title: Heparan sulfotransferases Hs6st1 and Hs2st keep Erk in check for mouse corpus callosum development.
abstract: The corpus callosum (CC) connects the left and right cerebral hemispheres in mammals and its development requires intercellular communication at the telencephalic midline mediated by signaling proteins. Heparan sulfate (HS) is a sulfated polysaccharide that decorates cell surface and extracellular matrix proteins and regulates the biological activity of numerous signaling proteins via sugar-protein interactions. HS is subject to regulated enzymatic sulfation and desulfation and an attractive, although not proven, hypothesis is that the biological activity of HS is regulated by a sugar sulfate code. Mutant mouse embryos lacking the heparan sulfotransferases Hs2st or Hs6st1 have severe CC phenotypes and form Probst bundles of noncrossing axons flanking large tangles of midline glial processes. Here, we identify a precocious accumulation of Sox9-expressing glial cells in the indusium griseum region and a corresponding depletion at the glial wedge associated with the formation of Probst bundles along the rostrocaudal axis in both mutants. Molecularly, we found a surprising hyperactivation of Erk signaling in Hs2st(-/-) (2-fold) and Hs6st1(-/-) (6-fold) embryonic telencephalon that was most striking at the midline, where Erk signaling is lowest in wild-types, and a 2-fold increase in Fgf8 protein levels in Hs6st1(-/-) embryos that could underpin Erk hyperactivation and excessive glial movement to the indusium griseum. The tightly linked Hs6st1(-/-) CC glial and axonal phenotypes can be rescued by genetic or pharmacological suppression of Fgf8/Erk axis components. Overall, our data fit a model in which Hs2st and Hs6st1 normally generate conditions conducive to CC development by generating an HS-containing environment that keeps Erk signaling in check.
authors: Centre for Integrative Physiology, The University of Edinburgh, Edinburgh EH8 9XD, United Kingdom, Centre for Glycobiology, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom, and Department of Craniofacial Development and Stem Cell Biology, King's College London, London SE5 9RW, United Kingdom.
authors: James M
authors: JM
authors: Clegg
authors: Christopher D
authors: CD
authors: Conway
authors: Kathy M
authors: KM
authors: Howe
authors: David J
authors: DJ
authors: Price
authors: John O
authors: JO
authors: Mason
authors: Jeremy E
authors: JE
authors: Turnbull
authors: M Albert
authors: MA
authors: Basson
authors: Thomas
authors: T
authors: Pratt
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D003337:Corpus Callosum / Q000201:enzymology* / Q000254:growth & development*; D005260:Female; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011247:Pregnancy; D015238:Sulfotransferases / Q000172:deficiency*
chemical_list: C485756:Hs6st1 protein, mouse; D015238:Sulfotransferases; C106358:heparan-sulfate 2-sulfotransferase; C021350:heparitin sulfotransferase
keywords: Fgf8; Sox9; axons; glia; heparan sulfate; mapk