Juvenile neuronal ceroid lipofuscinosis, also known as juvenile Batten disease, is caused by mutations in the CLN3 gene and represents a major form of juvenile dementia. Children with the condition typically develop vision loss in early childhood, followed by seizures, motor decline, and progressive cognitive deterioration, usually dying in their late twenties or thirties. The disease belongs to a family of lysosomal storage disorders in which cellular waste-processing machinery fails, leading to the accumulation of fatty waste materials called ceroid lipofuscin inside cells. Despite decades of research into the underlying genetics, effective therapies that slow the relentless neurodegeneration remain painfully out of reach.

The Korean team, led by Hyungkuen Kim, Eunmi Hwang, and Sung-Jo Kim, focused their investigation on parthanatos, a distinctive form of programmed cell death that has been extensively studied in Alzheimer’s disease but never before systematically characterized in JNCL. Parthanatos takes its name from poly(ADP-ribose), or PAR, a polymer produced by the enzyme PARP1. When cells experience excessive DNA damage, PARP1 becomes hyperactivated and floods the nucleus with PAR chains. These polymers eventually trigger the release of apoptosis-inducing factor from mitochondria, which migrates to the nucleus and orchestrates large-scale DNA fragmentation, killing the cell in a way that is distinct from classical apoptosis.

Using patient-derived lymphoblasts, immortalized white blood cells generated from JNCL patients, the researchers employed quantitative immunofluorescence microscopy to compare the disease cells with healthy controls. The results were striking. JNCL cells accumulated significantly higher levels of 8-oxoguanine, a pre-mutagenic DNA lesion produced when reactive oxygen species attack guanine bases, as well as elevated levels of PAR, the molecular signature of parthanatos. The accumulation of 8-oxoguanine is particularly insidious because it impairs DNA repair pathways, creating a vicious cycle in which oxidative damage begets repair failure, which begets further PARP1 overactivation and ultimately cell death.

The mechanistic logic connecting these observations to calcium is central to the study. JNCL is known to exhibit elevated intracellular calcium levels, a disturbance that has been documented in previous work on CLN3-deficient cells. Calcium overload is a well-established activator of PARP1, and studies in cardiomyocytes and other cell types have shown that calcium influx can directly stimulate PAR polymer production. In JNCL, this calcium-PARP1 axis appeared to be running unchecked, pushing vulnerable cells toward the parthanatos threshold. The researchers reasoned that if excess calcium was fueling the PARP1 fire, then dampening calcium entry might extinguish it.

Enter diltiazem. This L-type calcium channel blocker, which has been on pharmacy shelves since the 1970s, works by blocking voltage-gated calcium channels in heart and vascular smooth muscle. When the team treated JNCL patient-derived lymphoblasts with diltiazem, PAR accumulation dropped markedly. Critically, the protective effect persisted even when the cells were simultaneously exposed to a calcium ionophore, a chemical that forcibly floods cells with calcium. This suggested that diltiazem was not merely plugging calcium channels at the membrane but was intervening in the downstream signaling cascade that translates calcium excess into PARP1 activation, suppressing the expression of PARP1 itself and thereby limiting the raw material for parthanatos.

The drug’s benefits did not stop there. Diltiazem also reduced the accumulation of 8-oxoguanine in the JNCL cells, though intriguingly, this effect appeared to be largely independent of its calcium-blocking activity. Subcellular fractionation followed by immunoblotting, a technique that separates cellular compartments and identifies which proteins reside where, revealed that diltiazem enhanced the nuclear recruitment of OGG1, the primary enzyme responsible for excising 8-oxoguanine from DNA, along with its partner proteins. In other words, the drug was not just reducing the damage signal but was actively bolstering the cell’s repair crew, delivering the fix-it enzymes to the nucleus where the oxidative lesions accumulate.

To confirm that OGG1 was genuinely central to the drug’s protective mechanism, the researchers performed knockdown experiments, silencing the OGG1 gene in the treated cells. The results were unambiguous: when OGG1 was removed, diltiazem’s protective effects vanished entirely. This dependency establishes a dual role for the drug, acting simultaneously on calcium signaling to suppress PARP1 expression and on the OGG1-dependent base excision repair pathway to clear oxidative DNA damage. The finding also underscores a broader biological principle that has emerged from studies in Alzheimer’s disease and aging: OGG1-initiated repair is a double-edged sword, essential for genome maintenance but capable of exacerbating parthanatos when repair intermediates overstimulate PARP1.

The therapeutic implications are considerable. Diltiazem is an approved, well-characterized medication with decades of clinical safety data, which means that repurposing it for JNCL could potentially bypass some of the lengthy development timelines that plague novel drug candidates. Previous studies have already hinted at the drug’s relevance to neurodegeneration, with earlier work showing that L-type calcium channel blockers significantly lower intracellular calcium in CLN3-deficient neuroblastoma cells, and animal research demonstrating protective effects of diltiazem in chemically induced dementia models in mice. The new study adds a specific molecular mechanism, parthanatos suppression via PARP1 and OGG1 modulation, to this growing body of evidence.

