Reverse genetics reveals single gene of every candidate on Hybrid sterility, X Chromosome QTL 2 (Hstx2) are dispensable for spermatogenesis

Kento Morimoto,Keiko Kobayashi,Yuko Hamada,Satoru Takahashi,Shinya Ayabe,Fumihiro Sugiyama,Kazuya Murata,Hayate Suzuki,Seiya Mizuno,Koki Numata,Atsushi Yoshiki,Yoko Daitoku,Kanako Kato

doi:10.1038/s41598-020-65986-y

Kento Morimoto, Keiko Kobayashi + Show 11 more

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https://doi.org/10.1038/s41598-020-65986-y

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Abstract

F1 hybrid progenies between related subspecies often show hybrid sterility (HS) or inviability. HS is caused by failure of meiotic chromosome synapsis and sex body formation in house mouse. Previous studies identified two HS critical genomic regions named Hstx2 on Chr X and Hst1 on Chr 17 by murine forward genetic approaches. HS gene on Hst1 was reported to be Prdm9. Intersubspecific polymorphisms of Prdm9 induce HS in hybrids, and Prdm9 null mutation leads to sterility in the inbred strain. However, HS gene on Hstx2 remains unknown. Here, using knock-out studies, we showed that HS candidate genes on Hstx2 are not individually essential for spermatogenesis in B6 strain. We examined 12 genes on Hstx2: Ctag2, 4930447F04Rik, Mir743, Mir465d, Mir465c-2, Mir465b-1, Mir465c-1, Mir465, Gm1140, Gm14692, 4933436I01Rik, and Gm6812. These genes were expressed in adult testes, and showed intersubspecific polymorphisms on expressed regions. This first reverse genetic approach to identify HS gene on Hstx2 suggested that the loss of function of any one HS candidate gene does not cause complete sterility, unlike Prdm9. Thus, the mechanism(s) of HS by the HS gene on Hstx2 might be different from that of Prdm9.

Highlights

Postzygotic reproductive isolation between related subspecies often results in hybrid incompatibility such as hybrid sterility (HS) or inviability[1,2,3,4]
Testes expression was analysed using Fantom[5], BioGPS and miRbase, which revealed that of the 32 genes, 9 protein-coding genes: Ctag2, 4930447F04Rik, Gm1140, Gm14692, 4933436I01Rik, Fmr[1], Fmr1nb, Gm6812, and Aff[2], and all 22 miRNA genes were expressed in adult B6 testes (Table 1 and S1)
We focused on intersubspecific polymorphism on expressed regions, which are the coding region in protein-coding alleles and mature miRNA region in miRNA alleles

Summary

Introduction

Postzygotic reproductive isolation between related subspecies often results in hybrid incompatibility such as hybrid sterility (HS) or inviability[1,2,3,4]. This model shows asymmetric HS, wherein (PWD × B6) F1 hybrid (mating PWD female with B6 male) shows sterility, while (B6 × PWD) F1 hybrid (mating B6 female with PWD male) shows semi-fertility[35,36] To identify these HS loci, Gregorová, S. et al established intersubspecific chromosome substitution (consomic) strains C57BL/6-Chr#PWD/Ph/ForeJ carrying individual Mmm chromosomes or their parts on Mmd background[37]. We hypothesised that HS gene on Hstx[2] may have similar features to Prdm[9], such as expressing in adult testes[45], having intersubspecific polymorphisms on expressed region between Mmm and Mmd[43,44], explaining HS mechanism by single locus[43] and inducing sterility by knock-out (KO) in B6 genetic background[45,46]. We analysed intersubspecific polymorphisms on expressed regions between B6 and PWD, PWK/Phj (Mmm inbred strain, hereafter, PWK) by past reports and public database

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