 The abnormal (mutated) gene produces a misfolded protein product that deposits within cells of the renal tubules (in a part of the cell called the endoplasmic reticulum).The abnormal protein builds up in the cell and causes it slowly to die, leading to an ultimate loss of the kidney's function manifesting as a disease state.Mucin-1 kidney disease (MKD) is due to a mutation within the "MUC1" gene, which is located on chromosome 1.