Sperm quality parameters are increased and asymmetric in house mouse hybrids

Abstract

21Spermatogenesis is a tuned cascade of processes producing sperm; impairment of any phase of 22 this process can affect fitness of males. The level of impairment can be pronounced in hybrids 23 between genetically divergent populations. To explore the effect of hybridization on sperm quality 24 we produced F1 hybrids from 29 wild derived strains of two house mouse subspecies, M. m. 25 musculus and M. m. domesticus, which diverged 0.5 MY ago. The measured sperm quality traits 26 did not significantly differ between intrasubspecific crosses. Effects of intersubspecific 27 hybridization were dependent on sperm trait and cross direction. The proportion of sperm head 28 abnormalities was increased in F1 intersubspecific hybrids. The frequency of dissociated sperm 29 heads was increased in the M. m. musculus x M. m. domesticus (♀×♂) F1 but decreased in M. m. 30 domesticus x M. m. musculus (♀×♂) F1 hybrids, with the difference in medians being more than 31 180%. We deduce that the dissociated sperm heads trait is associated with the X chromosome and 32 modulated by interaction with the Y chromosome; nevertheless, the high proportion of 33 unexplained variance (55.46 %) suggests the presence of polymorphic autosomal interactions. The 34 reported differences in sperm quality between cross types may be highly relevant to male fitness 35 in zones of secondary contact between the two subspecies. The cross direction asymmetry in 36 frequency of dissociated sperm heads should favour the M. m. musculus Y chromosome. This is 37 consistent with the spread of the M. m. musculus Y chromosome in nature across the hybrid zone 38 between these two subspecies. 39 40

Stage-specific disruption of X chromosome expression during spermatogenesis in sterile house mouse hybrids

“…Indeed, mapping studies have identified multiple regions of the X chromosome ( Oka et al 2004 ; Good et al 2008a ; Dufková et al 2011 ; Turner et al 2014 ; Turner and Harr 2014 ; Morgan et al 2020 ) and numerous autosomal regions contributing to sterility in F1 hybrids ( Larson et al 2018b ), F2 crosses and backcrosses ( Good et al 2008a ; White et al 2011 ; Turner et al 2014 ; Schwahn et al 2018 ; Morgan et al 2020 ) and wild hybrids ( Turner and Harr 2014 ). There is also evidence that XY mismatch contributing to abnormal sperm morphology ( Campbell and Nachman 2014 ; Martincová et al 2019a , 2019b ), and patterns of directional introgression of the musculus Y chromosome into domesticus backgrounds ( Macholán et al 2008 , 2019 ; Ďureje et al 2012 ), consistent with postmeiotic X and Y chromosome conflict.…”

Stage-specific disruption of X chromosome expression during spermatogenesis in sterile house mouse hybrids

“…Indeed, mapping studies have identified multiple regions of the X chromosome (Oka et al 2004;Good et al 2008a;Dufková et al 2011;Turner and Harr 2014;Morgan et al 2020) and numerous autosomal regions contributing to sterility in F1 hybrids (Larson et al 2018b), F2 crosses and backcrosses (Good et al 2008a;White et al 2011;Schwahn et al 2018;Morgan et al 2020) and wild hybrids (Turner and Harr 2014). There is also evidence that XY mismatch contributing to abnormal sperm morphology (Campbell and Nachman 2014;Martincová et al 2019bMartincová et al , 2019a, and patterns of directional introgression of the musculus Y chromosome into domesticus backgrounds (Macholán et al 2008(Macholán et al , 2019Ďureje et al 2012), consistent with postmeiotic X and Y chromosome conflict.…”

Shifting focus from resistance to disease tolerance: A review on hybrid house mice

“…Studies performed on geographically independent transects of the HMHZ give strong support to the tension zone model in this system: the immigration of less hybridized mice to the center of the zone, increasing the hybrid population size, is balanced by endogenous selection against hybrids (Barton & Hewitt, 1985). This negative selection on hybrids seems to be linked with reduced fertility and especially disruption of spermatogenesis has been shown (Albrechtová et al, 2012; Martincová et al, 2019; Turner & Harr, 2014; Turner et al, 2012). Reduced fertility has very immediate fitness consequences showing how genetic incompatibilities reduce fitness without the influence of extrinsic factors.…”

“…Hybrid fitness is reduced in the house mouse hybrid zone (HMHZ). Reproduction is negatively affected in hybrids, for example, via disruption of spermatogenesis (Martincová et al, 2019). This reduction in reproductive fitness is a direct consequence of genetic incompatibilities without the involvement of extrinsic factors.…”