ner SUPT5H (homolog of Spt5), or both,
reduced C9orf72 sense and antisense RNA
foci and poly(glycine-proline) levels. Additionally, reducing SUPT4H1 expression in
c9ALS patient–induced pluripotent stem
cell–derived cortical neurons reduced the
amount of C9orf72 transcripts and poly-
(glycine-proline). Thus, targeting human
SUPT4H1 and SUPT5H can effectively reduce multiple key c9FTD/ALS pathologies
(see the figure).
One concern for SUPT4H1 as a therapeutic target is that it may regulate other
nonmutated genes. Deletion of Spt4 in
yeast changed the regulation of 149 genes
compared to controls (5). In the study of
Kramer et al., 95% depletion of SUPT4H1 in
human fibroblasts altered the expression of
301 genes. Of note, deletion of one copy of
Supt4h did not exhibit any overt phenotype
in mice up to 18 months of age, but deletion
of both copies is embryonic lethal (6). Thus,
the degree of SUPT4H1 depletion will be
critical for effective therapy development.
One of the most advanced potential ther-
apeutics for repeat expansion disorders,
including Huntington’s disease and c9FTD/
ALS, are antisense oligonucleotides that
specifically target the mutant expanded
allele. Compared to mutant gene–specific
antisense oligonucleotides, potential ad-
vantages of the SUPT4H1-targeting strat-
egy are its wider applicability and the
reduction of both sense and antisense tran-
scripts. However, the relative role of anti-
sense RNA and protein species in disease
pathogenesis is currently unclear, so target-
ing sense repeats may still have a beneficial
effect. In this context, Kramer et al. show
that an antisense oligonucleotide targeting
the sense C9orf72 strand almost completely
reduced poly(glycine-proline) levels in pa-
tient fibroblasts. In addition, antisense
oligonucleotides that specifically target the
gene of interest may have fewer off-target
effects. As the authors suggest, an exciting
possibility is the development of an anti-
sense oligonucleotide targeting SUPT4H1,
particularly because this may have broad
potential for repeat expansion diseases. j
1. M. Dejesus-Hernandez etal .,Neuron 72, 245 (2011).
2. A.E.Renton et al., Neuron 72,257(2011).
3. N. J. Kramer et al ., Science353, 708 (2016).
4. R. Batra, K. Charizanis, M. S. Swanson, Hum. Mol. Genet.
19, R77 (2010).
5. T.Zu et al., Proc. Natl. Acad. Sci. U.S. A.108,260(2011).
6. C. R. Liu et al ., Cell 148, 690 (2012).
7. H.-M. Cheng et al ., PLOS Genet.11, e1005043 (2015).
8. M. Wojciechowska, W.J.Krzyzosiak, Hum. Mol. Genet.20,
9. S. Mizielinska et al ., Science345, 1192 (2014).
of brain time
By Charles A. Czeisler1,2
The brain’s central circadian (near-24- hour) clock exerts a very powerful influence on sleep and wakefulness (1, 2), interacting with our increasing drive to sleep as time awake increases (3, 4). On page 687 of this issue, Muto
et al. (5) demonstrate that the interaction of
the circadian clock with this so-called homeostatic sleep drive—which had been inferred
from studies of human performance, sleep
propensity, and risk of error or accident (3, 4,
6)—is rooted in measurable changes in cortical and subcortical responsiveness. Moreover,
the nature of the interaction varies among
cortical and subcortical brain regions.
Muto et al. analyzed the brain activity of
33 healthy individuals who were subjected
to sleep deprivation for 42 hours under constant environmental conditions. During this
time, brain activity was assessed every 2 to
6 hours (during particular tasks) by both
electroencephalography and by functional
magnetic resonance imaging (fMRI). The
circadian component of the fMRI data was
modeled by two different techniques. In
one approach, sine and cosine waves (
corresponding to the phases of the near-24-hour
circadian clock) were fit to the fMRI data
with standard techniques. This revealed
significant circadian rhythmicity of brain
responses in all brain regions except the
dorsolateral prefrontal cortex, but with a
peak in responsiveness that was a few hours
earlier than anticipated from physiological
and behavioral data (5). Fewer brain regions
(subcortical regions such as the thalamus,
head of the caudate nucleus, and putamen)
showed significant circadian rhythmicity with a new but unconventional method
that used the observed profile of melatonin
production to fit the circadian component
RNA Pol II
Repeat RNA can
INSIGHTS | PERSPECTIVES
The SUPT4H1-SUPT5H complex binds RNA polymerase II (Pol II) and regulates transcription elongation of
expanded nucleotide repeats, which cause a range of diseases including ALS. Targeting SUPT4H1 reduces production of multiple toxic species, specifically sense and antisense repeat RNAs and repeat proteins.
1Division of Sleep and Circadian Disorders, Departments
of Medicine and Neurology, and the Sleep Health Institute,
Brigham and Women’s Hospital, Boston, MA 02115, USA.
2Division of Sleep Medicine, Harvard Medical School, Boston,
MA 02115, USA. Email: email@example.com
Many brain areas are
under both circadian and