Anoctamins, also known as TMEM16, is a family of ten proteins involved in a variety of functions including phospholipid scrambling, ion transport and the regulation of other membrane proteins. ANO1 (Anoctamin-1), ANO2 and ANO5 function as Ca²⁺-activated Cl^- channels (CaCCs) and play an important role in calcium dependent chloride secretion. All members of the Anoctamin family present high structural homology and consist of eight transmembrane domains and cytosolic N- and C-termini¹.

The ANO5 gene is widely distributed and expressed in bone, skeletal muscle, cardiac muscle, brain, lung and kidney and also in the mucosal layer of the GI tract and the skeletal muscle layer of the esophagus of mice².

In phylogenetic analysis ANO5 was found to be a close relative of ANO6. ANO6 has an association with phospholipid scramblase activity. Under both physiological and pathological conditions scramblase dissipates the normal asymmetry of the cell membrane by catalyzing the rapid externalization of phospholipids on the cell membrane and thus promoting apoptosis³.

Recessive mutations in the ANO5 gene were found to be linked to limb-girdle muscular dystrophies type 2L (LGMD2L) and non-dysferlin Miyoshi myopathy⁴. LGMD2L is characterized by proximal weakness, asymmetric quadriceps femoris and atrophy of the biceps brachii muscle⁵.

Mutations in the gene are also linked to the Gnathodiaphyseal dysplasia disease, an unusual generalized autosomal dominant disease. Patients with this syndrome show sclerosis of tubular bones, lesions of jawbones, an increased sensitivity for jaw infection and osteomyeletis and fragile bones⁶.