Serum NfL in spinocerebellar ataxia type 1 is increased already at the preataxic stage, correlating with proximity to clinical onset

Background and Objectives. Neurofilament light (NfL) appears a promising fluid biomarker in repeat-expansion spinocerebellar ataxias (SCAs), with piloting studies in mixed SCA cohorts suggesting that NfL might be increased at the ataxic stage of spinocerebellar ataxia type 1 (SCA1). We here hypothesised that NfL is increased not only at the ataxic stage of SCA1, but also at its - likely most treatment-relevant - preataxic stage. Methods. We assessed serum (sNfL) and cerebrospinal fluid (cNfL) levels of NfL in both preataxic and ataxic SCA1, leveraging a multicentric cohort of 40 SCA1 carriers (23 preataxic, 17 ataxic) and >80 controls, and clinical follow-up data including actually observed (rather than only predicted) conversion to the ataxic stage (11 carriers). Results. sNfL levels were increased with high age-corrected effect sizes at the preataxic (r=0.62) and ataxic stage (r=0.63), paralleling increases of cNfL levels. In preataxic subjects, sNfL levels increased with proximity to predicted ataxia onset, with significant sNfL elevations already 5 years before onset, and confirmed in preataxic subjects with actually observed ataxia onset. sNfL increases were detected already in preataxic SCA1 subjects without volumetric atrophy of cerebellum or pons, suggesting that sNfL might be more sensitive to early preataxic neurodegeneration than the currently known most change-sensitive regions in volumetric MRI. Using longitudinal sNfL measurements, we estimated sample sizes for clinical trials using the reduction of sNfL as endpoint. Conclusions. sNfL levels might thus provide easily accessible peripheral biomarkers in both preataxic and ataxic SCA1, allowing stratification of preataxic subjects regarding proximity-to-onset, early detection of neurodegeneration even before volumetric MRI alterations, and potentially capture of treatment response in clinical trials.

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Genetic Modeling of the Neurodegenerative Disease Spinocerebellar Ataxia Type 1 in Zebrafish

International Journal of Molecular Sciences ◽

10.3390/ijms22147351 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7351

Author(s):

Mohamed A. Elsaey ◽

Kazuhiko Namikawa ◽

Reinhard W. Köster

Keyword(s):

Spinocerebellar Ataxia ◽

Cag Repeats ◽

Spinocerebellar Ataxia Type ◽

Spinocerebellar Ataxias ◽

Spinocerebellar Ataxia Type 1 ◽

Reporter Protein ◽

Fluorescent Reporter ◽

Larval Stages

Dominant spinocerebellar ataxias (SCAs) are progredient neurodegenerative diseases commonly affecting the survival of Purkinje cells (PCs) in the human cerebellum. Spinocerebellar ataxia type 1 (SCA1) is caused by the mutated ataxin1 (Atx1) gene product, in which a polyglutamine stretch encoded by CAG repeats is extended in affected SCA1 patients. As a monogenetic disease with the Atx1-polyQ protein exerting a gain of function, SCA1 can be genetically modelled in animals by cell type-specific overexpression. We have established a transgenic PC-specific SCA1 model in zebrafish coexpressing the fluorescent reporter protein mScarlet together with either human wild type Atx1[30Q] as control or SCA1 patient-derived Atx1[82Q]. SCA1 zebrafish display an age-dependent PC degeneration starting at larval stages around six weeks postfertilization, which continuously progresses during further juvenile and young adult stages. Interestingly, PC degeneration is observed more severely in rostral than in caudal regions of the PC population. Although such a neuropathology resulted in no gross locomotor control deficits, SCA1-fish with advanced PC loss display a reduced exploratory behaviour. In vivo imaging in this SCA1 model may help to better understand such patterned PC death known from PC neurodegeneration diseases, to elucidate disease mechanisms and to provide access to neuroprotective compound characterization in vivo.

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