The identification of a novel mutation in the testis specific Y-like gene and association of the mutation with SIDDT syndrome are disclosed. Methods for diagnosing SIDDT syndrome are disclosed. Methods for identifying compounds for use in the diagnosis and treatment of disorders associated with mutation in the TSPYL gene are also disclosed. The invention therefore provides nucleic acid sequences, genes, polypeptides, antibodies, vectors containing the gene, host cells transformed with vectors containing the gene, animal models for the disease, methods for expressing the polypeptide, genetic screening methods and kits, diagnostic methods and kits.