Evidence for RNA or protein transport from somatic tissues to the male reproductive tract in mouse

Abstract

The development of tools to manipulate the mouse genome, including knockout and transgenic technology, revolutionized our ability to explore gene function in mammals. Moreover, for genes that are expressed in multiple tissues or at multiple stages of development, the use of tissue-specific expression of the Cre recombinase allows gene function to be perturbed in specific cell types and/or at specific times. However, it is well known that putative tissue-specific promoters often drive unanticipated off target expression. In our efforts to explore the biology of the male reproductive tract, we unexpectedly found that expression of Cre in the central nervous system resulted in recombination in the epididymis, a tissue where sperm mature for ~1-2 weeks following the completion of testicular development. Remarkably, we not only observed reporter expression in the epididymis when Cre expression was driven from neuron-specific transgenes, but also when Cre expression in the brain was induced from an AAV vector carrying a Cre expression construct. A surprisingly wide range of Cre drivers - including six different neuronal promoters as well as the adipose-specific AdipoQ Cre promoter - exhibited off target recombination in the epididymis, with a subset of drivers also exhibiting unexpected activity in other tissues such as the reproductive accessory glands. Finally, using a combination of parabiosis and serum transfer experiments, we find evidence supporting the hypothesis that Cre may be trafficked from its cell of origin to the epididymis through the circulatory system. Together, our findings should motivate extreme caution when interpreting conditional alleles, and suggest the exciting possibility of inter-tissue RNA or protein trafficking in modulation of reproductive biology.

Bubbling beyond the barrier: exosomal RNA as a vehicle for soma–germline communication

“…Crucially, miR-941 was also detected in embryos derived from pairings between miR-941-expressing males and wild-type females. Rinaldi et al (2023) most recently demonstrated that transgenic neural-and adipose-specific Cre recombinase mice, as well as AAV-mediated neural Cre expression, resulted in clear off-target recombination in the epididymis, and that this distal recombination involved transportation via the circulatory system using both parabiosis and either serum or serum-EV injections into reporter mice. Together, these data provide the first direct evidence that ncRNA transcribed in the soma can be shuttled inside EVs into animal gametes and even into the next generation (Fig.…”

High frequency of germline recombination in Nestin-Cre transgenic mice crossed with Glucagon-like peptide 1 receptor floxed mice

“…There are also various reports regarding the sites of Cre activity in the reproductive organs. Some investigators have observed Cre activity in the testis, whereas others have reported Cre expression in the epididymis [ 7 , 26 , 27 ]. Conversely, James et al reported a decline in Nestin expression in epididymal cells as individuals grow, with significantly reduced expression observed in adults [ 25 ].…”