Science Concentrates NEUROSCIENCE
Mother’s immune response linked to sons’ sexual orientation Antibodies against male-specific proteins could help explain why having older brothers increases a man’s likelihood of being gay The greater number of older brothers a man has, the more likely he will be homosexual. Researchers have observed this so-called fraternal birth order effect across societies and over time. Now scientists report a possible biological mechanism behind it. They found that mothers of gay men with older brothers have elevated levels of antibodies against a male-specific brain protein (Proc. Natl. Acad. Sci. USA 2017, DOI: 10.1073/pnas.1705895114). The findings support the hypothesis that a mother’s immune response could shape brain structures in male fetuses that are involved in the development of sexual orientation, the researchers say. The fraternal birth order effect is one of the most robust correlations uncovered in sexual orientation research, and this study is an important first step in understanding the biology underlying the effect, says Qazi Rahman of King’s College London, who was not involved in the work. Anthony F. Bogaert of Brock University and Ray Blanchard of the University of Toronto first observed the phenomenon in a Canadian population in 1996. The
Mothers’ immune systems may target brain proteins encoded on the Y chromosome (shown) in male fetuses. two psychologists had a hypothesis about the biology underpinning the phenomenon. They thought that mothers’ immune systems might treat a specific protein in male fetuses like a foreign invader and this response would grow stronger with each boy born to the same mother. Eventually, the immune response would influence the developing brain of a son born later among a line of male siblings.
To test the hypothesis, the psychologists teamed up with some immunologists and collected blood samples from 54 mothers of gay sons, 72 mothers of straight sons, 16 women with no sons, and 12 men. Mothers of homosexual sons had higher levels of antibodies for the protein neuroligin 4 Y-linked than did mothers of heterosexual sons, and mothers of gay sons with older brothers had even higher levels. Not a lot is known about the function of the neuroligin protein except that it helps form connections between brain cells and facilitates communication between them. Because the study’s sample size was small and the observed effect was modest, Rahman thinks the experiment should be replicated on a larger scale to confirm the results. Bogaert says it’s important not to think of this mechanism as a disorder—as something pathological caused by a mother’s immune response. “An atypical biological process creating a trait doesn’t mean that the trait it produces necessarily needs fixing,” he adds. In general, he says, work on uncovering the biological basis for sexual orientation has helped the gay rights movement. “It suggests that sexual orientation is not a choice,” Bogaert says. “It also resonates with gay people’s lived experience—that they have felt different from early on in their lives.”—MICHAEL TORRICE
MATERIALS
A porous material that sucks up record-breaking amounts of methane could pave the way to more economical natural-gas-powered vehicles (Nat. Mater. 2017, DOI: 10.1038/nmat5050). Cars powered by methane emit less CO2 than gasoline guzzlers, but they need expensive tanks and compressors to carry the gas at high pressure. Certain metal-organic framework (MOF) compounds can store methane at lower pressures because the gas molecules pack tightly inside their pores. So MOFs, in principle, could enable methane-powered cars to use cheaper,
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C&EN | CEN.ACS.ORG | DECEMBER 11/18, 2017
lighter, and safer tanks. But in practical tests, no material has met a U.S. Department of Energy gas storage target of 263 cm3 of methane per cm3 of adsorbent at room temperature and 64 atm. A team led by David Fairen-Jimenez at the University of Cambridge has now developed a synthesis method that endows a well-known MOF with a capacity of 259 cm3 of methane per cm3 under those conditions, at least 50% higher than its nearest rival. The MOF, HKUST-1, contains copper nodes connected by 1,3,5-benzenetricarboxylate linkers. Fairen-Jimenez’s team
made lumps of HKUST-1 using a sol-gel process. The researchers mixed the MOF’s precursors in ethanol, centrifuged the particles that formed, and then allowed them to dry overnight at room temperature. Fairen-Jimenez estimates that a car’s gas tank would need about 60 kg of this MOF to operate. So far, he and his team can produce hundreds of grams of high-capacity HKUST-1 using a continuous flow version of their synthesis method, and their spinout company, Immaterial Labs, aims to achieve kilogram-scale production next year.—MARK PEPLOW, special to C&EN
C R E D I T: BI O P H OTO AS S OC I AT ES /S CI E N C E S O URC E
MOF sets methane storage record
