref PubMed Scopus (28) Google Scholar, 2Skynner M.J. Slater R. Sim J.A. Allen N.D. Herbison A.E. J. Neurosci. 1999; 19: 5955-5966Crossref PubMed Google Scholar). Although the role of each of these populations of GnRH-producing neurons remains to be elucidated, the contribution of the septohypothalamic population is required for maturation of the hypothalamic-pituitarygonadal axis and fertility (3Mason A.J. Hayflick J.S. Zoeller R.T. Young W.S. Phillips H.S. Nikolics K. Seeburg P.H. Science. 1986; 234: 1366-1371Crossref PubMed Scopus (494) Google Scholar). The precursor cells of the septohypothalamic GnRH neurons have been reported to originate within the olfactory placode (4Dubois E.A. Zandbergen M.A. Peute J. Goos H.J. Brain Res. Bull. 2002; 57: 413-418Crossref PubMed Scopus (122) Google Scholar, 5Schwanzel-Fukuda M. Pfaff D.W. Nature. 1989; 338: 161-164Crossref PubMed Scopus (950) Google Scholar, 6Wray S. Grant P. Gainer H. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 8132-8136Crossref PubMed Scopus (628) Google Scholar) or the neural crest (7Whitlock K.E. Wolf C.D. Boyce M.L. Dev. Biol. 2003; 257: 140-152Crossref PubMed Scopus (116) Google Scholar) and begin to express the GnRH transcript in a discrete population of cells located in close proximity to the olfactory placode of the embryonic mouse by 11.5-days postcoitum (11.5 dpc). By 12.5 dpc, the full complement of septohypothalamic GnRH neurons (∼800) in the adult population is established (6Wray S. Grant P. Gainer H. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 8132-8136Crossref PubMed Scopus (628) Google Scholar), and over the course of the next several days, these neurons migrate toward the CNS, closely associated with the established position of the peripherin-positive nerve bundle of the olfactory nerve (8Wray S. Key S. Qualls R. Fueshko S.M. Dev. Biol. 1994; 166: 349-354Crossref PubMed Scopus (102) Google Scholar, 9Livne I. Gibson M.J. Silverman A.J. Dev. Biol. 1993; 159: 643-656Crossref PubMed Scopus (56) Google Scholar). By 16.5 dpc the majority of the septohypothalamic neurons have reached their destination, scattered throughout the preoptic area, the diagonal band of Broca and the medial septum (5Schwanzel-Fukuda M. Pfaff D.W. Nature. 1989; 338: 161-164Crossref PubMed Scopus (950) Google Scholar, 10Schwanzel-Fukuda M. Jorgenson K.L. Bergen H.T. Weesner G.D. Pfaff D.W. Endocr. Rev. 1992; 13: 623-634Crossref PubMed Scopus (99) Google Scholar). Expression of GnRH during prenatal development actively contributes to the identity and migratory ability of the septohypothalamic population. Indeed, GnRH itself, is involved in furthering the commitment and migratory state of the GnRH neuronal precursor in an ultrashort, positive feedback loop by upregulating expression of the GnRH gene, stimulating axon growth, cytoskeletal remodeling and increasing the migration of neuronal precursors (11Romanelli R.G. Barni T. Maggi M. Luconi M. Failli P. Pezzatini A. Pelo E. Torricelli F. Crescioli C. Ferruzzi P. Salerno R. Marini M. Rotella C.M. Vannelli G.B. J. Biol. Chem. 2004; 279: 117-126Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar). Thus, expression of GnRH during embryonic development likely promotes the characteristics of the maturing GnRH neuron that are essential for reproductive ability. Because of the limited number and dispersed nature of GnRH neurons, the in GnRH promoter expression in is The of GnRH neuronal the and in to GnRH P. C. J. Full Text PDF PubMed Scopus Google Scholar, S. S. E. H. J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). the characteristics of a GnRH-expressing the and are migratory in and to GnRH neurons P. C. J. Full Text PDF PubMed Scopus Google Scholar, S. S. E. H. J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, S. A. F. Maggi R. M. S. Res. 2002; PubMed Scopus Google Scholar, F. E. R. P. A. E. F. Maggi R. J. Neurosci. 2003; PubMed Scopus Google Scholar). with these have been for the transcription that expression of in and in have that well promoter and regions of the GnRH gene, ATTA are and for GnRH gene expression during embryonic development and in the adult P. C. J. Full Text PDF PubMed Scopus Google Scholar, M.A. J. 2002; PubMed Scopus Google Scholar). these sites are essential for as well as cell-specific expression of the GnRH promoter M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar). role for as MSX and in regulation of gene expression during development is well in and species S. Res. 2003; 13: PubMed Scopus Google Scholar, P. T. J. 1999; PubMed Google Scholar, T. M. Biol. PubMed Google Scholar, 2002; PubMed Google Scholar, PubMed Scopus Google Scholar). the MSX and DLX homeodomain transcription families have the expression patterns in the olfactory region and of the mouse to be as of the GnRH gene A. J. Neurosci. 