GnRHR gene polymorphisms and their effects on reproductive performance in Chinese goats

Candidate genes associated with reproductive traits in rabbits

In the era of scientific advances and genetic progress, opportunities in the livestock sector are constantly growing. The application of molecular-based methods and approaches in farm animal breeding would accelerate and improve the expected results. The current work aims to comprehensively review the most important causative mutations in candidate genes that affect prolificacy traits in rabbits. Rabbits are a source of excellent-tasting meat that is high in protein and low in fat. Their early maturity and intensive growth are highly valued all over the world. However, improving reproductive traits and prolificacy in rabbits could be very tricky with traditional selection. Therefore, traditional breeding programs need new methods based on contemporary discoveries in molecular biology and genetics because of the complexity of the selection process. The study and implementation of genetic markers related to production in rabbits will help to create populations with specific productive traits that will produce the desired results in an extremely short time. Many studies worldwide showed an association between different genes and productive traits in rabbits. The study of these polymorphisms and their effects could be useful for molecular-oriented breeding, particularly marker-assisted selection programs in rabbit breeding.

Characterization of gonadotropin releasing hormone receptor gene in Sokoto and Kalahari Red goats

The objective of this study was to characterize GnRHR gene in Sokoto (n = 70) and Kalahari Red (n = 70) goats. Three SNPs, (g.-29T > G, g.48 G > A and g.209 T > G), were detected in Sokoto Red (SR) and one (g.48 G > A) in Kalahari Red (KR) goats. All the mutations occurred within the 5'UTR and Exon one of the gene and the g.209 T > G was non-synonymous and, therefore, resulted in an amino acid change from methionine to arginine at Position 70 of the GnRHR polypeptide. The homozygous mutant genotypes at the three SNP loci were not detected in both breeds but minor allele frequencies were ≥ 0.1 for the three SNP loci in SR goats. Frequency of the T allele, however, was 0.93 at the only SNP locus detected in KR goats. There was a strong linkage disequilibrium (LD; r²>0.98) among the detected mutations in SR goats resulting in two haplotypes (T-G-T and G-A-G) with a frequency of 86% and 13%, respectively. There was no significant association between genotypes at the polymorphic loci and litter size (P > 0.05) in the two breeds. The non-synonymous mutation (g.209T>G) appears to have changed the nucleotide binding region and area spanning exposed/buried regions on the predicted secondary structure of the two variants of the receptor. This change led to variation in the tertiary structure between the two variants of the receptor and can influence the function of the transmembrane receptor. Comparison of the GnRH receptor domains for goats, sheep, cattle and swine confirmed that the seven transmembrane domains of the receptor are conserved in all the farm animals considered.

Population structure, genetic diversity and selection signatures within seven indigenous Pakistani goat populations

Goat farming in Pakistan depends on indigenous breeds that have adapted to specific agro-ecological conditions. Pakistan has a rich resource of goat breeds, and the genetic diversity of these goat breeds is largely unknown. In this study, genetic diversity and population structure were characterized from seven indigenous goat breeds using the goat 50K SNP chip. The genetic diversity analysis showed that Bugi toori goats have the highest inbreeding level, consistent with the highest linkage disequilibrium, lowest diversity and long run of heterozygosity segments. This indicates that this breed should be prioritized in future conservation activities. The population structure analysis revealed four fairly distinct clusters (including Bugi toori, Bari, Black Tapri and some Kamori) and three other breeds that are seemingly the results of admixture between these or related groups (some Kamori, Pateri, Tapri and White Tapri). The selection signatures were evaluated in each breed. A total of 2508 putative selection signals were reported. The 26 significant windows were identified in more than four breeds, and selection signatures spanned several genes that directly or indirectly influence traits included coat colour variation (KIT), reproduction (BMPR1B, GNRHR, INSL6, JAK2 and EGR4), body size (SOCS2), ear size (MSRB3) and milk composition (ABCG2, SPP1, CSN1S2, CSN2, CSN3 and PROLACTIN).

Polymorphisms of caprine GnRHR gene and their association with litter size in West African Dwarf goats

Gonadotropin-releasing hormone receptor (GnRHR) gene is considered a candidate gene for litter size due to its critical role in regulating the activities of hypothalamo-pituitary-gonadal axis which synthesizes and releases gonadotropins. This study was designed to identify mutations within the caprine GnRHR gene and investigate their association with litter size at various parities. Polymorphisms scanning and genotyping of GnRHR gene in West African Dwarf (WAD) goats (n = 226) revealed three single nucleotide polymorphisms (SNPs), one mutation (g.-29T > G) was detected within 5'UTR region while two others (g.48G > A and g.209T > G) were identified in exon 1. Mutation at g.209T > G locus resulted in amino acid change from Methionine to Arginine at position 70 on the polypeptide residue. Based on heterozygosity and polymorphism information content (PIC), WAD goat population diversity at the SNP loci was moderate. Strong linkage disequilibrium (LD) (r² > 0.98) existed among the detected mutations resulting in three observed haplotypes, two (T-G-T and G-A-G) had cumulative frequency of > 97%. The mutation within 5'UTR region of GnRHR gene (g.-29T > G) is novel, being reported in goats for the first time. Association analysis revealed a significant (p < 0.05) association between allele G at g.-29T > G with higher mean litter size for homozygous (GG) mutant does compared with heterozygotes (GT) or homozygotes (TT), while the relationship between SNPs at the two loci detected in exon 1 and litter size was not significant.

