Molecular characterization of a new member of the protein 4.1 family (brain 4.1) in rat brain.

In addition to the well-known erythroid 4.1 gene, two human genes (KIAA0338 and 4.1G) have recently been identified as members of the protein 4.1 family of genes. We compared the expression levels of these three genes and found that the KIAA0338 gene was predominantly expressed in human brain. To further characterize this novel protein 4.1, called brain 4.1, we isolated rat brain 4.1 cDNA and analyzed its gene products in rat brain. The results indicated that the mRNA and protein products of the brain 4.1 gene were more abundant in brain compared to any other tissues examined. The brain 4.1 mRNA appeared as multiple bands with estimated sizes of 3.9 kb, 6.2 kb and 8.7 kb on RNA blotting analysis, and was found to consist of various alternative forms as reported previously for the erythroid 4. 1 gene. As for the brain 4.1 gene product, many isoforms discernible by immunoblotting analysis were also observed depending on the tissue type and the brain region. The existence of multiple forms of the brain 4.1 implies that it has multiple and diverse functions like the erythroid 4.1 gene product.