What researchers reported
A Nature study describes a previously unrecognized route by which cells can produce bis(monoacylglycero)phosphate (BMP), a phospholipid associated with late endosomes and lysosomes. The researchers report that CLN8—a protein linked to certain forms of Batten disease—catalyzes an early step in this pathway.
Batten disease is a group of inherited neurodegenerative disorders. The publisher text notes that CLN8-associated disease involves the buildup of autofluorescent lipid-containing material, often called ceroid lipofuscin, in lysosomes. Lysosomes are cell structures that help break down and process cellular material.
A different starting point for phospholipid synthesis
Established models of glycerophospholipid production generally begin with glycerol-3-phosphate and proceed through phosphatidic acid. In this study, researchers describe an alternative pathway that starts with glycerophosphoglycerol (GPG), a glycerophosphodiester produced when certain phospholipids are broken down.
Using labeled tracer molecules and laboratory assays, the team found that cell and tissue samples could add a fatty-acid-containing group from acyl-CoA to GPG. This reaction produced lysophosphatidylglycerol (LPG). Activity was detected in human cell-line samples and mouse tissues, with the highest labeled LPG formation among the tested mouse tissues reported in brain lysates.
The authors identify CLN8 as the enzyme responsible for this acylation reaction. CLN8 is associated with the endoplasmic reticulum, another cell compartment involved in protein and lipid processing.
Link to BMP and lysosomal lipid balance
The tracer experiments indicated that LPG made through the CLN8-dependent route was selectively converted into BMP. According to the study, it was not converted into phosphatidylglycerol or cardiolipin, two other phospholipids.
BMP is found in internal membranes of late endosomes and lysosomes. The publisher text describes it as important for lysosomal lipid homeostasis, including the formation of internal membranes and the activity of proteins involved in lipid breakdown and transport.
In CLN8-knockout cells and mice, the researchers report that GPG could not be used to make BMP. These models showed BMP deficiency along with excess phospholipid accumulation in lysosomes. The authors propose that insufficient BMP may contribute to lysosomal storage in CLN8 deficiency and potentially in other lysosomal storage disorders.
Why this may matter
The work offers a biochemical explanation for one way CLN8 loss could affect lysosomal function: reduced production of BMP from GPG. It also expands understanding of how cells recycle lipid breakdown products rather than relying only on the better-known phospholipid synthesis routes.
For the inherited retinal disease and vision-loss community, the finding is relevant because Batten diseases can involve progressive neurological impairment and may affect vision. However, this paper reports mechanistic research rather than a clinical intervention.
Important limitations
The evidence described by the publisher comes from laboratory experiments, including human cell lines, cell and tissue lysates, and mouse models. The supplied material does not describe studies in people with CLN8-related Batten disease, clinical testing, a treatment, or evidence that changing BMP levels improves symptoms or vision.
The researchers’ suggestion that BMP deficiency could be causal in lysosomal storage is a scientific interpretation of their findings, not an independently established explanation for all forms of Batten disease or lysosomal storage disorders. Further research will be needed to clarify how this pathway operates in human disease and whether it can be safely targeted.
Publisher source
Nature: “Batten disease protein CLN8 enables a non-canonical phospholipid synthesis pathway”