| Sperm-specific lactate dehydrogenase, generally consisting of four copies of subunit C, is also referred to as lactate dehydrogenase C4, or LDHC4. Being a key enzyme for sperm energy metabolism, it is closely related to spermatogenesis, spermatic metabolism and sperm capacitation. The motility defect of sperm is associated with 82% of the patients with male infertility and seems to be directly responsible for 20% of those patients. The expression of LDHC4 is specific in spermatogenesis. The deletion or mutation of LDHC4 gene may lead to changes of lactate dehydrogenaseC4 in quanlity and quantity, and affect the motility of sperms, resulting in male infertility.In this study, the sperm LDHC4 was detected by using activity staining with LDHC4 specific substrate. PCR products with abnormal elution peaks in DHPLC were analyzed by sequencing. The mutation found was confirmed by T-cloning. Finally, the mutation screened by DHPLC was tested in a group of normal controls by ARMS. The results showed that a group of patients whose sperm LDHC4 activity were greatly lowered were screened out in patients with unknown infertility, accouting for at least 6%. The PCR products of one patient showed that there was an abnormal elution peak in DHPLC. By sequencing of this PCR product, it was found a heterozygous mutation, T→A, at base115 in exon 5 of LDHC4 gene. The mutation changed the codon 178TTG (coding for leucine) of LDHC4 gene into TAG (stop codon ). This mutation was not found in a group of 20 normal controls.by ARMS The mutation was further comfirmed by T-cloning.The mutation might greatly reduce the expression of LDHC4 in spermatogenesis,and affect energy metabolism and the motility of the sperms. This study demonstrates for the first time that there is LDHC4 gene mutation in male patients with unknown infertility, and iniatially substantiate the hypothesis that the mutation of LDHC4 gene can lead to male infertility. |
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