M. L.-S. Guevara et al. / Advances in Bioscience and Biotechnology 4 (2013) 945-948 947
wt IRS-1 ko
Figure 1. Representative camera lucida drawings of the barrel
field of wild type (wt) and IRS-1 knock out (IRS-1 ko) mice.
No qualitative differences were observed between mouse groups
(Scale = 1 mm).
4. DISCUSSION
Previous reports in rodents support that barrel circuitry in
S1 builds up following constructivist principles [10-13,
15]. We have shown that the precise and progressive ad-
dition of barrel neuropil is promoted by IGF-1 [15,16].
The signaling cascade involved in this event has not been
elucidated. We then explored the contribution of IRS-1 in
this process by comparing the adult size of SI barrels
between wt and IRS-1 ko mice. IRS-1 has been previ-
ously shown to be expressed in the cerebral cortex [24]
and its mutation retards brain growth and reduces brain
weight [25,26]. Unexpectedly, IRS-1 ko mice displayed
barrel and PMBSF areas fully comparable to those ob-
served in wt mice, thus supporting that IRS-1 is not es-
sential for promoting the precise addition of barrel neu-
ropil. In a previous report, Ye et al. [26] have shown that
IRS-2 and IRS-4 may compensate the lack of IRS-1 with
regard to myelination processes, and it is therefore con-
ceivable that either one or both could also “rescue” the
barrel’s phenotype in IRS-1 ko mice. In sum, IRS-1 does
not seem to mediate the trophic effects of IGF1 on the
barrel cortex. Future experiments must address whether
IRS-2 and/or IRS-4 participate in the construction of
barrel neuropil.
5. ACKNOWLEDGEMENTS
Authors thank Jesús Ramirez Santos, Ivonne Mora, Edel Pineda Lopez
and Raymundo Reyes for technical assistance. This work was sup-
ported in part by CONACyT (Grant No. 82879 to G. G. O.), PAPIIT-
UNAM (Grants Nos. IN203912-3 to G. G. O. and IA202013-2 to E. U.
Q.), CIC-UMSNH (Grant No. 8.37 to A. L. F. F.).
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