Altered testicular cell type composition in males of two outbred mouse lines selected for high fertility

Abstract

Background Recently we described two outbred mouse lines which have been selected for high fertility. These mouse models doubled the number of offspring per litter. Objectives Although selected for a primarily female‐trait of high fertility (increased litter size), we were interested whether also males of the fertility lines show differences within their reproductive organs. Materials and methods We investigated males from two outbred mouse lines which have been selected for the phenotype “high fertility” for more than 170 generations. In the present study, we analysed the testicular cell type composition by flow cytometry. We further investigated the weights of reproductive organs, histomorphometry of testis as well as studied sperm motility parameters using a thermal stress assay as well as a sperm hyperactivation assay. Results Here, we describe that males of the fertility line (FL) 1 show an increased percentage of diploid cells within the testis. Flow cytometric analysis identified this enlarged cell population as Leydig cells. Testis weights were unaffected whereas the weights of seminal vesicles of FL1 and FL2 were increased compared to Ctrl bucks. FL2 males show decreased diameter of tubulus seminiferi and an enhanced spermatid/Sertoli cell index. Sperm motility parameters of FL1 and Ctrl males are initially indistinguishable but FL1 spermatozoa show a better performance in a thermal stress experiment over a 5 hours observation period. Discussion These data indicate that although selected for a primarily female‐trait of high fertility also males from the fertility lines are effected by defined alterations in their reproductive organs. Conclusion Some of these alterations are FL1‐specific others are FL2‐associated, indicating that different molecular strategies warrant the high‐fertility phenotype on the female as well as on the male side.

Two mouse lines selected for large litter size display different lifetime fecundities

“…Based on selection over >45 years and 190 generations, these mouse lines almost doubled the number of offspring compared to a control line. From the very beginning of the selection process, both lines were developed separately and are now highly diverged mouse lines showing various differences in their physiological, behavioural, endocrine and molecular characteristics ( Langhammer et al 2014 , Michaelis et al 2013 , 2020 ). Nevertheless, both biodiverse mouse lines produce double the number of offspring, namely, 20.6 and 21.4 pups/litter ( Fig.…”

“…Since the two lines have been bred independently, they developed distinct biodiverse phenotypes. Although the two lines show similar litter sizes at first delivery, they differ in many physiological, behavioural and endocrine aspects ( Langhammer et al 2014 , Michaelis et al 2020 ). In addition, gene expression patterns in the testis differ among FL1, FL2 and an unselected control line ( Michaelis et al 2017 , 2018 ).…”