Significant caveats remain before patients can benefit. The current findings derive from patient-derived lymphoblasts, which are accessible but imperfect proxies for the neurons that actually die in JNCL, and the researchers note that their data identify parthanatos as a novel therapeutic target rather than a validated clinical intervention. Whether diltiazem can cross the blood-brain barrier at sufficient concentrations, whether it will slow neurodegeneration in living organisms, and what dosing regimens would be appropriate for children all require further study. Nevertheless, by pinpointing PAR accumulation as a hallmark of JNCL pathology and demonstrating that an existing cardiovascular drug can interrupt this deadly cascade at two distinct points, the Hoseo University team has given the Batten disease research community something it has long needed: a concrete, pharmacologically tractable target in a disease where hope has been in short supply.

Subject of Research: Parthanatos and DNA repair dysfunction in juvenile neuronal ceroid lipofuscinosis and its modulation by the calcium channel blocker diltiazem

Article Title: The calcium channel blocker diltiazem ameliorates parthanatos in juvenile neuronal ceroid lipofuscinosis

Article References: Kim, H., Hwang, E., & Kim, S.-J. (2026). The calcium channel blocker diltiazem ameliorates parthanatos in juvenile neuronal ceroid lipofuscinosis. Journal of Molecular Medicine, 104(1), Article 118. https://doi.org/10.1007/s00109-026-02726-1

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02726-1

Keywords: juvenile neuronal ceroid lipofuscinosis, Batten disease, CLN3, parthanatos, PARP1, diltiazem, 8-oxoguanine, OGG1, calcium signaling, DNA repair, drug repurposing, neurodegeneration

CLN3 Batten disease, formally known as juvenile neuronal ceroid lipofuscinosis, is the most common form of a family of inherited lysosomal storage disorders and affects roughly one in 100,000 live births worldwide. It is caused by mutations in the CLN3 gene, with approximately 85 percent of patients carrying the same genetic defect: a deletion of about one kilobase of DNA that removes exons 7 and 8. Children with the disease typically develop normally until between the ages of four and twelve, when vision loss begins. That vision loss progresses to blindness, followed by cognitive decline, motor deterioration, seizures and brain atrophy, culminating in premature death between the ages of 15 and 30. At the cellular level, the disease is marked by the buildup of autofluorescent storage material inside cells, whose major protein component is subunit C of the mitochondrial ATP synthase enzyme, a molecular fingerprint of failing cellular housekeeping.

The CLN3 protein itself is a transmembrane protein that resides primarily in endosomes and lysosomes, the cell’s recycling and degradation compartments, and although it has been linked to cellular homeostasis and neuronal survival, its precise function has remained elusive. For decades, research into the disease has been dominated by a neuron-centric view, focused on the nerve cells that die as the disease progresses. But an accumulating body of evidence has challenged that framing. Studies in mouse models have shown that glial activation precedes the loss of neurons, and that the locations where glial cells become activated accurately predict where neurons will subsequently die. Even more strikingly, laboratory co-culture experiments have demonstrated that glial cells lacking functional CLN3 are toxic to both healthy and mutant neurons, while adding healthy glial cells to mutant neurons largely rescues their survival. In other words, the supportive cells of the brain may be active participants in the neurodegeneration rather than innocent bystanders.

To interrogate the role of astrocytes specifically, the team took skin biopsy fibroblasts from a Norwegian CLN3 patient homozygous for the canonical 1 kb deletion and reprogrammed them into induced pluripotent stem cells using a Sendai virus-based reprogramming kit. Those pluripotent cells were then guided through a carefully choreographed differentiation pipeline: first into neural stem cells using small molecule inhibitors including CHIR99021 and SB431542, then into glial progenitor cells nourished with FGF-2 and EGF, and finally into mature astrocytes driven by leukemia inhibitory factor, EGF and ciliary neurotrophic factor over a maturation period of four weeks. The resulting cells expressed a suite of astrocyte markers — GFAP, S100β, ALDH1L1 and the glutamate transporter EAAT1/GLAST — at levels confirming successful and pure differentiation, while neuronal and oligodendrocyte markers remained minimal. Quantitative PCR confirmed the patient cells carried two mutated CLN3 alleles, and targeted mass spectrometry revealed that the truncated mutant CLN3 protein was not detectable at all in patient-derived cells, confirming that the deletion effectively abolishes CLN3 protein production.

With a validated cellular model in hand, the researchers performed an integrated analysis of both the transcriptome, using whole-transcriptome RNA sequencing, and the proteome, using label-free quantitative mass spectrometry on a timsTOF Pro 2 instrument in PASEF mode. The scale of the effort was considerable: multiple clones from two healthy control individuals and from the patient, each differentiated in triplicate, generated thousands of differentially expressed genes and proteins that could be compared across the developmental trajectory from stem cell to astrocyte. Gene set enrichment analysis of these datasets revealed the study’s central surprise. While conventional wisdom held that CLN3 loss should primarily disrupt lysosomal function, the young astrocytes showed only subtle lysosomal alterations. The lysosomal marker LAMP1 was present at similar levels in patient and control cells, and processes related to lysosomal protein catabolism were enriched to a similar degree in both genotypes during differentiation.

