José Félix Martí Massó

Mutations in Progranulin Gene: Clinical, Pathological, and Ribonucleic Acid Expression Findings

BACKGROUND There is an increasing interest in the clinico-pathological correlation of mutations in progranulin (PGRN) and frontotemporal lobar degeneration (FTLD) complex diseases. We aim to study the PGRN expression variability in patients with different clinical features for a better understanding of its roles in FTLD disease. METHODS We sequenced the PGRN gene in 72 patients suffering from FTLD (25 familial and 47 sporadic cases) and in 24 asymptomatic at-risk relatives. We also analyzed PGRN expression in blood by quantitative real-time polymerase chain reaction from 37 patients, 8 asymptomatic mutation carriers, and 10 control subjects as well as in brain tissue from 16 patients and 9 control subjects. RESULTS Four novel mutations were associated with familial and sporadic FTLD and familial dementia associated with amyotrophic lateral sclerosis. We identified a close association between the IVS6-1G>A mutation in PGRN and corticobasal syndrome. Brain tissue was available for carriers of two of the four mutations (IVS6-1 G>A and P357HfsX3). Immunohistochemical analysis revealed ubiquitin- and TDP-43positive and tau/alpha-synuclein negative immunoreactive neuronal intranuclear inclusions. The relative expression of PGRN in the clinical sample was significantly lower in carriers of the IVS6-1 G>A than in control subjects. CONCLUSIONS Progranulopathies are a major cause of the main phenotypes included in the FTLD complex. According to our results, the level of expression of PGRN in blood could be a useful marker both for diagnostics of part of the spectrum of FTLD conditions and for monitoring future treatments that might boost the level of PGRN in this disorder.

Olfactory deficits and cardiac 123I‐MIBG in Parkinson's disease related to the LRRK2 R1441G and G2019S mutations

It has been proposed that olfactory tests and metaiodobenzylguanidine cardiac scintigraphy may help diagnose idiopathic Parkinsons disease in the premotor phase. However, it is not clear what value these tests have in all patients with Parkinsons disease and, particularly, in those who carry mutations in LRRK2. The objective was to analyze olfactory dysfunction and the changes in cardiac I‐metaiodobenzylguanidine uptake in patients with Parkinsons disease carrying the R1441G and G2019S mutations in LRRK2, and in patients with Parkinsons disease with no known mutations. Patients with Parkinsons disease were screened for R1441G and G2019S LRRK2 gene mutations and classified as LRRK2 mutation carriers or noncarriers. A total of 190 patients with Parkinsons disease (44 LRRK2 mutation carriers) were tested for olfactory dysfunction using the Brief Smell Identification Test. Cardiac 123I‐metaiodobenzylguanidine scintigraphy was performed on 90 patients with Parkinsons disease (27 LRRK2 mutation carriers). Thirty‐six percent of patients with LRRK2 mutations have hyposmia, compared to 75% of noncarrier patients with Parkinsons disease (P < .001). Sixty‐six percent of LRRK2 mutation carriers have low early metaiodobenzylguanidine uptake, compared to 86% of noncarriers (P = .048). Similarly, the heart/mediastinum ratio in delayed metaiodobenzylguanidine images appeared to differ between these groups of patients with Parkinsons disease, although these results did not reach statistical significance. The data obtained indicate that olfactory and cardiac impairment is less prevalent when Parkinsons disease is associated with mutations in LRRK2, although the underlying mechanisms for this difference remain unclear. Thus, such screening would be less useful to detect the premotor phase in asymptomatic relatives who carry mutations in LRRK2 than in cases not associated with LRRK2.

Identification of a novel THAP1 mutation at R29 amino-acid residue in sporadic patients with early-onset dystonia.

