Molecular cloning of a novel human gene on chromosome 4p11 by immunoscreening of an ovarian carcinoma cDNA library.

In our efforts to identify immunoreactive antigens in ovarian cancer, we used the method of immunoscreening of an ovarian carcinoma cDNA expression library with ascites fluid from ovarian cancer patients. Among many positive clones, one was found to contain partial sequence of a novel gene. By searching expressed sequence tags (ESTs) and human genome project databases as well as by screening other cDNA libraries and by RT-PCR strategies, we were able to obtain the full-length cDNA sequence (1.4 kb) and establish the genomic organization of this new gene. We also identified two alternatively spliced forms, encoding for slightly different proteins. The longer form (1.4 kb) is predicted to encode for a 27.6 kDa protein of 245 amino acids. The shorter form (1.3 kb) encodes for a truncated protein of 20.7 kDa and 208 amino acids. These proteins are not significantly homologous to any known protein in the GenBank database. This gene is composed of nine exons and eight introns. By fluorescence in situ hybridization (FISH), it was mapped to chromosome 4p11. This gene is highly expressed in many tissues, including testis, brain, placenta, ovary, prostate, and mammary gland. The high level expression of the shorter form is restricted to the central nervous system, including brain, cerebellum, and spinal cord, suggesting that this form may have a unique function in the central nervous system.