Association of Egg Mass and Egg Sex: Gene Expression Analysis from Maternal RNA in the Germinal Disc Region of Layer Hens (Gallus gallus).

Female birds have been shown to manipulate offspring sex ratio. However, mechanisms of sex ratio bias are not well understood. Reduced feed availability and change in body condition can affect the mass of eggs in birds that could lead to a skew in sex ratio. We employed feed restriction in laying chickens (Gallus gallus) to induce a decrease in body condition and egg mass using 45 chicken hens in treatment and control groups. Feed restriction led to an overall decline of egg mass. In the second period of treatment (Days 9-18) with more severe feed restriction and a steeper decline of egg mass, the sex ratio per hen (proportion of male eggs) had a significant negative association with mean egg mass per hen. Based on this association, two groups of hens were selected from feed restriction group, that is, hens producing male bias with low egg mass and hens producing female bias with high egg mass with overall sex ratios of 0.71 and 0.44 respectively. Genomewide transcriptome analysis on the germinal disks of F1 preovulatory follicles collected at the time of occurrence of meiosis-I was performed. We did not find significantly differentially expressed genes in these two groups of hens. However, gene set enrichment analysis showed that a number of cellular processes related to cell cycle progression, mitotic/meiotic apparatus, and chromosomal movement were enriched in female-biased hens or high mean egg mass as compared with male-biased hens or low mean egg mass. The differentially expressed gene sets may be involved in meiotic drive regulating sex ratio in the chicken.

Gene expression patterns in four brain areas associate with quantitative measure of estrous behavior in dairy cows.

BACKGROUND: The decline noticed in several fertility traits of dairy cattle over the past few decades is of major concern. Understanding of the genomic factors underlying fertility, which could have potential applications to improve fertility, is very limited. Here, we aimed to identify and study those genes that associated with a key fertility trait namely estrous behavior, among genes expressed in four bovine brain areas (hippocampus, amygdala, dorsal hypothalamus and ventral hypothalamus), either at the start of estrous cycle, or at mid cycle, or regardless of the phase of cycle. RESULTS: An average heat score was calculated for each of 28 primiparous cows in which estrous behavior was recorded for at least two consecutive estrous cycles starting from 30 days post-partum. Gene expression was then measured in brain tissue samples collected from these cows, 14 of which were sacrificed at the start of estrus and 14 around mid cycle. For each brain area, gene expression was modeled as a function of the orthogonally transformed average heat score values using a Bayesian hierarchical mixed model. Genes whose expression patterns showed significant linear or quadratic relationships with heat scores were identified. These included genes expected to be related to estrous behavior as they influence states like socio-sexual behavior, anxiety, stress and feeding motivation (OXT, AVP, POMC, MCHR1), but also genes whose association with estrous behavior is novel and warrants further investigation. CONCLUSIONS: Several genes were identified whose expression levels in the bovine brain associated with the level of expression of estrous behavior. The genes OXT and AVP play major roles in regulating estrous behavior in dairy cows. Genes related to neurotransmission and neuronal plasticity are also involved in estrous regulation, with several genes and processes expressed in mid-cycle probably contributing to proper expression of estrous behavior in the next estrus. Studying these genes and the processes they control improves our understanding of the genomic regulation of estrous behavior expression.

The early transcriptional response of pig small intestinal mucosa to invasion by Salmonella enterica serovar typhimurium DT104.

Salmonella enterica serovar typhimurium (S. typhimurium) species are a leading cause of human invasive gastroenteritis. There is increasing in vitro evidence about Salmonella interaction with isolated cells or cell lines (macrophages, and enterocytes) on the molecular level, however, very little is known about in vivo interactions during actual invasion. We investigated the early interaction of S. typhimurium with intact small intestinal mucosa, in a pig model. Intestinal segments were infected with or without S. typhimurium DT104, and perfused. Whole mucosal gene expression was analyzed by cDNA array on 0, 2, 4, and 8h post-infection. Invasion resulted in the upregulation of only eight transcripts in jejunal mucosa, among those the proinflammatory IL-8 (at 4h only), and the antiinflammatory STAT3 (at 4 and 8h). The limited number of differentially expressed genes found here in vivo compared to in vitro is most likely due to the presence of multiple, heterogenous cell interactions in intact mucosa. Furthermore, it is concluded that S. typhimurium evades strong host responses by downregulating the local inflammatory response.

A reliable method for sexing unincubated bird eggs for studying primary sex ratio.

In birds, offspring sex ratio manipulation by mothers is now well established with potentially important consequences for evolution and animal breeding. In most studies on primary sex ratio of birds, eggs are sexed after incubation by the use of PCR methods targeted to the sex-linked CHD1 genes. Sexing of unincubated eggs would be preferred, but as fertile and infertile blastodiscs cannot be distinguished macroscopically, errors could arise from PCR amplifications of parental DNA associated with the vitelline membrane of infertile eggs. In this study, we stained blastodiscs without the vitelline membrane with Hoechst 33342. This allowed unequivocal distinction between fertile and infertile blastodiscs. Fertile blastodiscs contained thousands of fluorescent nuclei, whereas no nuclei were seen in infertile eggs. In addition, after nucleic acid analysis, fertile blastodiscs yielded much stronger chromosomal DNA and CHD1-targeted PCR bands on agarose gels compared with infertile blastodiscs. These findings indicate that fertile blastodiscs contain much more embryonic DNA than parental DNA, allowing reliable sexing of the fertile eggs. The differences between fertile and infertile blastodiscs in chromosomal DNA and CHD1 PCR banding intensities alone could also be used to distinguish fertile from infertile eggs without using Hoechst staining. We conclude that identifying fertile blastodiscs either by Hoechst staining or by analyzing the yield of chromosomal DNA and CHD1-PCR products, combined with CHD1-targeted PCR amplification, presents an easy and reliable method to sex unincubated eggs.