Homozygous Cb Cln3Δex7/8 cells were first examined for JNCL-like characteristics. Homozygous Cln3Δex7/8 knock-in mice express multiple Cln3 mRNA splice variants and mutant battenin protein that is detectable by batp1 antibody recognizing C-terminal epitopes [12]. To assess this molecular phenotype in CbCln3Δex7/8 cells, RT-PCR and anti-battenin (batp1) immunostaining were performed. As shown in Figure 2, Cln3 mRNA isoforms in wild-type and homozygous cells were similar to those observed in total RNA isolated from wild-type or homozygous Cln3Δex7/8 knock-in brain, respectively (Fig. 2). In addition, batp1 immunostaining detected mutant battenin product in homozygous CbCln3Δex7/8 cells, in a similar albeit reduced cytoplasmic, vesicular staining pattern as that seen in wild-type cells. Batp1 signal exhibited some overlap with the lysosomal marker, Lamp1, but had more significant overlap with early endosome antigen 1 (EEA1) and the late endosomal marker, Rab7 (Fig. 3). Only limited overlap was observed with recycling endosomes, as determined by transferrin receptor co-staining (data not shown). Intriguingly, Lamp1 and EEA1 immunocytochemical distribution were altered in homozygous CbCln3Δex7/8 cells, with less perinuclear clustering than in wild-type cells, and Rab7 staining was frequently less intense in homozygous CbCln3Δex7/8 cells (Fig. 3). Heterozygous CbCln3Δex7/8 cells contained a mixture of Cln3 mRNA products from both the wild-type allele and the mutant allele, and batp1 signal was similar to that seen in wild-type cells (data not shown).