Ebrahimi-Fakhari, DariusAgianda, Habibah Azzahra Putri2026-05-0820262026-05-082026Agianda, Habibah Azzahra Putri. 2026. Blood-Based Biomarker in Childhood-Onset Hereditary Spastic Paraplegias: Towards Clinical Trial Readiness. Masters Thesis, Harvard Medical School.32698375https://dash.harvard.edu/handle/1/42737039Manuscript 1: Longitudinal Dynamics of Plasma Neuro lament Light Chain in Hereditary Spastic Paraplegia Type 11 (HSP-SPG11) and Type 15 (HSP-ZFYVE26) ABSTRACT Background: HSP-SPG11 and HSP-ZFYVE26 are autosomal-recessive forms of hereditary spastic paraplegias (HSPs). As therapeutic trials emerge, validated biomarkers are critically needed. Objectives: To evaluate plasma neurofilament light chain (pNfL) as a biomarker for neurodegeneration and disease progression. Methods: We analyzed pNfL levels in 57 patients (36 HSP-SPG11, 21 HSP-ZFYVE26) and matched controls using single-molecule array technology. Longitudinal clinical and biomarker data were collected over 5 years. Results: Baseline pNfL levels were significantly elevated in patients: 33.85 pg/mL (IQR 25.15-47.38) in HSP-SPG11, 46.70 pg/mL (IQR 29.95-54.84) in HSP-ZFYVE26, and 4.90 pg/mL (IQR 3.48-6.90) in controls (P 0.001). No significant difference was observed between HSP-SPG11 and HSP-ZFYVE26. In matched pair analysis, pNfL showed inverse correlation with age (ρ = -0.463, P 0.001). Baseline pNfL did not predict future clinical progression. Conclusions: Elevated pNfL reflects early neuroaxonal injury in HSP-SPG11 and HSP-ZFYVE26; however, it could not be used as a surrogate for disease progression. KEYWORDS: axonal degeneration; biomarker; hereditary spastic paralysis; neurofilament light chain; spasticity. Manuscript 2: Plasma Proteomic Signatures in Prototypical Forms of Hereditary Spastic Paraplegia ABSTRACT Background: Hereditary spastic paraplegias are a group of neurogenetic disorders caused by axonopathy of corticospinal tract. To date, no validated fluid biomarkers exist for HSP, limiting clinical trial readiness. This study aims to identify plasma proteomic signatures associated with HSP subtypes and disease severity using a proximity extension assay approach. Methods: We performed a case-control study of 105 genetically confirmed HSP patients (SPG4, n = 42; AP-4-HSP, n = 41; SPG11/15, n = 22) and 45 age- and sex-matched healthy controls. Plasma proteins were measured using the Olink Target 48 Neurodegeneration panel. Differentially abundant proteins were identified using limma linear models adjusted for age, with Benjamini-Hochberg false discovery rate correction. Subtype-specific analyses with phenotype correlation were explored. Linear regression and logistic regression models associating protein levels with clinical scores were performed. Results: We discovered that there were no shared differentially abundant proteins in prototypical forms of HSP vs matched controls. Subtype-level analyses revealed partially overlapping but distinct profiles: AP-4-HSP was characterized by co-downregulation of BACE1 and Aβ40 with elevation of GLRX, HLA-DRA, and FOXO3; SPG4 by nine DEPs (NEFL, GLRX, TP53, EIF2AK2, FOXO3, Aβ40, Aβ42, BMP7, pTau217); and SPG11/15 by marked upregulation of NEFL and HLA-DRA. Some proteins are correlated with phenotypes in each subtypes. Within-subtype severity regressions identified subtype-dependent protein–severity associations. Cross-platform validation confirmed strong concordance between Olink NEFL and Simoa pNfL. Conclusion: Plasma proteomic profiling reveals distinct and diagnostically informative signatures across three prototypical forms of HSP. These findings provide a framework for integrating circulating protein biomarkers into disease monitoring and clinical trial design in HSP. Replication in larger longitudinal cohorts is needed. KEYWORDS: hereditary spastic paraplegia; neurodegeneration; plasma proteomics; proximity extension assay; biomarkerapplication/pdfenBiomarkerHereditary spastic paraplegiaMovement disordersNeurogeneticsProteomicsRare diseaseMedicineNeurosciencesPediatricsThesis or Dissertation2026-05-080000-0002-5346-5026