1994; PubMed Google Scholar, A.J. C. PubMed Scopus Google Scholar). These factors homeodomain binding sites in a of promoter regions C. Dev. 1995; PubMed Scopus Google Scholar, C. Res. PubMed Scopus Google Scholar, H. H. P. C. Biol. PubMed Scopus Google Scholar). Here, we report the contribution of DLX and MSX family members to regulation of GnRH promoter expression in and in show that spatiotemporal expression of Msx and Dlx family members with the septohypothalamic GnRH neuronal population. MSX and DLX family members are expressed in the GnRH bind to regulatory regions of the GnRH gene, and regulate promoter activity in In addition, of mouse that DLX1 and as well as MSX1 to GnRH expression in the prenatal septohypothalamic we that MSX and DLX family members in developmental regulation of GnRH gene and for to and Biol. 1995; PubMed Scopus Google Scholar). and with in a over of with 2 from cells or from or cells of in binding and for a at for 2 a and to for or 2 of MSX1 or in the for and and cells in with and in a at into for of or with or of or expression in to of as an The a the homeodomain sites to and to M.L. S. 2002; PubMed Scopus Google Scholar) and in each of the promoter to and to to and to in to as by the and as M.L. S. 2002; PubMed Scopus Google Scholar). for to of the expression with or an in and a of In and in with by the and at the of The or by of M. A. I. R. Dev. Biol. PubMed Scopus Google Scholar) or A. Dev. PubMed Scopus Google Scholar), and in a to at and at dpc to the the is dpc). by as M. A. I. R. Dev. Biol. PubMed Scopus Google Scholar, A. Dev. PubMed Scopus Google Scholar). at and in a of in and and at to with in and with for at by in for at The with and for to sequences as reported for A.J. C. PubMed Scopus Google Scholar), and K. 1995; PubMed Google Scholar), and A. M.A. J. Neurosci. 1993; 13: PubMed Google Scholar, T. T. A. M. J. Neurosci. PubMed Google Scholar). The GnRH to of the from to the to the used as of with as well as transcription and an or for 2 at The by and over The in to and at at in with and at in The with for The at a of and with the The in with in These in for at to the as M.A. J. 2002; PubMed Scopus Google Scholar). The GnRH with the at a of of R. and the of the neurons by from the upon of the in at and in as to GnRH-expressing to the number of for the developmental and for the developmental or at each with the of the at 16.5 dpc, as by the of and P. PubMed Scopus Google Scholar). The to the of F. J.S. PubMed Scopus Google Scholar). with at at the for the and at by an for at for and used in the by a Msx and Dlx for GnRH during the and mouse GnRH gene the gene been The well regulatory regions of the GnRH gene are a located at to to the and an conserved promoter of the transcriptional these regulatory four consensus homeodomain sites (ATTA) have been M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar). These sites and to be essential for basal and cell-specific expression of the GnRH promoter M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar). Thus, the transcriptional that and function through these homeodomain sites is for the regulation of GnRH transcriptional for their binding developmental expression and transcriptional the MSX and DLX families of transcriptional the in expression patterns of these transcription factors and the septohypothalamic population of GnRH neurons A. J. Neurosci. 1994; PubMed Google Scholar, A.J. C. PubMed Scopus Google Scholar), we to the expression patterns of and to that of GnRH in the embryonic and nasal region during development. of from mouse at dpc, the septohypothalamic population of GnRH neurons been By in we a of GnRH-expressing neurons from the olfactory the olfactory nerve and the into the anterior to the olfactory in a region the of the septum and show expression of and 2 and as well as and and in the nasal region and anterior with their reported expression These that the expression of these Msx and Dlx family members with the septohypothalamic GnRH neuronal population. the expression of Msx and Dlx family members in the GnRH neuronal and from the and as well as olfactory to the Msx and Dlx family members and as well as and expressed in the cells cells expressed and and through expression in cells in Dlx family members expressed in the olfactory M. I. J. 1999; PubMed Scopus Google Scholar). In addition, the cells as a for expression of or M.L. S. 2002; PubMed Scopus Google Scholar). Thus, members of the Dlx and Msx families are expressed in the different GnRH