NEU1 and sialidosis: Sialidosis-causing mutations in the NEU1 gene, located on chromosome 6p21.3, eliminate the activity or stability of lysosomal sialidase (also known as neuraminidase 1; EC 3.2.1.18), catalyzing the hydrolysis of terminal sialic acid molecules (N-acetylneuraminic acid or NANA) linked to the saccharide chains of glycolipids, glycoproteins, and oligo- and polysaccharides [1,2,3,4].