Goat CTNNB1: mRNA expression profile of alternative splicing in testis and association analysis with litter size

Catenin beta 1 (CTNNB1, also known as β-catenin), is a key gene involved in wnt-β-catenin signaling pathway and plays a significant role in animal reproduction. The aim of this study was to explore the expression profiles and different splice variants of the cashmere goat CTNNB1 gene in testis, as well as to find novel insertion/deletion mutations (indels) and to further evaluate their association with litter size in Shaanbei white cashmere (SBWC) goats (n = 850) using Inner Mongolia white cashmere (IMWC) goats as a control group (n = 311). In this study, the CTNNB1 mRNA was detectable in all tissues, and in testis its expression was significantly lower than kidney, heart and so on. Meanwhile, four transcript variants, named by Ctnnb1-A/-B/-C/-D, were identified for the first time in SBWC goats, and Ctnnb1-C had the highest expression in testis, indicating that it plays an effective role in male fertility. Furthermore, a novel 26-bp indel was found within the CTNNB1 gene in both SBWC and IMWC breeds. A Chi-square test (χ²-test) showed that the difference between the high-fecundity group (SBWC) and the low-fertility group (IMWC) was extremely significant (P = 1.09E-10). Only one insertion/deletion (ID) genotype in IMWC goats which was unable to perform association analysis. In association analysis, the 26-bp indel was significantly associated with the first-born litter size in SBWC female goats (P = 0.026), and the individuals with ID genotype (n = 96) significantly had more lambs than those with insertion/insertion (II) genotype (n = 611) (P = 0.019). These findings revealed that the alternative splicing was involved in the regulation of CTNNB1 expression and the 26-bp indel could be utilized as a candidate marker for marker-assisted selection (MAS) in cashmere goat industry.