👤 Tomasz Gallina

Glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) are proteins essential for neuronal survival and implicated in Parkinson's disease (PD) pathophysiology. Although reduced levels of these neurotrophins have been observed in PD, their relationship with disease progression remains unclear. We conducted a systematic review by independently searching four databases using predefined keywords: Parkinson AND (GDNF OR BDNF OR neurotroph) AND (serum OR blood OR cerebrospinal fluid). After screening 2132 records, 35 studies qualified for inclusion. Changes in neurotrophic factors' levels were evaluated in relation to disease severity and duration. Many studies reported a decline in BDNF levels associated with more severe motor symptoms. Some studies noted increased BDNF levels in advanced PD. This pattern may be affected by levodopa treatment, suggesting that elevated BDNF levels in advanced PD could reflect a treatment-related effect rather than disease progression itself. Reduced levels of both GDNF and BDNF were linked to cognitive decline, with BDNF also decreased in PD patients with depression. Serum BDNF levels were associated with motor severity and neuropsychiatric symptoms. BDNF levels in PD may increase with longer disease duration, likely due to levodopa treatment effects. However, lower BDNF levels are seen in cognitive decline and depression, frequent non-motor symptoms of PD. Further research is required to clarify BDNF dynamics and to determine GDNF's role in motor progression and cognitive decline. Show less

The healthy human brain is a mosaic of varied genomes. Long interspersed element-1 (LINE-1 or L1) retrotransposition is known to create mosaicism by inserting L1 sequences into new locations of somatic cell genomes. Using a machine learning-based, single-cell sequencing approach, we discovered that somatic L1-associated variants (SLAVs) are composed of two classes: L1 retrotransposition insertions and retrotransposition-independent L1-associated variants. We demonstrate that a subset of SLAVs comprises somatic deletions generated by L1 endonuclease cutting activity. Retrotransposition-independent rearrangements in inherited L1s resulted in the deletion of proximal genomic regions. These rearrangements were resolved by microhomology-mediated repair, which suggests that L1-associated genomic regions are hotspots for somatic copy number variants in the brain and therefore a heritable genetic contributor to somatic mosaicism. We demonstrate that SLAVs are present in crucial neural genes, such as DLG2 (also called PSD93), and affect 44-63% of cells of the cells in the healthy brain. Show less