Single nucleotide polymorphism of candidate genes in non-descript local goats of Sri Lanka

In the present study, genetic polymorphism in exon 4 of kappa casein (k-CSN3), exon 2-3 of alpha lactalbumin (LALBA) and exon 1 of gonadotropin releasing hormone receptor (GnRHR) genes were analyzed as candidate genes for milk production, milk quality and prolificacy in non-descriptive local goats in Sri Lanka. Altogether eleven, one and three single nucleotide polymorphisms (SNPs) were identified in k-CSN3, LALBA and GnRHR gene fragments, respectively utilizing the DNA sequencing technique for the first time in Sri Lanka. Seven polymorphic sites out of eleven in k-CSN3 gene fragment and the recorded variable site in LALBA gene fragment were homozygous while all three polymorphic sites in GnRHR gene fragment were heterozygous. Two of the SNPs recorded in the present study are known to be unique for Sri Lankan non-descript goat population at G203T and A730G in k-CSN3 and GnRHR genes, respectively. The study records another two SNPs in GnRHR gene, which are already known to be correlated with higher fecundity in goats (G757A and G891T). Results of the present study will be extremely important in future attempts to develop markers to improve the milk production, milk composition and litter size of non-descript local goats in Sri Lanka.

Prolificacy and Its Relationship with Age, Body Weight, Parity, Previous Litter Size and Body Linear Type Traits in Meat-type Goats

Data on age and body weight at breeding, parity, previous litter size, days open and some descriptive body linear traits from 389 meat-type, prolific Black Bengal goats in Tripura State of India, were collected for 3 and 1/2 years (2007 to 2010) and analyzed using logistic regression model. The objectives of the study were i) to evaluate the effect of age and body weight at breeding, parity, previous litter size and days open on litter size of does; and ii) to investigate if body linear type traits influenced litter size in meat-type, prolific goats. The incidence of 68.39% multiple births with a prolificacy rate of 175.07% was recorded. Higher age (>2.69 year), higher parity order (>2.31), more body weight at breeding (>20.5 kg) and larger previous litter size (>1.65) showed an increase likelihood of multiple litter size when compared to single litter size. There was a strong, positive relationship between litter size and various body linear type traits like neck length (>22.78 cm), body length (>54.86 cm), withers height (>48.85 cm), croup height (>50.67 cm), distance between tuber coxae bones (>11.38 cm) and distance between tuber ischii bones (>4.56 cm) for discriminating the goats bearing multiple fetuses from those bearing a single fetus.

Exploring polymorphisms and their effects on reproductive traits of the INHA and INHβA genes in three goat breeds

In this study, we report the analysis of INHA and INHβA gene polymorphisms in 786 goats of three breeds: Xinong Saanen (SN), Guanzhong (GZ) and Boer (BG). We identified three new allelic variants: P1-C80G and/126G (GenBank accession no. HQ202573) in the three goat breeds and P2-C936T (GenBank accession no. HQ202572) in SN and GZ goat breeds. At P1 locus, AA, AB and BB genotypes were found in the three goat breeds. At P2 locus, CC and CT genotypes were found in SN and GZ goat breeds. After comparing genotype distribution within the three goat breeds, BG had conspicuous differences from SN and GZ (P < 0.001) at P2 locus. The SNP locus was in Hardy-Weinberg disequilibrium at P1 locus in the three goat breeds (P < 0.05). At P2 locus, the SNP locus was in Hardy-Weinberg disequilibrium in SN and GZ goat breeds (P < 0.05). Association of polymorphisms with litter size was done at P1 locus in the three goat breeds. The result showed that AA genotype had remarkable litter size at P1 locus in the three goat breeds (P < 0.05). Therefore, these results suggest that INHA gene is a strong candidate gene that affects litter size in goats.

The association of two single nucleotide polymorphisms (SNPs) in growth hormone (GH) gene with litter size and superovulation response in goat-breeds

Two active mutations (A 781 G and A 1575 G) in growth hormone (GH) gene, and their associations with litter size (LS), were investigated in both a high prolificacy (Matou, n = 182) and a low prolificacy breed (Boer, n = 352) by using the PCR-RFLP method. Superovulation experiments were designed in 57 dams, in order to evaluate the effect of different genotypes of the GH gene on superovulation response. Two genotypes (AA and AB, CC and CD) in each mutation were detected in these two goat breeds. Neither BB nor DD homozygous genotypes were observed. The genotypic frequencies of AB and CC were significantly higher than those of AA and CD. In the third parity, Matou dams with AB or CC genotypes had significantly larger litter sizes than those with AA and CD (p < 0.05). On combining the two loci, both Matou and Boer dams with ABCD genotype had the largest litter sizes when compared to the other genotypes (p < 0.05). When undergoing like superovulation treatments, a significantly higher number of corpora lutea and ova, with a lower incidence of ovarian cysts, were harvested in the AB and CC genotypes than in AA and CD. These results show that the two loci of GH gene are highly associated with abundant prolificacy and superovulation response in goat breeds.

Novel polymorphisms of the growth hormone gene and their effect on growth traits in Chinese goats

The polymorphisms of the growth hormone (GH) gene were analyzed in 686 individuals from four goat populations, Three haplotypes (A, B and C) and three observed genotypes (AA, AB and AC) were detected at the P2 locus, and three haplotypes (E, F and G) and three observed genotypes (EE, EF and EG) were also detected at the P4 locus. In addition, five single nucleotide polymorphisms (SNPs)-A112G, C142T (Gly>Ser), C214T (P2 locus), C266A (Pro>His) and C214T (P4 locus, Arg>Trp), were identified by GH gene sequencing and PCR-SSCP analysis. The SNPs loci were in Hardy-Weinberg disequilibrium in three goat populations (P<0.05). Association of polymorphisms with growth traits was done in BG, F1 and F1 populations, which were shown to be associated with growth traits in three goat populations. The SNPs in the goat GH gene had significant effects on growth traits (P<0.05). suggesting that the GH gene is a strong candidate gene that affects growth traits in goat.