One afternoon as a second-year undergraduate, I called my parents from my dormitory. To them it was a routine call home, but to me it was a conversation long overdue. I’d rehearsed with my closest friends exactly how to start; my words needed to strike with confidence but should mitigate shock. Like protecting them from a grenade I’d thrown at them.
“So … I actually do have some romance in my life. With a boy.”
I practised answers to typical questions parents ask after their child comes out as gay: “Are you sure?”, “Why haven’t you told us?”, “Didn’t you like a girl once?” But those questions never came, and I wasn’t prepared for the one my mom did ask: “What about kids?” Whether out of sympathy for my aspirations to raise children or because of her plans of pampering grandchildren, my mother quickly recognized that my ability to start a family could be jeopardized by my sexuality. And she wasn’t wrong; 74% of American adults are parents, but only 35% of lesbian, gay, bisexual and transgender (LGBT) adults are parents even though 51% express the desire to have children, according to a 2013 survey. As of 2015, two-thirds of minors living with same-sex couples come from a previous relationship. But this is changing. With homosexuality becoming more accepted in parts of the world, people are recognizing their sexual identity earlier and might be less likely to enter a different-sex marriage. As such, fewer same-sex couples are raising children, but those children are more likely to be born during a same-sex relationship.
This trend is partly due to increased opportunities for same-sex couples to parent, by adoption and other means. In vitro fertilization (IVF) and surrogacy offer partial genetic relatedness for same-sex female and male couples, respectively. However, neither of these options delivers full genetic relatedness. Although no evidence suggests that genetic relatedness is necessary or sufficient for parenthood, surveys of biologically infertile different-sex couples show its significance. In 2017, one study found that more than 97% of respondents would prefer having a genetically related child (S. Hendriks et al. Hum. Reprod. 32, 2076–2087; 2017).
Now, as a graduate student performing research in chemical biology at the University of Chicago, Illinois, I think a lot about the intersection between my sexuality and my scientific interests. Genome-editing techniques are currently transforming our capacity to study fundamental biology. But, more importantly for me, they have offered a glimmer of hope that I could one day raise a biological descendant with my partner.
The road to same-sex human reproduction is one that many think is impossible to traverse. Aside from ethical and sociopolitical roadblocks, there are fundamental biological issues.
Parthenogenesis, or reproduction from an egg cell without fertilization, occurs naturally in birds and sharks. But mammalian reproduction is complicated by genomic ‘imprinting’, in which some genes are modified or shut down in either sperm or eggs while their opposite numbers are expressed — like the two halves of a zipper coming together. Seeking to address this, researchers have derived ‘imprint-free’ stem cells. A 2018 report in Cell Stem Cell described the use of CRISPR to delete imprinted regions from mouse genomes — removing the teeth from the biological zipper (Z.-K. Li et al. Cell Stem Cell 23, 665–676; 2018). Use of this technique with eggs from female mice produced living pups that grew to be healthy, fertile adults. However, pups produced using the technique with sperm from male mice did not survive to adulthood. While a significant achievement, many see the low success rate of birth (14% with embryos from two mothers, 2.5% with embryos from two fathers) as proof that mammals are limited to sexual reproduction. However, the technique offers optimism that same-sex human reproduction may be possible with a better understanding of imprinting, among other advances.
The development of same-sex reproduction technology might in 2019 be a scientific fantasy, and its use would be controversial. But IVF and same-sex marriage would have been just as unthinkable in 1869, when Nature launched from a foundation of academic liberalism and bold science. The disruptive innovation of same-sex reproduction would simply continue this endeavour and provide children to capable parents, as long as it is investigated enough to eliminate risks, made financially accessible and regulated responsibly.
As for me, I aspire to give my parents a grandchild by any plausible means when my partner and I are ready. But to raise a child genetically related to me and my partner? That’s a dream I’ll always have.
Nature 575, 55-56 (2019)