The Journal of Neuroscience, April 15, 1998, 18(8):2991-3002
Two Receptor Tyrosine Phosphatases of the LAR Family Are
Expressed in the Developing Leech by Specific Central Neurons as well
as Select Peripheral Neurons, Muscles, and Other Cells
Timothy R.
Gershon,
Michael W.
Baker,
Michael
Nitabach,
Peter
Wu, and
Eduardo R.
Macagno
Department of Biological Sciences, Columbia University, New York,
New York 10027
Receptor protein tyrosine phosphatases (rPTPs) are thought to play
a crucial role in neuronal development, particularly in pathfinding by
growing processes. We have cloned and sequenced two Hirudo
medicinalis rPTPs that are homologous to the
Drosophila and vertebrate rPTPs of the Leukocyte common
antigen-related (LAR) subfamily. These Hirudo rPTPs,
HmLAR1 and HmLAR2, are products of different, homologous genes, both
containing two tandem intracellular phosphatase domains and ectodomains
with three tandem Ig domains and different numbers of tandem
fibronectin type III (FIII) domains. They are expressed in distinct
patterns during embryogenesis. HmLAR1 mRNA is expressed by a subset of
central and peripheral neurons and by several peripheral muscular
structures, whereas HmLAR2 mRNA is expressed by a different subset of
central neurons and by the peripheral, neuron-like Comb cells. HmLAR1
and HmLAR2 proteins are located on the neurites of central neurons. In
addition, HmLAR2 is expressed on the cell body, processes, and growth
cones of the Comb cells. Because of their CAM-like ectodomains and
homology to proteins known to be involved in pathfinding and because
they are expressed by different subsets of neurons, we hypothesize that
HmLAR1 and HmLAR2 participate in navigational decisions that distinguish the sets of neurons that express them. Furthermore, we
hypothesize that HmLAR2 is also involved in setting up the highly
regular array of parallel processes established by the Comb cells.
Lastly, we propose that the HmLAR1 ectodomain on peripheral muscle
cells plays a role in target recognition via interactions with neuronal
receptors, which might include HmLAR1 or HmLAR2.
Key words:
receptor tyrosine phosphatases; neuronal development; muscle development; central neurons; peripheral neurons; Hirudo
medicinalis
Copyright © 1998 Society for Neuroscience 0270-6474/98/1882991-12$05.00/0