JAK/STAT pathway in Drosophila immunity.

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway controls multiple biological processes in metazoan development and tissue homoeostasis. This creates a need for tight regulatory mechanisms to ensure proper responses. The core components of the pathway, as well as many of the regulatory molecules, are conserved in evolution and thus share similarities in organisms such as humans and fruit flies. Therefore, the fruit fly provides an amenable model system for elucidating the in vivo roles of the JAK/STAT pathway and its regulators, which are challenging to demonstrate in mammalian systems. This review will focus on describing recent advances in understanding the importance of JAK/STAT signalling in Drosophila immunity.

Transcription factor zfh1 downregulates Drosophila Imd pathway.

The fruit fly Drosophila melanogaster has a powerful innate immune system, which culminates on the synthesis of potent antimicrobial peptides (AMPs). This is mainly controlled by two conserved signaling cascades, the Toll and the immune deficiency (Imd) pathways. Like in humans, Drosophila immune responses need to be under tight control at multiple levels to avoid harmful inflammation. We have identified the transcription factor Zn finger homeodomain 1 (zfh1) as a negative regulator of Drosophila Imd signaling. Knocking down zfh1 in Drosophila S2 cells hyperactivates Imd pathway-mediated AMP expression, whereas forced zfh1 expression blocks Imd pathway response downstream of, or parallel to, the Imd pathway transcription factor Relish. In vivo zfh1 RNAi hyperactivates CecropinB induction upon gram-negative bacterial infection. We conclude that zfh1 is an important regulator of the immune response in Drosophila.

Embryo production from superovulated Holstein-Friesian dairy heifers and cows after insemination with frozen-thawed sex-sorted X spermatozoa or unsorted semen.

The aim of this study was to evaluate embryo production in superovulated Holstein-Friesian dairy heifers and cows inseminated with either X-sorted spermatozoa (2 million/dose) or unsorted semen (15 million/dose). Experiment 1 at the research farm involved eight heifers, six cows and semen of one Holstein bull. All transferable embryos were diagnosed for sex. Experiment 2 included embryo collections on commercial dairy farms: X-sorted spermatozoa from three Holstein bulls were used for 59 collections on 28 farms and unsorted semen from 32 Holstein bulls were used for 179 collections on 79 farms. Superovulations were induced by eight declining doses of FSH (total of 12 ml for heifers and 19 ml for cows) starting on days 8-12 of the estrus cycle. Inseminations began 12h after the onset of estrus and were performed two to four times at 9-15 h intervals. Low-dose X-sorted inseminates were deposited into uterine horns and unsorted semen was placed into the uterine body. In Experiment 1, on average 70.3 and 75.0% of embryos recovered from heifers, and 48.4 and 100% of embryos recovered from cows were of transferable quality in X-sorted and unsorted groups, respectively. The proportion of transferable female embryos produced approximately doubled when insemination was with X-sorted spermatozoa compared to insemination with unsorted semen (heifers 96.4% versus 41.1%; cows 81.1% versus 39.8%). In Experiment 2, estimated 53.9 and 65.5% of embryos recovered from heifers, and 21.1 and 64.5% of embryos recovered from cows were of transferable quality in X-sorted and unsorted groups, respectively. Proportions of unfertilized oocytes were 21.1 and 10.6% for heifers and 56.0 and 14.4% for cows in X-sorted and unsorted groups, respectively. Consequently, cows inseminated with X-sorted spermatozoa produced significantly smaller proportions of transferable embryos (p<0.005) and significantly larger proportions of unfertilized oocytes (p<0.001) than those inseminated with unsorted semen. Proportions of quality 1 or degenerated embryos were similar for the two treatments in both heifers and cows. Within treatments, bulls did not significantly affect the proportions of transferable, unfertilized or degenerated oocytes/embryos. It was concluded that using low-dose X-sorted spermatozoa rather than normal-dose unsorted semen for the insemination of superovulated embryo donors can improve the proportion of transferable female embryos produced but this potential may not be achieved in commercial practice, particularly in cows, because of reduced fertilization rates when using low doses of X-sorted spermatozoa.