TGFB1 and juvenile Huntington disease: Amyloid processing, neuroinflammation signaling pathway, axonal guidance signaling, synaptogenesis signaling pathway, amyotrophic lateral sclerosis signaling, neuroprotective role of THOP1 in Alzheimer’s disease, TGF-β signaling, Parkinson’s signaling, synaptic long-term potentiation, dopamine receptor signaling, neuropathic pain signaling in dorsal horn neurons, and Huntington’s disease signaling