Association of birth type and LHX4 gene polymorphism with reproductive hormones, growth hormone, and prolactin in Awassi ewes

BACKGROUND

LIM homeobox transcription factor 4 (LHX4) is a promising candidate gene for mammalian reproductive traits. LHX4 polymorphism has previously been associated with phenotypic traits in goats and cattle. However, there have been no LHX4 gene polymorphisms identified in Awassi sheep. Therefore, this study investigated the effects of the LHX4 polymorphism on reproductive hormones, growth hormones, and prolactin in Awassi ewes.

METHODS AND RESULTS

A total of 232 ewes between the ages of 3 and 4 years were selected for this study (123 single-progeny ewes and 109 twin-producing ewes). Serum was collected to measure reproductive hormones, growth hormone, and prolactin using ELISA kits made by ELK Biotechnology. Genomic DNA was extracted from sheep blood, genotyped, and sequenced to confirm variations in LHX4 (exon 1, 207 bp). Genotyping revealed three genotypes in 207 bp: AA, AG, and GG. Sequence analysis detected a novel mutation in exon 1: 160 A > G. Statistically, the 160 A > G SNP was significantly associated with the phenotypic traits. Ewes carrying AA genotypes had higher estrogen, progesterone, follicle-stimulating hormones/luteinizing hormones, and growth hormone, and lower prolactin levels (65.63 ± 3.84) (pg/mL), (6.67 ± 0.38) (ng/mL), (22.34 ± 1.27) (ng/mL)/(23.89 ± 2.13) (ng/mL), (1.30 ± 0.05) (ng/mL), and (13.16 ± 0.75) (pg/mL), respectively, compared to AG and GG genotypes in the fourth month of twin-pregnant ewes compared to single-pregnant ewes.

CONCLUSION

This study suggests that the 160 A > G SNP negatively affects the Awassi sheep's hormone levels. It provides valuable insight into the sheep LHX4 gene, which could be an effective marker in marker-assisted selection.

Detection of insertions/deletions (InDels) within the goat Runx2 gene and their association with litter size and growth traits

Runt-related transcription factor 2 (Runx2) is characterized by its critical functions in osteoblastic and ovulatory processes. The goal of this study was to explore the insertion/deletion (indel) variants of this gene and to evaluate their association with productive traits. Herein, a 12 bp and 6 bp insertion within the Runx2 gene was uncovered in Shaanbei white cashmere goats (SBWC; n = 1200). Chi-square analysis revealed that the 12 bp insertion was related to litter size (p < 0.01). Further association analysis also found this insertion was significantly associated with litter size (p = 1.1E-5). Interestingly, this insertion was also significantly associated with chest circumference (p = 0.018). Additionally, the 6 bp insertion was associated with body length (p = 0.003), chest width (p = 0.011), and chest circumference (p = 0.005). Furthermore, diplotype associations also uncovered that the combined genotypes of these two indels also significantly affected litter size and growth traits (p < 0.05). These findings suggested that these two insertions within the Runx2 gene were significantly associated with reproduction and growth traits, which would make them beneficial functional DNA markers that can be used in goat breeding.

One 16 bp insertion/deletion (indel) within the KDM6A gene revealing strong associations with growth traits in goat

Lysine demethylase 6A (KDM6A), as a candidate gene associated with skeletal dysplasia and the differentiation of osteogenesis, might affect the growth traits in animals. In the previous study (Cui et al., 2018), one 16 bp intronic insertion/deletion (NW_017189516.1: g.138, 431_138,446delAATGTATAGCTTAAAA) within the KDM6A gene significantly influenced KDM6A gene expression. The objective of this work was to investigate the association between this 16 bp indel and growth-related traits in Shaanbei White Cashmere goat (SWCG). Association analyses showed the 16 bp indel was related to growth traits strongly (body height, chest depth, height across the hip, body length and chest circumference) in SWCG population (n = 1953, P < 0.05). Insertion/insertion (II) genotype individuals (n = 1502) had the best growth traits, by comparison of those of insertion/deletion (ID) (n = 410) and the deletion/deletion (DD) genotypes (n = 41). Particularly, the body weight of II genotype individuals were significantly higher than ID and DD genotypes (P < 0.01). Besides, the remarkable influence of this indel on traits might cause by the change of MEF2 binding site. These findings hinted that the 16 bp deletion mutation in KDM6A gene, which was significantly associated with growth-related traits, could be assigned to an effective molecular marker for growth traits in goat breeding.

The novel 22 bp insertion mutation in a promoter region of the <i>PITX2</i> gene is associated with litter size and growth traits in goats

Abstract. The paired-like homeodomain 2 (PITX2) gene plays a critical role in regulating development, reproduction, and growth traits in ruminants. Hence, the objective of this study was to explore the polymorphisms of this gene and to evaluate their associations with quantitative traits. Herein, a novel insertion in the promoter region of the PITX2 gene was reported in Shaanbei white cashmere (SBWC) goats (n=1012). The genotype distributions between mothers of single-kid and multi-kid groups within SBWC goats were significantly different (P<0.01), implying that this indel mutation might affect the litter size. Furthermore, association analysis found that this indel mutation was significantly associated with litter size (P=0.001). Individuals with genotype DD had a significantly smaller litter size than those with other genotypes (P<0.01). Besides, this indel was significantly associated with the body length (P=0.042) and the chest width (P=0.031). Especially, the individuals with genotype DD had a significantly lower body length than those with genotype II (P<0.05), which was consistent with the trend in litter size. These findings suggested that the new 22 bp indel mutation within the PITX2 gene is significantly associated with litter size and growth traits; this can be utilized as a functional molecular marker in goat breeding.

Detection of insertion/deletions (indels) of the <i>ATBF1</i> gene and their effects on growth-related traits in three indigenous goat breeds

Abstract. The AT motif-binding factor (ATBF1), also known as zinc finger homeobox 3 (ZFXH3), is necessary for activating the POU1F1 gene; thus, the ATBF1 gene greatly affects the grow traits in animals. The objective of this work was to explore novel indel (insertion/deletion) variations and their associations with growth traits in three native Chinese goat breeds. Two indels within the ATBF1 gene were found in the Shaanbei white cashmere goat (SWCG; n=581), the Guanzhong dairy goat (GZDG; n=334) and the Hainan black goat (HNBG; n=270) for the first time using 12 pairs of primers. Association analysis revealed that the P1-12-bp indel was consistently correlated with the body height of the three breeds, and individuals with ID (insertion/deletion) and DD (deletion/deletion) genotypes had a higher body weight than the II (insertion/insertion) genotype (P=0.036); the P11-6-bp indel was consistently correlated with chest circumference and hip width of the three breeds. Moreover, these two loci were associated with other several growth-related traits in different breeds. Hence, these findings indicated that the goat ATBF1 gene had marked effects on growth traits and the growth-trait-related loci, which would contribute to improving the growth-related traits of local breeds in the goat industry by implementing marker-assisted selection (MAS).