Miryam Carecchio

Progranulin plasma levels as potential biomarker for the identification of GRN deletion carriers. A case with atypical onset as clinical amnestic Mild Cognitive Impairment converted to Alzheimer's disease.

Progranulin (GRN) mutations are associated with different clinical phenotypes, including Frontotemporal Lobar Degeneration (FTLD), Corticobasal Degeneration and Alzheimers disease (AD). In addition, the range of age at onset is very wide and patients presenting initial symptoms around eighty years have been described. Previous studies demonstrated that progranulin plasma levels determination may be a reliable method to identify GRN deletion carriers. We thus evaluated progranulin plasma levels in all patients followed at our Alzheimers Centre whose plasma was available (n=176) and found four patients displaying low values. Three of them carried the CACT deletion in exon 7 and their clinical diagnosis was behavioral variant Frontotemporal Dementia. We also identified a patient carrying a previously reported CAGT deletion in exon 5. Here, we report on this case. The onset of symptoms was at 77 years and the initial diagnosis was of amnestic Mild Cognitive Impairment (aMCI), which converted to AD six months later. In the following years, the patient also developed behavioral disturbances, gait apraxia and parkinsonian symptoms. At present, she is 84 years old and is still followed-up periodically. This case confirms progranulin plasma levels as a reliable biomarker to identify GRN deletion carriers and discriminate between FTLD and other dementias which may mimic it. We thus encourage the inclusion of this non-invasive and easy test in clinical practice.

Phenotypic Heterogeneity of the GRN Asp22fs Mutation in a Large Italian Kindred

The Asp22fs(g.63_64insC) mutation in progranulin gene (GRN) has been so far reported in one patient who developed frontotemporal dementia (FTD) at the age of 65. Here, we describe the clinical heterogeneity associated with the GRN Asp22fs mutation in a large Italian family. Clinical and instrumental workup of two symptomatic carriers in two generations has been carried out, together with genetic analysis of probands and of nine asymptomatic family members. The first proband was a 47-year old male clinically diagnosed with FTD. Family history was positive and suggestive of an autosomal dominant pattern of inheritance. Evaluation of plasma GRN levels was consistent with the presence of a mutation in its encoding gene, that was demonstrated by sequencing [Asp22fs(g.63_64insC)]. Brain MRI showed multiple T2 and FLAIR hyperintense areas in the frontal lobe white matter and right hemisphere cortical atrophy. The second proband was his 79 year old uncle, presenting with mild cognitive impairment. Brain MRI showed small T2 hyperintense lesions and widespread cortical atrophy. Cerebrospinal fluid amyloid-β, tau, and phosphotau protein levels were in both cases in the range of normality. Additional nine asymptomatic family members were studied. This familys description expands the spectrum of clinical presentations of frontotemporal lobar degeneration caused by GRN mutations, suggesting that the diagnosis could be missed in some individuals with an atypical presentation, and points up the importance of GRN plasma level evaluation.

Osteopontin is Increased in the Cerebrospinal Fluid of Patients with Alzheimer's Disease and Its Levels Correlate with Cognitive Decline

Inflammation is believed to play a role in Alzheimers disease (AD). Osteopontin (OPN) is a molecule involved in macrophage recruitment and activation and implicated in neurodegeneration. In order to elucidate the role of OPN in AD, we evaluated its levels in serum and cerebrospinal fluid (CSF) of 67 AD patients, 46 frontotemporal dementia (FTD) patients, and 69 controls. We found that OPN levels: i) are significantly increased in the CSF of AD patients; ii) correlate with MMSE score; and iii) are higher in the early disease phases ( 2 years). These findings support a role of OPN in AD pathogenesis.

