Fetal-Onset Neuroaxonal Dystrophy

Fetal-onset neuroaxonal dystrophy in dogs is a rare inherited neurological disease that occurs in puppies shortly after birth and results in their death. It is thought to be caused by a mutation in the MFN2 gene that plays an important role in mitochondrial fusion.

Symptoms

Puppies with fetal-onset neuroaxonal dystrophy have abnormal neurological development and present with severe symptoms at birth leading to death such as respiratory failure, joint stiffness, scoliosis, pulmonary and cerebellar hypoplasia and swollen axons in the motor nervous system.

Disease Management

Currently, there is no cure for the disease. It is important for breeders to perform genetic testing on parents prior to breeding to identify if they carry the MFN2 gene mutation and prevent it from being passed on to their offspring.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

MFN2 is a gene that codes for the protein mitofusin 2, which is a protein involved in mitochondrial fusion. Mitochondria are organelles that are responsible for energy production in the cell, and mitochondrial fusion is an important process for maintaining the health and proper function of mitochondria. Mutations in the MFN2 gene can cause various mitochondrial diseases, including Charcot-Marie-Tooth type disease, an inherited disease of the peripheral nervous system characterized by degeneration of motor and sensory nerves. The causative variant of fetal-onset neuroaxonal dystrophy in dogs is a 3-bp deletion in exon 14 of MFN2 that was identified by Fyfe et al. in 2011. The c.1617_1619del deletion is thought to lead to the loss of a glutamate residue at position 539 of the protein that is highly conserved in vertebrates and invertebrates.

Most affected breeds

Schnauzer-Beagle cros

Bibliography

Fyfe JC, Al-Tamimi RA, Liu J,et al. A novel mitofusin 2 mutation causes canine fetal-onset neuroaxonal dystrophy. Neurogenetics. 2011 Aug;12(3):223-32.