Mammalian reproduction conventionally requires oocytes provided by a female and sperm provided by a male to achieve fertilization. We go beyond this convention and propose the hypothesis that an adult individual of any sex can be induced to produce gametes of the opposite sex, and that these gametes are functional in assisted fertilization. The premise for this hypothesis comes from our recently published studies demonstrating that genetically engineered male mice with limited or no Y chromosome genes can successfully reproduce by assisted fertilization (ART), and from significant advancements in field of cell reprogramming and differentiation. Our laboratory has shown that in the mouse only two Y chromosome genes, testis determinant Sry and spermatogenesis driver Eif2s3y, are sufficient for a male to produce haploid male gametes functional in ART. We have subsequently demonstrated that the function of these two genes could be replaced by that of their homologues encoded on other chromosomes, and that a mouse with a single X chromosome (XO) lacking all Y chromosome genes can produce male gametes and sire healthy offspring after assisted fertilization. The laboratory of our collaborator, Mitinori Saitou, has shown that both male and female gametes can be obtained from induced pluripotent stem cells (iPSC) differentiated into primordial germ cell like-cells (PGCLC). In this proposal, we marry our findings and expertise and ask 3 questions:
Aim 1. Can an adult female mouse produce male gametes functional in assisted fertilization? Aim 2. Can an adult male mouse produce female gametes functional in assisted fertilization? Aim 3. Can an adult mouse of either sex sire uniparental offspring? To address these questions we will develop somatic cell lines from an adult mouse of a given sex, reprogram to iPSC, identify the clones that have lost one sex chromosome and became XO, and differentiate into PGCLC. To produce male gametes we will transgenically add a spermatogenesis driver and transplant PGCLC to testes from neonatal males. To produce female gametes we will reconstitute ovaries in vitro and transplant them under ovarian bursa of recipient females. We will test the function of such derived male and female gametes using assisted reproduction. To produce uniparental offspring, male and female gametes derived from the same individual will be used for fertilization. The findings from this project will impact on our understanding of sex specific differences, especially pertaining to effects of sex chromosomes and X and Y genes on germline development. If successful, we will also provide the field with a proof-of-principle that offspring of both sexes can be obtained from a single individual, which will impact on species preservation.

Public Health Relevance

The project will assess, in a mouse model, whether it is possible for an individual of a given sex to produce gametes of the opposite sex, and whether these gametes are functional in assisted fertilization. We will also test if a single individual of either sex can produce both male and female gametes and sire uniparental offspring. Our findings will impact on species preservation and understanding of sex specific differences.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Taymans, Susan
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University of Hawaii
Anatomy/Cell Biology
Schools of Medicine
United States
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Ortega, Egle A; Salvador, Quinci; Fernandez, Mayumi et al. (2018) Alterations of sex determination pathway in the genital ridges of males with limited Y chromosome genes. Biol Reprod :
Ruthig, Victor A; Nielsen, Torbjoern; Riel, Jonathan M et al. (2017) Testicular abnormalities in mice with Y chromosome deficiencies. Biol Reprod 96:694-706
Yamauchi, Yasuhiro; Riel, Jonathan M; Ruthig, Victor A et al. (2016) Two genes substitute for the mouse Y chromosome for spermatogenesis and reproduction. Science 351:514-6
Ruthig, Victor A; Labrash, Steven; Lozanoff, Scott et al. (2016) Macroscopic demonstration of the male urogenital system with evidence of a direct inguinal hernia utilizing room temperature plastination. Anatomy 10:211-220
Ortega, Egle A; Ruthig, Victor A; Ward, Monika A (2015) Sry-Independent Overexpression of Sox9 Supports Spermatogenesis and Fertility in the Mouse. Biol Reprod 93:141
Comish, P B; Liang, L Y; Yamauchi, Y et al. (2015) Increasing testicular temperature by exposure to elevated ambient temperatures restores spermatogenesis in adult Utp14b (jsd) mutant (jsd) mice. Andrology 3:376-84
Yamauchi, Yasuhiro; Riel, Jonathan M; Ruthig, Victor et al. (2015) Mouse Y-Encoded Transcription Factor Zfy2 Is Essential for Sperm Formation and Function in Assisted Fertilization. PLoS Genet 11:e1005476
Sato, Brittany L; Ward, Monika A; Astern, Joshua M et al. (2015) Validation of murine and human placental explant cultures for use in sex steroid and phase II conjugation toxicology studies. Toxicol In Vitro 29:103-12
Vernet, Nad├Ęge; Mahadevaiah, Shantha K; Yamauchi, Yasuhiro et al. (2014) Mouse Y-linked Zfy1 and Zfy2 are expressed during the male-specific interphase between meiosis I and meiosis II and promote the 2nd meiotic division. PLoS Genet 10:e1004444
Yamauchi, Yasuhiro; Riel, Jonathan M; Stoytcheva, Zoia et al. (2014) Two Y genes can replace the entire Y chromosome for assisted reproduction in the mouse. Science 343:69-72

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