Phosphorylated neurofilament antigen redistribution in intercostal nerve subsequent to retrograde axonal transport of diphtheria toxin

Impaired oxysterol-liver X receptor signaling underlies aberrant cortical neurogenesis in a stem cell model of neurodevelopmental disorder

The mechanisms by which genomic risks contribute to the onset of neuropsychiatric conditions remain a key challenge and a prerequisite for successful development of effective therapies. 15q11.2 copy number variation (CNV) containing the CYFIP1 gene is associated with autism and schizophrenia. Using stem cell models, we show that 15q11.2 deletion (15q11.2del) and CYFIP1 loss of function (CYFIP1-LoF) lead to premature neuronal differentiation, while CYFIP1 gain of function (CYFIP1-GoF) favors neural progenitor maintenance. CYFIP1 dosage changes led to dysregulated cholesterol metabolism and altered levels of 24S,25-epoxycholesterol, which can mimic the 15q11.2del and CYFIP1-LoF phenotypes by promoting cortical neuronal differentiation and can restore the impaired neuronal differentiation of CYFIP1-GoF neural progenitors. Moreover, the neurogenic activity of 24S,25-epoxycholesterol is lost following genetic deletion of liver X receptor (LXRβ), while compound deletion of LXRβ in CYFIP1-/- background rescued their premature neurogenesis. This work delineates LXR-mediated oxysterol regulation of neurogenesis as a pathological mechanism in neural cells carrying 15q11.2 CNV and provides a potential target for therapeutic strategies for associated disorders.

Hyperphosphorylation and accumulation of neurofilament proteins in Alzheimer disease brain and in okadaic acid-treated SY5Y cells

We investigated the role of neurofilament (NF) proteins in Alzheimer disease (AD) neurofibrillary degeneration. The levels and degree of phosphorylation of NF proteins in AD neocortex were determined by Western blots developed with a panel of phosphorylation-dependent NF antibodies. Levels of all three NF subunits and the degree of phosphorylation of NF-H and NF-M were significantly increased in AD as compared to Huntington disease brains used as control tissue. The increase in the levels of NF-H and NF-M was 1.7- and 1.5-fold (P<0.01) as determined by monoclonal antibody SMI33, and was 1.6-fold (P<0.01) in NF-L using antibody NR4. The phosphorylation of NF-H and NF-M in AD was increased respectively at the SMI31 epitope by 1.6- and 1.9-fold (P<0.05) and at the SMI33 epitope by 2.7- and 1.3-fold (P<0.01 and P<0.05). Essentially similar effects were observed in SY5Y human neuroblastoma cells when treated with okadaic acid, an inhibitor of protein phosphatase (PP)-2A and -1. This is the first biochemical evidence which unambiguously demonstrates the hyperphosphorylation and the accumulation of NF subunits in AD brain, and shows that the inhibition of PP-2A/PP-1 activities can lead to the hyperphosphorylation of NF-H and NF-M subunits.