Our early studies revealed that a missense heterozygous mutation of R249 to H of GRTH found in 5.8% of Japanese patients with non-obstructive azoospermia and 1% of normal controls, when expressed in COS1 cells, causes loss of the 61 kDa cytoplasmic phospho-GRTH species with preservation of the nuclear 56 kDa non-phospho form (38). Here, DDX25 is linked to Azoospermia.