Ubiquitin-specific protease (USP26) gene alterations associated with male infertility and recurrent pregnancy loss (RPL) in Iranian infertile patients

Abstract

Background and purpose: The human X chromosome is enriched with testis-specific genes that may be crucial for male fertility. Mutations in USP26 gene have been proposed to be associated with male infertility. Moreover, the importance of the ubiquitin pathway during different stages of mammalian fertilization and even embryo development has been addressed. Some mutations and haplotypes on this gene have been proposed to be associated with male infertility. In this study, five different mutations on USP26 were investigated: 1737 G > A, 1090 C > T, 370-371ins ACA, 494 T > C and 1423 C > T.

Methods: The study included 166 infertile men with non-obstructive azoospermia, 72 male partners of couples who had previously experienced ≥3 clinical first trimester spontaneous abortions and 60 fertile men. Besides family history of reproduction, hormonal evaluation and semen analysis were performed. DNA was extracted from blood samples. PCR-SSCP, PCR-RFLP and PCR Product Cloning methods were used and resumed by sequencing to insure about the mutations. Moreover, USP26 gene expression was studied by Real-Time PCR after RNA extraction followed by cDNA synthesis from 24 testis biopsies in obstructive and non-obstructive azoospermia patients.

Results: The results indicate that there is a haplotype between three observed mutations in Iranian population include: 370-371insACA, 1423C > T and 494 T > C. This haplotype was seen in control group as well. Surprisingly, total frequency of mutations in men with history of idiopathic RPL and azoospermic cases were significantly higher than that of in control groups (p < 0.05). Serum testosterone concentrations and testicular volume did not differ in the mutation positive group compared with the non-mutation group. About the USP26 gene expression, there is a significant difference between the expression levels of obstructive azoospermia, complete maturation arrest samples and SCO samples (P < 0.05).

Conclusions: According to our results, the USP26 gene may play an important role in male reproduction. The alterations of this gene may be involved in male infertility and RPL in Iranian population and may negatively affect testicular function.

Fig. 1

Above figure shows sequence with ACA insertion and the following shows one without any insertion

Fig. 2

Frequency of different USP26 mutations in the study groups. The same letter show not significant different with P- value >0.05

Fig. 3

Result of 2^-Δct of usp26 expression level relative to GAPDH in different groups. The same letter show not significant different with P- value >0.05