The absence of detectable fetal microchimerism in nontransgenic goats (Capra aegagrus hircus) bearing transgenic offspring

Maternal transmission of bacterial microbiota during embryonic development in a viviparous lizard

IMPORTANCE

We investigated the presence and diversity of bacteria in the embryos of the viviparous lizard Sceloporus grammicus and their amniotic environment. We compared this diversity to that found in the maternal intestine, mouth, and cloaca. We detected bacterial DNA in the embryos, albeit with a lower bacterial species diversity than found in maternal tissues. Most of the bacterial species detected in the embryos were also found in the mother, although not all of them. Interestingly, we detected a high similarity in the composition of bacterial species among embryos from different mothers. These findings suggest that there may be a mechanism controlling the transmission of bacteria from the mother to the embryo. Our results highlight the possibility that the interaction between maternal bacteria and the embryo may affect the development of the lizards.

Validation of fetal microchimerism after pregnancy in the ovine using qPCR

Fetal microchimerism has been detected in maternal tissues of humans and rodents during and after pregnancy. Studies focusing on fetal DNA transfer to maternal tissues in domestic animals are limited, especially in sheep. Fetal ram DNA was observed in the maternal circulation during pregnancy, but it is not known if this chimerism persists in soft tissues after parturition. The objectives of this exploratory study were to: 1) determine if male fetal DNA is detectable in soft tissues of mature ewes after parturition and if so, determine if detection repeatability differed with lifetime offspring sex ratio and 2) determine if male fetal DNA was present in soft tissues of yearling (primiparous) ewes shortly after parturition. Eight mature (open, non-lactating) and 8 yearling (primiparous, periparturient) Rambouillet ewes were used. Mature ewes (5- to 7-yr old) had given birth to primarily 82% males (n = 4) or 71% female (n = 4) over a lifetime. Yearling ewes had birthed either a singleton male (n = 4) or female (n = 4) lambs. DNA was extracted from 10 and 11 different soft tissues from the mature and yearling ewes, respectively. Real-time PCR (qPCR) was used to identify the presence of the SRY gene in each tissue sample. Male DNA was detected in the brain and liver from one mature open ewe that had given birth to two males and six females during her lifetime. In younger ewes that gave birth to a ram lamb, male DNA was observed in the thyroid of one ewe and the pancreas and brain of a second ewe. Male DNA was detected in the ovary of one ewe that had given birth to a female lamb. Based on these data, we suggest fetal microchimerism in soft maternal tissues is possible in sheep and may remain after pregnancy has ended. The detection repeatability of male fetal DNA was not associated with sex ratio of lifetime offspring. Male DNA was observed in maternal soft tissues collected shortly after parturition. The greater detection of fetal male DNA found in younger ewes shortly after parturition may be due to not having enough time for fetal DNA clearance to occur. Future studies are warranted to further study XY chimerism in maternal tissues of the ewe and its potential role in ovine physiology.

Assessment of microchimerism following somatic cell nuclear transfer and natural pregnancies in goats

Microchimerism is defined as the presence of a small population of cells or DNA in 1 organism originated from a genetically different organism. It is well established that this phenomenon occurs in humans and mice as cells are exchanged between mother and fetus during gestation. Currently, no information is available about the presence of maternal microchimerism in goats, and the only published study is limited to an evaluation of fetal and fetal-fetal microchimerism in blood samples following natural breeding. In order to determine whether bidirectional fetal-maternal cell or DNA trafficking occurs in goats, we assessed: 1) fetal microchimerism in surrogates that gave birth to somatic cell nuclear transfer (SCNT)-derived transgenic offspring (n = 4), 2) maternal microchimerism following natural breeding of SCNT-derived transgenic does with a nontransgenic buck (n = 4), and 3) fetal-fetal microchimerism in nontransgenic twins of transgenic offspring (n = 3). Neomycin-resistance gene (NEO) gene was selected as the marker to detect the presence of the αMHC-TGF-β1-Neo transgene in kidney, liver, lung, lymph node, and spleen. We found no detectable maternal or fetal-fetal microchimerism in the investigated tissues of nontransgenic offspring. However, fetal microchimerism was detected in lymph node tissue of one of the surrogate dams carrying a SCNT pregnancy. These results indicate occurrence of cell trafficking from fetus to mother during SCNT pregnancies. The findings of this study have direct implications on the use and disposal of nontransgenic surrogates and nontransgenic offspring.

Monitoring of Venus transgenic cell migration during pregnancy in non-transgenic rabbits

Cell transfer between mother and fetus were demonstrated previously in several species which possess haemochorial placenta (e.g. in humans, mice, rats, etc.). Here we report the assessment of fetal and maternal microchimerism in non-transgenic (non-TG) New Zealand white rabbits which were pregnant with transgenic (TG) fetuses and in non-TG newborns of TG does. The TG construct, including the Venus fluorophore cDNA driven by a ubiquitous cytomegalovirus enhancer, chicken ß-actin promoter (CAGGS), was previously integrated into the rabbit genome by Sleeping Beauty transposon system. Three different methods [fluorescence microscopy, flow cytometry and quantitative polymerase chain reaction (QPCR)] were employed to search for TG cells and gene products in blood and other tissues of non-TG rabbits. Venus positive peripheral blood mononuclear cells (PBMCs) were not detected in the blood of non-TG littermates or non-TG does by flow cytometry. Tissue samples (liver, kidney, skeletal and heart muscle) also proved to be Venus negative examined with fluorescence microscopy, while histology sections and PBMCs of TG rabbits showed robust Venus protein expression. In case of genomic DNA (gDNA) sourced from tissue samples of non-TG rabbits, CAGGS promoter-specific fragments could not be amplified by QPCR. Our data showed the lack of detectable cell transfer between TG and non-TG rabbits during gestation.

Assessment of fetal cell chimerism in transgenic pig lines generated by Sleeping beauty transposition

Human cells migrate between mother and fetus during pregnancy and persist in the respective host for long-term after birth. Fetal microchimerism occurs also in twins sharing a common placenta or chorion. Whether microchimerism occurs in multiparous mammals such as the domestic pig, where fetuses have separate placentas and chorions, is not well understood. Here, we assessed cell chimerism in litters of wild-type sows inseminated with semen of transposon transgenic boars. Segregation of three independent monomeric transposons ensured an excess of transgenic over non-transgenic offspring in every litter. Transgenic siblings (n = 35) showed robust ubiquitous expression of the reporter transposon encoding a fluorescent protein, and provided an unique resource to assess a potential cell trafficking to non-transgenic littermates (n = 7) or mothers (n = 4). Sensitive flow cytometry, fluorescence microscopy, and real-time PCR provided no evidence for microchimerism in porcine littermates, or piglets and their mothers in both blood and solid organs. These data indicate that the epitheliochorial structure of the porcine placenta effectively prevents cellular exchange during gestation.

Recombinant DNA production of spider silk proteins

Spider dragline silk is considered to be the toughest biopolymer on Earth due to an extraordinary combination of strength and elasticity. Moreover, silks are biocompatible and biodegradable protein-based materials. Recent advances in genetic engineering make it possible to produce recombinant silks in heterologous hosts, opening up opportunities for large-scale production of recombinant silks for various biomedical and material science applications. We review the current strategies to produce recombinant spider silks.