BET Inhibitor JQ1 Reduces Cholesterol Accumulation in NPC1 Patient-Derived Neurons

A Human Neuronal Model of Cholesterol Trafficking Disease

Niemann–Pick type C1 disease disrupts the movement of cholesterol out of late endosomes and lysosomes and causes progressive neurological disease. Researchers at Bambino Gesù Children’s Hospital, Roma Tre University and collaborating institutions generated cortical neurons from a patient-derived induced pluripotent stem cell line to test whether inhibition of BET proteins could modify selected cellular features of the disorder.

The patient line carried two copies of NPC1 c.3182T>C, producing the I1061T protein variant. Differentiated patient and healthy-control cultures expressed the neuronal markers TUJ1 and TBR1 and had broadly comparable early morphology. The patient neurons nevertheless accumulated unesterified cholesterol, expressed less NPC1 protein and showed more apoptotic staining. These measurements provided distinct endpoints for evaluating a pharmacological response.

Comparing Cholesterol, Cell Death and Protein Abundance

At differentiation day 30, cultures received the BET inhibitor JQ1 at 0.3, 1 or 3 μM. The investigators followed responses for up to 72 hours, using untreated and vehicle-treated cultures as references. Phase-contrast inspection found no major treatment-associated morphological disruption under the reported conditions.

Filipin staining detected unesterified cholesterol in neuronal cell bodies and processes. The signal was stronger in untreated NPC1 cultures than in controls. JQ1 reduced that signal in a concentration- and time-dependent pattern, with the largest reduction at the later 72-hour observation. Co-staining with a neuronal marker helped locate the cholesterol signal within the neuronal cultures.

The investigators measured apoptotic-cell staining separately using TUNEL. Untreated patient-derived neurons had approximately twice the TUNEL-positive proportion of control neurons. JQ1 lowered the apoptotic-cell measurement, again with the strongest response after 72 hours. The staining result adds a cell-survival-related observation to the change in cholesterol accumulation; neither endpoint was inferred from the appearance of the cultures alone.

Western blotting provided a third comparison. NPC1 protein abundance increased after JQ1 exposure in both control and patient-derived neurons. The response was strongest at the highest tested concentration and longest treatment period. The protein and imaging experiments therefore showed related changes across cholesterol handling, apoptosis and NPC1 abundance.

What the Drug Response Reveals

BET proteins recognize acetylated chromatin and regulate transcription. The preprint investigates their pharmacological inhibition as a way to modify disease-associated neuronal phenotypes, building on earlier non-neuronal work discussed by the authors. The human neurons make it possible to test that idea in a cell type directly relevant to the neurological component of NPC1 disease.

The measured outcomes do not identify a complete molecular pathway connecting BET inhibition with cholesterol export. The authors discuss possible contributions from lysosomal activity, autophagy and protein handling, but the experiment does not distinguish those explanations. The increase in NPC1 protein also leaves open whether other, NPC1-independent effects contribute to the response.

The study uses one patient genetic background and a healthy-control comparison, with selected assays reporting three repeats. Those repeats do not provide evidence of consistency across three patients. Longer exposure, additional variants and more complex neural cultures would address aspects of the response outside this model.

The contribution is a defined patient-derived screening setting with three separately measured disease-associated outcomes. It offers a basis for studying BET-dependent pathways and comparing candidate interventions, while the short-term neuronal findings and preprint status remain part of its experimental scope.