Dystonia is a movement disorder characterized by involuntary, sustained muscular contractions affecting one or more sites of the body and abnormal postures. The clinical spectrum of dystonia is diverse: however, the most common form of the disease is primary torsion dystonia (PTD). PTD usually onsets in infancy or adolescence and affects the trunk, neck, or limbs. Two genes are associated with PTD, DYT1 (OMIM 128100; TOR1A) and DYT6 (OMIM 609520; THAP1). Mutations in THAP1 were, first, identified in families presenting with cranial or cervical dystonia that frequently progressed to involve other body regions, and later, in families presenting with early-onset generalized dystonia with prominent spasmodic dysphonia. Here, 24 patients presenting with either generalized (6) or cervical dystonia (18) were investigated for the presence of THAP1 mutations. The mean age at onset was 48 years (range 9–77 years). All patients provided written informed consent to participate in this study. Sequencing analysis of the coding region of the THAP1 gene revealed the presence of a novel c.86G>A transition resulting in p.Arg29Gln in two sporadic cases suffering from early-onset cervical dystonia and early-onset generalized dystonia, respectively. This novel mutation, located in exon 2 of the THAP1 gene, affects an amino-acid previously identified as mutated in families presenting with multifocal and generalized dystonia. Furthermore, R29 amino acid is conserved between species; suggesting, p.Arg29Gln is likely to be pathogenic. Although both p.Arg29Gln mutation carriers are from the same geographical region, there is no evidence of a common founder. A novel silent, mutation which resulted in c.81T>C transition causing p.Leu27Leu was also identified in a sporadic, late-onset dystonia patient presenting with involuntary movements in the neck at the age of sixty; however, its pathogenic role remains unclear. Both novel THAP1 mutations were absent in a Spanish series of 182 control chromosomes. We concluded that pathogenic mutations were only found in early-onset cases. THAP1 mutations occur throughout the entire gene; however, many seem to cluster in the THAP domain of the protein, including the novel THAP1 mutations described here (Fig. 1). It has been suggested that mutations in the THAP domain may reduce the DNA binding ability of THAP; therefore we speculate that mutations at R29 may also act via this mechanism. Clinical features of both patients carrying p.Arg29Gln mutation are described below. This case is a 55 years old man who, at the age of 9, presented with a right-sided torticollis which persisted for more than a year. A surgical intervention was given around his neck and in the right upper limb. Since then, no improvement was determined however the disease showed slow progression. At 54, he noted having cognitive changes and difficulties in speech and ingestion. There was no family history of movement disorders and his mother died with cognitive decline of late onset. Dystonia was mainly present in the face and proximal left upper limb. Left sided torticollis was found with a tendency of retrocollis and fluctuating involvement of both platysma. The trapezia and ECMs were hypertrophic. MRI brain was normal. The cervical spine showed mild disc protrusion at C5-C6 and C6-C7 without radicular involvements. To control the dystonia, increased dose of Botulinum toxin (Dysport), up to 700 units, was required. This case is a 33 years old man who, at the age of 14, presented with abnormal pain sensation in the left upper limb. He progressed to develop dystonic movements in the hand which usually presented as wrist flexion on the radial side and, occasionally, on the ulnar side. In addition, the left upper limb showed forced abduction. Dystonia has now spread to the left foot. His grandmother was diagnosed as having Parkinson’s disease and his great-aunt with possible blepharospasm. Brain MRI was normal and cervical spine showed minimal disc protrusion at C5-C6 without any compression noted. The arm abduction was controlled with botulinum toxin; however, dystonia remained uncontrolled and no additional medication was given. Serum copper, ceruloplasmin, calcium, phosphate, ferritin, and glucose were normal in both cases. To summarize, THAP1 mutations may be present in sporadic, early-onset, cervical, and generalized dystonia.

