Identification of a Novel Splice-Site variant in TACR3 (c.888 + 1G > A) Associated with Asthenozoospermia and Hypogonadotropic Hypogonadism in an Iranian Family.

Abstract

BACKGROUND: TACR3 encodes the receptor for neurokinin B, a key regulator of the hypothalamic-pituitary-gonadal axis. Disruption of this pathway can impair gonadotropin release and male reproductive function. Given the genetic heterogeneity of male infertility, this study aimed to identify novel variants in TACR3 that may underlie asthenozoospermia and related hormonal abnormalities. METHODS: Fifteen infertile men with confirmed asthenozoospermia were enrolled. Whole-exome sequencing (WES) was performed on genomic DNA from peripheral blood, and the candidate variant was validated by Sanger sequencing. Functional predictions were made using PolyPhen-2, SIFT, MutationTaster, and REVEL. TACR3 mRNA expression levels were assessed by real-time PCR in available samples. RESULTS: A novel splice-site variant, TACR3 (NM_001059.3:c.888 + 1G > A), was detected and found to segregate with infertility in one family, appearing homozygously in two infertile brothers and heterozygously in the proband with severe asthenozoospermia. The variant was absent in public and local genomic databases, suggesting its extremely rare frequency. Furthermore, RT-PCR showed a dramatic reduction or complete loss of TACR3 expression in affected individuals, confirming its deleterious effect on splicing and mRNA stability. CONCLUSION: We identified a previously unreported splice-site mutation in TACR3 (c.888 + 1G > A) that likely causes familial infertility by disrupting the neurokinin B/NK3R signaling pathway. While the heterozygous proband exhibited severe asthenozoospermia, the homozygous brothers displayed hormonal profiles typical of hypogonadotropic hypogonadism. These findings extend the mutational landscape of TACR3 and highlight its essential contribution to male reproductive endocrinology.