title: Facial whisker pattern is not sufficient to instruct a whisker-related topographic map in the mouse somatosensory brainstem.
abstract: Facial somatosensory input is relayed by trigeminal ganglion (TG) neurons and serially wired to brainstem, thalamus and cortex. Spatially ordered sets of target neurons generate central topographic maps reproducing the spatial arrangement of peripheral facial receptors. Facial pattern provides a necessary template for map formation, but may be insufficient to impose a brain somatotopic pattern. In mice, lower jaw sensory information is relayed by the trigeminal nerve mandibular branch, whose axons target the brainstem dorsal principal sensory trigeminal nucleus (dPrV). Input from mystacial whiskers is relayed by the maxillary branch and forms a topographic representation of rows and whiskers in the ventral PrV (vPrV). To investigate peripheral organisation in imposing a brain topographic pattern, we analysed Edn1(-/-) mice, which present ectopic whisker rows on the lower jaw. We found that these whiskers were innervated by mandibular TG neurons which initially targeted dPrV. Unlike maxillary TG neurons, the ectopic whisker-innervating mandibular neuron cell bodies and pre-target central axons did not segregate into a row-specific pattern nor target the dPrV with a topographic pattern. Following periphery-driven molecular repatterning to a maxillary-like identity, mandibular neurons partially redirected their central projections from dPrV to vPrV. Thus, while able to induce maxillary-like molecular features resulting in vPrV final targeting, a spatially ordered lower jaw ectopic whisker pattern is insufficient to impose row-specific pre-target organisation of the central mandibular tract or a whisker-related matching pattern of afferents in dPrV. These results provide novel insights into periphery-dependent versus periphery-independent mechanisms of trigeminal ganglion and brainstem patterning in matching whisker topography.
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, Basel 4058, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Laumonnerie
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, Basel 4058, Switzerland.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Bechara
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, Basel 4058, Switzerland.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vilain
authors.affiliation: Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo, 102-0075, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kurihara
authors.affiliation: Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo, 102-0075, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kurihara
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, Basel 4058, Switzerland University of Basel, Basel 4056, Switzerland filippo.rijli@fmi.ch.
authors.forename: Filippo M
authors.initials: FM
authors.lastname: Rijli
mesh_terms: D000818:Animals; D001931:Brain Mapping; D001933:Brain Stem / Q000502:physiology*; D019332:Endothelin-1 / Q000378:metabolism; D051379:Mice / Q000502:physiology*; D010465:Perception; D012249:Rhombencephalon / Q000502:physiology; D013788:Thalamus / Q000502:physiology; D012668:Trigeminal Ganglion / Q000502:physiology; D014738:Vibrissae / Q000502:physiology*
chemical_list: D019332:Endothelin-1
keywords: Cdh13; Edn1; Hindbrain; Hmx1; Mandibular brainstem representation; Tbx3; Topographic map; Trigeminal ganglion; Trigeminal somatotopy; Whisker-related barrelette map