Journal of Neuroscience, Vol 15, 5551-5559, Copyright © 1995 by Society for Neuroscience
The leech homeobox gene Lox4 may determine segmental differentiation of identified neurons
VY Wong, GO Aisemberg, WB Gan and ER Macagno
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
We cloned and characterized a new leech homeobox gene, Lox4, a homolog of
the Drosophila genes Ultrabithorax and abdominal-A. Lox4 has a complex and
dynamic pattern of expression within a series of segmentally homologous
neurons. These include a pair of specialized motor neurons of one segmental
ganglion, the rostral penile evertors (RPEs), and their segmental homologs
in other midbody ganglia. During gangliogenesis, Lox4 was expressed within
this series of neurons in three different temporal patterns: (1) it was
never expressed in the RPE homologs of ganglia 1-3; (2) it was expressed in
the RPEs during gangliogenesis, but was turned off when these neurons
started to differentiate after gangliogenesis; and (3) it was expressed in
the RPE homologs of segments 4-5 and 7-21 during gangliogenesis and the
subsequent period of axonogenesis. We found that these neurons have three
distinct peripheral axonal morphologies that correlate with the three
temporal patterns of expression. Our results suggest that the homeobox gene
Lox4 may determine neuronal identities within this series of segmental
homologs.
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