Shared and differential features of Robo3 expression pattern in amniotes

• Published in: Journal of comparative neurology (1911) Vol. 527; no. 12; pp. 2009 - 2029
• Main Authors: Friocourt, François, Kozulin, Peter, Belle, Morgane, Suárez, Rodrigo, Di‐Poï, Nicolas, Richards, Linda J., Giacobini, Paolo, Chédotal, Alain
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 15.08.2019; Wiley Subscription Services, Inc; Wiley
• Subjects: amniotes; Axon guidance; Cognitive ability; commissures; development; Embryos; evolution; habenula; Hindbrain; inferior olive; Life Sciences; Mesencephalon; Nervous system; Neurons; pontine nucleus; Robo3; RRID:AB_1078266; RRID:AB_2107107; RRID:AB_2107124; RRID:AB_2181865; RRID:AB_2307443; RRID:AB_2313773; RRID:AB_2315065; RRID:AB_2340880; RRID:AB_2340885; RRID:AB_2492288; RRID:AB_262133; RRID:AB_2651135; RRID:AB_2732861; RRID:AB_881306; RRID:SCR_007370; Spinal cord; RRID:AB_2492288; RRID:AB_881306; RRID:AB_2313773; development; RRID:AB_2340885; inferior olive; RRID:AB_2340880; RRID:AB_2307443; RRID:AB_2181865; commissures; evolution; RRID:AB_262133; habenula; RRID:AB_2107107; RRID:SCR_007370; amniotes; RRID:AB_2732861; RRID:AB_2107124; RRID:AB_1078266; RRID:AB_2315065; RRID:AB_2651135; Robo3; pontine nucleus
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.24648

In Bilaterians, commissural neurons project their axons across the midline of the nervous system to target neurons on the opposite side. In mammals, midline crossing at the level of the hindbrain and spinal cord requires the Robo3 receptor which is transiently expressed by all commissural neurons. Unlike other Robo receptors, mammalian Robo3 receptors do not bind Slit ligands and promote midline crossing. Surprisingly, not much is known about Robo3 distribution and mechanism of action in other vertebrate species. Here, we have used whole‐mount immunostaining, tissue clearing and light‐sheet fluorescent microscopy to study Robo3 expression pattern in embryonic tissue from diverse representatives of amniotes at distinct stages, including squamate (African house snake), birds (chicken, duck, pigeon, ostrich, emu and zebra finch), early postnatal marsupial mammals (fat‐tailed dunnart), and eutherian mammals (mouse and human). The analysis of this rich and unique repertoire of amniote specimens reveals conserved features of Robo3 expression in midbrain, hindbrain and spinal cord commissural circuits, which together with subtle but meaningful modifications could account for species‐specific evolution of sensory‐motor and cognitive capacities. Our results also highlight important differences of precerebellar nuclei development across amniotes. Here, we have used tissue clearing and 3D light‐sheet microscopy to study the expression pattern of the axon guidance receptor Robo3 in multiple embryonic tissues from diverse representatives of amniotes, including squamate, birds, marsupial, and eutherian mammals. In all species, such as in an 8 day post‐oviposition house snake embryo (image ), Robo3 (red) is expressed by commissural neurons in the spinal cord, hindbrain, and midbrain but not in the peripheral nervous system (green). Our results also highlight developmental differences between commissural nuclei in amniotes.