Esteban C. DellAngelica

The function(s) of the Biogenesis of Lysosome-related Organelles Complex-1 (BLOC-1) during brain development is to date largely unknown. Here, we investigated how its absence alters the trajectory of postnatal brain development using as model the pallid mouse. Most of the defects observed early postnatally in the mutant mice were more prominent in males than in females and in the hippocampus. Male mutant mice, but not females, had smaller brains as compared to sex-matching wild types at postnatal day 1 (P1), this deficit was largely recovered by P14 and P45. An abnormal cytoarchitecture of the pyramidal cell layer of the hippocampus was observed in P1 pallid male, but not female, or juvenile mice (P45), along with severely decreased expression levels of the radial glial marker Glutamate-Aspartate Transporter. Transcriptomic analyses showed that the overall response to the lack of functional BLOC-1 was more pronounced in hippocampi at P1 than at P45 or in the cerebral cortex. These observations suggest that absence of BLOC-1 renders males more susceptible to perinatal brain maldevelopment and although most abnormalities appear to have been resolved in juvenile animals, still permanent defects may be present, resulting in faulty neuronal circuits, and contribute to previously reported cognitive and behavioral phenotypes in adult BLOC-1-deficient mice.

Neuronal ceroid lipofuscinoses (NCLs) are neurodegenerative storage diseases characterized by mental retardation, visual failure, and brain atrophy as well as accumulation of storage material in multiple cell types. The diseases are caused by mutations in the ubiquitously expressed genes, of which six are known. Herein, we report that three NCL disease forms with similar tissue pathology are connected at the molecular level: CLN5 polypeptides directly interact with the CLN2 and CLN3 proteins based on coimmunoprecipitation and in vitro binding assays. Furthermore, disease mutations in CLN5 abolished interaction with CLN2, while not affecting association with CLN3. The molecular characterization of CLN5 revealed that it was synthesized as four precursor forms, due to usage of alternative initiator methionines in translation. All forms were targeted to lysosomes and the longest form, translated from the first potential methionine, was associated with membranes. Interactions between CLN polypeptides were shown to occur with this longest, membrane-bound form of CLN5. Both intracellular targeting and posttranslational glycosylation of the polypeptides carrying human disease mutations were similar to wild-type CLN5.