Biology subjects

Kogo, H.

Publications and source records attributed to Kogo, H..

3 recordsLinked to original sources

bioRxiv2024

A simple immunohistochemical method for perinatal mammalian ovaries revealed different kinetics of oocyte apoptosis caused by DNA damage and asynapsis.

Oocytes having meiotic defects are assumed to be eliminated by apoptosis in perinatal period. However, the oocyte apoptosis caused by meiotic defects has not been well analyzed, partly due to the great technical demands for tissue sectioning of perinatal ovaries. In the present study, we applied a squash method for immunohistochemical analysis of perinatal mouse ovaries as a substitute for tissue sectioning. As a result, we could show different kinetics of apoptosis caused by DMC1- and SPO11-deficiencies, indicating that DNA damage-induced apoptosis precedes asynapsis-induced apoptosis in mouse oocytes. Double mutant analysis revealed that only asynapsis-induced apoptosis was significantly dependent on HORMAD2. The present method is simple, easy, and able to analyze a sufficient number of oocytes for detecting infrequent events in a single specimen, accelerating detailed immunohistochemical analyses of mammalian ovaries during the fetal and perinatal periods.

developmental biology↗

bioRxiv2021

Rats show a preference for certain unfamiliar strains of rats

Humans show distinct social behaviours when we recognise social similarity in opponents that are members of the same social group. However, little attention has been paid to the role of social similarity in non-human animals. In Wistar subject rats, the presence of an unfamiliar Wistar rat mitigated stress responses, suggesting the importance of social similarity in this phenomenon. We found that the presence of unfamiliar Sprague-Dawley (SD) or Long-Evans (LE) rats, but not an unfamiliar Fischer 344 (F344) rat, similarly mitigated stress in subject rats. It is therefore possible that the subject rats recognised social similarity to unfamiliar SD and LE rats. In this study, we demonstrated that Wistar subject rats were capable of categorizing unfamiliar rats based on their strain, and that Wistar subjects showed a preference for unfamiliar Wistar, SD, and LE rats over F344 rats. However, the subject rats did not show a preference among Wistar, SD, and LE rats. In addition, the results were not due to an aversion to F344 rats, and preference was not affected when anaesthetised rats were presented to subject rats. The findings suggested that rats recognise social similarity to certain unfamiliar strains of rats.

animal behavior and cognition↗

bioRxiv2017

A Single Checkpoint Pathway Eliminates Mouse Oocytes With DNA Damage Or Chromosome Synapsis Failure

Pairing and synapsis of homologous chromosomes during meiosis is crucial for producing genetically normal gametes, and is dependent upon repair of SPO11-induced double stranded breaks (DSBs) by homologous recombination. To prevent transmission of genetic defects, diverse organisms have evolved mechanisms to eliminate meiocytes containing unrepaired DSBs or unsynapsed chromosomes. Here, we show that the CHK2 (CHEK2)-dependent DNA damage checkpoint culls not only recombination-defective mouse oocytes, but also SPO11-deficient oocytes that are severely defective in homolog synapsis. The checkpoint is triggered by spontaneous DSBs that arise in late prophase I, accumulating above the checkpoint activation threshold ([~]10 DSBs) because presence of HORMAD1/2 on unsynapsed chromosome axes prevents their repair. Furthermore, Hormad2 deletion rescued fertility and meiotic DSB repair of oocytes containing a synapsis-proficient, non-crossover recombination defective mutation in a gene (Trip13) required for removal of HORMADs from synapsed chromosomes, indicating that a substantial fraction of meiotic DSBs are normally repaired by intersister recombination in mice.

genetics↗