with the in we that Msx and Dlx family members with neurons at embryonic for the Msx and Dlx family members and an the GnRH we in of expression of in the olfactory and the olfactory neuron in the nasal region and neurons in region a expression to that of and neurons and GnRH the olfactory neuron in the nasal region GnRH neurons located the and in the of the septum that expressed a expression to that of and with neurons and expressed in cells in the forebrain. we GnRH neurons in the nasal region These show that Msx and Dlx are expressed in the neurons during embryonic development and are for GnRH promoter activity through the conserved homeodomain binding DLX and MSX to ATTA in the GnRH and of the binding to the ATTA homeodomain sites in the region of the GnRH gene that are of homeodomain M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar). MSX and DLX are members of the Antennapedia class of non-Hox homeodomain that a at position of the homeodomain F. C. M. S. J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). MSX and DLX have been to transcription by binding consensus ATTA sites in regulatory regions H. H. P. C. Biol. PubMed Scopus Google Scholar). Thus, we that or members of the MSX and DLX families regulate GnRH transcription by binding to ATTA sequences within the promoter and these directly bind to the ATTA sequences in the GnRH and we with the homeodomain sites of the GnRH and promoter with from M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar), a complex in with the ATTA sequences of the GnRH or promoter. a complex of the complex complex been M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar). The of an to MSX1 binding of the complex In an the complex the the and as well as the complex the promoter These that the in cells the ATTA sites within the GnRH and promoter and The binding with the the to the GnRH homeodomain binding is in to patterns from M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar). the binding of and is to the M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar). we the that these in and cells DLX and of the homeodomain in the GnRH with the GnRH with of an DLX1 binding of complex in cells an binding of complex with the binding as that with the the or MSX and DLX family members the in the and in the and These that the the and the to the homeodomain sites in the GnRH gene MSX and DLX family members in GnRH neuron DLX and MSX GnRH have that the MSX and DLX with each and the consensus H. H. P. C. Biol. PubMed Scopus Google Scholar). In addition, members of the MSX family have been as transcriptional the DLX family transcription H. H. P. C. Biol. PubMed Scopus Google Scholar, T. T. A. M. J. Neurosci. PubMed Google Scholar, H. C. Dev. PubMed Scopus Google Scholar, H. J.A. C. Biol. 1995; PubMed Google Scholar, H. C. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, T. M. Brain Res. Dev. Brain Res. PubMed Scopus Google Scholar). the of these transcription factors the expression of the GnRH gene, we expressed MSX or DLX family members in the cells by The GnRH of the well regulatory regions of the GnRH gene, the conserved and promoter the gene. These sequences are to expression to GnRH neurons in M.A. J. 2002; PubMed Scopus Google Scholar). MSX1 and activity to and as with an In expression of or in the cells activity of the and of DLX1 activity of expression for and activity over the These show that MSX expression DLX expression GnRH transcription in four homeodomain sites in the GnRH promoter that are by MSX and DLX in we next the of the MSX and DLX family members dependent upon these ATTA to binding to the homeodomain M.L. S. 2002; PubMed Scopus Google Scholar, M.A. Google Scholar) in the at the sites to and to and the promoter sites to and to of the these four sites in cells activity with a that these sites are for basal activity of the GnRH promoter in Although the basal activity with the activity expression of MSX1 or activity of the the expression of or the in activity the of DLX1 in with the or transcriptional with the These that MSX and DLX family members function through the homeodomain binding sites and these sites are for GnRH promoter MSX and DLX for of the and the GnRH the transcriptional activity of MSX and DLX family members the GnRH promoter we the and for binding to the ATTA of the GnRH regulatory MSX1 and for binding been and that MSX1 and is of binding H. H. P. C. Biol. PubMed Scopus Google Scholar). we from cells the for in the of the complex the complex with the binding of 2 and These in the from cells the DLX1 in of expression of increasing of GnRH promoter activity These that MSX1 and for of the ATTA in the GnRH and GnRH Expression in GnRH of the and or that the cells a GnRH neuron the or cells the migratory stages of GnRH neuron development P. C. J. Full Text PDF PubMed Scopus Google Scholar, S. S. E. H. J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, S. A. F. Maggi R. M. S. Res. 2002; PubMed Scopus Google Scholar, F. E. R. P. A. E. F. Maggi R. J. Neurosci. 