Data di Pubblicazione:
2014
Citazione:
MOLECULAR AND GENETIC CHARACTERIZATION OF ALS PATIENTS / C. Tarlarini ; coordinatore: F. Bonomi ; tutor: E.Gianazza; supervisore: S. Penco. DIPARTIMENTO DI SCIENZE FARMACOLOGICHE E BIOMOLECOLARI, 2014 Feb 27. 26. ciclo, Anno Accademico 2013. [10.13130/tarlarini-claudia_phd2014-02-27].
Abstract:
Amyotrophic lateral sclerosis (ALS) is an adult‑onset, rapidly progressive and ultimately fatal
neurodegenerative disorder characterised by degeneration of upper and lower motor neurons.
This leads to weakness, muscular atrophy and spasticity, which relentlessly progress to complete
paralysis with a low survival rate beyond 5 years from symptom onset. In 10% of cases the
disease is considered to be genetically transmitted (FALS) while in the remaining cases it occurs
sporadically in the population (SALS). To date cases of hereditary ALS have been attributed to
mutations in more than 16 different genes, the most common being SOD1, FUS, TARDBP and
C9ORF72; mutations in other genes are rare. The above genes explain 60% of the cases of
familial ALS and 15% of sporadic cases.
The disease can be subdivided into bulbar (25%) and spinal‑onset (75‑80%) forms. Nevertheless,
it is currently recognized that pathological changes are not limited to the motor system: patients
with ALS may exhibit cognitive abnormalities ranging from impaired frontal executive dysfunction to
overt frontotemporal dementia (FTD).
In spite of the above evidence, ALS is regarded as a complex disease in which multiple
environmental and genetic risk factors contribute to disease susceptibility. Furthermore it is
possible that the phenotypic variability, which is frequently detected within families, could be due to
multiple genetic factors as devised in the oligogenic disease model.
In the present study we analysed 285 SALS and 17 FALS cases. Globally, our molecular analysis
explained 10.3% of all ALS cases (31/302). The genes screened were SOD1, TARDBP, FUS and
C9ORF72. Genomic DNA was extracted from peripheral blood through a salting out procedure;
coding regions and exon‑intron boundaries of SOD1 (5 exons), TARDBP (1 exon), and FUS
(5 exons) genes were amplified from genomic DNA and sequenced. Otherwise the repeat‑primed
PCR assay, used for C9ORF72 gene, was performed in order to screen for the presence of the
GGGGCC hexanucleotide repeats expansion in ALS patients. The repeat unit of 6 nucleotides
expands up to more than several hundred times in the affected individuals. Fewer than 10 repeats
are not associated with a pathological phenotype, while more than 30 repeats are associated.
However we still do not know the meaning of intermediate repeat sizes (11‑29). This fact
complicates the attribution of the size expansion to the pathological phenotype observed.
According to the oligogenic disease model, all patients were screened for the most common
ALS‑associated genes and all mutated subjects were tested also for ANG. The affected/unaffected
family members, when available for the study, were screened for SOD1, TARDBP, FUS and
C9ORF72 in order to identify their genetic difference from the proband and to evaluate if this
difference could explain an heterogeneous phenotypic expression of the disease.
Following these analyses we selected and described in detail 5 FALS and 2 SALS cases and
one SETX case, with different intrafamilial phenotypic expression. In one of our SOD1 mutation
carriers, the proband manifested the disease after the delivery; together with a specific angiogenin
genetic variant this condition seems to have anticipated the age of disease onset and contributed
to the aggressive clinical course observed in the proband compared to other family members.
We also found one case in which we observed the phenomenon of anticipation, which could be
due to hormonal treatments together with the simultaneous presence of 2 mutations (C9ORF72/
TARDBP), as suggested in the oligogenic disease model. Indeed, the neuroprotective effects of
estrogens could account for the later age at onset in women as we have tested
Tipologia IRIS:
Tesi di dottorato
Keywords:
amyotrophic lateral sclerosis ; ALS ; genetic ; mutation
Elenco autori:
C. Tarlarini
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