title: Zygotic LvBMP5-8 is required for skeletal patterning and for left-right but not dorsal-ventral specification in the sea urchin embryo.
abstract: Skeletal patterning in the sea urchin embryo requires coordinated signaling between the pattern-dictating ectoderm and the skeletogenic primary mesenchyme cells (PMCs); recent studies have begun to uncover the molecular basis for this process. Using an unbiased RNA-Seq-based screen, we have previously identified the TGF-ß superfamily ligand, LvBMP5-8, as a skeletal patterning gene in Lytechinus variegatus embryos. This result is surprising, since both BMP5-8 and BMP2/4 ligands have been implicated in sea urchin dorsal-ventral (DV) and left-right (LR) axis specification. Here, we demonstrate that zygotic LvBMP5-8 is required for normal skeletal patterning on the left side, as well as for normal PMC positioning during gastrulation. Zygotic LvBMP5-8 is required for expression of the left-side marker soxE, suggesting that LvBMP5-8 is required for left-side specification. Interestingly, we also find that LvBMP5-8 knockdown suppresses serotonergic neurogenesis on the left side. While LvBMP5-8 overexpression is sufficient to dorsalize embryos, we find that zygotic LvBMP5-8 is not required for normal DV specification or development. In addition, ectopic LvBMP5-8 does not dorsalize LvBMP2/4 morphant embryos, indicating that, in the absence of BMP2/4, BMP5-8 is insufficient to specify dorsal. Taken together, our data demonstrate that zygotic LvBMP5-8 signaling is essential for left-side specification, and for normal left-side skeletal and neural patterning, but not for DV specification. Thus, while both BMP2/4 and BMP5-8 regulate LR axis specification, BMP2/4 but not zygotic BMP5-8 regulates DV axis specification in sea urchin embryos.
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States; Program in Molecular Biology, Cell Biology and Biochemistry, Boston University, Boston, MA 02215, United States.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Piacentino
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States.
authors.forename: Oliver
authors.initials: O
authors.lastname: Chung
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States.
authors.forename: Janani
authors.initials: J
authors.lastname: Ramachandran
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States; Program in Molecular Biology, Cell Biology and Biochemistry, Boston University, Boston, MA 02215, United States.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Zuch
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States.
authors.forename: Jia
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States.
authors.forename: Evan A
authors.initials: EA
authors.lastname: Conaway
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States.
authors.forename: Arlene E
authors.initials: AE
authors.lastname: Reyna
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215, United States; Program in Molecular Biology, Cell Biology and Biochemistry, Boston University, Boston, MA 02215, United States; Program in Bioinformatics, Boston University, Boston, MA 02215, United States. Electronic address: cbradham@bu.edu.
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Bradham
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D001846:Bone Development / Q000502:physiology*; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D010641:Phenotype; D012617:Sea Urchins / Q000196:embryology*
chemical_list: D019485:Bone Morphogenetic Proteins
keywords: BMP5-8; Dorsal–ventral; Left–right; Neurogenesis; Sea urchin; Skeletal patterning