0-TESTO COMPLETO.pdf - Fondazione Santa Lucia

CAMPUS.1 – Analysis of developmental interactions between reelin haploinsufficiency, male…
P5 in the cisterna magna reverted this profile. In males, however, no genotype-dependent
effect appeared. In the homing test on P9, a significant lower
percentage of rl/+ mice reached the nest area than corresponding wt pups. In
the absence of motor changes, this indicates a genotype-dependent alteration
in sensitivity to, or in central processing of social stimuli. Remarkably, this
deficient profile was reverted by neonatal estradiol administration. In a social
task performed at adulthood, early estradiol administration increased time
spent in proximity of a novel social stimulus by wt males and by rl/+ females.
When adult males were assessed in an attentional set-shifting task, involving
the formation of new rules to obtain a palatable reward, rl/+ males showed a
higher number of perseverative responses. Neonatal estradiol abolished the
differences between rl/+ and wt males. Behavioral analysis is still in progress,
and the results will be presented at the 2008 Society for Neuroscience Meeting
[Laviola et al. 2008; see attached abstract].
Also relevant to the present issue of Hg toxicity on Purkinje cells, we
recently performed an extensive mapping of PCs in a few male wild-type and
male rl/+ mice, using calbindin immunohistochemistry to label PCs. These
maps confirm the PC loss detected with stereological counting methods in
male rl/+ mice.
The abovementioned in vivo model in mice contains two of the factors
which we mentioned earlier in this introduction, i.e. genetic vulnerability
(Reelin haploinsufficiency), and a strong role of the gender and/or sex hormone
setting. Thus, by using this experimental model, we have the unique
opportunity to investigate the interaction of the three factors: the “ internal
milieu” of the organism, which in this setting is determined by gender
and/or sex hormone environment, “the genetic/gender background ”, and the
“ external milieu-environmental agents ”, i.e. early chronic exposure to lowlevel
Hg.
In order to further dissect the perinatal period of maximal sensitivity to
Hg toxicity in our animal model, we will evaluate its effects in a group in
which MeHg has been supplemented to the litter during gestation, and in a
group in which it has been supplemented to the mother during lactation.
METHODS
Overview of the experimental design
For the experiments we will use a reeler line originally bred from heterozygous
B6C3Fe-a/a-rl adults, obtained from the Jackson Laboratory (background
C57/BL6J), crossed with an L7-EGFP strain [Oberdick 1990, Swiss
Webster FVB/N] to obtain the double transgenic line reeler-L7-EGFP. These
transgenic mice display distinct expression of EGFP in dendrites, axons and
soma of PCs. By this approach we were able to produce F1 rl/+ and wt mice in
which spontaneous fluorescence is selectively localised in the PC soma, dendrites
and axons. This will allow us to perform cell counts and determinations
of spine density in non-processed histological slices. During the project we
plan to backcross the F1 generation to carry the EGFP-transgene into the
2009 585