***** seminarMLから情報転載 *****


開催日時:平成19年6月20日(水) 17:00~18:00


講 師:Yutaka Yoshida (吉田 富)

吉田先生は東大医科研で学位取得後、助手をへてTom Jessell博士のラボに留学し研

所 属:Department of Biochemistry and Molecular Biophysics&s_comma;
Columbia University&s_comma; New York&s_comma; USA

演  題:Plexin signaling and sensory organization in the developing spinal

概 要:The connections formed between proprioceptive sensory and motor
neurons provide critical sensory feedback control during locomotors. During
development&s_comma; proprioceptive sensory neurons project axons into the spinal
cord and form both direct and indirect connections with motor neurons. Cell
surface molecules in these guidance decisions remain unclear.
Semaphorins form a major family of cell surface and secreted proteins with
diverse roles in the axon guidance. Semaphorins exert their developmental
effects through interactions with plexin or neuropilin receptors. We
identified plexinA1 as a proprioceptive axon-specific receptor&s_comma; and revealed
that two semas expressed by spinal cord cells&s_comma; sema6C and sema6D&s_comma; act as
ligands for plexinA1. Analysis of plexinA1 mutant mice revealed that the
loss of plexinA1 signaling elicits a dramatic defect in the positioning of
proprioceptive axon shafts&s_comma; which invade the dorsal horn and disrupt the
organization of cutaneous sensory axons. These axonal interactions appear to
be mediated by oligodendrocytes&s_comma; which accompany displaced proprioceptive
axon shafts into the superficial dorsal horn. Our results reveal an active
program of axon shaft positioning in the mammalian CNS&s_comma; and indicate that
this program orchestrates the projection pattern of diverse classes of
sensory neurons.
Other plexins are expressed by subsets of proprioceptive sensory neurons&s_comma;
raising the possibility that semaphorin-plexin signaling contributes more
extensively to the establishment of sensory-motor connectivity in the spinal

世話人: ○井上純一郎、真鍋俊也