ISTS defect in which sperm tail is short and fibrous sheath and axoneme are disorganized, is one of the syndromes that cause male infertility. Although a few studies have been done in this regard, its exact etiology in human is unclear yet. Four candidate genes causing ISTS are SPEF2, RABL2B, and A-kinas anchoring proteins genes (AKAP3 and AKAP4). Proteins which coded by SPEF2 and RABL2B are essential for correct sperm tail assembly and development, besides, AKAP3 and AKAP4 are most abundant structural proteins of the fibrous sheath. In the present study, the variations of candidate genes were investigated in 35 men with ISTS and 40 fertile men. To study the genetic variations, DNA was extracted from peripheral blood of patient (with more than 80% short tail sperms in at least two spermograms) and control groups, initially primers were designed for each target segment of candidate genes, and then PCR sequencing was done. Sequence analysis of SPEF2 did not identify any mutation in exon 3 and 28. However, one polymorphism (363A>C) was identified in exon 3 in four of patients and three persons of controls (P>0.05). Analysis of genetic data revealed that no mutations or single-nucleotide polymorphisms in exon 4 ofRABL2B was identified, but an intronic variant [(C) nucleotide deletion (rs: 144944885)] was found in heterozygote form in 5 patients (P<0.05). No alteration was identified in controls. Moreover, a polymorphism 1499T>C in AKAP3 was seen in 5 patients whereas none of the individuals in the control group had this alternation (P<0.05). No genetic alteration but one was found in AKAP4 gene which was a >1350 bp deletion in exon 5. Our results revealed that some specific gene alterations in AKAP3, AKAP4 and RABL2B can take part an important role in sperm tail malformation and can be assumed as the etiology of ISTS although genetic alterations in SPEF2 gene are not involved in this defect.
Materials and methods