2003; PubMed Scopus Google Scholar). findings that GnRH expression is involved in furthering the commitment and migratory state of the GnRH neurons (11Romanelli R.G. Barni T. Maggi M. Luconi M. Failli P. Pezzatini A. Pelo E. Torricelli F. Crescioli C. Ferruzzi P. Salerno R. Marini M. Rotella C.M. Vannelli G.B. J. Biol. Chem. 2004; 279: 117-126Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar). that GnRH transcriptional activity the migratory and GnRH neuronal the of GnRH promoter activity in these cells by with the Because the the these cells used to GnRH promoter activity in the cells a cells with the a in promoter activity with the cells the of a in expression of the Finally, the GnRH regulatory regions of activity in the cells as the activity of the in these cells that of an that the promoter be actively in these for the activity of the in cells be the of transcriptional in the cells that are in the Indeed, we expression of in the Thus, we the that expression of the DLX family members in cells the of GnRH transcription in these of 2 and with the in the cells GnRH promoter expression by DLX of GnRH promoter expression required the of the homeodomain binding sites within the GnRH and promoter. that the promoter activity of the GnRH gene in the cells be by the of the DLX family of MSX1 and DLX1 and 2 to the of the GnRH in we have that DLX1 and 2 function as regulatory and MSX1 as a of GnRH promoter expression through binding to homeodomain within the GnRH regulatory region In addition, in of Msx and Dlx in the neurons MSX1 or DLX1 and a role in and GnRH expression in we in to the number of neurons and or mice at developmental stages the population of septohypothalamic GnRH neurons been In the dpc, cells within the olfactory as well as the and into the CNS, with findings (6Wray S. Grant P. Gainer H. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 8132-8136Crossref PubMed Scopus (628) Google Scholar). In numbers of neurons, the number of neurons that have yet into the central nervous in the and In the number of neurons in the of mice with mice and By 16.5 dpc, a number of neurons the position of these neurons that the majority of cells in the In the mice in the neurons and Thus, lacking DLX1 and 2 have a number of cells in the septohypothalamic that DLX1 and expression of GnRH in cells by in of mouse In an for GnRH to the number of of mouse and for of the in a In to the septohypothalamic population of cells at 16.5 dpc in the region of the that the population is by the promoter as the septohypothalamic population different transcription of the spatiotemporal expression of GnRH in the M.J. Slater R. Sim J.A. Allen N.D. Herbison A.E. J. Neurosci. 1999; 19: 5955-5966Crossref PubMed Google Scholar). population of cells in the in to GnRH promoter activity that is directly by as the Dlx are expressed in region of the by in we and in cells in the population and and that the population of GnRH neurons in the be of a of DLX1 and 2 and an developmental of the and at 12.5 and dpc in the population of By 12.5 dpc, cells in the positive cells in the Although the the number of cells in the be to a population of positive cells in the nasal region in to a cells in the olfactory dpc cells scattered throughout the nasal into the of the septum, the and dpc, the nasal populations of cells in in with and the cells in the scattered throughout the nasal region located in the olfactory of the of the septohypothalamic population In addition, these cells by an the GnRH that expressed GnRH a population of cells located in the tectum at dpc and several days these cells begin GnRH in the By 16.5 dpc, in the number of cells and cells in the with in the and the nasal and population of cells the and the population of cells located in the olfactory at 16.5 dpc These findings that as an essential in the development of craniofacial the development of the septohypothalamic population of GnRH neurons and likely GnRH promoter expression during stages of embryonic development. In to the septohypothalamic population of cells 16.5 dpc, the population of GnRH-expressing cells in the and cells be in the as as dpc, population to in number or in the as with the and Although the role for these GnRH-expressing cells yet been elucidated, GnRH expression is by the promoter that the septohypothalamic population M.J. Slater R. Sim J.A. Allen N.D. Herbison A.E. J. Neurosci. 