The mitochondrial story was entirely different, and it unfolded in two distinct phases. In the patient’s induced pluripotent stem cells, gene expression data showed underrepresentation of the mitochondrial respiratory chain complex I, accompanied by signatures of negative regulation of TORC1, a master growth and metabolism regulator — a combination previously observed in yeast models lacking the CLN3 homologue. But when the cells matured into astrocytes, the pattern inverted dramatically: proteins belonging to respiratory chain complexes I and IV, including NADH dehydrogenase components and the mitochondrial respirasome, were significantly overrepresented in the patient-derived cells. This contrasts sharply with the downregulation of these same complexes typically observed in CLN3-deficient neurons. Mitochondrial DNA copy number measurements confirmed that the patient astrocytes did not simply contain more mitochondria; instead, they appeared to pack more respiratory supercomplex proteins into their inner mitochondrial membranes, which themselves showed signs of disorganized structure, with genes governing mitochondrial fusion and inner membrane organization downregulated.

This mitochondrial upheaval rippled into lipid metabolism. The team found elevated levels of ELOVL1, the enzyme responsible for elongating very-long-chain saturated fatty acids, suggesting a shift toward production of longer saturated lipid species — a potentially dangerous change, given that elevated ELOVL1 activity has been linked to neurotoxicity in reactive astrocytes through saturated lipid production. At the same time, ELOVL5 levels dropped slightly, implying reduced synthesis of polyunsaturated fatty acids that maintain membrane fluidity. Fatty acid synthesis enzymes such as ACACA and FASN were downregulated, while the β-oxidation enzymes ACOX1 and ACADVL were upregulated, pointing to a metabolic pivot away from lipid construction and toward fatty acid burning. Notably, ACADS, which handles short-chain fatty acid oxidation and is normally upregulated during healthy astrocyte differentiation, failed to rise in the patient cells, suggesting the metabolic adaptation itself was broken. Because astrocytes account for the oxidation of free fatty acids that represents roughly 20 percent of the brain’s total energy expenditure, these defects strike at the heart of cerebral energy economics.

The dysregulated fat metabolism and aberrant respiratory chain activity came with a third signature: an intensified oxidative stress response. Levels of glutathione synthetase, which produces the cell’s principal antioxidant, were substantially increased in patient cells, as were the glutathione-conjugating enzymes GSTK1 and GSTZ1, along with catalase, NQO1 and the mitochondrial superoxide dismutase SOD2. The researchers interpret this as a compensatory counterattack against elevated reactive oxygen species generated by runaway peroxisomal β-oxidation — ACOX1 activity produces hydrogen peroxide as a byproduct — combined with impaired detoxification of partially oxidized fatty acid intermediates. Prior studies have documented increased oxidative stress in CLN3 lymphoblasts and fibroblasts, and work in fruit flies has shown that CLN3 loss increases vulnerability to oxidative damage while CLN3 overexpression confers resistance, lending independent support to the connection the Norwegian team has now drawn in human astrocytes.

Beyond metabolism, the analysis surfaced evidence of deeper epigenetic rewiring. A multifactorial statistical analysis disentangling the effects of genotype and cell type identified 363 genes whose expression patterns diverge specifically in the patient during astrocyte differentiation, with significant overrepresentation of genes involved in histone H3 and H4 lysine methylation. In patient cells, chromatin-related terms associated with open, transcriptionally active states — such as binding of acetylated histones — were underrepresented, while repressive machinery, including polycomb group complexes and heterochromatin-associated terms, was upregulated. The authors suggest this reflects a global shift toward a more compacted, transcriptionally restrictive chromatin landscape, potentially locking developing astrocytes into aberrant functional states. Additional dysregulation was seen in extracellular matrix genes involved in remodeling, synaptic support and neuroinflammatory signaling, hinting that mutant astrocytes undergo a reactive transformation that could compromise their support of neurons even before overt cell death begins.

The study is not without limitations, which the authors acknowledge candidly. All patient-derived material came from a single individual, so some observed phenotypes could reflect that patient’s unique genetic background rather than CLN3 loss alone, and extending the work to additional patient lines or gene-corrected isogenic controls would strengthen the conclusions. Nevertheless, the findings carry significant therapeutic implications. If mitochondrial dysfunction in astrocytes indeed precedes the lysosomal breakdown that defines advanced disease, then interventions aimed at restoring mitochondrial health — improving respiration, normalizing lipid metabolism, or bolstering antioxidant capacity — could preserve astrocyte function, and through it neuronal survival, potentially delaying disease progression. The team proposes that future work in more complex human models, such as brain organoids incorporating multiple cell types, should be used to establish the precise temporal relationship between astrocytic mitochondrial failure and neuronal death. Because mitochondrial dysfunction is a common thread linking Alzheimer’s, Parkinson’s, Huntington’s and ALS, insights from this rare pediatric disease may ultimately illuminate mechanisms of far more common neurodegenerative conditions, including those associated with aging, underscoring once again that understanding rare diseases can pay dividends well beyond the patient communities they directly affect.