Mitofusin 1 is required for oocyte growth and communication with follicular somatic cells.

Mitochondrial function, largely regulated by the dynamics of this organelle, is inextricably linked to the oocyte health. In comparison with most somatic cells, mitochondria in oocytes are smaller and rounder in appearance, suggesting limited fusion. The functional implications of this distinct morphology, and how changes in the mitochondrial shape translate to mitochondrial function in oogenesis is little understood. We, therefore, asked whether the pro-fusion proteins mitofusins 1 (MFN1) and 2 (MFN2) are required for the oocyte development. Here we show that oocyte-specific deletion of Mfn1, but not Mfn2, prevents the oocyte growth and ovulation due to a block in folliculogenesis. We pinpoint the loss of oocyte growth and ovulation to impaired PI3K-Akt signaling and disrupted oocyte-somatic cell communication. In support, the double loss of Mfn1 and Mfn2 partially rescues the impaired PI3K-Akt signaling and defects in oocyte development secondary to the single loss of Mfn1. Together, this work demonstrates that the mitochondrial function influences the cellular signaling during the oocyte development, and highlights the importance of distinct, nonredundant roles of MFN1 and MFN2 in oogenesis.

Oocyte mitochondria: role on fertility and disease transmission.

Oocyte mitochondria are increased in number, smaller, and rounder in appearance than mitochondria in somatic cells. Moreover, mitochondrial numbers and activity are narrowly tied with oocyte quality because of the key role of mitochondria to oocyte maturation. During oocyte maturation, mitochondria display great mobility and cluster at specific sites to meet the high energy demand. Conversely, oocyte mitochondria are not required during early oogenesis as coupling with granulosa cells is sufficient to support gamete's needs. In part, this might be explained by the importance of protecting mitochondria from oxidative damage that result in mutations in mitochondrial DNA (mtDNA). Considering mitochondria are transmitted exclusively by the mother, oocytes with mtDNA mutations may lead to diseases in offspring. Thus, to counterbalance mutation expansion, the oocyte has developed specific mechanisms to filter out deleterious mtDNA molecules. Herein, we discuss the role of mitochondria on oocyte developmental potential and recent evidence supporting a purifying filter against deleterious mtDNA mutations in oocytes.

Strategies for increasing fertility in high productivity dairy herds.

Over the years, the dairy cow has been selected and managed for high performance and efficiency in milk production. Thus, different factors influence the fertility of dairy cows of high productivity. It has been observed that genetic selection for large productions and metabolic adaptations may explain the greater requirement to maintain reproduction at satisfactory levels. Also, these animals are more susceptible to environmental factors such as increased temperature and humidity. Studies have shown that heat stress results in reduced estrous expression and impairs ovarian function, interfering with folliculogenesis and steroidogenesis. Likewise, under heat stress conditions, dry matter intake is reduced, prolonging the after calving negative energy balance and calving-conception interval. Thus, suboptimal reproductive performance is one of the main factors responsible for the economic losses in large dairy farms. In this context, numerous management practices have been introduced to improve reproduction in high productivity animals, making reproductive management increasingly complex in dairy farms. Among them, we can mention the implementation of management and nutrition conditions adapted to the periods of heat stress, as well as protocols and biotechniques that improve the quality of the follicles and oocytes. Thus, because genetic selection for better fertility animals is a characteristic of low heritability, the success of reproductive programs in highly productive herds depends on the association of the control of genetic and physiological factors with those of environmental, nutritional and management. This paper aims to discuss reproductive aspects of dairy cows of high productivity, the role of heat stress in this context, and the implementation of management, nutrition and biotechnology conditions, to minimize the adverse effects on the reproduction of these animals.

Mining a differential sialotranscriptome of Rhipicephalus microplus guides antigen discovery to formulate a vaccine that reduces tick infestations.

BACKGROUND: Ticks cause massive damage to livestock and vaccines are one sustainable substitute for the acaricides currently heavily used to control infestations. To guide antigen discovery for a vaccine that targets the gamut of parasitic strategies mediated by tick saliva and enables immunological memory, we exploited a transcriptome constructed from salivary glands from all stages of Rhipicephalus microplus ticks feeding on genetically tick-resistant and susceptible bovines. RESULTS: Different levels of host anti-tick immunity affected gene expression in tick salivary glands; we thus selected four proteins encoded by genes weakly expressed in ticks attempting to feed on resistant hosts or otherwise abundantly expressed in ticks fed on susceptible hosts; these sialoproteins mediate four functions of parasitism deployed by male ticks and that do not induce antibodies in naturally infected, susceptible bovines. We then evaluated in tick-susceptible heifers an alum-adjuvanted vaccine formulated with recombinant proteins. Parasite performance (i.e. weight and numbers of females finishing their parasitic cycle) and titres of antigen-specific antibodies were significantly reduced or increased, respectively, in vaccinated versus control heifers, conferring an efficacy of 73.2%; two of the antigens were strong immunogens, rich in predicted T-cell epitopes and challenge infestations boosted antibody responses against them. CONCLUSION: Mining sialotranscriptomes guided by the immunity of tick-resistant hosts selected important targets and infestations boosted immune memory against salivary antigens.