Welcome to the 31st IUBS General Assembly and Conference on ...

<strong>to</strong> pollution <strong>and</strong> can survive only in pollution free
environments. From <strong>the</strong> presence <strong>the</strong>se species, we can
know <strong>the</strong> water quality of a river.
Natural Selection in Genome Evolution
Giorgio BERNARDI
Department of Biology, Rome 3 University, Italy. Email:
gbernardi@uniroma3.it
“Most of <strong>the</strong> familiar features of living organisms show
clear signs of adaptation of structure <strong>to</strong> function. There is
overwhelming evidence that this is <strong>the</strong> outcome of
evolution by natural selection” (B Charlesworth). Whe<strong>the</strong>r
<strong>the</strong> same applies <strong>to</strong> <strong>the</strong> genomes of vertebrates (<strong>and</strong>
o<strong>the</strong>r eukaryotes) with <strong>the</strong>ir overwhelming amount of
non‐protein‐coding DNA is, however, an open question.
Many years ago, we developed a compositional strategy,
which revealed that those genomes are mosaics of
isochores. These are long DNA stretches fairly
homogeneous in base composition that belong <strong>to</strong> a small
number of families characterized by different GC levels
<strong>and</strong> different short‐sequence patterns (i.e.different DNA
structures <strong>and</strong> different DNA‐protein interactions). This
genome organization led us <strong>to</strong> 2 discoveries: (i) <strong>the</strong>
genomic code, a collective definition for <strong>the</strong> correlations
that hold between coding <strong>and</strong> non‐coding sequences;
between coding sequences <strong>and</strong> <strong>the</strong> structural properties
of <strong>the</strong> encoded proteins; <strong>and</strong> between <strong>the</strong> frequencies of
short sequences of isochore families <strong>and</strong> nucleosome
positioning/transcription fac<strong>to</strong>r binding. (ii) The genome
phenotypes, which correspond, at low resolution, <strong>to</strong> <strong>the</strong>
patterns of isochore families in <strong>the</strong> genome; at high
resolution, <strong>to</strong> isochore maps on chromosomes. While <strong>the</strong>
latter may be used <strong>to</strong> study genomic variation <strong>and</strong>
genomic diseases, <strong>the</strong> former showed that genome
evolution may proceed according <strong>to</strong> a conservative mode
or <strong>to</strong> a transitional (shifting) mode. The conservation <strong>and</strong>
<strong>the</strong> changes of isochore patterns depend upon whe<strong>the</strong>r
<strong>the</strong> environment is constant or shifting. According <strong>to</strong> <strong>the</strong>
‘neo‐selectionist <strong>the</strong>ory’, natural selection is responsible
for both modes <strong>and</strong> plays a dominant role in genome
evolution.
Neutral sphingomyelinase 2 <strong>and</strong> HA
Department of Pediatrics, University of Chicago, Chicago, USA.
Email: qjingdong@peds.bsd.uchicago.edu. This is a recent
study published in JBC.
Fibroblasts from <strong>the</strong> fro/fro mouse, with a deletion in
<strong>the</strong> Smpd3 gene coding for <strong>the</strong> active site of neutral
sphingomyelinase2 (NSMase2), secreted increased
amounts of hyaluronan (HA). This was reversed by
transfection with <strong>the</strong> Smpd3 gene, suggesting a
connection between sphingolipid <strong>and</strong>
glycosaminoglycan metabolism. The deficiency of
NSMase2 resulted in s<strong>to</strong>rage of sphingomyelin (SM)
<strong>and</strong> cholesterol with a 50% reduction in ceramides
(Cer). RT‐PCR <strong>and</strong> Western blot analysis showed that
<strong>the</strong> increased HA secretion resulted from increased
hyaluronan synthase 2 (HAS2) activity localized <strong>to</strong>
sphingolipid‐enriched lipid rafts. Although cholesterol
levels were also elevated in lipid rafts from mouse
fibroblasts deficient in lysosomal acid SMase activity
(deletion of <strong>the</strong> Smpd1 ‐/‐ gene), <strong>the</strong>re was no increase in
HA secretion. We <strong>the</strong>n showed that in fro/fro fibroblasts,
<strong>the</strong> reduced ceramide was associated with decreased
phosphorylation of protein phosphatase 2A (PP2A) <strong>and</strong>
increased phosphorylation of its substrate Akt‐p,
<strong>to</strong>ge<strong>the</strong>r with PI3K, PDK1, mTOR <strong>and</strong> p‐70S6K whereas
PTEN was unaffected. Exogenous ceramide, as well as
inhibi<strong>to</strong>rs of Akt (Akt inhibi<strong>to</strong>r VIII), PI3kinase
(LY294002 <strong>and</strong> wortmannin) <strong>and</strong> mTOR (rapamycin)
reduced secretion of HA whereas <strong>the</strong> NSMase2
inhibi<strong>to</strong>r GW4869 increased HA syn<strong>the</strong>sis <strong>and</strong>
secretion. We propose that NSMase2/Cer are <strong>the</strong> key
media<strong>to</strong>rs of <strong>the</strong> regulation of HA syn<strong>the</strong>sis, via
microdomains <strong>and</strong> <strong>the</strong> Akt /mTOR pathway.
New au<strong>to</strong>matic methods for detecting
quarantine pests <strong>and</strong> diseases
M FACCOLI, F CHINELLATO, E PETRUCCO
TOFFOLO, M SIMONATO <strong>and</strong> A BATTISTI
Department of Agronomy, Food, Natural Resources, Animals
<strong>and</strong> Environment, Università di Padova, Italy <strong>and</strong> Agripolis,
Viale dell'Università, 16–35020 Legnaro (PD), Italy. Email:
massimo.faccoli@unipd.it
Jingdong QIN
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