Penetrance in Parkinson's disease related to the LRRK2 R1441G mutation in the Basque country (Spain)†

The LRRK2 R1441G mutation was first identified in Basque families and it is responsible for 46% of familial Parkinsons disease (PD) and for 2.5% of sporadic PD in the PD population of Basque ascent. The aim of this study was to determine LRRK2 R1441G penetrance in PD in the Basque Country (Spain) to help in a more accurate genetic counseling. A total of 59 sibships containing 244 individuals, with a total of 40 PD‐affected relatives, were studied. Genetic testing for the R1441G mutation in the LRRK2 gene was performed in 133 individuals and was positive in 51% of them. Lifetime penetrance of R1441G mutations turned out to be 12.5% at 65 years to 83.4% at 80 years. No gender differences were found in penetrance.

Prevalence of cancer in Parkinson's disease related to R1441G and G2019S mutations in LRRK2

An inverse relationship between Parkinsons disease (PD) and cancer has been described. However, the association between cancers and genetic forms of PD, in particular the R1441G mutation in the LRRK2 gene, is not well known. The objective of this work was to analyze cancer prevalence in PD patients with R1441G or G2019S mutations in LRRK2, and in idiopathic PD (iPD). A total of 732 patients with PD (70 and 25 carriers of R1441G or G2019S mutations, respectively), and 177 controls, were linked using a population‐based cancer registry of the Spanish province of Gipuzkoa. Cancer prevalence was not significantly higher in PD‐G2019S carriers (20%) than in PD‐R1441G carriers (14.3%), iPD (13.8%), or controls (12.5%). With the exception of a high prevalence of hematological cancers (crude odds ratio of 7.1) in the R1441G group, specific cancer types were not increased in PD mutation carriers. In both the carrier and iPD groups, cancers were diagnosed after the onset of PD. PD patients had a similar prevalence of cancer to control subjects. There was no increased association between G2019S or R1441G mutations and any type of cancer. Although there was a higher prevalence of hematological cancers in the R1441G group, the low number of such cancers overall makes this finding of uncertain significance. There was a slightly higher but not statistically significant prevalence of non‐skin cancers in the G2019S group, suggesting that further study to evaluate the association should be undertaken prior to ascribing an increased cancer risk to this population.

Prion protein codon 129 polymorphism modifies age at onset of frontotemporal dementia with the C.709-1G>A progranulin mutation.

Frontotemporal lobar degeneration because of mutations in the progranulin (PGRN) gene presents a high variability both in the clinical phenotype and age of onset of disease. Factors that influence this variability remain largely unknown. The aim of our study was to determine whether selected genetic variables modify age at onset of disease in our series of 21 patients with a single splicing mutation (c.709-1G>A) in the PGRN gene, all of whom were of Basque descent. In our analysis, we included the following genetic variables: PGRN rs5848 and rs9897526 polymorphisms, APOE and microtubule-associated protein tau genotypes, and PRNP codon 129 polymorphism. We found no association between PGRN polymorphisms, APOE and microtubule-associated protein tau genotypes, and age at onset of the disease; whereas we report evidence for an association between PRNP codon 129 polymorphism and age at onset of disease in frontotemporal dementia-PGRN(+) patients. MM homozygous carriers presented onset of disease on average 8.5 years earlier than patients who carried at least 1 valine on their PRNP codon 129 (MV or VV). The biological justification for this association remains speculative.

Neuropsychological Features of Asymptomatic c.709-1G>A Progranulin Mutation Carriers

Mutations in the progranulin (PGRN) gene have been identified as a cause of frontotemporal dementia (FTD). However, little is known about the neuropsychological abilities of asymptomatic carriers of these mutations. The aim of the study was to assess cognitive functioning in asymptomatic c.709-1G>A PGRN mutation carriers. We hypothesized that poorer neuropsychological performance could be present before the development of clinically significant FTD symptoms. Thirty-two asymptomatic first-degree relatives of FTD patients carrying the c.709-1G>A mutation served as study participants, including 13 PGRN mutation carriers (A-PGRN+) and 19 non-carriers (PGRN-). A neuropsychological battery was administered. We found that the A-PGRN+ participants obtained significantly poorer scores than PGRN- individuals on tests of attention (Trail-Making Test Part A), mental flexibility (Trail-Making Test Part B), and language (Boston Naming Test). Poorer performance on these tests in asymptomatic PGRN mutation carriers may reflect a prodromal phase preceding the onset of clinically significant symptoms of FTD.