Cerebrospinal Fluid Biomarkers in Progranulin Mutations Carriers

Cerebrospinal fluid (CSF) biomarkers (Aβ₁₋₄₂, total tau, P-181 tau) are currently used to support a clinical diagnosis of Alzheimers disease (AD). The CSF profile in frontotemporal lobar degeneration (FTLD) caused by Progranulin (GRN) mutation is unknown. We assessed CSF biomarkers in 145 AD, 140 FTLD (20 GRN positive, 120 GRN negative) patients, and 38 controls. Taking into account the reference values used in clinical practice, GRN mutation carriers and controls did not differ significantly for any biomarker, whereas GRN negative FTLD patients had higher tau levels than controls (p < 0.001) and patients carrying GRN Thr272fs mutation (p = 0.033, Chi-Square test). Comparing CSF biomarkers mean values among groups, total tau was significantly increased in GRN negative FTLD and in mutation carriers compared with controls (p < 0.001). P-181 tau CSF was increased in AD patients and in GRN negative FTLD compared with controls (p < 0.001), but not in 17 patients carrying the Thr272fs mutation. 88.2% of mutation carriers had normal CSF tau, despite the neurodegenerative nature of FTLD. Our results suggest that GRN mutation carriers have normal or borderline CSF biomarkers. In patients with an AD-like phenotype but normal or borderline CSF biomarkers, a diagnosis of FTLD-U caused by GRN mutations should be considered.

A Missense Mutation in KCTD17 Causes Autosomal Dominant Myoclonus-Dystonia

Myoclonus-dystonia (M-D) is a rare movement disorder characterized by a combination of non-epileptic myoclonic jerks and dystonia. SGCE mutations represent a major cause for familial M-D being responsible for 30%-50% of cases. After excluding SGCE mutations, we identified through a combination of linkage analysis and whole-exome sequencing KCTD17 c.434 G>A p.(Arg145His) as the only segregating variant in a dominant British pedigree with seven subjects affected by M-D. A subsequent screening in a cohort of M-D cases without mutations in SGCE revealed the same KCTD17 variant in a German family. The clinical presentation of the KCTD17-mutated cases was distinct from the phenotype usually observed in M-D due to SGCE mutations. All cases initially presented with mild myoclonus affecting the upper limbs. Dystonia showed a progressive course, with increasing severity of symptoms and spreading from the cranio-cervical region to other sites. KCTD17 is abundantly expressed in all brain regions with the highest expression in the putamen. Weighted gene co-expression network analysis, based on mRNA expression profile of brain samples from neuropathologically healthy individuals, showed that KCTD17 is part of a putamen gene network, which is significantly enriched for dystonia genes. Functional annotation of the network showed an over-representation of genes involved in post-synaptic dopaminergic transmission. Functional studies in mutation bearing fibroblasts demonstrated abnormalities in endoplasmic reticulum-dependent calcium signaling. In conclusion, we demonstrate that the KCTD17 c.434 G>A p.(Arg145His) mutation causes autosomal dominant M-D. Further functional studies are warranted to further characterize the nature of KCTD17 contribution to the molecular pathogenesis of M-D.

De Novo Mutations in PDE10A Cause Childhood-Onset Chorea with Bilateral Striatal Lesions

Chorea is a hyperkinetic movement disorder resulting from dysfunction of striatal medium spiny neurons (MSNs), which form the main output projections from the basal ganglia. Here, we used whole-exome sequencing to unravel the underlying genetic cause in three unrelated individuals with a very similar and unique clinical presentation of childhood-onset chorea and characteristic brain MRI showing symmetrical bilateral striatal lesions. All individuals were identified to carry a de novo heterozygous mutation in PDE10A (c.898T>C [p.Phe300Leu] in two individuals and c.1000T>C [p.Phe334Leu] in one individual), encoding a phosphodiesterase highly and selectively present in MSNs. PDE10A contributes to the regulation of the intracellular levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Both substitutions affect highly conserved amino acids located in the regulatory GAF-B domain, which, by binding to cAMP, stimulates the activity of the PDE10A catalytic domain. In silico modeling showed that the altered residues are located deep in the binding pocket, where they are likely to alter cAMP binding properties. In vitro functional studies showed that neither substitution affects the basal PDE10A activity, but they severely disrupt the stimulatory effect mediated by cAMP binding to the GAF-B domain. The identification of PDE10A mutations as a cause of chorea further motivates the study of cAMP signaling in MSNs and highlights the crucial role of striatal cAMP signaling in the regulation of basal ganglia circuitry. Pharmacological modulation of this pathway could offer promising etiologically targeted treatments for chorea and other hyperkinetic movement disorders.

