Rats are effective model animals and have contributed to the development of human medicine and basic research. However, the application of reproductive engineering techniques to rats is not as advanced compared with mice, and genome editing in rats has not been achieved using embryos obtained by in vitro fertilization (IVF). In this study, we conducted superovulation, IVF, and knock out and knock in using IVF rat embryos. We found that superovulation effectively occurred in the synchronized oestrus cycle and with anti-inhibin antiserum treatment in immature rats, including the Brown Norway rat, which is a very difficult rat strain to superovulate. Next, we collected superovulated oocytes under anaesthesia, and offspring derived from IVF embryos were obtained from all of the rat strains that we examined. When the tyrosinase gene was targeted by electroporation in these embryos, both alleles were disrupted with 100% efficiency. Furthermore, we conducted long DNA fragment knock in using adeno-associated virus and found that the knock-in litter was obtained with high efficiency (33.3–47.4%). Thus, in this study, we developed methods to allow the simple and efficient production of model rats.

Prefoldin is a hexameric molecular chaperone found in the cytosol of archaea and eukaryotes. Its hexameric complex is built from two related classes of subunits, and has the appearance of a jellyfish: Its body consists of a double β-barrel assembly with six long tentacle-like coiled coils protruding from it. Using the tentacles, prefoldin captures an unfolded protein substrate and transfers it to a group II chaperonin. Based on structural information from archaeal prefoldins, mechanisms of substrate recognition and prefoldin-chaperonin cooperation have been investigated. In contrast, the structure and mechanisms of eukaryotic prefoldins remain unknown. In this study, we succeeded in obtaining recombinant prefoldin from a thermophilic fungus, Chaetomium thermophilum (CtPFD). The recombinant CtPFD could not protect citrate synthase from thermal aggregation. However, CtPFD formed a complex with actin from chicken muscle and tubulin from porcine brain, suggesting substrate specificity. We succeeded in observing the complex formation of CtPFD and the group II chaperonin of C. thermophilum (CtCCT) by atomic force microscopy and electron microscopy. These interaction kinetics were analyzed by surface plasmon resonance using Biacore. Finally, we have shown the transfer of actin from CtPFD to CtCCT. The study of the folding pathway formed by CtPFD and CtCCT should provide important information on mechanisms of the eukaryotic prefoldin–chaperonin system.

Aggregation of the 43 kDa TAR DNA‐binding protein (TDP‐43) is a pathological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). RNA binding and TDP‐43 N‐terminal domain dimerisation has been suggested to ameliorate TDP‐43 aggregation. However, the relationship between these factors and the solubility of TDP‐43 is largely unknown. Therefore, we developed new oligonucleotides that can recruit two TDP‐43 molecules and interfere with their intermolecular interactions via spatial separation. Using these oligonucleotides and TDP‐43‐preferable UG‐repeats, we uncovered two distinct mechanisms for modulating TDP‐43 solubility by RNA binding: One is N‐terminal domain dimerisation, and the other is the spatial separation of two TDP‐43 molecules. This study provides new molecular insights into the regulation of TDP‐43 solubility.

The rat is a multiparous rodent that has long been used in biomedical research, but the low reproductive performance in some rat strains hampers their broader use as research models. This study examined whether superovulation using an anti-inhibin monoclonal antibody (AIMA) could increase the litter size following natural mating in rats. In outbred Wistar rats, AIMA administration increased the number of ovulated oocytes by 1.3-fold. Importantly, AIMA did not affect fertilization and subsequent embryonic development, resulting in a 1.4-fold increase in litter size with a high pregnancy rate (89%). In contrast, conventional superovulation by equine/ human chorionic gonadotrophin administrations decreased the pregnancy rate to 6% and failed to increase the litter size. In inbred Brown Norway rats, AIMA increased the litter size 1.2-fold, and the pregnancy rate increased more than twice (86% vs. 38% in controls). AIMA also increased the litter size 2.0- and 1.5-fold in inbred Fischer 344 and Tokai High Avoider rats, respectively. Overall, when considering the pregnancy rate, AIMA increased the efficiency of offspring production 1.4-, 2.7-, 1.8-, and 1.5-fold in four rat strains. Thus, AIMA may consistently improve the reproductive performance by natural mating in rats, readily enabling their efficient use in biomedical research.

This Article contains errors in Table 5. The 'No. of KI offspring (%)' value is missing and the 'No. of offspring with partial insertion (%)' value should read "1 (5.3)" and not "9 (47.4)". The correct Table 5 appears below as Table 1.