Lysosomal storage disease associated with a CNP sequence variant in Dalmatian dogs

• Published in: Gene 2022-07, Vol.830, p.146513-146513, Article 146513
• Main Authors: Bullock, Garrett, Johnson, Gary S., Mhlanga-Mutangadura, Tendai, Petesch, Scott C., Thompson, Samantha, Goebbels, Sandra, Katz, Martin L.
• Format: Article
• Language: English
• Subjects: alleles; antigens; anxiety; cerebellum; cerebral cortex; cognitive disorders; Dalmatian; defecation; DNA; enzymes; frameshift mutation; heterozygosity; histopathology; homozygosity; hypersensitivity; immunohistochemistry; loss-of-function mutation; myocardium; nerve tissue; neurons; purebreds; sleep deprivation; urination; vision disorders
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2022.146513

•A progressive hereditary neurodegenerative disorder was characterized in Dalmatian dogs.•The disease was characterized by widespread accumulation of autofluorescent lysosomal storage bodies.•Like a similar human disorder, the disease was associated with a mutation in CNP.•Based on the disease phenotype, the disorder can be classified as a form of neuronal ceroid lipofuscinosis. A progressive neurological disorder was identified in purebred Dalmatian dogs. The disease is characterized by anxiety, pacing and circling, hypersensitivity, cognitive decline, sleep disturbance, loss of coordination, loss of control over urination and defecation, and visual impairment. Neurological signs first became apparent when the dogs were approximately 18 months of age and progressed slowly. Two affected littermates were euthanized at approximately 7 years, 5 months and 8 years, 2 months of age due to the severity of neurological impairment. The mother of the affected dogs and four other relatives exhibited milder, later-onset neurological signs. Pronounced accumulations of autofluorescent intracellular inclusions were found in cerebral cortex, cerebellum, optic nerve, and cardiac muscle of the affected dogs. These inclusions co-localized with immunolabeling of the lysosomal marker protein LAMP2 and bound antibodies to mitochondrial ATPase subunit c, indicating that the dogs suffered from a lysosomal storage disease with similarities to the neuronal ceroid lipofuscinoses. Ultrastructural analysis indicated that the storage bodies were surrounded by a single-layer membrane, but the storage granules were distinct from those reported for other lysosomal storage diseases. Whole genome sequences, generated with DNA from the two euthanized Dalmatians, both contained a rare, homozygous single-base deletion and reading-frame shift in CNP which encodes the enzyme CNPase (EC 3.1.4.37). The late-onset disease was exhibited by five of seven related Dalmatians that were heterozygous for the deletion allele and over 8 years of age, whereas none of 16 age-matched reference-allele homozygotes developed neurologic signs. No CNPase antigen could be detected with immunohistochemical labeling in tissues from the dogs with the earlier-onset disorder. Similar to the later-onset Dalmatians, autofluorescent storage granules were apparent in brain and cardiac tissue from transgenic mice that were nullizygous for Cnp. Based on the clinical signs, the histopathological, immunohistochemical, ultrastru