Movement Disorders in Adult Patients With Classical Galactosemia

Classical galactosemia is an autosomal recessive inborn error of metabolism leading to toxic accumulation of galactose and derived metabolites. It presents with acute systemic complications in the newborn. Galactose restriction resolves these symptoms, but long‐term complications, such as premature ovarian failure and neurological problems including motor dysfunction, may occur despite adequate treatment. The objective of the current study was to determine the frequency and phenotype of motor problems in adult patients with classical galactosemia. In this cross‐sectional study, adult patients with a biochemically confirmed diagnosis of galactosemia attending our clinic were assessed with an interview and neurological examination and their notes retrospectively reviewed. Patients were classified according to the presence/absence of motor dysfunction on examination. Patients with motor dysfunction were further categorized according to the presence/absence of reported motor symptoms. Forty‐seven patients were included. Thirty‐one patients showed evidence of motor dysfunction including: tremor (23 patients), dystonia (23 patients), cerebellar signs (6 patients), and pyramidal signs (4 patients). Tremor and dystonia were often combined (16 patients). Thirteen patients reported motor symptoms, with 8 describing progressive worsening. Symptomatic treatment was effective in 4 of 5 patients. Nonmotor neurological features (cognitive, psychiatric, and speech disorders) and premature ovarian failure were more frequent in patients with motor dysfunction. Motor dysfunction is a common complication of classical galactosemia, with tremor and dystonia the most frequent findings. Up to one third of patients report motor symptoms and may benefit from appropriate treatment. Progressive worsening is not uncommon and may suggest ongoing brain damage in a subset of patients.

The Role of Osteopontin in Neurodegenerative Diseases

Osteopontin (OPN) was shown to be involved in inflammatory and degenerative processes of the nervous system. In multiple sclerosis, the role of OPN has been studied in the inflammatory phase, where it was shown that the protein levels increase during disease relapses. Moreover, it was shown that subjects who carry a genotype associated with decreased protein levels tend to display a benign course. Taken altogether, these findings suggest that OPN may play a detrimental role in multiple sclerosis, at least in the inflammatory phase. In common neurodegenerative diseases, such as Parkinsons and Alzheimers disease, OPN seems to act as a double-edged sword triggering neuronal toxicity and death in some contexts and functioning as a neuroprotectant in others. The involvement of OPN in several biological pathways and networks calls for more extensive research in order to unravel its role in the different disease phases and its potential as a therapeutic target.

C2orf37 mutational spectrum in Woodhouse–Sakati syndrome patients

Alazami AM, Schneider SA, Bonneau D, Pasquier L, Carecchio M, Kojovic M, Steindl K, de Kerdanet M, Nezarati MM, Bhatia KP, Degos B, Goh E, Alkuraya FS. C2orf37 mutational spectrum in Woodhouse–Sakati syndrome patients.

Defective Fas‐mediated T‐cell apoptosis predicts acute onset CIDP

Guillain‐Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP) are immune‐mediated neuropathies. GBS is characterized by acute onset and subsequent remission of symptoms, whereas CIDP displays slow progression over at least 2 months. However, a small proportion of CIDP patients display acute onset CIDP (a‐CIDP) resembling that of GBS. The Fas receptor is involved in shutting off the immune response and its defective function predisposes to auto‐immune diseases. In CIDP patients, Fas function is lower than in GBS patients and healthy controls. This study is aimed at assessing whether evaluation of T‐cell Fas function helps in early discrimination between GBS and a‐CIDP. Fas function was evaluated in patients with acute onset polyneuropathy: 55 retrospective patients analyzed after development of GBS or a‐CIDP before year 2005; 50 prospective patients analyzed at onset after year 2005 and followed up for development of GBS or a‐CIDP. In both groups, a‐CIDP patients displayed defective Fas function, whereas GBS patients displayed normal function. These findings suggest that the evaluation of Fas function in acute onset polyneuropathy helps in early prediction of long‐term outcome.