The effect of SNP rs400827589 in exon 2 of the MTNR1B gene on reproductive seasonality and litter size in sheep

Analysis of MTNR1A Genetic Polymorphisms and Their Association with the Reproductive Performance Parameters in Two Mediterranean Sheep Breeds

Sheep farming plays an important economic role, and it contributes to the livelihoods of many rural poor in several regions worldwide and particularly in Tunisia. Therefore, the steady improvement of ewes' reproductive performance is a pressing need. The MTNR1A gene has been identified as an important candidate gene that plays a key role in sheep reproduction and its sexual inactivity. It is involved in the control of photoperiod-induced seasonality mediated by melatonin secretion. The aim of this study was to identify SNPs in the MTNR1A gene in two Tunisian breeds, Barbarine (B) and Queue Fine de l'Ouest (QFO). DNA extracted from the blood of 77 adult ewes was sequenced. Selected ewes were exposed to adult fertile rams. A total of 26 SNPs were detected; 15 SNPs in the promoter region and 11 SNPs in the exon II were observed in both (B) and (QFO) breeds. The SNP rs602330706 in exon II is a novel SNP detected for the first time only in the (B) breed. The SNPs rs430181568 and rs40738822721 (SNP18 and SNP20 in our study, respectively) were totally linked in this study and can be considered a single marker. DTL was associated with SNP18 and SNP20 in (B) ewes (p < 0.05); however, no significant difference was detected between the three genotypes (G/G, G/A, and A/A) at these two SNPs. Fertility rate and litter size parameters were not affected by SNP18 and SNP20. There was an association between these two polymorphisms and (B) lambs' birth weights (p < 0.05). Furthermore, the ewes with the A/A genotype gave birth to lambs with a higher weight compared to the other two genotypes for this breed (p < 0.05). There was not an association between SNP 18 and SNP20 and (QFO) ewes' reproductive parameters. These results might be considered in future sheep selection programs for reproductive genetic improvement.

Anatomy of hypothalamic and diencephalic nuclei involved in seasonal fertility regulation in ewes

In this study, we describe in detail the anatomy of nuclei involved in seasonal fertility regulation (SFR) in ewes. For this purpose, the intergeniculate leaflet of the visual thalamus, the caudal hypothalamic arcuate nucleus, and suprachiasmatic, paraventricular and supraoptic nuclei of the rostral hypothalamus were morphometrically and qualitatively analyzed in Nissl-stained serial sections, in the three anatomical planes. In addition, data were collected on calcium-binding proteins and cell phenotypes after immunostaining alternate serial sections for calretinin, parvalbumin and calbindin. For a complete neuroanatomical study, glial architecture was assessed by immunostaining and analyzing alternate sections for glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (IBA1). The results showed a strong microglial and astroglia reaction around the hypothalamic nuclei of interest and around the whole 3^rd ventricle of the ewe brain. Moreover, we correlated cytoarchitectonic coordinates of panoramic serial sections with their macroscopic localization and extension in midline sagittal-sectioned whole brain to provide guidelines for microdissecting nuclei involved in SFR.

Polymorphisms of SORBS1 Gene and Their Correlation with Milk Fat Traits of Cattleyak

Simple Summary

Increasing milk fat rate has a good effect on the milk quality of cattleyak. SNPs can help us find potential molecular markers for the milk fat traits of cattleyak, and they can be screened according to molecular markers when they are young. It provides a reference for cultivating high milk fat cattle population in the future. The results of this study suggest that the SORBS1 gene polymorphism is closely related to the milk fat traits of cattleyak, which could be used as a candidate genetic marker for milk fat trait selection in cattleyak. This study provides a new molecular marker and theoretical basis for screening the milk fat traits of cattleyak. It has a certain reference value for the research and improvement of milk quality.

Abstract

This study aimed to find the SNPs in the SORBS1 gene of cattleyak, analyze the relationship between its polymorphisms and the milk fat traits, and find potential molecular markers for the milk fat traits of cattleyak. The polymorphism of the SORBS1 gene in 350 cattleyak from Hongyuan County (Sichuan, China) were detected by PCR and DNA sequencing, and the correlation between these SNPs and the milk production traits of cattleyak was analyzed. The results showed that there were nine SNPs in the CDS and their adjacent non-coding regions of the SORBS1 gene, and all SNPs have three genotypes. The correlation analysis found that the genotypes with superior milk fat traits in the other eight alleles were homozygous genotypes with a high genotype frequency except the g.96284 G > A (c.3090 G > A) (p < 0.05). However, at locus g.96284 G > A, the milk fat percentage, monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) and saturated fatty acids (SFAs) of the GA genotype were significantly higher than that of GG and AA genotypes (p < 0.05). Among these SNPs, three SNPs (g.6256 C > T (c.298 C > T), g.24791 A > G (c.706 A > G) and g.29121 A > G (c.979 A > G)) caused the amino acids change. The genotypes of the three SNPs consist of three haplotypes and four diplotypes. The amino acid mutation degree of diplotype H1–H1 (CCAAAA) was the highest, and its milk fat percentage, MUFAs, PUFAs and SFAs were also the highest (p < 0.05). Taken together, we found nine SNPs in the SORBS1 gene that are closely related to the milk fat traits of cattleyak. Moreover, the mutation of amino acids caused by SNPs had positive effects on the milk fat traits of cattleyak. H1-H1 is the dominant diplotype which significantly related to the milk fat traits of cattleyak. This study provides a new molecular marker and theoretical basis for screening the milk fat traits of cattleyak.

The effect of SNP rs400827589 in exon 2 of the MTNR1B gene on reproductive seasonality and litter size in sheep

In mammals, the melatonin receptor gene has been widely studied since it has a great influence on reproductive traits. However, little is known about the association between polymorphism of the coding region of the MTNR1B gene and year‐round oestrus or the litter size in Small Tail Han sheep. To better understand the effects of single nucleotide polymorphism (SNP) rs400827589 in MTNR1B, a population polymorphism analysis was conducted using genotyping data in 45 sheep breeds around the world. The results indicated that TT was the dominant genotype in all sheep breeds. The associations of this SNP with reproductive seasonality and litter size in Small Tail Han sheep showed rs400827589 was correlated with fecundity as assessed by reproductive seasonality and litter size (p < .05). Bioinformatics analysis indicated the change in amino acid from Ile to Leu may affect the function of the MTNR1B protein by impacting the secondary and tertiary protein structures. The present results demonstrate that rs400827589 could be used in the marker‐assisted selection of the litter size in Small Tail Han sheep.