Meeting Abstract

P2.44  Jan. 5  Evolution of cephalopod learning and memory centers: insights from gene expression, proliferation events, and zonal network systems in embryonic brains SHIGENO, S.*; PARNAIK, R.; TARUI, H.; NISHIMURA, O.; MURAKAMI, Y.; KASUGAI, T.; MORITAKI, T.; AGATA, K.; Univ. of Chicago, Chicago; Univ. of Chicago, Chicago; RIKEN CDB, Kobe; RIKEN CDB, Kobe; Univ. of Ehime, Matsuyama; Nagoya Aqua, Nagoya; Toba Aqua, Mie; Kyoto Univ., Kyoto sshigeno@uchicago.edu

Cephalopod brains are the largest among invertebrates and rival in size to those of vertebrates. Moreover, learning and memory centers in the cephalopod frontal-vertical lobes form network systems that appear analogous to those seen in the cerebral cortex of mammals and pallial regions of other vertebrates. The processes involved in cephalopod brain development remain, however, largely unexplored despite their importance for understanding convergent evolution. We first studied the distribution of postmitotic neurons by tubulin immunostaining in nautilus, squid, and octopus embryonic brains. This analysis revealed that there is a shared brain plan among cephalopods. For extensive studies, expressed sequenced tag analysis was performed from dissected squid brain cDNA library and 4,752 non-redundant genes were obtained and categorized. We found that the expression patterns for some selected genes were restricted to subsets of neurons. Moreover, the expressions of neurocalcin genes revealed a previously unidentified lobule in the anterior region of the vertical lobe. In the immunocytochemical analysis, we found that the expression for squid Pax-6/eyeless and Dlx/distalless-like proteins were localized at the anterior region of learning centers that are considered higher visual and olfactory centers. We also studied cell proliferation and the morphology using cell cycle markers and in vivo short time-lapse imaging of cells. These findings established that cephalopod developing associative centers have an simple zonal arealization with distinct molecular and cellular properties.