Importacion De Lenceria De España A Mexico

Revi ew series

smell
S hannon DeMaria a nd John Ngai
Depo rtment of MoI eculor ond Cell Biology. Helen W rlls N euroscience Institute and Functionol G enomics lobora tory. University of Colilo rnio, Berkeley. Berkeley, CA 9 4 720

The olfactory system detects a nd d iscriminates myriad
chemical structures across a wide r ange of concentrations.
To meet this task, the system utilizes a large family of
G protein-coupled receptors - the o dorant r eceptors­
which a re the chemical sensors underlying the perception
of smell. Interestingly,the odorant receptors a re also involved
in a number of developmental decisions, includ ing the
regulation of their own expression a nd the patterning of
the olfactory s ensory n eurons ' s ynaptic c onnections in
the brain. This review willfocus on the d iverse roles of the
o dorant r eceptor in the function a nd d evelopment of the
olfactory system .

a nd "-' I,800 g lomeru li in e ac h olfacto ry bulb , which tran slates
to an "-' 10 3-fo ld co nverge nce o f prim ary se nsory axons ont o
each olfactory glomerulus (Fires tein, 200 I) . Thi s convergence
lies at the heart o f the e odin g strateg y fo r ol fact ory se nsory
information. In parall el to the main olfactory epithelium, the
vomeronasal organ- an anato mical specia lization of the nose in
terr estrial vert ebrates that is separate from the main olfactory
e pithel iu m- s e ns es non vol atil e c hemi e al sti muli, includin g
pher omone s (Dulac and Tor ello , 2 00 3; Mombacrts, 2004). T he
pre sent revi ew fo cuse s o n the main olfactoryepithelium and the
m ultiple roles that the " OR " family of odo rant recept ors play,
not only as detectors o f volat ile chemical s in the enviro nme nt,
but also as regulator s o f key developmental dec ision s made by
d ifferentiat ing OSN s.

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Figure 1, A natomy of the rodent p eripheral o lfactory system. (AI Sche­
motic rep re senta tion of a para sagitta l section thro ugh adult mouse h ead ,
Axo ns of the OS N s in the main olfactory epith elium comprise the ol fac­
tory nerve and in nerva te the ol fac tory b ulb. Vomeron asal sensor y neur ons
pro ject their o xons via a sepa ra te trac t, the vo meronasal nerve, to inner ­
vate the acce ssory olfacto ry b ulb , (B) Each OS N o f the ma in o lfacto ry
epithelium ex presses only on e odora nt rece ptor gene lOR A, OR B, OR C,
etc.] out of a rep ertoire of over 1,0 0 0 ge nes. N euron s ex pre ssing a g iven
OR are org a nized into b roa d zones al ang the dorsal- ventral axi s of the
olfactory epi theli um (OEI a nd can verge to a common glo merulus at cor­
respondin g dorsal-ventral zones in the alfactory b ulb (OB) . Each glo merulus
thus receives innervation from sensaryneuro ns expressing a sing le odo rant
receptor, p ravid ing the anatomica l ba sis of the olfac tory sensory ma p.

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V 2R , and formyl peptide- like recep tors (Mo mbae rts, 2004 ;
Yang et aI., 2005 ; Riviere ct a I., 2 (09) .
Upon binding its cognate odor ligand, the activated OR (and
presum ably also TAAR ) couples through Go:olf, a Gos isoform en­
riched in OSN s (Belluscio ct al., 1998). Activated Go:olf in tum ac­
tivates type III adenylyl cyclase (Wong et aI., 20 (0 ), which cataly zes
the production of cAMP, The increase in intrace llular cAMP "gates"
or opens a cyclic nucleotide-gated (CNG) channel, leading to an in­
nux of sodi um and calcium ions and depolarization of the neuron
(Brunet ct al., 1996). Thisinitial depolarization is further amplified
by the subsequent activation of ca lcium-activated ch loride chan­
nels and, owing to the low concentration of extrace llular C I- in the
mucus bathing the olfactory cilia, the efflux of CI- from the cell
(Stephan et aI., 2009 ; Fig, 2 A). The odor-induced depolarization in
the olfactory cilia spreads throughout the neuron, resulting in the
opening o...