Neurofilament light protein as a biomarker for spinal muscular atrophy: a review and reference ranges.

Spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality, characterized by progressive neuromuscular degeneration resulting from mutations in the survival motor neuron (SMN1) gene. The availability of disease-modifying therapies for SMA therapies highlights the pressing need for easily accessible and cost-effective blood biomarkers to monitor treatment response and for better disease management. Additionally, the wide implementation of newborn genetic screening programs in Western countries enables presymptomatic diagnosis of SMA and immediate treatment administration. However, the absence of monitoring and prognostic blood biomarkers for neurodegeneration in SMA hinders effective disease management. Neurofilament light protein (NfL) is a promising biomarker of neuroaxonal damage in SMA and reflects disease progression in children with SMA undergoing treatment. Recently, the European Medicines Agency issued a letter of support endorsing the potential utilization of NfL as a biomarker of pediatric neurological diseases, including SMA. Within this review, we comprehensively assess the potential applications of NfL as a monitoring biomarker for disease severity and treatment response in pediatric-onset SMA. We provide reference ranges for normal levels of serum based NfL in neurologically healthy children aged 0-18 years. These reference ranges enable accurate interpretation of NfL levels in children and can accelerate the implementation of NfL into clinical practice.

Plasma biomarkers predict amyloid pathology in cognitively normal monozygotic twins after 10 years.

Blood-based biomarkers could prove useful to predict Alzheimer's disease core pathologies in advance of clinical symptoms. Implementation of such biomarkers requires a solid understanding of their long-term dynamics and the contribution of confounding to their association with Alzheimer's disease pathology. Here we assess the value of plasma amyloid-ß1-42/1-40, phosphorylated-tau181 and glial fibrillary acidic protein to detect early Alzheimer's disease pathology, accounting for confounding by genetic and early environmental factors. Participants were 200 monozygotic twins, aged ≥60 years with normal cognition from the european medical information framework for Alzheimer's disease study. All twins had amyloid-ß status and plasma samples available at study enrolment. For 80 twins, additional plasma samples were available that had been collected approximately 10 years prior to amyloid-ß status assessment. Single-molecule array assays were applied to measure amyloid-ß1-42/1-40, phosphorylated-tau181 and glial fibrillary acidic protein. Predictive value of and longitudinal change in these biomarkers were assessed using receiver operating characteristic curve analysis and linear mixed models. Amyloid pathology could be predicted using blood-based biomarkers obtained at the time of amyloid status assessment (amyloid-ß1-42/1-40: area under the curve = 0.65, P = 0.01; phosphorylated-tau181: area under the curve = 0.84, P < 0.001; glial fibrillary acidic protein: area under the curve = 0.74, P < 0.001), as well as using those obtained 10 years prior to amyloid status assessment (amyloid-ß1-42/1-40: area under the curve = 0.69, P = 0.03; phosphorylated-tau181: area under the curve = 0.92, P < 0.001; glial fibrillary acidic protein: area under the curve = 0.84, P < 0.001). Longitudinally, amyloid-ß1-42/1-40 levels decreased [ß (SE) = -0.12 (0.01), P < 0.001] and phosphorylated-tau181 levels increased [ß (SE) = 0.02 (0.01), P = 0.004]. Amyloid-ß-positive individuals showed a steeper increase in phosphorylated-tau181 compared with amyloid-ß-negative individuals [ß (SE) = 0.06 (0.02), P = 0.004]. Also amyloid-ß-positive individuals tended to show a steeper increase in glial fibrillary acidic protein [ß (SE) = 0.04 (0.02), P = 0.07]. Within monozygotic twin pairs, those with higher plasma phosphorylated-tau181 and lower amyloid-ß1-42/1-40 levels were more likely to be amyloid-ß positive [ß (SE) = 0.95 (0.26), P < 0.001; ß (SE) = -0.28 (0.14), P < 0.05] indicating minimal contribution of confounding by genetic and early environmental factors. Our data support the use of amyloid-ß1-42/1-40, phosphorylated-tau181 and glial fibrillary acidic protein as screening tools for Alzheimer's disease pathology in the normal aging population, which is of importance for enrolment of high-risk subjects in secondary, or even primary, prevention trials. Furthermore, these markers show potential as low-invasive monitoring tool of disease progression and possibly treatment effects in clinical trials.

Clinical and analytical comparison of six Simoa assays for plasma P-tau isoforms P-tau181, P-tau217, and P-tau231.

