Partial structure and mapping of the human myelin P₂ protein gene

The myelin P₂ protein, a 14,800-Da cytosolic protein found primarily in peripheral nerves, belongs to a family of fatty acid binding proteins. Although it is similar in amino acid sequence and tertiary structure to fatty acid binding proteins found in the liver, adipocytes, and intestine, its expression is limited to the nervous system. It is detected only in myelin- producing cells of the central and peripheral nervous systems, i.e., the oligodendrocytes and Schwann cells, respectively. As part of a program to understand the regulation of expression of this gene, to determine its function in myelin-producing cells, and to study its role in peripheral nerve disease, we have isolated and characterized overlapping human genomic clones encoding the P₂ protein. We report here on the partial structure of this gene, and on its localization within the genome. By using a panel of human- hamster somatic cell hybrids and by in situ hybridization, we have mapped the human P₂ gene to segment q21 on the long arm of chromosome 8. This result identifies the myelin P₂ gene as a candidate gene for autosomal recessive Charcot-Marie-Tooth disease type 4A.