title: Novel role for the orphan nuclear receptor Dax1 in embryogenesis, different from steroidogenesis.
abstract: Cytomegalic adrenal hypoplasia congenita (AHC) is an X-linked disease caused by mutations in DAX1-encoding gene NR0B1, previously thought to function primarily in steroidogenesis. We sought to determine the expression pattern for Dax1 along with known network partners in early embryogenesis and to determine a steroidogenic capacity for the embryo prior to the establishment of the urogenital ridge at embryonic day 9 (E9). Here, we report that murine Dax1 is a unique marker in early embryonic development, distinguishing the extraembryonic (proximal) endoderm from the remainder of the developing embryo. We showed that Wilms tumor 1, steroidogenic factor 1, and estrogen receptor beta were expressed throughout the embryo, but the progesterone, estrogen alpha and androgen receptors, cytochrome P450 (Cyp11a1) and Nur77 were not observed in any of the embryonic layers. Lack of Cyp11A1 expression at this stage confirmed an absence of inherent steroidogenic capacity for the early embryo. The role of Nr0b1 in embryonic stem (ES) cells was investigated using siRNA knockdown, resulting in differentiation toward endoderm-like fate. Nr0b1 conditional knockout in ES cells led to differentiation, confirming our knockdown results. Our investigations suggest that Nr0b1 functions in a novel role in the maintenance of a relatively undifferentiated state. Our results further suggest that the failure of conventional murine Nr0b1 knockout attempts may be due to disregulated differentiation.
authors.affiliation: Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: Kathy K
authors.initials: KK
authors.lastname: Niakan
authors.forename: Emily C
authors.initials: EC
authors.lastname: Davis
authors.forename: Robert C
authors.initials: RC
authors.lastname: Clipsham
authors.forename: Meisheng
authors.initials: M
authors.lastname: Jiang
authors.forename: Deborah B
authors.initials: DB
authors.lastname: Dehart
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Sulik
authors.forename: Edward R B
authors.initials: ER
authors.lastname: McCabe
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism; D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000502:physiology*; D004622:Embryo, Mammalian / Q000378:metabolism; D047108:Embryonic Development; D047629:Estrogen Receptor beta / Q000096:biosynthesis*; D016162:Genes, Wilms Tumor / Q000502:physiology; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis*; D018398:Homeodomain Proteins / Q000096:biosynthesis*; D051379:Mice; D008810:Mice, Inbred C57BL; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis*; D011987:Receptors, Steroid / Q000096:biosynthesis; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000096:biosynthesis*
chemical_list: D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins; D047629:Estrogen Receptor beta; D012739:Gonadal Steroid Hormones; D018398:Homeodomain Proteins; C539965:NR0B1 protein, human; C539821:NR4A1 protein, human; C539966:Nr0b1 protein, mouse; C539818:Nr4a1 protein, mouse; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse; D002786:Cholesterol Side-Chain Cleavage Enzyme