Characterization of two neurogenin genes from the brook lamprey lampetra planeri and their expression in the lamprey nervous system

Background: Neurogenins are required for the specification of neuronal precursors and regulate the expression of basic Helix-Loop-Helix genes involved in neuronal differentiation. Jawed vertebrates possess three Neurogenin paralogy groups and their combined expression covers the entire nervous system, apart from the autonomic nervous system. Results: Here we report the isolation of two Neurogenin genes, LpNgnA and LpNgnB, from the lamprey Lampetra planeri. Phylogenetic analyses show both genes have orthologues in other lamprey species and in a hagfish. Neither gene shows evidence of orthology to specific jawed vertebrate Neurogenin paralogues. LpNgnA is expressed in the ventricular zone of regions of the brain and spinal cord, with expression in the brain demarcating brain sub-compartments including the pallium, tegmentum, tectum, and dorsal thalamus. In the peripheral nervous system, LpNgnA is expressed in cranial sensory placodes and their derivatives, and in the dorsal root ganglia. LpNgnB is expressed transiently in placodal head ectoderm and throughout the central nervous system in early development, and in a small population cells that form part of the macula. Conclusions: Combined, LpNgnA and LpNgnB were detected in most cell populations marked by Neurogenin gene expression in jawed vertebrates, with the exception of the cerebellum, retina and the non-neural expression sites. (c) 2015 Wiley Periodicals, Inc.