Association of INHA polymorphism with fertility in Kreishi ewes

Litter size is an important reproductive trait in sheep, and INHA is a candidate gene involved in reproductive regulation. However, the association of specific INHA variants with litter size in Kreishi sheep remains insufficiently characterized. This study examined INHA polymorphisms in 100 Kreishi ewes aged 3-4 years.

The animals were classified according to litter size into single-bearing (n = 46) and twin-bearing (n = 54) groups. PCR amplification and bidirectional Sanger sequencing were used to identify the variant. The association between genotype and litter size was evaluated using the chi-square test and binary logistic regression. The potential functional and structural effects of the resulting substitution were assessed using SIFT, PolyPhen-2, DynaMut2, and PyMOL. The c.425 C > T substitution resulted in the missense change p.Ser142Phe and was detected in three genotypes: CC, CT, and TT. Genotype distribution differed significantly between single- and twin-bearing ewes (χ² = 30.87, P < 0.0001). Relative to the TT genotype, CT was associated with increased odds of twin birth (odds ratio [OR] = 6.77, 95% confidence interval [CI]: 1.59-28.72), while CC showed a higher estimated association with twin birth (OR = 16.51, 95% CI: 5.56-49.08).

The INHA c.425 C > T (p.Ser142Phe) variant was significantly associated with litter size in the studied Kreishi ewes. SIFT, PolyPhen-2, and DynaMut2 predicted deleterious, potentially damaging, and destabilizing effects, respectively, while PyMOL indicated a conserved overall protein fold with localized structural changes around residue 142. Validation in larger, independent populations is needed before using it as a molecular marker for reproductive selection.