We isolated and sequenced a cDNA clone of the human gene encoded by the 5' half of the ret transforming gene. The nucleotide sequence indicates that it encodes a protein with "finger" structures which represent putative metal- and nucleic acid-binding domains. Transcription of this gene was detected at high levels in a variety of human and rodent tumor cell lines, mouse testis, and embryos. In addition, a unique transcript was observed in testis RNA. When the expression of the unique transcript was examined at different stages of spermatogenesis, a striking increase in mRNA levels accompanied progression from meiotic prophase pachytene spermatocytes to postmeiotic round spermatids. This finger-containing gene may thus function in male germ cell development.