MAP1S (also known as C19ORF5 or VCY2IP1) is a novel member of the microtubule-associated protein 1 family and a homologue of the exclusively neuronal distributed microtubule-associated protein 1A and 1B (MAP1A/B). In contrast to MAP1A and MAP1B, MAP1S is expressed in a wide range of tissues in addition to neurons. MAP1S is synthesized as a precursor protein that is partially cleaved into heavy and light chains in a tissue-specific manner. In addition, a short chain isoform may be induced under prolonged mitotic arrest or inhibiton of the 26S proteasome. Recently it has been reported that the short chain isoform associates with mitochondria in addition to microtubules and causes irreversible aggregation of dysfunctional mitochondria resulting in cell death. Western blot analysis in human brain using this antibody detected two main bands between 100-130 kDa corresponding to heavy and light chains of MAP1S.