Distinctive age-related temporal cortical thinning in asymptomatic granulin gene mutation carriers

Studies in asymptomatic granulin gene (GRN) mutation carriers are essential to improve our understanding of the pattern and timing of early morphologic brain changes in frontotemporal lobar degeneration. The main objectives of this study were to assess the effect of age in cortical thickness changes (CTh) in preclinical GRN mutation carriers and to study the relationship of CTh with cognitive performance in GRN mutation carriers. We calculated CTh maps in 13 asymptomatic carriers of the c.709-1G>A GRN mutation and 13 age- and sex-matched healthy subjects. Asymptomatic GRN mutation carriers presented different patterns of age-related cortical thinning in the right superior temporal and middle temporal gyri and the banks of the superior temporal sulcus bilaterally when compared with controls. Cortical thickness was correlated with neuropsychological test scores: Trail Making Tests A and B, and the Boston Naming Test. Distinctive age-related cortical thinning in asymptomatic GRN mutation carriers in lateral temporal cortices suggests an early and disease-specific effect in these areas.

Análisis de la marcha en la enfermedad de Parkinson y su respuesta al tratamiento dopaminérgico

Fundamento y objetivo Analizar objetivamente las alteraciones de la marcha en pacientes con enfermedad de Parkinson (EP) y los cambios observados tras la administracion de medicacion dopaminergica. Pacientes y metodo Se incluyo a 15 pacientes con enfermedad de Parkinson para la comparacion de la marcha con un grupo de 15 individuos sanos de la misma edad y a 24 pacientes para la comparacion antes y despues de la administracion de la medicacion.Se realizo el analisis con un Nuevo sistema de fotogrametria tridimensional. Resultados Los pacientes presentaron de forma significativa una menor velocidad,longitud de zancada, de paso y menores amplitudes articulares de cadera y rodilla que el grupo control, sin diferencias en la cadencia, base de sustentacion ni en los tiempos relativos del ciclo de la marcha.No se encontraron diferencias significativas en la comparacion de la marcha antes y despues de la administracion de la medicacion dopaminergica. Conclusiones El analisis de la marcha permite cuantificar las alteraciones de la marcha en pacientes con enfermedad de Parkinson y el potencial efecto de intervenciones terapeuticas. Los resultados indicant un cierto grado de resistencia a la levodopa en la marcha de estos pacientes.

Neurogenetic Disorders in the Basque Population

In the molecular era, the study of neurogenetic disorders in relict populations provides an opportunity to discover new genes by linkage studies and to establish clearer genotype‐phenotype correlations in large cohorts of individuals carrying the same mutation. The Basque people are one of the most ancient populations living in Europe and represent an excellent resource for this type of analysis in certain genetic conditions. Our objective was to describe neurogenetic disorders reported in the Basque population due to the presence of ancestral mutations or an accumulation of cases or both. We conducted a search in PubMed with the terms: Basque, neurogenetic disorders, genetic risk, and neurological disorders. We identified nine autosomal and two recessive disorders in the Basque population attributable to ancestral mutations (such as in PNRP, PARK8, FTDP‐TDP43, LGMD2A, VCP, c9ORF72, and CMT4A), highly prevalent (DM1) or involving unique mutations (PARK1 or MAPT). Other genes were reported for their role as protective/risk factors in complex diseases such as multiple sclerosis, Alzheimers disease, and Parkinsons disease. At the present time, when powerful sequencing techniques are identifying large numbers of genetic variants associated with unique phenotypes, the scrutiny of these findings in genetically homogeneous populations can help analyze genotype‐phenotype correlations.