INTRODUCTION: Studies using different assays and technologies showed highly promising diagnostic value of plasma phosphorylated (P-)tau levels for Alzheimer's disease (AD). We aimed to compare six P-tau Simoa assays, including three P-tau181 (Eli Lilly, ADx, Quanterix), one P-tau217 (Eli Lilly), and two P-tau231 (ADx, Gothenburg). METHODS: We studied the analytical (sensitivity, precision, parallelism, dilution linearity, and recovery) and clinical (40 AD dementia patients, age 66±8years, 50%F; 40 age- and sex-matched controls) performance of the assays. RESULTS: All assays showed robust analytical performance, and particularly P-tau217 Eli Lilly; P-tau231 Gothenburg and all P-tau181 assays showed robust clinical performance to differentiate AD from controls, with AUCs 0.936-0.995 (P-tau231 ADx: AUC = 0.719). Results obtained with all P-tau181 assays, P-tau217 Eli Lilly assay, and P-tau231 Gothenburg assay strongly correlated (Spearman's rho > 0.86), while correlations with P-tau231 ADx results were moderate (rho < 0.65). DISCUSSION: P-tau isoforms can be measured robustly by several novel high-sensitive Simoa assays.

The NER protein Rad33 shows functional homology to human Centrin2 and is involved in modification of Rad4.

In the yeast Saccharomyces cerevisiae the Rad4-Rad23 complex is implicated in the initial damage recognition of the Nucleotide Excision Repair (NER) pathway. NER removes a variety of lesions via two subpathways: Transcription Coupled Repair (TCR) and Global Genome Repair (GGR). We previously showed that the new NER protein Rad33 is involved in both NER subpathways TCR and GGR. In the present study we show UV induced modification of Rad4 that is strongly increased in cells deleted for RAD33. Modification of Rad4 in rad33 cells does not require the incision reaction but is dependent on the TCR factor Rad26. The predicted structure of Rad33 shows resemblance to the Centrin homologue Cdc31. In human cells, Centrin2 binds to XPC and is involved in NER. We demonstrate that Rad4 binds Rad33 directly and via the same conserved amino acids required for the interaction of XPC with Centrin2. Disruption of the Rad4-Rad33 interaction is sufficient to enhance the modification of Rad4 and results in a repair defect similar to that of a rad33 mutant. The current study suggests that the role of Rad33 in the Rad4-Rad23 complex might have parallels with the role of Centrin2 in the XPC-HHR23B complex.

Rad33, a new factor involved in nucleotide excision repair in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae the Rad4-Rad23 complex is involved in initial damage recognition and responsible for recruiting the other NER proteins to the site of the lesion. The Rad4-Rad23 complex is essential for both NER subpathways, Transcription Coupled Repair (TCR) and Global Genome Repair (GGR). Previously, we reported on the role of the Rad4 homologue YDR314C in NER. YDR314C is essential for preferential repair of the transcribed strand in RNA pol I transcribed rDNA. In large scale interaction studies it was shown that YDR314C physically interacts with a small protein encoded by the ORF YML011C. In the present study we show that YML011C is involved in NER and we propose to designate the YML011C ORF RAD33. Cells deleted for RAD33 display intermediate UV sensitivity that is epistatic with NER. Strand specific repair analysis shows that GGR in RNA pol II transcribed regions is completely defective in rad33 mutants whereas TCR is still active, albeit much less efficient. In RNA pol I transcribed rDNA both GGR and TCR are fully dependent on Rad33. We show that in both rad23 and rad33 cells Rad4 and YDR314C protein levels are significantly reduced. The homology of YDR314C to Rad4, together with the similar relation of both proteins to Rad33 prompted us to propose RAD34 as name for the YDR314C gene. Although the rad23rad33 double mutant is considerably more UV sensitive than a rad23 or rad33 single mutant, deletion of RAD33 in a rad23 background does not lead to a further reduction of Rad4 or Rad34 protein levels. This suggests that the role of Rad33 is not solely the stabilization of Rad4 and Rad34 but that Rad33 has an additional role in NER.

The Rad4 homologue YDR314C is essential for strand-specific repair of RNA polymerase I-transcribed rDNA in Saccharomyces cerevisiae.

Summary The Saccharomyces cerevisiae protein Rad4 is involved in damage recognition in nucleotide excision repair (NER). In RNA polymerase II-transcribed regions Rad4 is essential for both NER subpathways global genome repair (GGR) and transcription coupled repair (TCR). In ribosomal DNA (rDNA), however, the RNA polymerase I-transcribed strand can be repaired in the absence of Rad4. In Saccharomyces cerevisiae the YDR314C protein shows homology to Rad4. The possible involvement of YDR314C in NER was studied by analysing strand-specific cyclobutane pyrimidine dimer (CPD) removal in both RNA pol I- and RNA pol II-transcribed genes. Here we show that the Rad4-independent repair of rDNA is dependent on YDR314C. Moreover, in Rad4 proficient cells preferential repair of the transcribed strand of RNA pol I-transcribed genes was lost after deletion of YDR314C, demonstrating that Rad4 cannot replace YDR314C. CPD removal from the RNA pol II-transcribed RPB2 gene was unaffected in ydr314c mutants. We conclude that the two homologous proteins Rad4 and YDR314C are both involved in NER and probably have a similar function, but operate at different loci in the genome and are unable to replace each other.