N. Shimokawa et M. Miura, Rhombex-29, a novel gene of the PLP/DM20-M6 family cloned from rat medullaoblongata by differential display, J NEUROSC R, 62(1), 2000, pp. 1-8
The ventral medullary surface (VMS) is known as the site of the central che
mosensitive neurons. These neurons sense excess CO2/H+ dissolved in the cer
ebrospinal fluid that superfuses the VMS and induce hyperventilation. We hy
pothesized that genes specific for hyperventilation are expressed much more
highly in VMS neurons than in extra-VMS neurons in other parts of the cent
ral nervous system (CNS). Applying the differential display technique to th
e brain of adult rats, we differentiated the mRNAs of the VMS neurons from
those of cerebral cortex neurons. Seventeen candidate clones were selected,
and their sequences were analyzed. Among these 17 clones, one encodes a no
vel four-transmembrane protein, which we named rat Rhombex-29. Structural a
nalysis and the phylogenic tree showed that rat Rhombex-29 is homologous to
the major CNS myelin protein PLP/DM20-M6 family and belongs to the interme
diate type between mouse M6b and shark DM gamma. As the embryos grew into a
dult rats, constant expression of rat Rhombex-29 mRNA was found in the brai
n. Hypercapnic stimulation increased expression of rat Rhombex-29 mRNA in t
he VMS neurons but not in the cerebral cortex neurons. These results indica
te that the VMS neurons are endowed with a novel gene, rat Rhombex-29, that
is sensitive to H+. (C) 2000 Wiley-Liss, Inc.