Type A and Type B<unk>  are caused by mutations in two sets of different genes. Both gene sets are responsible for producing proteins and enzymes that are heavily involved in protein degradation and excretion in the cell – specifically, the nerve cell. Type A Mutations to the CLN6 and PPT1 genes result in<unk>  Type A. CLN6 produces proteins that facilitate fat transport throughout a cell, as well as excretion out of the cell. The PPT1 gene codes for the enzyme palmotoyl-protein thioesterase-1. This enzyme is responsible for removing the fatty-acid side chains off of proteins that have been translocated into the lysozyme. By removing the surrounding fats, palmotoyl-protein thioesterase-1 creates easier access for other enzymes to break down the rest of the protein. Fatty substance build up in the brain is a consequence of the mutated genes. The fats and proteins that build up are called lipopigments. Eventually the buildup of lipopigments results in death of the neuron cells, giving way to the phenotypic symptoms. Type A is an autosomal recessive disease, indicating that it is inherited from the parents. Each parent must carry one copy of the mutation; however, the recessive designation indicates that with only one copy, the parents are not affected, and do not show any symptoms. Type B<unk>  Type B is caused by mutations to the DNAJC5 and CTSF genes. This form of<unk>  is autosomal dominant, meaning that only one copy of each mutated gene is enough for the disease to manifest. When there is a mutation in the DNAJC5 gene, it affects the production of a cysteine string protein (CSP) that is coded within DNAJC5. CSP aids in transmitting signals through the nerves found in the brain. When the CTSF gene is mutated, it cannot produce Cathepsin F an enzyme that cuts proteins in the lysozyme. By cutting proteins, Cathepsin F can modify the function of the proteins as well as help break them down. Similar to Type A, when both DNAJC5 and CTSF are non-functional, it results in the incomplete breakdown of proteins. Once again, lipopigments build up and brain function is decreased as the neuron cells die.
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