1999; 19: 5955-5966Crossref PubMed Google Scholar) is by an of MSX1 DLX1 and The of is expressed in region E.A. S. J. PubMed Google Scholar, A. M.A. C. M. 2003; PubMed Scopus Google Scholar), have in or regulation of the GnRH promoter in these transcriptional activity the for the identity and maturation of the septohypothalamic population of GnRH neurons during embryonic development. of migratory and adult GnRH-expressing neurons in the expression of transcriptional factors that regulate spatiotemporal transcriptional of the GnRH gene M.A. PubMed Scopus Google Scholar, M.L. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar). Thus, GnRH neurons are a population that at stages of embryonic in in regulation of GnRH promoter Indeed, the transcriptional activity of the GnRH gene to be during the migratory of the septohypothalamic neurons. reported that the GnRH promoter at in neurons located in the olfactory region and in neurons in close proximity to the and in that have the Herbison A.E. PubMed Scopus Google Scholar). Thus, been reported that GnRH promoter activity is dependent upon the position of the neuron Herbison A.E. PubMed Scopus Google Scholar), in is by the of embryonic development. The findings members of the DLX and MSX homeodomain families as transcriptional of GnRH gene and of the GnRH regulatory region by MSX and are dependent upon the conserved ATTA homeodomain sites MSX and DLX bind homeodomain within the GnRH gene and promoter and and have have been in as the activity of and the promoter T. PubMed Scopus Google Scholar) and and MSX1 the promoter A.J. J. C. 1999; PubMed Google Scholar). In addition, we that expression of Msx and Dlx family members with the migratory route of septohypothalamic GnRH neurons during embryonic development The and 2 are expressed in the nasal region where GnRH promoter activity is the transcriptional and 2 are expressed at the migratory route of GnRH neurons into the hypothalamus GnRH promoter activity is Herbison A.E. PubMed Scopus Google Scholar). In support of with characteristics of GnRH neurons at developmental stages in their expression of several Msx and Dlx family The GnRH neuronal of the Dlx family of transcriptional as well as the Msx In the the of the GnRH express the Msx GnRH promoter activity in be in to expression of DLX family Indeed, expression of the DLX family members in cells in in GnRH promoter expression Thus, we that the and expression of Msx and Dlx family members in the contributes to regulation of the GnRH promoter. In support of DLX and MSX family members to be required to spatiotemporal populations of GnRH neurons in of and mice in the number of neurons during development with mice The number of cells in these be directly to of GnRH promoter in and in strongly support the for DLX1 and in GnRH we an contribution from been in the M. A. J. R. 19: Full Text Full Text PDF PubMed Scopus Google Scholar, K. S. J. M. 2002; PubMed Google Scholar). the GnRH promoter in and is expressed in the spatiotemporal for the GnRH neuron for the numbers of cells in the of the is In we a of cells as as dpc in these is that these neurons expression of GnRH or in the of The number of cells in the number in dpc and the in the number and of the GnRH population in the is to that of mouse with in an role in development of craniofacial the nasal of the GnRH neuron H. P. M. R. Nature. PubMed Scopus Google Scholar, J. S. J. T. Nature. PubMed Scopus Google Scholar). with neurons as as in the adult R. S. PubMed Scopus Google Scholar) and show a in the nasal population of cells and dpc, developmental stages with GnRH in the R. S. Dev. PubMed Scopus Google Scholar). In that of the nasal population to and of in the of R. S. Dev. PubMed Scopus Google Scholar). Thus, an is that an in the population of cells in the a of the GnRH neuronal as MSX been in H. S.M. C. PubMed Google Scholar). and in the number of cells positive for the Thus, the in cells in the an in cells that express the GnRH transcript at in a and be with the role of as a transcriptional of GnRH promoter we have that the MSX and DLX transcription families are for regulation of the GnRH promoter during development. the identity of the GnRH neuronal population throughout development a of the factors involved in cell-specific as well as expression of the GnRH gene. into the development of the hypothalamic-pituitary-gonadal axis and reproductive function. R. for the GnRH C. for expression for MSX1 and for and in A. for the expression and S. for the and the of M. A. J. S. K. M. J. and T. K. for and critical as well as K. and R. S. for