Amyotrophic lateral sclerosis (ALS) and related motor neuron degenerative diseases affect more than 30,000
people in the US, and 90% of patients die within five years of diagnosis. Although ALS and ALS-like disease
manifestation varies, all forms are characterized by progressive loss of motor neurons. These disorders have a
strong genetic component, and although more than 50 genes involved in ALS have been identified, much still
remains to be learned about the genes and mechanisms that contribute to ALS susceptibility and protection.
Aberrant RNA metabolism and processing plays an important mechanistic role in neurodegeneration, and
mutations in genes encoding RNA-binding proteins underscore several of the more common causes of ALS.
The general idea that altered RNA metabolism and processing leads to neurodegenerative disease suggests
that additional genes encoding RNA-binding or RNA processing factors are likely to be involved in the genetics
of ALS and related neurodegenerative disorders. The ZNF106 gene encodes an RNA binding protein and maps
to human chromosome 15q15.1, the site of an incompletely described rare form of juvenile onset ALS. Genetic
inactivation of Zfp106, the mouse ortholog of ZNF106, results in an early onset, profound ALS-like
neurodegenerative phenotype with a corresponding loss of motor neurons, suggesting that this factor plays a
neuroprotective role in vivo and that its loss-of-function could be involved in ALS in humans. Zfp106 is expressed
in the nucleolus and nuclear speckles in both motor neurons and skeletal muscle and its function is essential for
maintenance of neuromuscular junctions in vivo. Zfp106 binds selectively to G-quadruplex-forming RNA
molecules and strongly associates biochemically with other RNA binding proteins, including several with strong
causative roles in ALS, further suggesting the possibility that Zfp106/ZNF106 might play a role in ALS. Consistent
with this notion, unpublished work has identified two unrelated patients with a rare, homozygous variant in
ZNF106 that is associated with adolescent onset ALS-like neurodegenerative disease. Introduction of the human
disease-associated ZNF106 variant into mouse Zfp106 also results in profound juvenile onset ALS-like
neurodegeneration similar to the disease observed in the patients and in Zfp106-null mice. This proposal will
test the hypotheses that mutations in human ZNF106 cause or contribute to ALS-like neurodegeneration and
that Zfp106 plays a protective role in maintaining neuromuscular junctions through its RNA binding function and
its autonomous functions in either motor neurons or skeletal muscle. Studies proposed in this application will
define the functional consequences ALS0associated ZNF106 variants by characterizing the ALS-like
neurodegenerative phenotype in mice harboring knock-in of the variant and by determining the effect of the
variant in cell culture-based and in vitro assays of ZNF106/Zfp106 protein function. These studies will also
determine the cell autonomous requirement for Zfp106 in motor neurons and skeletal muscle using conditional
genetic approaches in mice.
